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Subject svn commit: r1660193 - /accumulo/site/trunk/content/release_notes/1.6.2.mdtext
Date Mon, 16 Feb 2015 20:05:50 GMT
Author: elserj
Date: Mon Feb 16 20:05:50 2015
New Revision: 1660193

Stub out 1.6.2 release notes.


Modified: accumulo/site/trunk/content/release_notes/1.6.2.mdtext
--- accumulo/site/trunk/content/release_notes/1.6.2.mdtext (original)
+++ accumulo/site/trunk/content/release_notes/1.6.2.mdtext Mon Feb 16 20:05:50 2015
@@ -16,14 +16,16 @@ Notice:    Licensed to the Apache Softwa
            specific language governing permissions and limitations
            under the License.
-Apache Accumulo 1.6.1 is a maintenance release on the 1.6 version branch.
-This release contains changes from over 175 issues, comprised of bug-fixes, performance
-improvements and better test cases. As this is a maintenance release, Apache Accumulo
-1.6.1 has no client API  incompatibilities over Apache Accumulo 1.6.0. Users of 1.6.0
-are strongly encouraged to update as soon as possible to benefit from the improvements.
-New users are encouraged to use this release over 1.6.0 or any other older releases. For
-information about improvements since Accumulo 1.5, see the [1.6.0 release notes][32].
+Apache Accumulo 1.6.2 is a maintenance release on the 1.6 version branch.
+This release contains changes from over 150 issues, comprised of bug-fixes, performance
+improvements and better test cases. Apache Accumulo 1.6.2 is the first release since the
+community has adopted [Semantic Versioning][1] which means that all changes to the [public
+are guaranteed to be made without adding to or removing from the public API. This ensures
+that client code that runs against 1.6.1 is guaranteed to run against 1.6.2 and vice versa.
+Users of 1.6.0 or 1.6.1 are strongly encouraged to update as soon as possible to benefit
+the improvements with very little concern in change of underlying functionality. For
+information about improvements since Accumulo 1.5, see the [1.6.0][3] and [1.6.1][4] release
 ## Performance Improvements
@@ -31,134 +33,24 @@ Apache Accumulo 1.6.1 includes a number
 Many of these improvements were also included in the recently released Apache Accumulo 1.5.2.
-### Write-Ahead Log sync performance
-The Write-Ahead Log (WAL) files are used to ensure durability of updates made to Accumulo.
-A sync is called on the file in HDFS to make sure that the changes to the WAL are persisted
-to disk, which allows Accumulo to recover in the case of failure. [ACCUMULO-2766][9] fixed
-an issue where an operation against a WAL would unnecessarily wait for multiple syncs, slowing
-down the ingest on the system.
-### Minor-Compactions not aggressive enough
-On a system with ample memory provided to Accumulo, long hold-times were observed which
-blocks the ingest of new updates. Trying to free more server-side memory by running minor
-compactions more frequently increased the overall throughput on the node. These changes
-were made in [ACCUMULO-2905][10].
-### HeapIterator optimization
-Iterators, a notable feature of Accumulo, are provided to users as a server-side programming
-construct, but are also used internally for numerous server operations. One of these system
-is the HeapIterator which implements a PriorityQueue of other Iterators. One way this iterator
-used is to merge multiple files in HDFS to present a single, sorted stream of Key-Value pairs.
-introduces a performance optimization to the HeapIterator which can improve the speed of
-HeapIterator in common cases.
-### Write-Ahead log sync implementation
-In Hadoop-2, two implementations of sync are provided: hflush and hsync. Both of these
-methods provide a way to request that the datanodes write the data to the underlying
-medium and not just hold it in memory (the *fsync* syscall). While both of these methods
-inform the Datanodes to sync the relevant block(s), *hflush* does not wait for acknowledgement
-from the Datanodes that the sync finished, where *hsync* does. To provide the most reliable
-"out of the box", Accumulo defaults to *hsync* so that your data is as secure as possible
-a variety of situations (notably, unexpected power outages).
-The downside is that performance tends to suffer because waiting for a sync to disk is a
-expensive operation. [ACCUMULO-2842][12] introduces a new system property, tserver.wal.sync.method,
-that lets users to change the HDFS sync implementation from *hsync* to *hflush*. Using *hflush*
-of *hsync* may result in about a 30% increase in ingest performance.
+### Improvement 1
-For users upgrading from Hadoop-1 or Hadoop-0.20 releases, *hflush* is the equivalent of
-sync was implemented in these older versions of Hadoop and should give comparable performance.
