accumulo-commits mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From ctubb...@apache.org
Subject [20/50] [abbrv] accumulo-website git commit: Jekyll build from gh-pages:358b7b4
Date Tue, 22 Nov 2016 19:41:17 GMT
http://git-wip-us.apache.org/repos/asf/accumulo-website/blob/c0655661/feed.xml
----------------------------------------------------------------------
diff --git a/feed.xml b/feed.xml
index c133379..f7e080d 100644
--- a/feed.xml
+++ b/feed.xml
@@ -6,8 +6,8 @@
 </description>
     <link>https://accumulo.apache.org/</link>
     <atom:link href="https://accumulo.apache.org/feed.xml" rel="self" type="application/rss+xml"/>
-    <pubDate>Thu, 03 Nov 2016 12:05:50 -0400</pubDate>
-    <lastBuildDate>Thu, 03 Nov 2016 12:05:50 -0400</lastBuildDate>
+    <pubDate>Thu, 10 Nov 2016 16:36:52 -0500</pubDate>
+    <lastBuildDate>Thu, 10 Nov 2016 16:36:52 -0500</lastBuildDate>
     <generator>Jekyll v3.2.1</generator>
     
       <item>
@@ -78,9 +78,9 @@ and checksums were stored in-line, then 1 sync could be done instead of 4.&lt;/p
 
 &lt;h2 id=&quot;configuring-wal-flushsync-in-accumulo-16&quot;&gt;Configuring WAL flush/sync in Accumulo 1.6&lt;/h2&gt;
 
-&lt;p&gt;Accumulo 1.6.0 only supported &lt;code class=&quot;highlighter-rouge&quot;&gt;hsync&lt;/code&gt; and this caused &lt;a href=&quot;/release_notes/1.6.0#slower-writes-than-previous-accumulo-versions&quot;&gt;performance
+&lt;p&gt;Accumulo 1.6.0 only supported &lt;code class=&quot;highlighter-rouge&quot;&gt;hsync&lt;/code&gt; and this caused &lt;a href=&quot;/release/accumulo-1.6.0#slower-writes-than-previous-accumulo-versions&quot;&gt;performance
 problems&lt;/a&gt;.  In order to offer better performance, the option to
-configure &lt;code class=&quot;highlighter-rouge&quot;&gt;hflush&lt;/code&gt; was &lt;a href=&quot;/release_notes/1.6.1#write-ahead-log-sync-implementation&quot;&gt;added in 1.6.1&lt;/a&gt;.  The
+configure &lt;code class=&quot;highlighter-rouge&quot;&gt;hflush&lt;/code&gt; was &lt;a href=&quot;/release/accumulo-1.6.1#write-ahead-log-sync-implementation&quot;&gt;added in 1.6.1&lt;/a&gt;.  The
 &lt;a href=&quot;/1.6/accumulo_user_manual#_tserver_wal_sync_method&quot;&gt;tserver.wal.sync.method&lt;/a&gt; configuration option was added to support
 this feature.  This was a tablet server wide option that applied to everything
 written to any table.&lt;/p&gt;
@@ -161,7 +161,7 @@ config -t accumulo.root -d table.durability
 
 &lt;p&gt;Even with these settings adjusted, minor compactions could still force &lt;code class=&quot;highlighter-rouge&quot;&gt;hsync&lt;/code&gt;
 to be called in 1.7.0 and 1.7.1.  This was fixed in 1.7.2 and 1.8.0.  See the
-&lt;a href=&quot;/release_notes/1.7.2#minor-performance-improvements&quot;&gt;1.7.2 release notes&lt;/a&gt; and &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4112&quot;&gt;ACCUMULO-4112&lt;/a&gt; for more details.&lt;/p&gt;
+&lt;a href=&quot;/release/accumulo-1.7.2#minor-performance-improvements&quot;&gt;1.7.2 release notes&lt;/a&gt; and &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4112&quot;&gt;ACCUMULO-4112&lt;/a&gt; for more details.&lt;/p&gt;
 
 &lt;p&gt;In addition to the per table durability setting, a per batch writer durability
 setting was also added in 1.7.0.  See
@@ -186,585 +186,1302 @@ problems with Per-durability write ahead logs.&lt;/p&gt;
       </item>
     
       <item>
-        <title>Replicating data across Accumulo clusters</title>
-        <description>&lt;p&gt;Originally posted at &lt;a href=&quot;https://blogs.apache.org/accumulo/entry/data_center_replication&quot;&gt;https://blogs.apache.org/accumulo/entry/data_center_replication&lt;/a&gt;&lt;/p&gt;
+        <title>Apache Accumulo 1.6.6</title>
+        <description>&lt;p&gt;Apache Accumulo 1.6.6 is a maintenance release on the 1.6 version branch. This
+release contains changes from more than 40 issues, comprised of bug-fixes,
+performance improvements, build quality improvements, and more. See
+&lt;a href=&quot;https://issues.apache.org/jira/secure/ReleaseNote.jspa?projectId=12312121&amp;amp;version=12334846&quot;&gt;JIRA&lt;/a&gt; for a complete list.&lt;/p&gt;
 
-&lt;p&gt;Traditionally, Apache Accumulo can only operate within the confines of a single physical location. The primary reason for this restriction is that Accumulo relies heavily on Apache ZooKeeper for distributed lock management and some distributed state. Due to the consistent nature of ZooKeeper and its protocol, it doesn’t handle wide-area networks (WAN) well. As such, Accumulo suffers the same problems operating over a WAN.&lt;/p&gt;
+&lt;p&gt;Below are resources for this release:&lt;/p&gt;
 
-&lt;p&gt;Data-Center Replication is a new feature, to be included in the upcoming Apache Accumulo 1.7.0, which aims to address the limitation of Accumulo to one local-area network (LAN). The implementation makes a number of decisions with respect to consistency and available which aim to avoid the normal “local” operations of the primary Accumulo instance. That is to say, replication was designed in such a way that enabling the feature on an instance should not affect the performance of that system. However, this comes at a cost of consistency across all replicas. Replication from one instance to others is performed lazily. Succinctly, replication in Accumulo can be described as an eventually-consistent system and not a strongly-consistent system (an Accumulo instance is strongly-consistent).&lt;/p&gt;
+&lt;ul&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.6/accumulo_user_manual.html&quot;&gt;User Manual&lt;/a&gt;&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.6/apidocs&quot;&gt;Javadocs&lt;/a&gt;&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.6/examples&quot;&gt;Examples&lt;/a&gt;&lt;/li&gt;
+&lt;/ul&gt;
+
+&lt;p&gt;Users of any previous 1.6.x release are strongly encouraged to update as soon
+as possible to benefit from the improvements with very little concern in change
+of underlying functionality.&lt;/p&gt;
+
+&lt;p&gt;As of this release, active development has ceased for the 1.6 release line, so
+users should consider upgrading to a newer, actively maintained version when
+they can. While the developers may release another 1.6 version to address a
+severe issue, there’s a strong possibility that this will be the last 1.6
+release. That would also mean that this will be the last Accumulo version to
+support Java 6 and Hadoop 1.&lt;/p&gt;
 
-&lt;p&gt;Because replication is performed lazily, this implies that the data to replicate must be persisted in some shape until the actual replication takes place. This is done using Accumulo’s write-ahead log (WAL) files for this purpose. The append-only nature of these files make them obvious candidates for reuse without the need to persist the data in another form for replication. The only necessary changes internally to Accumulo to support this is changing the conditions that the Accumulo garbage collector will delete WAL files. Using WAL files also has the benefit of making HDFS capacity the limiting factor in how “lazy” replication can be. This means that the amount of time replication can be offline or stalled is only limited by the amount of extra HDFS space available which is typically ample.&lt;/p&gt;
+&lt;h2 id=&quot;highlights&quot;&gt;Highlights&lt;/h2&gt;
 
-&lt;p&gt;&lt;img src=&quot;/images/blog/201504_replication/replication1.png&quot; alt=&quot;image1&quot; /&gt;&lt;/p&gt;
+&lt;h3 id=&quot;write-ahead-logs-can-be-prematurely-deleted&quot;&gt;Write-Ahead Logs can be prematurely deleted&lt;/h3&gt;
 
-&lt;h2 id=&quot;terminology&quot;&gt;Terminology&lt;/h2&gt;
+&lt;p&gt;There were cases where the Accumulo Garbage Collector may inadvertently delete
+a WAL for a tablet server that it has erroneously determined to be down,
+causing data loss. This has been corrected. See &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4157&quot;&gt;ACCUMULO-4157&lt;/a&gt;
+for additional detail.&lt;/p&gt;
 
-&lt;p&gt;Before getting into details on the feature, it will help to define some basic terminology. Data in Accumulo is replicated from a “primary” Accumulo instance to a “peer” Accumulo instance. Each instance here is a normal Accumulo instance – each instance is only differentiated by a few new configuration values. Users ingest data into the primary instance, and that data will eventually be replicated to a peer. Each instance requires a unique name to identify itself among all Accumulo instances replicating with each other. Replication from a primary to a peer is defined on a per-table basis – that is, the configuration states that tableA on the primary will be replicated to tableB on the peer. A primary can have multiple peers defined, e.g. tableA on the primary can will be replicated to tableB on peer1 and tableC on peer2.
- Overview&lt;/p&gt;
+&lt;h3 id=&quot;upgrade-to-commons-vfs-21&quot;&gt;Upgrade to Commons-VFS 2.1&lt;/h3&gt;
 
-&lt;p&gt;Internally, replication is comprised of a few components to make up the user-facing feature: the management of data ingested on the primary which needs to be replicated, the assignment of replication work within the primary, the execution of that work within the primary to send the data to a peer, and the application of the data to the appropriate table within the peer.&lt;/p&gt;
+&lt;p&gt;Upgrading to Apache Commons VFS 2.1 fixes several issues with classloading out
+of HDFS. For further detail see &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4146&quot;&gt;ACCUMULO-4146&lt;/a&gt;. Additional
+fixes to a potential HDFS class loading deadlock situation were made in
+&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4341&quot;&gt;ACCUMULO-4341&lt;/a&gt;.&lt;/p&gt;
 
-&lt;h3 id=&quot;state-management-on-primary&quot;&gt;State Management on Primary&lt;/h3&gt;
+&lt;h3 id=&quot;native-map-failed-to-increment-mutation-count-properly&quot;&gt;Native Map failed to increment mutation count properly&lt;/h3&gt;
 
-&lt;p&gt;The most important state to manage for replication is the tracking the data that was ingested in the primary. This is what ensures that all of the data will be eventually replicated to the necessary peer(s). This state is kept in both the Accumulo metadata table and a new table in the accumulo namespace: replication. Through the use of an Accumulo Combiner on these tables, updates to the replication state are simple updates to the replication table. This makes management of the state machine across all of the nodes within the Accumulo instance extremely simple. For example, TabletServers reporting that data was ingested into a write-ahead log, the Master preparing data to be replicated and the TabletServer reporting that data has been replicated to the peer are all updates to the replication table.&lt;/p&gt;
+&lt;p&gt;There was a bug (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4148&quot;&gt;ACCUMULO-4148&lt;/a&gt;) where multiple put calls with
+identical keys and no timestamp would exhibit different behaviour depending on
+whether native maps were enabled or not. This behaviour would result in hidden
+mutations with native maps, and has been corrected.&lt;/p&gt;
 
