[jira] Updated: (JCR-2483) Out of memory error while adding a new host due to large number of revisions

["aasoj (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/JCR-2483?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

aasoj updated JCR-2483:
-----------------------

    Fix Version/s: 1.6.0
           Status: Patch Available  (was: Open)

The patch adds a new configuration to DatabaseJournal, syncLimit. The value will be used to reduce the number of revisions returned. Finally AbstractJournal's doSync() is modified to loop till all the revisions are used.

> Out of memory error while adding a new host due to large number of revisions
> ----------------------------------------------------------------------------
>
>                 Key: JCR-2483
>                 URL: https://issues.apache.org/jira/browse/JCR-2483
>             Project: Jackrabbit Content Repository
>          Issue Type: Improvement
>          Components: clustering
>         Environment: MySQL DB. 512 MB memory allocated to java app.
>            Reporter: aasoj
>             Fix For: 1.6.0
>
>
> In a cluster deployment, revisions are saved in Journal Table in the DB. After a while a huge number of revisions can get created (around 70 k in our test). When a new host is added to the cluster, it tries to read all the revisions and hence the following error:
> Caused by: java.lang.OutOfMemoryError: Java heap space
>         at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2931)
>         at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2871)
>         at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3414)
>         at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:910)
>         at com.mysql.jdbc.MysqlIO.nextRow(MysqlIO.java:1405)
>         at com.mysql.jdbc.MysqlIO.readSingleRowSet(MysqlIO.java:2816)
>         at com.mysql.jdbc.MysqlIO.getResultSet(MysqlIO.java:467)
>         at com.mysql.jdbc.MysqlIO.readResultsForQueryOrUpdate(MysqlIO.java:2510)
>         at com.mysql.jdbc.MysqlIO.readAllResults(MysqlIO.java:1746)
>         at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2135)
>         at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2542)
>         at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1734)
>         at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:995)
>         at org.apache.jackrabbit.core.journal.DatabaseJournal.getRecords(DatabaseJournal.java:460)
>         at org.apache.jackrabbit.core.journal.AbstractJournal.doSync(AbstractJournal.java:201)
>         at org.apache.jackrabbit.core.journal.AbstractJournal.sync(AbstractJournal.java:188)
>         at org.apache.jackrabbit.core.cluster.ClusterNode.sync(ClusterNode.java:329)
>         at org.apache.jackrabbit.core.cluster.ClusterNode.start(ClusterNode.java:270)
> This can also happen to an existing host in the cluster when the number of revisions returned is very high.
> Possible solutions:
> 1. Cleaning old revisions using Janitor thread: This may be good for new hosts. But it will fail in a scenario when sync delay is high (few hours) and number of updates is high in existing hosts in the cluster
> 2. Increases memory allocated to Java process: This is not a feasible option always
> 3. Limit the number of updates read from the DB in any cycle.

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