+### Improvement 2
 ## Other improvements
-### Use of Hadoop CredentialProviders
-Apache Hadoop 2.6.0 introduced a new API aimed at providing ways to separate sensitive values
-from being stored in plaintext as a part of [HADOOP-10607][28]. Accumulo has had two sensitive
-configuration properties stored in *accumulo-site.xml* for every standard installation: instance.secret
-and If either of these properties are compromised, it could
lead to
-unwanted access of Accumulo. [ACCUMULO-2464][29] modifies Accumulo so that it can stored
any sensitive
-configuration properties in a Hadoop CredentialProvider. With sensitive values removed from
-it can be shared without concern and security can be focused solely on the CredentialProvider.
+### Improvement 1
 ## Notable Bug Fixes
-### Add configurable maximum frame size to Thrift proxy
-The Thrift proxy server was subject to memory exhaustion, typically
-due to bad input, where the server would attempt to allocate a very large
-buffer and die in the process. [ACCUMULO-2658][2] introduces a configuration
-parameter, like [ACCUMULO-2360][3], to prevent this error.
-### Offline tables can prevent tablet balancing
-Before 1.6.1, when a table with many tablets was created, ingested into, and
-taken offline, tablet balancing may have stoppped. This would happen if there
-were tablet migrations for the table, because the migrations couldn't occur.
-The balancer will not run when there are outstanding migrations; therefore, a
-system could become unbalanced. [ACCUMULO-2694][4] introduces a fix to ensure
-that offline tables do not block balancing and improves the server-side
-### MiniAccumuloCluster process management
-MiniAccumuloCluster had a few issues which could cause deadlock or a method that
-never returns. Most of these are related to management of the Accumulo processes
-([ACCUMULO-2764][5], [ACCUMULO-2985][6], and [ACCUMULO-3055][7]).
-### IteratorSettings not correctly serialized in RangeInputSplit
-The Writable interface methods on the RangeInputSplit class accidentally omitted
-calls to serialize the IteratorSettings configured for the Job. [ACCUMULO-2962][8]
-fixes the serialization and adds some additional tests.
-### Constraint violation causes hung scans
-A failed bulk import transaction had the ability to create an infinitely retrying
-loop due to a constraint violation. This directly prevents scans from completing,
-but will also hang compactions. [ACCUMULO-3096][14] fixes the issue so that the
-constraint no longer hangs the entire system.
-### Unable to upgrade cleanly from 1.5
-When upgrading a table from 1.5.1 to 1.6.0, a user experienced an error where the table
-never came online. [ACCUMULO-2974][27] fixes an issue from the change of file references
-stored as absolute paths instead of relative paths in the Accumulo metadata table.
-### Guava dependency changed
-[ACCUMULO-3100][30] lowered the dependency on Guava from 15.0 to 14.0.1. This dependency
-now matches what Hadoop is depending on for the 2.x.y version line. Depending on a newer
-version of Guava introduces many issues stemming from deprecated classes in use by Hadoop
-which have been removed. While installations of Accumulo will likely work as expected with
-newer versions of Guava on the classpath (because the Hadoop processes will have their own
-classpath), use of MiniDfsClusters with the new Guava version will result in errors.
-Users can attempt to use a newer version of Guava on the Accumulo server classpath; however,
-the success is dependent on Hadoop client libraries not using (missing) Guava methods internally.
-### Scanners eat InterruptedException
+### Bug fix 1
-Scanners previously consumed InterruptedExceptions and did not exit after. In multi-threaded
-environments, this is very problematic as there is no means to stop the Scanner from reading
-[ACCUMULO-3030][31] fixes the Scanner so that interrupts are observed and the Scanner exits
as expected.
+### Bug fix 2
 ## Documentation
 The following documentation updates were made: 
- * [ACCUMULO-2767][15]
- * [ACCUMULO-2796][16]
- * [ACCUMULO-2919][17]
- * [ACCUMULO-3008][18]
- * [ACCUMULO-2874][19]
- * [ACCUMULO-2821][20]
- * [ACCUMULO-3097][21]
- * [ACCUMULO-3097][22]
 ## Testing
@@ -176,48 +68,24 @@ and, in HDFS High-Availability instances
-    <td>Apache 2.6.0-SNAPSHOT</td>
-    <td>2</td>
-    <td>Apache 3.4.5</td>
+    <td>N/A</td>
+    <td>1</td>
+    <td>N/A</td>
-    <td>Unit and Functional Tests, ContinuousIngest w/ verification (2B entries)</td>
+    <td>Unit and Integration Tests</td>
     <td>CentOS 6</td>
-    <td>Apache 2.3.0</td>
+    <td>Keith TBD</td>
-    <td>Apache 3.4.5</td>
+    <td>Keith TBD</td>
-    <td>24/hr RandomWalk, ContinuousIngest w/ verification w/ and w/o agitation (17B
entries), 24hr Randomwalk test</td>
+    <td>(Keith Verify this) ContinuousIngest w/ verification w/ and w/o agitation (31B
and 21B entries, respectively)</td>
-[32]: /release_notes/1.6.0.html
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