-&lt;p&gt;To “seed” the state machine, TabletServers first write to the metadata table at the end of a minor compaction. The Master will read records from the metadata table and add them to the replication table. Each Key-Value pair in the replication table represents a WAL’s current state within the replication “state machine” with different column families representing different states. For example, one column family represents the status of a WAL file being replicated to a specific peer while a different column family represents the status of a WAL file being replicated to all necessary peers.&lt;/p&gt;
+&lt;h3 id=&quot;open-wal-files-could-prevent-datanode-decomission&quot;&gt;Open WAL files could prevent DataNode decomission&lt;/h3&gt;
 
-&lt;p&gt;The Master is the primary driver of this state machine, reading the replication table and making the necessary updates repeatedly. This allows the Master to maintain a constant amount of memory with respect to the amount of data that needs to be replicated. The only limitation on persisted state for replication is the size of the replication table itself and the amount of space the WAL files on HDFS consume.&lt;/p&gt;
+&lt;p&gt;An improvement was introduced to allow a max age before WAL files would be
+automatically rolled. Without a max age, they could stay open for writing
+indefinitely, blocking the Hadoop DataNode decomissioning process. For more
+information, see &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4004&quot;&gt;ACCUMULO-4004&lt;/a&gt;.&lt;/p&gt;
 
-&lt;h3 id=&quot;rpc-from-primary-to-peer&quot;&gt;RPC from primary to peer&lt;/h3&gt;
+&lt;h3 id=&quot;remove-unnecessary-copy-of-cached-rfile-index-blocks&quot;&gt;Remove unnecessary copy of cached RFile index blocks&lt;/h3&gt;
 
-&lt;p&gt;Like the other remote procedure calls in Accumulo, Apache Thrift is used to make RPCs from the primary Accumulo instance to a peer instance. The purpose of these methods is to send the relevant data from a WAL file to the peer. The Master advertises units of replication work, a WAL file that needs to be replicated to a single peer, and all TabletServers in the primary instance will try to reserve, and then perform, that work. ZooKeeper provides this feature to us with very little code in Accumulo.&lt;/p&gt;
+&lt;p&gt;Accumulo maintains an cache for file blocks in-memory as a performance
+optimization. This can be done safely because Accumulo RFiles are immutable,
+thus their blocks are also immutable. There are two types of these blocks:
+index and data blocks. Index blocks refer to the b-tree style index inside of
+each Accumulo RFile, while data blocks contain the sorted Key-Value pairs. In
+previous versions, when Accumulo extracted an Index block from the in-memory
+cache, it would copy the data. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4164&quot;&gt;ACCUMULO-4164&lt;/a&gt; removes this
+unnecessary copy as the contents are immutable and can be passed by reference.
+Ensuring that the Index blocks are not copied when accessed from the cache is a
+big performance gain at the file-access level.&lt;/p&gt;
 
-&lt;p&gt;Once a TabletServer obtains the work, it will read through the WAL file extracting updates only for the table in this unit of work and send the updates across the wire to a TabletServer in the peer. The TabletServer on the primary asks the active Master in the peer for a TabletServer to communicate with. As such, ignoring some very quick interactions with the Master, RPC for replication is primarily a TabletServer to TabletServer operation which means that replication should scale in performance with respect to the number of available TabletServers on the primary and peer.&lt;/p&gt;
+&lt;h3 id=&quot;analyze-key-length-to-avoid-choosing-large-keys-for-rfile-index-blocks&quot;&gt;Analyze Key-length to avoid choosing large Keys for RFile Index blocks&lt;/h3&gt;
 
-&lt;p&gt;The amount of data read from a WAL and sent to the peer per RPC is a configurable parameter defaulting to 50MB. Increasing the amount of data read at a time will have a large impact on the amount of memory consumed by a TabletServer when using replication, so take care when altering this property. It is also important to note that the Thrift server used for the purposes of replication is completely separate from the thrift server used by clients. Replication and the client service servers will not compete against one another for RPC resources.&lt;/p&gt;
+&lt;p&gt;Accumulo’s RFile index blocks are made up of a Key which exists in the file and
+points to that specific location in the corresponding RFile data block. Thus,
+the size of the RFile index blocks is largely dominated by the size of the Keys
+which are used by the index. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4314&quot;&gt;ACCUMULO-4314&lt;/a&gt; is an improvement
+which uses statistics on the length of the Keys in the Rfile to avoid choosing
+Keys for the index whose length is greater than three standard deviations for
+the RFile. By choosing smaller Keys for the index, Accumulo can access the
+RFile index faster and keep more Index blocks cached in memory. Initial tests
+showed that with this change, the RFile index size was nearly cut in half.&lt;/p&gt;
 
-&lt;h3 id=&quot;replay-of-data-on-peer&quot;&gt;Replay of data on peer&lt;/h3&gt;
+&lt;h3 id=&quot;gson-version-bump&quot;&gt;Gson version bump&lt;/h3&gt;
 
-&lt;p&gt;After a TabletServer on the primary invokes an RPC to a TabletServer on the peer, but before that RPC completes, the TabletServer on the peer must apply the updates it received to the local table. The TabletServer on the peer constructs a BatchWriter and simply applies the updates to the table. In the event of an error in writing the data, the RPC will return in error and it will be retried by a TabletServer on the primary. As such, in these failure conditions, it is possible that data will be applied on the peer multiple times. The use of Accumulo Combiners on tables used being replicated is nearly always a bad idea which will result in inconsistencies between the primary and replica.&lt;/p&gt;
+&lt;p&gt;Due to an &lt;a href=&quot;https://github.com/google/gson/issues/362&quot;&gt;upstream bug with Gson 2.2.2&lt;/a&gt;, we’ve bumped our bundled
+dependency (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4345&quot;&gt;ACCUMULO-4345&lt;/a&gt;) to version 2.2.4. Please take note
+of this when you upgrade, if you were using the version shipped with Accumulo,
+and were relying on the buggy behavior in the previous version in your own
+code.&lt;/p&gt;
 
-&lt;p&gt;Because there are many TabletServers, each with their own BatchWriter, potential throughput for replication on the peer should be equivalent to the ingest throughput observed by clients normally ingesting data uniformly into Accumulo.&lt;/p&gt;
+&lt;h3 id=&quot;minor-performance-improvements&quot;&gt;Minor performance improvements.&lt;/h3&gt;
 
-&lt;p&gt;&lt;img src=&quot;/images/blog/201504_replication/replication2.png&quot; alt=&quot;image2&quot; /&gt;&lt;/p&gt;
+&lt;p&gt;A performance issue was identified and corrected
+(&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-1755&quot;&gt;ACCUMULO-1755&lt;/a&gt;) where the BatchWriter would block calls to
+addMutation while looking up destination tablet server metadata. The writer has
+been fixed to allow both operations in parallel.&lt;/p&gt;
+
+&lt;h2 id=&quot;other-notable-changes&quot;&gt;Other Notable Changes&lt;/h2&gt;
+
+&lt;ul&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4155&quot;&gt;ACCUMULO-4155&lt;/a&gt; No longer publish javadoc for non-public API
+to website. (Still available in javadoc jars in maven)&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4334&quot;&gt;ACCUMULO-4334&lt;/a&gt; Ingest rates reported through JMX did not
+match rates reported by Monitor.&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4335&quot;&gt;ACCUMULO-4335&lt;/a&gt; Error conditions that result in a Halt should
+ensure non-zero process exit code.&lt;/li&gt;
+&lt;/ul&gt;
 
-&lt;h2 id=&quot;complex-replication-configurations&quot;&gt;Complex replication configurations&lt;/h2&gt;
+&lt;h2 id=&quot;testing&quot;&gt;Testing&lt;/h2&gt;
+
+&lt;p&gt;Each unit and functional test only runs on a single node, while the RandomWalk
+and Continuous Ingest tests run on any number of nodes. &lt;em&gt;Agitation&lt;/em&gt; refers to
+randomly restarting Accumulo processes and Hadoop Datanode processes, and, in
+HDFS High-Availability instances, forcing NameNode failover.&lt;/p&gt;
+
+&lt;table id=&quot;release_notes_testing&quot; class=&quot;table&quot;&gt;
+  &lt;thead&gt;
+    &lt;tr&gt;
+      &lt;th&gt;OS/Environment&lt;/th&gt;
+      &lt;th&gt;Hadoop&lt;/th&gt;
+      &lt;th&gt;Nodes&lt;/th&gt;
+      &lt;th&gt;ZooKeeper&lt;/th&gt;
+      &lt;th&gt;HDFS HA&lt;/th&gt;
+      &lt;th&gt;Tests&lt;/th&gt;
+    &lt;/tr&gt;
+  &lt;/thead&gt;
+  &lt;tbody&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 7&lt;/td&gt;
+      &lt;td&gt;1.2.1&lt;/td&gt;
+      &lt;td&gt;1&lt;/td&gt;
+      &lt;td&gt;3.3.6&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;Unit tests and Integration Tests&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 7&lt;/td&gt;
+      &lt;td&gt;2.2.0&lt;/td&gt;
+      &lt;td&gt;1&lt;/td&gt;
+      &lt;td&gt;3.3.6&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;Unit tests and Integration Tests&lt;/td&gt;
+    &lt;/tr&gt;
+  &lt;/tbody&gt;
+&lt;/table&gt;
+
+</description>
+        <pubDate>Sun, 18 Sep 2016 00:00:00 -0400</pubDate>
+        <link>https://accumulo.apache.org/release/accumulo-1.6.6/</link>
+        <guid isPermaLink="true">https://accumulo.apache.org/release/accumulo-1.6.6/</guid>
+        
+        
+        <category>release</category>
+        
+      </item>
+    
+      <item>
+        <title>Apache Accumulo 1.8.0</title>
+        <description>&lt;p&gt;Apache Accumulo 1.8.0 is a significant release that includes many important
+milestone features which expand the functionality of Accumulo. These include
+features related to security, availability, and extensibility. Over
+350 JIRA issues were resolved in this version. This includes over
+200 bug fixes and 71 improvements and 4 new features. See &lt;a href=&quot;https://issues.apache.org/jira/secure/ReleaseNote.jspa?projectId=12312121&amp;amp;version=12329879&quot;&gt;JIRA&lt;/a&gt;
+for the complete list.&lt;/p&gt;
 
