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Subject [3/3] git commit: Merge branch '1.6.1-SNAPSHOT'
Date Fri, 16 May 2014 19:38:14 GMT
Merge branch '1.6.1-SNAPSHOT'



Branch: refs/heads/master
Commit: 6b36d53a90f817af6c53d4324f0d731ef7537450
Parents: c312fa6 f61abc0
Author: Christopher Tubbs <>
Authored: Fri May 16 15:37:08 2014 -0400
Committer: Christopher Tubbs <>
Committed: Fri May 16 15:37:08 2014 -0400

 README                                           |  7 +++++++
 .../main/asciidoc/chapters/administration.txt    | 19 +++++++++++++------
 2 files changed, 20 insertions(+), 6 deletions(-)
diff --cc docs/src/main/asciidoc/chapters/administration.txt
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@@@ -1,396 -1,0 +1,403 @@@
 +// Licensed to the Apache Software Foundation (ASF) under one or more
 +// contributor license agreements.  See the NOTICE file distributed with
 +// this work for additional information regarding copyright ownership.
 +// The ASF licenses this file to You under the Apache License, Version 2.0
 +// (the "License"); you may not use this file except in compliance with
 +// the License.  You may obtain a copy of the License at
 +// Unless required by applicable law or agreed to in writing, software
 +// distributed under the License is distributed on an "AS IS" BASIS,
 +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 +// See the License for the specific language governing permissions and
 +// limitations under the License.
 +== Administration
 +=== Hardware
 +Because we are running essentially two or three systems simultaneously layered
 +across the cluster: HDFS, Accumulo and MapReduce, it is typical for hardware to
 +consist of 4 to 8 cores, and 8 to 32 GB RAM. This is so each running process can have
 +at least one core and 2 - 4 GB each.
 +One core running HDFS can typically keep 2 to 4 disks busy, so each machine may
 +typically have as little as 2 x 300GB disks and as much as 4 x 1TB or 2TB disks.
 +It is possible to do with less than this, such as with 1u servers with 2 cores and 4GB
 +each, but in this case it is recommended to only run up to two processes per
 +machine -- i.e. DataNode and TabletServer or DataNode and MapReduce worker but
 +not all three. The constraint here is having enough available heap space for all the
 +processes on a machine.
 +=== Network
 +Accumulo communicates via remote procedure calls over TCP/IP for both passing
 +data and control messages. In addition, Accumulo uses HDFS clients to
 +communicate with HDFS. To achieve good ingest and query performance, sufficient
 +network bandwidth must be available between any two machines.
 +In addition to needing access to ports associated with HDFS and ZooKeeper, Accumulo will
 +use the following default ports. Please make sure that they are open, or change
 +their value in conf/accumulo-site.xml.
 +.Accumulo default ports
 +|Port | Description | Property Name
 +|4445 | Shutdown Port (Accumulo MiniCluster) | n/a
 +|4560 | Accumulo monitor (for centralized log display) | monitor.port.log4j
 +|9997 | Tablet Server | tserver.port.client
 +|9999 | Master Server | master.port.client
 +|12234 | Accumulo Tracer | trace.port.client
 +|42424 | Accumulo Proxy Server | n/a
 +|50091 | Accumulo GC | gc.port.client
 +|50095 | Accumulo HTTP monitor | monitor.port.client
 +In addition, the user can provide +0+ and an ephemeral port will be chosen instead. This
 +ephemeral port is likely to be unique and not already bound. Thus, configuring ports to
 +use +0+ instead of an explicit value, should, in most cases, work around any issues of
 +running multiple distinct Accumulo instances (or any other process which tries to use the
 +same default ports) on the same hardware.
 +=== Installation
 +Choose a directory for the Accumulo installation. This directory will be referenced
 +by the environment variable +$ACCUMULO_HOME+. Run the following:
 +  $ tar xzf accumulo-1.6.0-bin.tar.gz    # unpack to subdirectory
 +  $ mv accumulo-1.6.0 $ACCUMULO_HOME # move to desired location
 +Repeat this step at each machine within the cluster. Usually all machines have the
 +same +$ACCUMULO_HOME+.
