The BookKeeper journal manager is an implementation of the HDFS JournalManager interface. The JournalManager interface allows you to plug custom write ahead logging into the HDFS NameNode.

Setting up the BookKeeper Journal Manager

http://zookeeper.apache.org/bookkeeper/docs/r4.0.0/bookkeeperConfig.html covers the step necessary to set up a BookKeeper cluster. We recommend that you use at least 3 servers to ensure fault tolerance.

Once BookKeeper has been set up, you can configure the journal manager. Currently, JournalManagers are only available in trunk and 0.23.3 branches. BookKeeper JournalManager is available in trunk, but the most recent version is at https://github.com/ivankelly/hadoop-common/tree/BKJM-benching. All the changes in this branch are pending submission into trunk. For this guide we will use this branch.

Pull HDFS trunk from github and compile.

~ $ git clone git://github.com/ivankelly/hadoop-common.git
~ $ cd hadoop-common
~/hadoop-common $ mvn package -Pdist -DskipTests

Once compiled, you must configure the namenode.

 
~/hadoop-common $ export HADOOP_COMMON_HOME=$(pwd)/$(ls -d hadoop-common-project/hadoop-common/target/hadoop-common-*-SNAPSHOT)
~/hadoop-common $ export HADOOP_HDFS_HOME=$(pwd)/$(ls -d hadoop-hdfs-project/hadoop-hdfs/target/hadoop-hdfs-*-SNAPSHOT)
~/hadoop-common $ export PATH=$HADOOP_COMMON_HOME/bin:$HADOOP_HDFS_HOME/bin:$PATH

Copy the BookKeeperJournalManager jar into the HDFS lib directory.

~/hadoop-common $ cp hadoop-hdfs-project/hadoop-hdfs/src/contrib/bkjournal/target/hadoop-hdfs-bkjournal-0.24.0-SNAPSHOT.jar \
 $HADOOP_HDFS_HOME/share/hadoop/hdfs/lib/

Edit $HADOOP_COMMON_HOME/etc/hadoop/hdfs-site.xml and add the following configuration.

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>
<configuration>
  <property>
    <name>fs.default.name</name>
    <value>hdfs://localhost/</value>
  </property>
  
  <property>
    <name>dfs.namenode.name.dir</name>
    <value>file:///tmp/bk-nn-local-snapshot</value>
  </property>

  <property>
    <name>dfs.namenode.edits.dir</name>
    <value>file:///tmp/bk-nn-local-edits</value>
  </property>

  <property>
    <name>dfs.namenode.shared.edits.dir</name>
    <value>bookkeeper://localhost:2181/hdfsjournal</value>
  </property>

  <property>
    <name>dfs.namenode.edits.journal-plugin.bookkeeper</name>
    <value>org.apache.hadoop.contrib.bkjournal.BookKeeperJournalManager</value>
  </property>
</configuration>

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