-&lt;p&gt;So far, we’ve only touched on configurations which have a single primary and one to many peers; however, the feature allows multiple primary instances in addition to multiple peers. This primary-primary configuration allows data to be replicated in both directions instead of just one. This can be extended even further to allow replication between a trio of instances: primaryA replicates to primaryB which replicates to primaryC which replicates to primaryA. This aspect is supported by including provenance of which systems an update was seen inside of each Mutation. In “cyclic” replication setups, this prevents updates from being replicated indefinitely.&lt;/p&gt;
+&lt;p&gt;Below are resources for this release:&lt;/p&gt;
 
-&lt;p&gt;Supporting these cycles allows for different collections of users to access physically separated instances and eventually see the changes made by other groups. For example, consider two instance of Accumulo, one in New York City and another San Francisco. Users on the west coast can use the San Francisco instance while users on the east coast can use the instance in New York. With the two instances configured to replicate to each other, data created by east coast users will eventually be seen by west coast users and vice versa.&lt;/p&gt;
+&lt;ul&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.8/accumulo_user_manual.html&quot;&gt;User Manual&lt;/a&gt;&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.8/apidocs&quot;&gt;Javadocs&lt;/a&gt;&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.8/examples&quot;&gt;Examples&lt;/a&gt;&lt;/li&gt;
+&lt;/ul&gt;
 
-&lt;p&gt;&lt;img src=&quot;/images/blog/201504_replication/replication3.png&quot; alt=&quot;image3&quot; /&gt;&lt;/p&gt;
+&lt;p&gt;In the context of Accumulo’s &lt;a href=&quot;http://semver.org&quot;&gt;Semantic Versioning&lt;/a&gt; &lt;a href=&quot;https://github.com/apache/accumulo/blob/1.8/README.md#api&quot;&gt;guidelines&lt;/a&gt;,
+this is a “minor version”. This means that new APIs have been created, some
+deprecations may have been added, but no deprecated APIs have been removed.
+Code written against 1.7.x should work against 1.8.0 – binary compatibility
+has been preserved with one exception of an already-deprecated Mock Accumulo
+utility class. As always, the Accumulo developers take API compatibility
+very seriously and have invested much time to ensure that we meet the promises set forth to our users.&lt;/p&gt;
+
+&lt;h2 id=&quot;major-changes&quot;&gt;Major Changes&lt;/h2&gt;
+
+&lt;h3 id=&quot;speed-up-wal-roll-overs&quot;&gt;Speed up WAL roll overs&lt;/h3&gt;
+
+&lt;p&gt;Performance of writing mutations is improved by refactoring the
+bookeeping required for Write-Ahead Log (WAL) files and by creating a
+standby WAL for faster switching when the log is full. This was a
+substantial refactor in the way WALs worked, but smoothes overall
+ingest performance in addition to provides a increase in write speed
+as shown by the simple test below. The top entry is before
+&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3423&quot;&gt;ACCUMULO-3423&lt;/a&gt; and the bottom graph is after the
+refactor.&lt;/p&gt;
+
+&lt;p&gt;&lt;img src=&quot;https://issues.apache.org/jira/secure/attachment/12705402/WAL-slowdown-graphs.jpg&quot; alt=&quot;Graph of WAL speed up after ACCUMULO-3423&quot; title=&quot;Graph of WAL speed up after ACCUMULO-3423&quot; /&gt;&lt;/p&gt;
+
+&lt;h3 id=&quot;user-level-api-for-rfile&quot;&gt;User level API for RFile&lt;/h3&gt;
+
+&lt;p&gt;Previously the only public API available to write RFiles was via the AccumuloFileOutputFormat. There was no way to read RFiles in the public
+API. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4165&quot;&gt;ACCUMULO-4165&lt;/a&gt; exposes a brand new public &lt;a href=&quot;../1.8/apidocs/org/apache/accumulo/core/client/rfile/RFile.html&quot;&gt;API&lt;/a&gt; for reading and writing RFiles as well as cleans up some of the internal APIs.&lt;/p&gt;
+
+&lt;h3 id=&quot;suspend-tablet-assignment-for-rolling-restarts&quot;&gt;Suspend Tablet assignment for rolling restarts&lt;/h3&gt;
+
+&lt;p&gt;When a tablet server dies, Accumulo attempted to reassign the tablets as quickly as possible to maintain availability.
+A new configuration property &lt;code class=&quot;highlighter-rouge&quot;&gt;table.suspend.duration&lt;/code&gt; (with a default of zero seconds) now controls how long to wait before reassigning
+a tablet from a dead tserver. The property is configurable via the
+Accumulo shell, so you can set it, do a rolling restart, and then
+set it back to 0. A new state as introduced, TableState.SUSPENDED to support this feature. By default, metadata tablet
+reassignment is not suspended, but that can also be changed with the &lt;code class=&quot;highlighter-rouge&quot;&gt;master.metadata.suspendable&lt;/code&gt; property that is false by
+default. Root tablet assignment can not be suspended. See &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4353&quot;&gt;ACCUMULO-4353&lt;/a&gt; for more info.&lt;/p&gt;
+
+&lt;h3 id=&quot;run-multiple-tablet-servers-on-one-node&quot;&gt;Run multiple Tablet Servers on one node&lt;/h3&gt;
+
+&lt;p&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4328&quot;&gt;ACCUMULO-4328&lt;/a&gt; introduces the capability of running multiple tservers on a single node. This is intended for nodes with a large
+amounts of memory and/or disk. This feature is disabled by default. There are several related tickets: &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4072&quot;&gt;ACCUMULO-4072&lt;/a&gt;, &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4331&quot;&gt;ACCUMULO-4331&lt;/a&gt;
+and &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4406&quot;&gt;ACCUMULO-4406&lt;/a&gt;. Note that when this is enabled, the names of the log files change. Previous log file names were defined in the
+generic_logger.xml as &lt;code class=&quot;highlighter-rouge&quot;&gt;${org.apache.accumulo.core.application}_{org.apache.accumulo.core.ip.localhost.hostname}.log&lt;/code&gt;.
+The files will now include the instance id after the application with
+&lt;code class=&quot;highlighter-rouge&quot;&gt;${org.apache.accumulo.core.application}_${instance}_${org.apache.accumulo.core.ip.localhost.hostname}.log&lt;/code&gt;.&lt;/p&gt;
+
+&lt;p&gt;For example: tserver_host.domain.com.log will become tserver_1_host.domain.log when multiple TabletServers
+are run per host. The same change also applies to the debug logs provided in the example configurations. The log
+names do not change if this feature is not used.&lt;/p&gt;
+
+&lt;h3 id=&quot;rate-limiting-major-compactions&quot;&gt;Rate limiting Major Compactions&lt;/h3&gt;
+
+&lt;p&gt;Major Compactions can significantly increase the amount of load on
+TabletServers. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4187&quot;&gt;ACCUMULO-4187&lt;/a&gt; restricts the rate at which data is
+read and written when performing major compactions. This has a direct
+effect on the IO load caused by major compactions with a similar
+effect on the CPU utilization. This behavior is controlled by a new
+property &lt;code class=&quot;highlighter-rouge&quot;&gt;tserver.compaction.major.throughput&lt;/code&gt; with a defaults of 0B
+which disables the rate limiting.&lt;/p&gt;
+
+&lt;h3 id=&quot;table-sampling&quot;&gt;Table Sampling&lt;/h3&gt;
+
+&lt;p&gt;Queryable sample data was added by &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3913&quot;&gt;ACCUMULO-3913&lt;/a&gt;.  This allows users to configure a pluggable
+function to generate sample data.  At scan time, the sample data can optionally be scanned.
+Iterators also have access to sample data.  Iterators can access all data and sample data, this
+allows an iterator to use sample data for query optimizations.  The new user level RFile API
+supports writing RFiles with sample data for bulk import.&lt;/p&gt;
+
+&lt;p&gt;A simple configurable sampler function is included with Accumulo.  This sampler uses hashing and
+can be configured to use a subset of Key fields.  For example if it was desired to have entire rows
+in the sample, then this sampler would be configured to hash+mod the row.   Then when a row is
+selected for the sample, all of its columns and all of its updates will be in the sample data.
+Another scenario is one in which a document id is in the column qualifier.  In this scenario, one
+would either want all data related to a document in the sample data or none.  To achieve this, the
+sample could be configured to hash+mod on the column qualifier.  See the sample &lt;a href=&quot;../1.8/examples/sample&quot;&gt;Readme
+example&lt;/a&gt; and javadocs on the new APIs for more information.&lt;/p&gt;
+
+&lt;p&gt;For sampling to work, all tablets scanned must have pre-generated sample data that was generated in
+the same way.  If this is not the case then scans will fail.  For existing tables, samples can be
+generated by configuring sampling on the table and compacting the table.&lt;/p&gt;
+
+&lt;h3 id=&quot;upgrade-to-apache-thrift-093&quot;&gt;Upgrade to Apache Thrift 0.9.3&lt;/h3&gt;
+
+&lt;p&gt;Accumulo relies on Apache Thrift to implement remote procedure calls
+between Accumulo services. Ticket &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4077&quot;&gt;ACCUMULO-4077&lt;/a&gt;
+updates our dependency to 0.9.3. See the
+&lt;a href=&quot;https://github.com/apache/thrift/blob/0.9.3/CHANGES&quot;&gt;Apache Thrift 0.9.3 Release Notes&lt;/a&gt; for details on
+the changes to Thrift.  &lt;strong&gt;NOTE:&lt;/strong&gt; The Thrift 0.9.3 Java library is not
+compatible other versions of Thrift. Applications running against Accumulo
+1.8 must use Thrift 0.9.3. Different versions of Thrift on the classpath
+will not work.&lt;/p&gt;
+
+&lt;h3 id=&quot;iterator-test-harness&quot;&gt;Iterator Test Harness&lt;/h3&gt;
+
+&lt;p&gt;Users often write a new iterator without fully understanding its limits and lifetime. Previously, Accumulo did
+not provide any means in which a user could test iterators to catch common issues that only become apparent
+in multi-node production deployments. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-626&quot;&gt;ACCUMULO-626&lt;/a&gt; provides a framework and a collection of initial tests
+which can be used to simulate common issues with Iterators that only appear in production deployments. This test
+harness can be used directly by users as a supplemental tool to unit tests and integration tests with MiniAccumuloCluster.&lt;/p&gt;
+
+&lt;p&gt;Please see the &lt;a href=&quot;../1.8/accumulo_user_manual.html#_iterator_testing&quot;&gt;Accumulo User Manual chapter on Iterator Testing&lt;/a&gt; for more information&lt;/p&gt;
+
+&lt;h3 id=&quot;default-port-for-monitor-changed-to-9995&quot;&gt;Default port for Monitor changed to 9995&lt;/h3&gt;
+
+&lt;p&gt;Previously, the default port for the monitor was 50095. You will need to update your links to point to port 9995. The default
+port for the GC process was also changed from 50091 to 9998, although this an RPC port used internally and automatically discovered.
+These default ports were changed because the previous defaults fell in the Linux Ephemeral port range. This means that the operating
+system, when a port in this range was unusued, would allocate this port for dynamic network communication. This has the side-effect of
+temporal bind issues when trying to start these services (as the operating
+system might have allocated them elsewhere). By moving these
+defaults out of the ephemeral range, we can guarantee that the Monitor and GC
+will reliably start. These values are still configurable by setting
+&lt;code class=&quot;highlighter-rouge&quot;&gt;monitor.port.client&lt;/code&gt;and &lt;code class=&quot;highlighter-rouge&quot;&gt;gc.port.client&lt;/code&gt; in the accumulo-site.xml.&lt;/p&gt;
+
+&lt;h2 id=&quot;other-notable-changes&quot;&gt;Other Notable Changes&lt;/h2&gt;
 