 +=== Dependencies
 +Accumulo requires HDFS and ZooKeeper to be configured and running
 +before starting. Password-less SSH should be configured between at least the
 +Accumulo master and TabletServer machines. It is also a good idea to run Network
 +Time Protocol (NTP) within the cluster to ensure nodes' clocks don't get too out of
 +sync, which can cause problems with automatically timestamped data.
 +=== Configuration
 +Accumulo is configured by editing several Shell and XML files found in
 ++$ACCUMULO_HOME/conf+. The structure closely resembles Hadoop's configuration
 +==== Edit conf/
 +Accumulo needs to know where to find the software it depends on. Edit
 +and specify the following:
 +. Enter the location of the installation directory of Accumulo for +$ACCUMULO_HOME+
 +. Enter your system's Java home for +$JAVA_HOME+
 +. Enter the location of Hadoop for +$HADOOP_PREFIX+
 +. Choose a location for Accumulo logs and enter it for +$ACCUMULO_LOG_DIR+
 +. Enter the location of ZooKeeper for +$ZOOKEEPER_HOME+
 +By default Accumulo TabletServers are set to use 1GB of memory. You may change
 +this by altering the value of +$ACCUMULO_TSERVER_OPTS+. Note the syntax is that of
 +the Java JVM command line options. This value should be less than the physical
 +memory of the machines running TabletServers.
 +There are similar options for the master's memory usage and the garbage collector
 +process. Reduce these if they exceed the physical RAM of your hardware and
 +increase them, within the bounds of the physical RAM, if a process fails because of
 +insufficient memory.
 +Note that you will be specifying the Java heap space in You should
 +make sure that the total heap space used for the Accumulo tserver and the Hadoop
 +DataNode and TaskTracker is less than the available memory on each slave node in
 +the cluster. On large clusters, it is recommended that the Accumulo master, Hadoop
 +NameNode, secondary NameNode, and Hadoop JobTracker all be run on separate
 +machines to allow them to use more heap space. If you are running these on the
 +same machine on a small cluster, likewise make sure their heap space settings fit
 +within the available memory.
 +==== Native Map
 +The tablet server uses a data structure called a MemTable to store sorted key/value
 +pairs in memory when they are first received from the client. When a minor compaction
 +occurs, this data structure is written to HDFS. The MemTable will default to using
 +memory in the JVM but a JNI version, called the native map, can be used to significantly
 +speed up performance by utilizing the memory space of the native operating system. The
 +native map also avoids the performance implications brought on by garbage collection
 +in the JVM by causing it to pause much less frequently.
- 32-bit and 64-bit Linux versions of the native map ship with the Accumulo dist package.
- For other operating systems, the native map can be built from the codebase in two ways-
- from maven or from the Makefile.
++32-bit and 64-bit Linux and Mac OS X versions of the native map can be built
++from the Accumulo bin package by executing
+++$ACCUMULO_HOME/bin/ If your system's
++default compiler options are insufficient, you can add additional compiler
++options to the command line, such as options for the architecture. These will be
++passed to the Makefile in the environment variable +USERFLAGS+.
- . Build from maven using the following command: +mvn clean package -Pnative+.
- . Build from the c++ source by running +make+ in the `$ACCUMULO_HOME/server/src/main/c++`
++. +$ACCUMULO_HOME/bin/
++. +$ACCUMULO_HOME/bin/ -m32+
 +After building the native map from the source, you will find the artifact in
 ++$ACCUMULO_HOME/lib/native+. Upon starting up, the tablet server will look
 +in this directory for the map library. If the file is renamed or moved from its
- target directory, the tablet server may not be able to find it.
++target directory, the tablet server may not be able to find it. The system can
++also locate the native maps shared library by setting +LD_LIBRARY_PATH+
++(or +DYLD_LIBRARY_PATH+ on Mac OS X) in +$ACCUMULO_HOME/conf/
 +==== Cluster Specification
 +On the machine that will serve as the Accumulo master:
 +. Write the IP address or domain name of the Accumulo Master to the +$ACCUMULO_HOME/conf/masters+
 +. Write the IP addresses or domain name of the machines that will be TabletServers in +$ACCUMULO_HOME/conf/slaves+,
one per line.
