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Posted to dev@manifoldcf.apache.org by "Karl Wright (JIRA)" <ji...@apache.org> on 2014/11/14 03:00:36 UTC
[jira] [Commented] (CONNECTORS-1101) ^C of single-process example
sometimes hangs under MySQL
[ https://issues.apache.org/jira/browse/CONNECTORS-1101?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14211701#comment-14211701 ]
Karl Wright commented on CONNECTORS-1101:
-----------------------------------------
This code is causing the hang:
{code}
ExecuteQueryThread t = new ExecuteQueryThread(connection,query,params,bResults,maxResults,spec,returnLimit);
try
{
t.start();
return t.finishUp();
}
catch (InterruptedException e)
{
// Try to kill the background thread - but we can't wait for it...
t.interrupt();
// VERY IMPORTANT: Try to close the connection, so nothing is left dangling. The connection will be abandoned anyhow.
try
{
if (!connection.getAutoCommit())
connection.rollback();
connection.close();
}
catch (Exception e2)
{
}
// We need the caller to abandon any connections left around, so rethrow in a way that forces them to process the event properly.
throw new ManifoldCFException(e.getMessage(),e,ManifoldCFException.INTERRUPTED);
}
{code}
As can be seen, I believe that the close is there to avoid locking up resources which may otherwise persist during the shutdown. Clearly there was an issue in this code once before, which was resolved by attempting to close the connection. But this flow is inappropriate for MySQL because of the hang issue.
> ^C of single-process example sometimes hangs under MySQL
> --------------------------------------------------------
>
> Key: CONNECTORS-1101
> URL: https://issues.apache.org/jira/browse/CONNECTORS-1101
> Project: ManifoldCF
> Issue Type: Bug
> Components: Framework agents process
> Affects Versions: ManifoldCF 1.8
> Reporter: Karl Wright
> Assignee: Karl Wright
> Fix For: ManifoldCF 1.8, ManifoldCF 2.0
>
>
> A ^C of the agents process using the MySQL database driver hung and had the following in its thread dump:
> {code}
> "Thread-34778" daemon prio=6 tid=0x00000000152f2000 nid=0x2d18 waiting for monitor entry [0x000000000b92e000]
> java.lang.Thread.State: BLOCKED (on object monitor)
> at com.mysql.jdbc.ConnectionImpl.getCharacterSetMetadata(ConnectionImpl.java:2798)
> - waiting to lock <0x00000000f0610a20> (a com.mysql.jdbc.JDBC4Connection)
> at com.mysql.jdbc.Field.getStringFromBytes(Field.java:710)
> at com.mysql.jdbc.Field.getTableName(Field.java:781)
> at com.mysql.jdbc.Field.getFullName(Field.java:545)
> at com.mysql.jdbc.ResultSetImpl.buildIndexMapping(ResultSetImpl.java:751)
> at com.mysql.jdbc.ResultSetImpl.findColumn(ResultSetImpl.java:1108)
> - locked <0x00000000fb82ba28> (a com.mysql.jdbc.JDBC4ResultSet)
> at org.apache.manifoldcf.core.database.Database.findColumn(Database.java:1128)
> at org.apache.manifoldcf.core.database.Database.getData(Database.java:976)
> at org.apache.manifoldcf.core.database.Database.execute(Database.java:884)
> at org.apache.manifoldcf.core.database.Database$ExecuteQueryThread.run(Database.java:683)
> "Worker thread '32'" daemon prio=6 tid=0x0000000009dce000 nid=0x2f68 waiting for monitor entry [0x000000000fb8e000]
> java.lang.Thread.State: BLOCKED (on object monitor)
> at com.mysql.jdbc.ResultSetImpl.realClose(ResultSetImpl.java:7477)
> - waiting to lock <0x00000000fb82ba28> (a com.mysql.jdbc.JDBC4ResultSet)
> at com.mysql.jdbc.ResultSetImpl.close(ResultSetImpl.java:907)
> at com.mysql.jdbc.StatementImpl.realClose(StatementImpl.java:2478)
> - locked <0x00000000f10d7c60> (a com.mysql.jdbc.JDBC4PreparedStatement)
> at com.mysql.jdbc.PreparedStatement.realClose(PreparedStatement.java:3091)
> - locked <0x00000000f10d7c60> (a com.mysql.jdbc.JDBC4PreparedStatement)
> at com.mysql.jdbc.ConnectionImpl.closeAllOpenStatements(ConnectionImpl.java:1584)
> at com.mysql.jdbc.ConnectionImpl.realClose(ConnectionImpl.java:4364)
> at com.mysql.jdbc.ConnectionImpl.close(ConnectionImpl.java:1556)
> - locked <0x00000000f0610a20> (a com.mysql.jdbc.JDBC4Connection)
> at org.apache.manifoldcf.core.database.Database.executeViaThread(Database.java:739)
> at org.apache.manifoldcf.core.database.Database.executeUncachedQuery(Database.java:762)
> at org.apache.manifoldcf.core.database.Database$QueryCacheExecutor.create(Database.java:1435)
> at org.apache.manifoldcf.core.cachemanager.CacheManager.findObjectsAndExecute(CacheManager.java:146)
> at org.apache.manifoldcf.core.database.Database.executeQuery(Database.java:191)
> at org.apache.manifoldcf.core.database.DBInterfaceMySQL.performQuery(DBInterfaceMySQL.java:875)
> at org.apache.manifoldcf.core.database.BaseTable.performQuery(BaseTable.java:221)
> at org.apache.manifoldcf.crawler.jobs.HopDeleteDeps.getDeleteDependencies(HopDeleteDeps.java:191)
> at org.apache.manifoldcf.crawler.jobs.HopCount.doRecord(HopCount.java:470)
> at org.apache.manifoldcf.crawler.jobs.HopCount.recordReferences(HopCount.java:361)
> at org.apache.manifoldcf.crawler.jobs.JobManager.addDocuments(JobManager.java:5057)
> at org.apache.manifoldcf.crawler.system.WorkerThread$ProcessActivity.processDocumentReferences(WorkerThread.java:1966)
> at org.apache.manifoldcf.crawler.system.WorkerThread$ProcessActivity.flush(WorkerThread.java:1909)
> at org.apache.manifoldcf.crawler.system.WorkerThread.run(WorkerThread.java:427)
> {code}
> It looks like the database handle close hung waiting for a mysql operation to finish up, which was in turn probably disrupted by a Thread.interrupt().
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