-&lt;h2 id=&quot;conclusion-and-future-work&quot;&gt;Conclusion and future work&lt;/h2&gt;
+&lt;ul&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-1055&quot;&gt;ACCUMULO-1055&lt;/a&gt; Configurable maximum file size for merging minor compactions&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-1124&quot;&gt;ACCUMULO-1124&lt;/a&gt; Optimization of RFile index&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-2883&quot;&gt;ACCUMULO-2883&lt;/a&gt; API to fetch current tablet assignments&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3871&quot;&gt;ACCUMULO-3871&lt;/a&gt; Support for running integration tests in MapReduce&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3920&quot;&gt;ACCUMULO-3920&lt;/a&gt; Deprecate the MockAccumulo class and remove usage in our tests&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4339&quot;&gt;ACCUMULO-4339&lt;/a&gt; Make hadoop-minicluster optional dependency of acccumulo-minicluster&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4318&quot;&gt;ACCUMULO-4318&lt;/a&gt; BatchWriter, ConditionalWriter, and ScannerBase now extend AutoCloseable&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4326&quot;&gt;ACCUMULO-4326&lt;/a&gt; Value constructor now accepts Strings (and Charsequences)&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4354&quot;&gt;ACCUMULO-4354&lt;/a&gt; Bump dependency versions to include gson, jetty, and sl4j&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3735&quot;&gt;ACCUMULO-3735&lt;/a&gt; Bulk Import status page on the monitor&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4066&quot;&gt;ACCUMULO-4066&lt;/a&gt; Reduced time to processes conditional mutations.&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4164&quot;&gt;ACCUMULO-4164&lt;/a&gt; Reduced seek time for cached data.&lt;/li&gt;
+&lt;/ul&gt;
 
-&lt;p&gt;The addition of the replication feature fills a large gap in the architecture of Accumulo where the system does not easily operate across WANs. While strong consistency between a primary and a peer is sacrificed, the common case of using replication for disaster recovery favors availability of the system over strong consistency and has the added benefit of not significantly impacting the ingest performance on the primary instance. Replication provides active backup support while enabling Accumulo to automatically share data between instances across large physical distances.&lt;/p&gt;
+&lt;h2 id=&quot;testing&quot;&gt;Testing&lt;/h2&gt;
+
+&lt;p&gt;Each unit and functional test only runs on a single node, while the RandomWalk
+and Continuous Ingest tests run on any number of nodes. &lt;em&gt;Agitation&lt;/em&gt; refers to
+randomly restarting Accumulo processes and Hadoop Datanode processes, and, in
+HDFS High-Availability instances, forcing NameNode failover.&lt;/p&gt;
+
+&lt;table id=&quot;release_notes_testing&quot; class=&quot;table&quot;&gt;
+  &lt;thead&gt;
+    &lt;tr&gt;
+      &lt;th&gt;OS/Environment&lt;/th&gt;
+      &lt;th&gt;Hadoop&lt;/th&gt;
+      &lt;th&gt;Nodes&lt;/th&gt;
+      &lt;th&gt;ZooKeeper&lt;/th&gt;
+      &lt;th&gt;HDFS HA&lt;/th&gt;
+      &lt;th&gt;Tests&lt;/th&gt;
+    &lt;/tr&gt;
+  &lt;/thead&gt;
+  &lt;tbody&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS7/openJDK7/EC2; 3 m3.xlarge leaders, 8 d2.xlarge workers&lt;/td&gt;
+      &lt;td&gt;2.6.4&lt;/td&gt;
+      &lt;td&gt;11&lt;/td&gt;
+      &lt;td&gt;3.4.8&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;24 HR Continuous Ingest without Agitation.&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS7/openJDK7/EC2; 3 m3.xlarge leaders, 8 d2.xlarge workers&lt;/td&gt;
+      &lt;td&gt;2.6.4&lt;/td&gt;
+      &lt;td&gt;11&lt;/td&gt;
+      &lt;td&gt;3.4.8&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;16 HR Continuous Ingest with Agitation.&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS7/openJDK7/OpenStack VMs (16G RAM 2cores 2disk3; 1 leader, 5 workers&lt;/td&gt;
+      &lt;td&gt;HDP 2.5 (Hadoop 2.7)&lt;/td&gt;
+      &lt;td&gt;7&lt;/td&gt;
+      &lt;td&gt;HDP 2.5 (ZK 3.4)&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;24 HR Continuous Ingest without Agitation.&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS7/openJDK7/OpenStack VMs (16G RAM 2cores 2disk3; 1 leader, 5 workers&lt;/td&gt;
+      &lt;td&gt;HDP 2.5 (Hadoop 2.7)&lt;/td&gt;
+      &lt;td&gt;7&lt;/td&gt;
+      &lt;td&gt;HDP 2.5 (ZK 3.4)&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;24 HR Continuous Ingest with Agitation.&lt;/td&gt;
+    &lt;/tr&gt;
+  &lt;/tbody&gt;
+&lt;/table&gt;
 
-&lt;p&gt;One interesting detail about the implementation of this feature is that the code which performs replication between two Accumulo instances, the AccumuloReplicaSystem, is pluggable via the ReplicaSystem interface. It is reasonable to consider other implementations which can automatically replicate data from Accumulo to other systems for purposes of backup or additional query functionality through other data management systems. For example, Accumulo could be used to automatically replicate data to other indexing systems such as Lucene or even relational databases for advanced query functionality. Certain implementations of the ReplicaSystem could perform special filtering to limit the set of columns replicated to certain systems resulting in a subset of the complete dataset stored in one Accumulo instance without forcing clients to write the data to multiple systems. Each of these considerations are only theoretical at this point; however, the potential for advancement is def
 initely worth investigating.&lt;/p&gt;
 </description>
-        <pubDate>Mon, 06 Apr 2015 13:00:00 -0400</pubDate>
-        <link>https://accumulo.apache.org/blog/2015/04/06/replicating-data-across-accumulo-clusters.html</link>
-        <guid isPermaLink="true">https://accumulo.apache.org/blog/2015/04/06/replicating-data-across-accumulo-clusters.html</guid>
+        <pubDate>Tue, 06 Sep 2016 00:00:00 -0400</pubDate>
+        <link>https://accumulo.apache.org/release/accumulo-1.8.0/</link>
+        <guid isPermaLink="true">https://accumulo.apache.org/release/accumulo-1.8.0/</guid>
         
         
-        <category>blog</category>
+        <category>release</category>
         
       </item>
     
       <item>
-        <title>Balancing Groups of Tablets</title>
-        <description>&lt;p&gt;Originally posted at &lt;a href=&quot;https://blogs.apache.org/accumulo/entry/balancing_groups_of_tablets&quot;&gt;https://blogs.apache.org/accumulo/entry/balancing_groups_of_tablets&lt;/a&gt;&lt;/p&gt;
+        <title>Apache Accumulo 1.7.2</title>
+        <description>&lt;p&gt;Apache Accumulo 1.7.2 is a maintenance release on the 1.7 version branch. This
+release contains changes from more than 150 issues, comprised of bug-fixes,
+performance improvements, build quality improvements, and more. See
+&lt;a href=&quot;https://issues.apache.org/jira/secure/ReleaseNote.jspa?projectId=12312121&amp;amp;version=12333776&quot;&gt;JIRA&lt;/a&gt; for a complete list.&lt;/p&gt;
+
+&lt;p&gt;Below are resources for this release:&lt;/p&gt;
+
+&lt;ul&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.7/accumulo_user_manual.html&quot;&gt;User Manual&lt;/a&gt;&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.7/apidocs&quot;&gt;Javadocs&lt;/a&gt;&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;/1.7/examples&quot;&gt;Examples&lt;/a&gt;&lt;/li&gt;
+&lt;/ul&gt;
+
+&lt;p&gt;Users of any previous 1.7.x release are strongly encouraged to update as soon
+as possible to benefit from the improvements with very little concern in change
+of underlying functionality. Users of 1.6 or earlier that are seeking to
+upgrade to 1.7 should consider 1.7.2 as a starting point.&lt;/p&gt;
+
+&lt;h2 id=&quot;highlights&quot;&gt;Highlights&lt;/h2&gt;
+
+&lt;h3 id=&quot;write-ahead-logs-can-be-prematurely-deleted&quot;&gt;Write-Ahead Logs can be prematurely deleted&lt;/h3&gt;
+
+&lt;p&gt;There were cases where the Accumulo Garbage Collector may inadvertently delete a WAL for a tablet server that it has erroneously determined to be down, causing data loss. This has been corrected. See &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4157&quot;&gt;ACCUMULO-4157&lt;/a&gt; for additional detail.&lt;/p&gt;
+
+&lt;h3 id=&quot;upgrade-to-commons-vfs-21&quot;&gt;Upgrade to Commons-VFS 2.1&lt;/h3&gt;
 
-&lt;p&gt;Accumulo has a pluggable tablet balancer that decides where tablets should be placed. Accumulo’s default configuration spreads each tables tablets evenly and randomly across the tablet servers. Each table can configure a custom balancer that does something different.&lt;/p&gt;
+&lt;p&gt;Upgrading to Apache Commons VFS 2.1 fixes several issues with classloading out of HDFS. For further detail see &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4146&quot;&gt;ACCUMULO-4146&lt;/a&gt;. Additional fixes to a potential HDFS class loading deadlock situation were made in &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4341&quot;&gt;ACCUMULO-4341&lt;/a&gt;.&lt;/p&gt;
 
-&lt;p&gt;For some applications to perform optimally, sub-ranges of a table need to be spread evenly across the cluster. Over the years I have run into multiple use cases for this situation. The latest use case was &lt;a href=&quot;https://github.com/fluo-io/fluo/issues/361&quot;&gt;bad performance&lt;/a&gt; on the &lt;a href=&quot;http://fluo.io/&quot;&gt;Fluo&lt;/a&gt; &lt;a href=&quot;https://github.com/fluo-io/fluo-stress&quot;&gt;Stress Test&lt;/a&gt;. This test stores a tree in an Accumulo table and creates multiple tablets for each level in the tree. In parallel, the test reads data from one level and writes it up to the next level. Figure 1 below shows an example of tablet servers hosting tablets for different levels of the tree. Under this scenario if many threads are reading data from level 2 and writing up to level 1, only Tserver 1 and Tserver 2 will be utilized. So in this scenario 50% of the tablet servers are idle.&lt;/p&gt;
+&lt;h3 id=&quot;native-map-failed-to-increment-mutation-count-properly&quot;&gt;Native Map failed to increment mutation count properly&lt;/h3&gt;
 