 +Note that if using domain names rather than IP addresses, DNS must be configured
 +properly for all machines participating in the cluster. DNS can be a confusing source
 +of errors.
 +==== Accumulo Settings
 +Specify appropriate values for the following settings in
 ++$ACCUMULO_HOME/conf/accumulo-site.xml+ :
 +    <name></name>
 +    <value>zooserver-one:2181,zooserver-two:2181</value>
 +    <description>list of zookeeper servers</description>
 +This enables Accumulo to find ZooKeeper. Accumulo uses ZooKeeper to coordinate
 +settings between processes and helps finalize TabletServer failure.
 +    <name>instance.secret</name>
 +    <value>DEFAULT</value>
 +The instance needs a secret to enable secure communication between servers. Configure your
 +secret and make sure that the +accumulo-site.xml+ file is not readable to other users.
 +Some settings can be modified via the Accumulo shell and take effect immediately, but
 +some settings require a process restart to take effect. See the configuration documentation
 +(available in the docs directory of the tarball and in <<configuration>>) for
 +==== Deploy Configuration
 +Copy the masters, slaves,, and if necessary, accumulo-site.xml
 +from the +$ACCUMULO_HOME/conf/+ directory on the master to all the machines
 +specified in the slaves file.
 +=== Initialization
 +Accumulo must be initialized to create the structures it uses internally to locate
 +data across the cluster. HDFS is required to be configured and running before
 +Accumulo can be initialized.
 +Once HDFS is started, initialization can be performed by executing
 ++$ACCUMULO_HOME/bin/accumulo init+ . This script will prompt for a name
 +for this instance of Accumulo. The instance name is used to identify a set of tables
 +and instance-specific settings. The script will then write some information into
 +HDFS so Accumulo can start properly.
 +The initialization script will prompt you to set a root password. Once Accumulo is
 +initialized it can be started.
 +=== Running
 +==== Starting Accumulo
 +Make sure Hadoop is configured on all of the machines in the cluster, including
 +access to a shared HDFS instance. Make sure HDFS and ZooKeeper are running.
 +Make sure ZooKeeper is configured and running on at least one machine in the
 +Start Accumulo using the +bin/ script.
 +To verify that Accumulo is running, check the Status page as described under
 +_Monitoring_. In addition, the Shell can provide some information about the status of
 +tables via reading the metadata tables.
 +==== Stopping Accumulo
 +To shutdown cleanly, run +bin/ and the master will orchestrate the
 +shutdown of all the tablet servers. Shutdown waits for all minor compactions to finish,
so it may
 +take some time for particular configurations.
 +==== Adding a Node
 +Update your +$ACCUMULO_HOME/conf/slaves+ (or +$ACCUMULO_CONF_DIR/slaves+) file to account
for the addition.
 +  $ACCUMULO_HOME/bin/accumulo admin start <host(s)> {<host> ...}
 +Alternatively, you can ssh to each of the hosts you want to add and run:
 +Make sure the host in question has the new configuration, or else the tablet
 +server won't start; at a minimum this needs to be on the host(s) being added,
 +but in practice it's good to ensure consistent configuration across all nodes.
 +==== Decomissioning a Node
 +If you need to take a node out of operation, you can trigger a graceful shutdown of a tablet
 +server. Accumulo will automatically rebalance the tablets across the available tablet servers.
 +  $ACCUMULO_HOME/bin/accumulo admin stop <host(s)> {<host> ...}
 +Alternatively, you can ssh to each of the hosts you want to remove and run:
 +Be sure to update your +$ACCUMULO_HOME/conf/slaves+ (or +$ACCUMULO_CONF_DIR/slaves+) file
 +account for the removal of these hosts. Bear in mind that the monitor will not re-read the
 +slaves file automatically, so it will report the decomissioned servers as down; it's
 +recommended that you restart the monitor so that the node list is up to date.
 +=== Monitoring
 +The Accumulo Master provides an interface for monitoring the status and health of
 +Accumulo components. This interface can be accessed by pointing a web browser to
 +=== Tracing
 +It can be difficult to determine why some operations are taking longer
 +than expected. For example, you may be looking up items with very low
 +latency, but sometimes the lookups take much longer. Determining the
 +cause of the delay is difficult because the system is distributed, and
 +the typical lookup is fast.
 +Accumulo has been instrumented to record the time that various
 +operations take when tracing is turned on. The fact that tracing is
 +enabled follows all the requests made on behalf of the user throughout
 +the distributed infrastructure of accumulo, and across all threads of
 +These time spans will be inserted into the +trace+ table in
 +Accumulo. You can browse recent traces from the Accumulo monitor
 +page. You can also read the +trace+ table directly like any
 +other table.
 +The design of Accumulo's distributed tracing follows that of
 +[Google's Dapper].
 +==== Tracers
 +To collect traces, Accumulo needs at least one server listed in
 + +$ACCUMULO_HOME/conf/tracers+. The server collects traces
 +from clients and writes them to the +trace+ table. The Accumulo
 +user that the tracer connects to Accumulo with can be configured with
 +the following properties
 +  trace.user
 +==== Instrumenting a Client
 +Tracing can be used to measure a client operation, such as a scan, as
 +the operation traverses the distributed system. To enable tracing for
 +your application call
 +DistributedTrace.enable(instance, new ZooReader(instance), hostname, "myApplication");
 +Once tracing has been enabled, a client can wrap an operation in a trace.
 +Trace.on("Client Scan");
 +BatchScanner scanner = conn.createBatchScanner(...);
 +// Configure your scanner
 +for (Entry entry : scanner) {
 +Additionally, the user can create additional Spans within a Trace.
 +Trace.on("Client Update");
 +Span readSpan = Trace.start("Read");
 +Span writeSpan = Trace.start("Write");
 +Like Dapper, Accumulo tracing supports user defined annotations to associate additional
data with a Trace.
 +int numberOfEntriesRead = 0;
 +Span readSpan = Trace.start("Read");
 +// Do the read, update the counter
 +..."Number of Entries Read", String.valueOf(numberOfEntriesRead));
 +Some client operations may have a high volume within your
 +application. As such, you may wish to only sample a percentage of
 +operations for tracing. As seen below, the CountSampler can be used to
 +help enable tracing for 1-in-1000 operations
 +Sampler sampler = new CountSampler(1000);
 +if ( {
 +  Trace.on("Read");
 +It should be noted that it is safe to turn off tracing even if it
 +isn't currently active. The +Trace.offNoFlush()+ should be used if the
 +user does not wish to have block while flushing trace
 +==== Viewing Collected Traces
 +To view collected traces, use the "Recent Traces" link on the Monitor
 +UI. You can also programmatically access and print traces using the
 ++TraceDump+ class.
 +==== Tracing from the Shell
 +You can enable tracing for operations run from the shell by using the
 ++trace on+ and +trace off+ commands.
 +root@test test> trace on
 +root@test test> scan
 +a b:c []    d
 +root@test test> trace off
 +Waiting for trace information
 +Waiting for trace information
 +Trace started at 2013/08/26 13:24:08.332
 +Time  Start  Service@Location       Name
 + 3628+0      shell@localhost shell:root
 +    8+1690     shell@localhost scan
 +    7+1691       shell@localhost scan:location
 +    6+1692         tserver@localhost startScan
 +    5+1692           tserver@localhost tablet read ahead 6
 +=== Logging
 +Accumulo processes each write to a set of log files. By default these are found under
 +=== Recovery
 +In the event of TabletServer failure or error on shutting Accumulo down, some
 +mutations may not have been minor compacted to HDFS properly. In this case,
 +Accumulo will automatically reapply such mutations from the write-ahead log
 +either when the tablets from the failed server are reassigned by the Master (in the
 +case of a single TabletServer failure) or the next time Accumulo starts (in the event of
 +failure during shutdown).
 +Recovery is performed by asking a tablet server to sort the logs so that tablets can easily
find their missing
 +updates. The sort status of each file is displayed on
 +Accumulo monitor status page. Once the recovery is complete any
 +tablets involved should return to an ``online'' state. Until then those tablets will be
 +unavailable to clients.
 +The Accumulo client library is configured to retry failed mutations and in many
 +cases clients will be able to continue processing after the recovery process without
 +throwing an exception.

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