-&lt;p&gt;&lt;img src=&quot;/images/blog/201503_balancer/figure1.png&quot; alt=&quot;figure1&quot; /&gt;
-&lt;em&gt;Figure 1&lt;/em&gt;&lt;/p&gt;
+&lt;p&gt;There was a bug (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4148&quot;&gt;ACCUMULO-4148&lt;/a&gt;) where multiple put calls with identical keys and no timestamp would exhibit different behaviour depending on whether native maps were enabled or not. This behaviour would result in hidden mutations with native maps, and has been corrected.&lt;/p&gt;
 
-&lt;p&gt;[ACCUMULO-3439][accumulo-3949] remedied this situation with the introduction of the &lt;a href=&quot;https://git-wip-us.apache.org/repos/asf?p=accumulo.git;a=blob;f=server/base/src/main/java/org/apache/accumulo/server/master/balancer/GroupBalancer.java;hb=b0815affade66ab04ca27b6fc3abaac400097469&quot;&gt;GroupBalancer&lt;/a&gt; and &lt;a href=&quot;https://git-wip-us.apache.org/repos/asf?p=accumulo.git;a=blob;f=server/base/src/main/java/org/apache/accumulo/server/master/balancer/RegexGroupBalancer.java;hb=51fbfaf0a52dc89e8294c86c30164fb94c9f644c&quot;&gt;RegexGroupBalancer&lt;/a&gt; which will be available in Accumulo 1.7.0. These balancers allow a user to arbitrarily group tablets. Each group defined by the user will be evenly spread across the tablet servers. Also, the total number of groups on each tablet server is minimized. As tablets are added or removed from the table, the balancer will migrate tablets to satisfy these goals.  Much of the complexity in the GroupBalan
 cer code comes from trying to minimize the number of migrations needed to reach a good state.&lt;/p&gt;
+&lt;h3 id=&quot;open-wal-files-could-prevent-datanode-decomission&quot;&gt;Open WAL files could prevent DataNode decomission&lt;/h3&gt;
 
-&lt;p&gt;A GroupBalancer could be configured for the table in figure 1 in such a way that it grouped tablets by level. If this were done, the result may look like Figure 2 below. With this tablet to tablet server mapping, many threads reading from level 2 and writing data up to level 1 would utilize all of the tablet servers yielding better performance.&lt;/p&gt;
+&lt;p&gt;An improvement was introduced to allow a max age before WAL files would be automatically rolled. Without a max age, they could stay open for writing indefinitely, blocking the Hadoop DataNode decomissioning process. For more information, see &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4004&quot;&gt;ACCUMULO-4004&lt;/a&gt;.&lt;/p&gt;
 
-&lt;p&gt;&lt;img src=&quot;/images/blog/201503_balancer/figure2.png&quot; alt=&quot;figure2&quot; /&gt;
-&lt;em&gt;Figure 2&lt;/em&gt;&lt;/p&gt;
+&lt;h3 id=&quot;remove-unnecessary-copy-of-cached-rfile-index-blocks&quot;&gt;Remove unnecessary copy of cached RFile index blocks&lt;/h3&gt;
 
-&lt;p&gt;&lt;a href=&quot;https://git-wip-us.apache.org/repos/asf?p=accumulo.git;a=blob;f=docs/src/main/resources/examples/README.rgbalancer;hb=51fbfaf0a52dc89e8294c86c30164fb94c9f644c&quot;&gt;README.rgbalancer&lt;/a&gt; provides a good example of configuring and using the RegexGroupBalancer. If a regular expression can not accomplish the needed grouping, then a grouping function can be written in Java. Extend GroupBalancer to write a grouping function in java. RegexGroupBalancer provides a good example of how to do this.&lt;/p&gt;
+&lt;p&gt;Accumulo maintains an cache for file blocks in-memory as a performance optimization. This can be done safely because Accumulo RFiles are immutable, thus their blocks are also immutable. There are two types of these blocks: index and data blocks. Index blocks refer to the b-tree style index inside of each Accumulo RFile, while data blocks contain the sorted Key-Value pairs. In previous versions, when Accumulo extracted an Index block from the in-memory cache, it would copy the data. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4164&quot;&gt;ACCUMULO-4164&lt;/a&gt; removes this unnecessary copy as the contents are immutable and can be passed by reference. Ensuring that the Index blocks are not copied when accessed from the cache is a big performance gain at the file-access level.&lt;/p&gt;
 
-&lt;p&gt;When using a GroupBalancer, how Accumulo automatically splits tablets must be kept in mind. When Accumulo decides to split a tablet, it chooses the shortest possible row prefix from the tablet data that yields a good split point. Therefore its possible that a split point that is shorter than what is expected by a GroupBalancer could be chosen. The best way to avoid this situation is to pre-split the table such that it precludes this possibility.&lt;/p&gt;
+&lt;h3 id=&quot;analyze-key-length-to-avoid-choosing-large-keys-for-rfile-index-blocks&quot;&gt;Analyze Key-length to avoid choosing large Keys for RFile Index blocks&lt;/h3&gt;
 
-&lt;p&gt;The Fluo Stress test is a very abstract use case. A more concrete use case for the group balancer would be using it to ensure tablets storing geographic data were spread out evenly. For example consider &lt;a href=&quot;https://ngageoint.github.io/geowave/&quot;&gt;GeoWave’s&lt;/a&gt; Accumulo &lt;a href=&quot;http://ngageoint.github.io/geowave/documentation.html#architecture-accumulo&quot;&gt;Persistence Model&lt;/a&gt;. Tablets could be balanced such that bins related to different regions are spread out evenly. For example tablets related to each continent could be assigned a group ensuring data related to each continent is evenly spread across the cluster. Alternatively, each Tier could spread evenly across the cluster.&lt;/p&gt;
+&lt;p&gt;Accumulo’s RFile index blocks are made up of a Key which exists in the file and points to that specific location in the corresponding RFile data block. Thus, the size of the RFile index blocks is largely dominated by the size of the Keys which are used by the index. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4314&quot;&gt;ACCUMULO-4314&lt;/a&gt; is an improvement which uses statistics on the length of the Keys in the Rfile to avoid choosing Keys for the index whose length is greater than three standard deviations for the RFile. By choosing smaller Keys for the index, Accumulo can access the RFile index faster and keep more Index blocks cached in memory. Initial tests showed that with this change, the RFile index size was nearly cut in half.&lt;/p&gt;
+
+&lt;h3 id=&quot;minor-performance-improvements&quot;&gt;Minor performance improvements.&lt;/h3&gt;
+
+&lt;p&gt;Tablet servers would previously always hsync at the start of a minor compaction, causing delays in the write pipeline. These additional syncs were determined to provide no additional durability guarantees and have been removed. See &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4112&quot;&gt;ACCUMULO-4112&lt;/a&gt; for additional detail.&lt;/p&gt;
+
+&lt;p&gt;A performance issue was identified and corrected (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-1755&quot;&gt;ACCUMULO-1755&lt;/a&gt;) where the BatchWriter would block calls to addMutation while looking up destination tablet server metadata. The writer has been fixed to allow both operations in parallel.&lt;/p&gt;
+
+&lt;h2 id=&quot;other-notable-changes&quot;&gt;Other Notable Changes&lt;/h2&gt;
+
+&lt;ul&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3923&quot;&gt;ACCUMULO-3923&lt;/a&gt; bootstrap_hdfs.sh script would copy incorrect jars to hdfs.&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4146&quot;&gt;ACCUMULO-4146&lt;/a&gt; Avoid copy of RFile Index Blocks when already in cache.&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4155&quot;&gt;ACCUMULO-4155&lt;/a&gt; No longer publish javadoc for non-public API to website. (Still available in javadoc jars in maven)&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4173&quot;&gt;ACCUMULO-4173&lt;/a&gt; Provide balancer to balance table within subset of hosts.&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4334&quot;&gt;ACCUMULO-4334&lt;/a&gt; Ingest rates reported through JMX did not match rates reported by Monitor.&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4335&quot;&gt;ACCUMULO-4335&lt;/a&gt; Error conditions that result in a Halt should ensure non-zero process exit code.&lt;/li&gt;
+&lt;/ul&gt;
+
+&lt;h2 id=&quot;testing&quot;&gt;Testing&lt;/h2&gt;
+
+&lt;p&gt;Each unit and functional test only runs on a single node, while the RandomWalk
+and Continuous Ingest tests run on any number of nodes. &lt;em&gt;Agitation&lt;/em&gt; refers to
+randomly restarting Accumulo processes and Hadoop Datanode processes, and, in
+HDFS High-Availability instances, forcing NameNode failover.&lt;/p&gt;
+
+&lt;table id=&quot;release_notes_testing&quot; class=&quot;table&quot;&gt;
+  &lt;thead&gt;
+    &lt;tr&gt;
+      &lt;th&gt;OS/Environment&lt;/th&gt;
+      &lt;th&gt;Hadoop&lt;/th&gt;
+      &lt;th&gt;Nodes&lt;/th&gt;
+      &lt;th&gt;ZooKeeper&lt;/th&gt;
+      &lt;th&gt;HDFS HA&lt;/th&gt;
+      &lt;th&gt;Tests&lt;/th&gt;
+    &lt;/tr&gt;
+  &lt;/thead&gt;
+  &lt;tbody&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 7; EC2 m3.xlarge, d2.xlarge workers&lt;/td&gt;
+      &lt;td&gt;2.6.3&lt;/td&gt;
+      &lt;td&gt;9&lt;/td&gt;
+      &lt;td&gt;3.4.8&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;24 HR Continuous Ingest with and without Agitation.&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 6: EC2 m3.2xlarge&lt;/td&gt;
+      &lt;td&gt;2.6.1&lt;/td&gt;
+      &lt;td&gt;1&lt;/td&gt;
+      &lt;td&gt;3.4.5&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;Unit tests and Integration Tests&lt;/td&gt;
+    &lt;/tr&gt;
+  &lt;/tbody&gt;
+&lt;/table&gt;
 
 </description>
-        <pubDate>Fri, 20 Mar 2015 13:00:00 -0400</pubDate>
-        <link>https://accumulo.apache.org/blog/2015/03/20/balancing-groups-of-tablets.html</link>
-        <guid isPermaLink="true">https://accumulo.apache.org/blog/2015/03/20/balancing-groups-of-tablets.html</guid>
+        <pubDate>Wed, 22 Jun 2016 00:00:00 -0400</pubDate>
+        <link>https://accumulo.apache.org/release/accumulo-1.7.2/</link>
+        <guid isPermaLink="true">https://accumulo.apache.org/release/accumulo-1.7.2/</guid>
         
         
-        <category>blog</category>
+        <category>release</category>
         
       </item>
     
       <item>
-        <title>Generating Keystores for configuring Accumulo with SSL</title>
-        <description>&lt;p&gt;Originally posted at &lt;a href=&quot;https://blogs.apache.org/accumulo/entry/generating_keystores_for_configuring_accumulo&quot;&gt;https://blogs.apache.org/accumulo/entry/generating_keystores_for_configuring_accumulo&lt;/a&gt;&lt;/p&gt;
+        <title>Apache Accumulo 1.7.1</title>
+        <description>&lt;p&gt;Apache Accumulo 1.7.1 is a maintenance release on the 1.7 version branch. This
+release contains changes from more than 150 issues, comprised of bug-fixes,
+performance improvements, build quality improvements, and more. See
+&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO/fixforversion/12329940&quot;&gt;JIRA&lt;/a&gt; for a complete list.&lt;/p&gt;
 
-&lt;p&gt;One of the major features added in Accumulo 1.6.0 was the ability to configure Accumulo so that the Thrift communications will run over SSL. &lt;a href=&quot;http://thrift.apache.org/&quot;&gt;Apache Thrift&lt;/a&gt; is the remote procedure call library that is leverage for both intra-server communication and client communication with Accumulo. Issuing these calls over a secure socket ensures that unwanted actors cannot inspect the traffic sent across the wire. Given the sometimes sensitive nature of data stored in Accumulo and the authentication details for users, ensuring that no prying eyes have access to these communications is critical.&lt;/p&gt;
+&lt;p&gt;Users of any previous 1.7.x release are strongly encouraged to update as soon
+as possible to benefit from the improvements with very little concern in change
+of underlying functionality. Users of 1.6 or earlier that are seeking to
+upgrade to 1.7 should consider 1.7.1 as a starting point.&lt;/p&gt;
 
-&lt;p&gt;Due to the complex and deployment specific nature of the security model for some system, Accumulo expects users to provide their own certificates, guaranteeing that they are, in fact, secure. However, for those who want to get security who do not already operate within the confines of an established security infrastructure, OpenSSL and the Java keytool command can be used to generate the necessary components to enable wire encryption.&lt;/p&gt;
+&lt;h2 id=&quot;highlights&quot;&gt;Highlights&lt;/h2&gt;
 
-&lt;p&gt;To enable SSL with Accumulo, it is necessary to generate a certificate authority and certificates which are signed by that authority. Typically, each client and server has its own certificate which provides the finest level of control over a secure cluster when the certificates are properly secured.&lt;/p&gt;
+&lt;h3 id=&quot;silent-data-loss-via-bulk-imported-files&quot;&gt;Silent data-loss via bulk imported files&lt;/h3&gt;
 
-&lt;h2 id=&quot;generate-a-certificate-authority&quot;&gt;Generate a Certificate Authority&lt;/h2&gt;
+&lt;p&gt;A user recently reported that a simple bulk-import application would
+occasionally lose some records. Through investigation, it was found that when
+bulk imports into a table failed the initial assignment, the logic that
+automatically retries the imports was incorrectly choosing the tablets to
+import the files into. &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3967&quot;&gt;ACCUMULO-3967&lt;/a&gt; contains more information
+on the cause and identification of the bug. The data-loss condition would only
+affect entire files. If records from a file exist in Accumulo, it is still
+guaranteed that all records within that imported file were successful.&lt;/p&gt;
 
-&lt;p&gt;The certificate authority (CA) is what controls what certificates can be used to authenticate with each other. To create a secure connection with two certificates, each certificate must be signed by a certificate authority in the “truststore” (A Java KeyStore which contains at least one Certificate Authority’s public key). When creating your own certificate authority, a single CA is typically sufficient (and would result in a single public key in the truststore). Alternatively, a third party can also act as a certificate authority (to add an additional layer of security); however, these are typically not a free service.&lt;/p&gt;
+&lt;p&gt;As such, users who have bulk import applications using previous versions of
+Accumulo should verify that all of their data was correctly ingested into
+Accumulo and immediately update to Accumulo 1.7.1 (This is the same bug that
+was fixed in 1.6.4, so you won’t be affected if you’re running 1.6.4 or newer).&lt;/p&gt;
 
-&lt;p&gt;The below is an example of creating a certificate authority and adding its public key to a Java KeyStore to provide to Accumulo.&lt;/p&gt;
+&lt;h3 id=&quot;queued-compactions-not-running&quot;&gt;Queued Compactions Not Running&lt;/h3&gt;
 
-&lt;div class=&quot;language-bash highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c&quot;&gt;# Create a private key&lt;/span&gt;
-openssl genrsa -des3 -out root.key 4096
+&lt;p&gt;Found and fixed a bug (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4016&quot;&gt;ACCUMULO-4016&lt;/a&gt;) in which some queued
+compactions would never run if the number of files changed while the tablet was
+queued.&lt;/p&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Create a certificate request using the private key&lt;/span&gt;
-openssl req -x509 -new -key root.key -days 365 -out root.pem
+&lt;h3 id=&quot;kerberos-ticket-renewals&quot;&gt;Kerberos Ticket Renewals&lt;/h3&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Generate a Base64-encoded version of the PEM just created&lt;/span&gt;
-openssl x509 -outform der -in root.pem -out root.der
+&lt;p&gt;A bug was fixed which caused Accumulo clients and services to fail to check and
+(if necessary) renew their Kerberos credentials. This would eventually lead to
+these components failing to properly authenticate until they were restarted.
+(&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4069&quot;&gt;ACCUMULO-4069&lt;/a&gt;)&lt;/p&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Import the key into a Java KeyStore&lt;/span&gt;
-keytool -import -alias root-key -keystore truststore.jks -file root.der
+&lt;h3 id=&quot;updated-commons-collection&quot;&gt;Updated commons-collection&lt;/h3&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Remove the DER formatted key file (as we don't need it anymore)&lt;/span&gt;
-rm root.der
-&lt;/code&gt;&lt;/pre&gt;
-&lt;/div&gt;
+&lt;p&gt;The bundled commons-collection library was updated from version 3.2.1 to 3.2.2
+because of a reported vulnerability in that library.
+(&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4056&quot;&gt;ACCUMULO-4056&lt;/a&gt;)&lt;/p&gt;
 
-&lt;p&gt;Remember to protect root.key and never distribute it as the private key is the basis for your circle of trust. The keytool command will prompt you about whether or not the certificate should be trusted: enter “yes”. The truststore.jks file, a “truststore”, is meant to be shared with all parties communicating with one another. The password provided to the truststore verifies that the contents of the truststore have not been tampered with.&lt;/p&gt;
+&lt;h3 id=&quot;faster-processing-of-conditional-mutations&quot;&gt;Faster Processing of Conditional Mutations&lt;/h3&gt;
 
-&lt;h2 id=&quot;generate-a-certificatekeystore-per-host&quot;&gt;Generate a certificate/keystore per host&lt;/h2&gt;
+&lt;p&gt;Improved ConditionalMutation processing time by a factor of 3.
+(&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4066&quot;&gt;ACCUMULO-4066&lt;/a&gt;)&lt;/p&gt;
 
-&lt;p&gt;For each host in the system, it’s desirable to generate a certificate. Typically, this corresponds to a certificate per host. Additionally, each client connecting to the Accumulo instance running with SSL should be issued their own certificate. By issuing individual certificates to each entity, it gives proper control to revoke/reissue certificates to clients as necessary, without widespread interruption.&lt;/p&gt;
+&lt;h3 id=&quot;slow-gc-while-bulk-importing&quot;&gt;Slow GC While Bulk Importing&lt;/h3&gt;
 
-&lt;div class=&quot;language-bash highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;c&quot;&gt;# Create the private key for our server&lt;/span&gt;
-openssl genrsa -out server.key 4096
+&lt;p&gt;Found and worked around an issue where lots of bulk imports creating many new
+files would significantly impair the Accumulo GC service, and possibly prevent
+it from running to completion entirely. (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4021&quot;&gt;ACCUMULO-4021&lt;/a&gt;)&lt;/p&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Generate a certificate signing request (CSR) with our private key&lt;/span&gt;
-openssl req -new -key server.key -out server.csr
+&lt;h3 id=&quot;unnoticed-per-table-configuration-updates&quot;&gt;Unnoticed Per-table Configuration Updates&lt;/h3&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Use the CSR and the CA to create a certificate for the server (a reply to the CSR)&lt;/span&gt;
-openssl x509 -req -in server.csr -CA root.pem -CAkey root.key -CAcreateserial -out server.crt -days 365
+&lt;p&gt;Fixed a bug which caused tablet servers to not notice changes to the per-table
+constraints, under some circumstances. (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3859&quot;&gt;ACCUMULO-3859&lt;/a&gt;)&lt;/p&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Use the certificate and the private key for our server to create PKCS12 file&lt;/span&gt;
-openssl pkcs12 -export -in server.crt -inkey server.key -certfile server.crt -name &lt;span class=&quot;s1&quot;&gt;'server-key'&lt;/span&gt; -out server.p12
+&lt;h3 id=&quot;tabletservers-kill-themselves-on-centos7&quot;&gt;TabletServers kill themselves on CentOS7&lt;/h3&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Create a Java KeyStore for the server using the PKCS12 file (private key)&lt;/span&gt;
-keytool -importkeystore -srckeystore server.p12 -srcstoretype pkcs12 -destkeystore server.jks -deststoretype JKS
+&lt;p&gt;Reduced the aggressiveness with which Accumulo Tablet Servers preemptively
+killed themselves when a local filesystem switched to read-only (indicating a
+possible failure). To reduce false positives, such as those which can occur
+with systemd’s extra cgroup mounts in CentOS7, an additional check was added to
+ensure that tablet servers would only kill themselves if an ext- or
+xfs-formatted disk switched to read-only. (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4080&quot;&gt;ACCUMULO-4080&lt;/a&gt;)&lt;/p&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Remove the PKCS12 file as we don't need it&lt;/span&gt;
-rm server.p12
+&lt;h3 id=&quot;improvements-in-locating-client-configuration-file&quot;&gt;Improvements in Locating Client Configuration File&lt;/h3&gt;
 
-&lt;span class=&quot;c&quot;&gt;# Import the CA-signed certificate to the keystore&lt;/span&gt;
-keytool -import -trustcacerts -alias server-crt -file server.crt -keystore server.jks
-&lt;/code&gt;&lt;/pre&gt;
-&lt;/div&gt;
+&lt;p&gt;Fixed some unexpected error messages related to setting
+ACCUMULO_CLIENT_CONF_PATH, and improved the detection of the client.conf file if
+ACCUMULO_CLIENT_CONF_PATH was set to a directory containing client.conf.
+(&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4026&quot;&gt;ACCUMULO-4026&lt;/a&gt;,&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4027&quot;&gt;ACCUMULO-4027&lt;/a&gt;)&lt;/p&gt;
 
-&lt;p&gt;These commands create a private key for the server, generated a certificate signing request created from that private key, used the certificate authority to generate the certificate using the signing request and then created a Java KeyStore with the certificate and the private key for our server. This, paired with the truststore, provide what is needed to configure Accumulo servers to run over SSL. Both the private key (server.key), the certificate signed by the CA (server.pem), and the keystore (server.jks) should be restricted to only be accessed by the user running Accumulo on the host it was generated for. Use chown and chmod to protect the files and do not distribute them over insecure networks.&lt;/p&gt;
-
-&lt;h2 id=&quot;configure-accumulo-servers&quot;&gt;Configure Accumulo Servers&lt;/h2&gt;
-
-&lt;p&gt;Now that the Java KeyStores have been created with the necessary information, the Accumulo configuration must be updated so that Accumulo creates the Thrift server over SSL instead of a normal socket. In accumulo-site.xml, configure the following:&lt;/p&gt;
-
-&lt;div class=&quot;language-xml highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;&lt;span class=&quot;nt&quot;&gt;&amp;lt;property&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;name&amp;gt;&lt;/span&gt;rpc.javax.net.ssl.keyStore&lt;span class=&quot;nt&quot;&gt;&amp;lt;/name&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;value&amp;gt;&lt;/span&gt;/path/to/server.jks&lt;span class=&quot;nt&quot;&gt;&amp;lt;/value&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;/property&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;property&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;name&amp;gt;&lt;/span&gt;rpc.javax.net.ssl.keyStorePassword&lt;span class=&quot;nt&quot;&gt;&amp;lt;/name&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;value&amp;gt;&lt;/span&gt;server_password&lt;span class=&quot;nt&quot;&gt;&amp;lt;/value&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;/property&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;property&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;name&amp;gt;&lt;/span&gt;rpc.javax.net.ssl.trustStore&lt;span class=&quot;nt&quot;&gt;&amp;lt;/name&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;value&amp;gt;&lt;/span&gt;/path/to/truststore.jks&lt;span class=&quot;nt&quot;&gt;&amp;lt;/value&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;/property&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;property&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;name&amp;gt;&lt;/span&gt;rpc.javax.net.ssl.trustStorePassword&lt;span class=&quot;nt&quot;&gt;&amp;lt;/name&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;value&amp;gt;&lt;/span&gt;truststore_password&lt;span class=&quot;nt&quot;&gt;&amp;lt;/value&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;/property&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;property&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;name&amp;gt;&lt;/span&gt;instance.rpc.ssl.enabled&lt;span class=&quot;nt&quot;&gt;&amp;lt;/name&amp;gt;&lt;/span&gt;
-  &lt;span class=&quot;nt&quot;&gt;&amp;lt;value&amp;gt;&lt;/span&gt;true&lt;span class=&quot;nt&quot;&gt;&amp;lt;/value&amp;gt;&lt;/span&gt;
-&lt;span class=&quot;nt&quot;&gt;&amp;lt;/property&amp;gt;&lt;/span&gt;
-&lt;/code&gt;&lt;/pre&gt;
-&lt;/div&gt;
+&lt;h3 id=&quot;transient-zookeeper-disconnect-causes-fate-threads-to-exit&quot;&gt;Transient ZooKeeper disconnect causes FATE threads to exit&lt;/h3&gt;
 
-&lt;p&gt;The keystore and truststore paths are both absolute paths on the local filesystem (not HDFS). Remember that the server keystore should only be readable by the user running Accumulo and, if you place plaintext passwords in accumulo-site.xml, make sure that accumulo-site.xml is also not globally readable. To keep these passwords out of accumulo-site.xml, consider configuring your system with the new Hadoop CredentialProvider class, see &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-2464&quot;&gt;ACCUMULO-2464&lt;/a&gt; for more information which will be available in Accumulo-1.6.1.&lt;/p&gt;
+&lt;p&gt;ZooKeeper clients are expected to handle the situation where they become
+disconnected from the ZooKeeper server and must wait to be reconnected
+before continuing ZooKeeper operations.&lt;/p&gt;
 
-&lt;p&gt;Also, be aware that if unique passwords are used for each server when generating the certificate, this will result in different accumulo-site.xml files for each host. Unique configuration files per host will add much complexity to the configuration management of your instance. The use of a CredentialProvider, a feature from Hadoop which allows for acquisitions of passwords from alternate systems) can be used to help alleviate the unique accumulo-site.xml files on each host. A Java KeyStore can be created using the CredentialProvider tools which removes the necessity of passwords to be stored in accumulo-site.xml and can instead point to the CredentialProvider URI which is consistent across hosts.&lt;/p&gt;
+&lt;p&gt;The dedicated threads running inside the Accumulo Master process for FATE
+actions had the potential unexpectedly exit in this disconnected state.
+This caused a scenario where all future FATE-based operations would
+be blocked until the Accumulo Master process was restarted. (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4060&quot;&gt;ACCUMULO-4060&lt;/a&gt;)&lt;/p&gt;
 
-&lt;h2 id=&quot;configure-accumulo-clients&quot;&gt;Configure Accumulo Clients&lt;/h2&gt;
+&lt;h3 id=&quot;incorrect-management-of-certain-apache-thrift-rpcs&quot;&gt;Incorrect management of certain Apache Thrift RPCs&lt;/h3&gt;
 
-&lt;p&gt;To configure Accumulo clients, use $HOME/.accumulo/config. This is a simple &lt;a href=&quot;http://en.wikipedia.org/wiki/.properties&quot;&gt;Java properties file&lt;/a&gt;: each line is a configuration, key and value can be separated by a space, and lines beginning with a # symbol are ignored. For example, if we generated a certificate and placed it in a keystore (as described above), we would generate the following file for the Accumulo client.&lt;/p&gt;
+&lt;p&gt;Accumulo relies on Apache Thrift to implement remote procedure calls between
+Accumulo services. Accumulo’s use of Thrift uncovered an unfortunate situation
+where a special RPC (a “oneway” call) would leave unwanted data on the underlying
+Thrift connection. After this extra data was left on connection, all subsequent RPCs
+re-using that connection would fail with “out of sequence response” error messages.
+Accumulo would be left in a bad state until the mishandled connections were released
+or Accumulo services were restarted. (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4065&quot;&gt;ACCUMULO-4065&lt;/a&gt;)&lt;/p&gt;
 
-&lt;div class=&quot;highlighter-rouge&quot;&gt;&lt;pre class=&quot;highlight&quot;&gt;&lt;code&gt;instance.rpc.ssl.enabled true
-rpc.javax.net.ssl.keyStore  /path/to/client-keystore.jks
-rpc.javax.net.ssl.keyStorePassword  client-password
-rpc.javax.net.ssl.trustStore  /path/to/truststore.jks
-rpc.javax.net.ssl.trustStorePassword  truststore-password
-&lt;/code&gt;&lt;/pre&gt;
-&lt;/div&gt;
-&lt;p&gt;When creating a ZooKeeperInstance, the implementation will automatically look for this file and set up a connection with the methods defined in this configuration file. The ClientConfiguration class also contains methods that can be used instead of a configuration file on the filesystem. Again, the paths to the keystore and truststore are on the local filesystem, not HDFS.&lt;/p&gt;
+&lt;h2 id=&quot;other-notable-changes&quot;&gt;Other Notable Changes&lt;/h2&gt;
+
+&lt;ul&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3509&quot;&gt;ACCUMULO-3509&lt;/a&gt; Fixed some lock contention in TabletServer, preventing resource cleanup&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3734&quot;&gt;ACCUMULO-3734&lt;/a&gt; Fixed quote-escaping bug in VisibilityConstraint&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4025&quot;&gt;ACCUMULO-4025&lt;/a&gt; Fixed cleanup of bulk load fate transactions&lt;/li&gt;
+  &lt;li&gt;&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4098&quot;&gt;ACCUMULO-4098&lt;/a&gt;,&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4113&quot;&gt;ACCUMULO-4113&lt;/a&gt; Fixed widespread misuse of ByteBuffer&lt;/li&gt;
+&lt;/ul&gt;
+
+&lt;h2 id=&quot;testing&quot;&gt;Testing&lt;/h2&gt;
+
+&lt;p&gt;Each unit and functional test only runs on a single node, while the RandomWalk
+and Continuous Ingest tests run on any number of nodes. &lt;em&gt;Agitation&lt;/em&gt; refers to
+randomly restarting Accumulo processes and Hadoop Datanode processes, and, in
+HDFS High-Availability instances, forcing NameNode failover.&lt;/p&gt;
+
+&lt;table id=&quot;release_notes_testing&quot; class=&quot;table&quot;&gt;
+  &lt;thead&gt;
+    &lt;tr&gt;
+      &lt;th&gt;OS/Environment&lt;/th&gt;
+      &lt;th&gt;Hadoop&lt;/th&gt;
+      &lt;th&gt;Nodes&lt;/th&gt;
+      &lt;th&gt;ZooKeeper&lt;/th&gt;
+      &lt;th&gt;HDFS HA&lt;/th&gt;
+      &lt;th&gt;Tests&lt;/th&gt;
+    &lt;/tr&gt;
+  &lt;/thead&gt;
+  &lt;tbody&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 7.1 w/Oracle JDK8 on EC2 (1 m3.xlarge, 8 d2.xlarge)&lt;/td&gt;
+      &lt;td&gt;2.6.3&lt;/td&gt;
+      &lt;td&gt;9&lt;/td&gt;
+      &lt;td&gt;3.4.6&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;Random walk (All.xml) 24-hour run, saw &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-3794&quot;&gt;ACCUMULO-3794&lt;/a&gt; and &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4151&quot;&gt;ACCUMULO-4151&lt;/a&gt;.&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 7.1 w/Oracle JDK8 on EC2 (1 m3.xlarge, 8 d2.xlarge)&lt;/td&gt;
+      &lt;td&gt;2.6.3&lt;/td&gt;
+      &lt;td&gt;9&lt;/td&gt;
+      &lt;td&gt;3.4.6&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;21 hr run of CI w/ agitation, 23.1B entries verified.&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 7.1 w/Oracle JDK8 on EC2 (1 m3.xlarge, 8 d2.xlarge)&lt;/td&gt;
+      &lt;td&gt;2.6.3&lt;/td&gt;
+      &lt;td&gt;9&lt;/td&gt;
+      &lt;td&gt;3.4.6&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;24 hr run of CI w/o agitation, 23.0B entries verified; saw performance issues outlined in comment on &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4146&quot;&gt;ACCUMULO-4146&lt;/a&gt;.&lt;/td&gt;
+    &lt;/tr&gt;
+    &lt;tr&gt;
+      &lt;td&gt;CentOS 6.7 (OpenJDK 7), Fedora 23 (OpenJDK 8), and CentOS 7.2 (OpenJDK 7)&lt;/td&gt;
+      &lt;td&gt;2.6.1&lt;/td&gt;
+      &lt;td&gt;1&lt;/td&gt;
+      &lt;td&gt;3.4.6&lt;/td&gt;
+      &lt;td&gt;No&lt;/td&gt;
+      &lt;td&gt;All unit tests and ITs pass with -Dhadoop.version=2.6.1; Kerberos ITs had a problem with earlier versions of Hadoop&lt;/td&gt;
+    &lt;/tr&gt;
+  &lt;/tbody&gt;
+&lt;/table&gt;
 
 </description>
-        <pubDate>Tue, 02 Sep 2014 13:00:00 -0400</pubDate>
-        <link>https://accumulo.apache.org/blog/2014/09/02/generating-keystores-for-configuring-accumulo-with-ssl.html</link>
-        <guid isPermaLink="true">https://accumulo.apache.org/blog/2014/09/02/generating-keystores-for-configuring-accumulo-with-ssl.html</guid>
+        <pubDate>Fri, 26 Feb 2016 00:00:00 -0500</pubDate>
+        <link>https://accumulo.apache.org/release/accumulo-1.7.1/</link>
+        <guid isPermaLink="true">https://accumulo.apache.org/release/accumulo-1.7.1/</guid>
         
         
-        <category>blog</category>
+        <category>release</category>
         
       </item>
     
       <item>
-        <title>Functional reads over Accumulo</title>
-        <description>&lt;p&gt;Originally posted at &lt;a href=&quot;https://blogs.apache.org/accumulo/entry/thinking_about_reads_over_accumulo&quot;&gt;https://blogs.apache.org/accumulo/entry/thinking_about_reads_over_accumulo&lt;/a&gt;&lt;/p&gt;
+        <title>Apache Accumulo 1.6.5</title>
+        <description>&lt;p&gt;Apache Accumulo 1.6.5 is a maintenance release on the 1.6 version branch. This
+release contains changes from 55 issues, comprised of bug-fixes, performance
+improvements, build quality improvements, and more. See &lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO/fixforversion/12333674&quot;&gt;JIRA&lt;/a&gt; for a
+complete list.&lt;/p&gt;
 
-&lt;p&gt;Table structure is a common area of discussion between all types of Accumulo users. In the relational database realm, there was often a straightforward way that most users could agree upon that would be ideal to store and query some dataset. Data was identified by its schema, some fixed set of columns where each value within that column had some given characteristic. One of the big pushes behind the “NoSQL” movement was a growing pain in representing evolving data within a static schema. Applications like Accumulo removed that notion for a more flexible layout where the columns vary per row, but this flexibility often sparks debates about how data is “best” stored that often ends without a clear-cut winner.&lt;/p&gt;
+&lt;p&gt;Users of any previous 1.6.x release are strongly encouraged to update as soon as
+possible to benefit from the improvements with very little concern in change of
+underlying functionality. Users of 1.4 or 1.5 that are seeking to upgrade to 1.6
+should consider 1.6.5 as a starting point.&lt;/p&gt;
 
-&lt;p&gt;In general, I’ve found that, with new users to Accumulo, it’s difficult to move beyond the basic concept of GETs and PUTs of some value for a key. Rightfully so, it’s analogous to a spreadsheet: get or update the cell in the given row and column. However, there’s a big difference in that the spreadsheet is running on your local desktop, instead of running across many machines. In the same way, while a local spreadsheet application has some similar functionality to Accumulo, it doesn’t really make sense to think about using Accumulo as you would a spreadsheet application. Personally, I’ve developed a functional-programming-inspired model which I tend to follow when implementing applications against Accumulo. The model encourages simple, efficient and easily testable code, mainly as a product of modeling the client interactions against Accumulo’s APIs.&lt;/p&gt;
+&lt;h2 id=&quot;outstanding-known-issues&quot;&gt;Outstanding Known Issues&lt;/h2&gt;
 
-&lt;h3 id=&quot;read-apis&quot;&gt;Read APIs&lt;/h3&gt;
+&lt;p&gt;Be aware that a small documentation bug exists with the compact command in the
+shell (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4138&quot;&gt;ACCUMULO-4138&lt;/a&gt;). The documentation for the begin row and
+end row should be described as exclusive and inclusive, respectively, rather
+than the incorrect description of both being inclusive.&lt;/p&gt;
 
-&lt;p&gt;Accumulo has two main classes for reading data from an Accumulo table: the Scanner and BatchScanner. Both accept Range(s) which limit the data read from the table based on a start and stop Key. Only data from the table that falls within those start and stop keys will be returned to the client. The reason that we have two “types” of classes to read data is that a Scanner will return data from a single Range in sorted order whereas the BatchScanner accepts multiple Ranges and returns the data unordered. In terms of Java language specifics, both the Scanner and BatchScanner are also Iterables, which return a Java Iterator that can be easily passed to some other function, transformation or for-loop.&lt;/p&gt;
+&lt;h2 id=&quot;highlights&quot;&gt;Highlights&lt;/h2&gt;
 
-&lt;p&gt;Having both a sorted, synchronous stream and an unsorted stream of Key-Value pairs from many servers in parallel allows for a variety of algorithms to be implemented against Accumulo. Both constructs allow for the transparency in where the data came from and encourage light-weight processing of those results on the client.&lt;/p&gt;
+&lt;h3 id=&quot;queued-compactions-not-running&quot;&gt;Queued Compactions Not Running&lt;/h3&gt;
 
-&lt;h3 id=&quot;accumulo-iterators&quot;&gt;Accumulo Iterators&lt;/h3&gt;
+&lt;p&gt;Found and fixed a bug (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4016&quot;&gt;ACCUMULO-4016&lt;/a&gt;) in which some queued
+compactions would never run if the number of files changed while the tablet was
+queued.&lt;/p&gt;
 
-&lt;p&gt;One notable feature of Accumulo is the SortedKeyValueIterator interface, or, more succinctly, Accumulo Iterators. Typically, these iterators run inside of the TabletServer process and perform much of the heavy lifting. Iterators are used to implement a breadth of internal features such as merged file reads, visibility label filtering, versioning, and more. However, users also have the ability to leverage this server-side processing mechanism to deploy their own custom code.&lt;/p&gt;
+&lt;h3 id=&quot;faster-processing-of-conditional-mutations&quot;&gt;Faster Processing of Conditional Mutations&lt;/h3&gt;
 
-&lt;p&gt;One interesting detail about these iterators is that they each have an implicit source which provides them data to operate on. This source is also a SortedKeyValueIterator which means that the “local” SortedKeyValueIterator can use its own API on its data source. With this implicit hierarchy, Iterators act in concert with each other in some fixed order - they are stackable. The order in which Iterators are constructed, controlled by an Iterator’s priority, determines the order of the stack. An Iterator uses its “source” Iterator to read data, performs some operation, and then passes it on (the next element could be a client or another Iterator). The design behind iterators deserves its own blog post; however, the concept to see here is that iterators are best designed as stateless as possible (transformations, filters, or aggregations that always net the same results given the same input).&lt;/p&gt;
+&lt;p&gt;Improved ConditionalMutation processing time by a factor of 3.
+(&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4066&quot;&gt;ACCUMULO-4066&lt;/a&gt;)&lt;/p&gt;
 
-&lt;h3 id=&quot;functional-influences&quot;&gt;Functional Influences&lt;/h3&gt;
+&lt;h3 id=&quot;slow-gc-while-bulk-importing&quot;&gt;Slow GC While Bulk Importing&lt;/h3&gt;
 
-&lt;p&gt;In practice, these two concepts mesh very well with each other. Data read from a table can be thought of as a “stream” which came from some number of operations on the server. For a Scanner, this stream of data is backed by one tablet at a time to preserve sorted-order of the table. In the case of the BatchScanner, this is happening in parallel across many tablets from many tabletservers, with the client receiving data from many distinct hosts at one time. Likewise, the Scanner and BatchScanner APIs also encourage stateless processing of this data by presenting the data as a Java Iterator. Exposing explicit batches of Key-Value pairs would encourage blocking processing of each batch would be counter-intuitive to what the server-side processing model is. It creates a more seamless implementation paradigm on both the client and the server.&lt;/p&gt;
+&lt;p&gt;Found and worked around an issue where lots of bulk imports creating many new
+files would significantly impair the Accumulo GC service, and possibly prevent
+it from running to completion entirely. (&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4021&quot;&gt;ACCUMULO-4021&lt;/a&gt;)&lt;/p&gt;
 
-&lt;p&gt;When we take a step back from Object-Oriented Java and start to think about applications in a Functional mindset, it becomes clear how these APIs encourage functional-esque code. We are less concerned about mutability and encapsulation, and more concerned about stateless operations over some immutable data. Modeling our client code like this helps encourage parallelism as application in some multi-threaded environment is much simpler.&lt;/p&gt;
+&lt;h3 id=&quot;improvements-in-locating-client-configuration-file&quot;&gt;Improvements in Locating Client Configuration File&lt;/h3&gt;
 
-&lt;h3 id=&quot;practical-application&quot;&gt;Practical Application&lt;/h3&gt;
+&lt;p&gt;Fixed some unexpected error messages related to setting
+ACCUMULO_CLIENT_CONF_PATH, and improved the detection of the client.conf file if
+ACCUMULO_CLIENT_CONF_PATH was set to a directory containing client.conf.
+(&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4026&quot;&gt;ACCUMULO-4026&lt;/a&gt;,&lt;a href=&quot;https://issues.apache.org/jira/browse/ACCUMULO-4027&quot;&gt;ACCUMULO-4027&lt;/a&gt;)&lt;/p&gt;
 
-&lt;p&gt;I started out talking about schemas and table layouts which might seem a bit unrelated to this discussion on the functional influences in the Accumulo API. Any decisions made on a table structure must take query requirements with respect to the underlying data into account. As a practical application of what might otherwise seem like pontification, let’s consider a hypothetical system that processes clickstream data using Accumulo.&lt;/p&gt;
+&lt;h3 id=&quot;transient-zookeeper-disconnect-causes-fate-threads-to-exit&quot;&gt;Transient ZooKeeper disconnect causes FATE threads to exit&lt;/h3&gt;
 
-&lt;p&gt;Clickstream data refers to logging users who visit a website, typically for the purpose of understanding usage patterns. If a website is thought of as a directed graph, where an anchor on one page which links to another page is an edge in that graph, a user’s actions on that website can be thought of as a “walk” over that graph. In managing a website, it’s typically very useful to understand usage patterns of your site: what page is most common? which links are most commonly clicked? what changes to a page make users act differently?&lt;/p&gt;
+&lt;p&gt;ZooKeeper clients are expected to handle the situation where they become
+disconnected from the ZooKeeper server and must wait to be reconnected
+before continuing ZooKeeper operations.&lt;/p&gt;
 
-&lt;p&gt;Now, let’s abstractly consider that we store this clickstream data in Accumulo. Let’s not go into specifics, but say we retain the typical row-with-columns idea: each row represents some user visiting a page on your website using a globally unique identifier. Each column would contain some information about that visit: the user who is visiting the website, the page they’re visiting, the page they came from, the web-browser user-agent string, etc. Say you’re the owner of this website, and you recently made a modification to you website which added a prominent link to some new content on the front-page. You want to know how many people are visiting your new

<TRUNCATED>

Mime
View raw message