[CONNECTORS-1101] ^C of single-process example sometimes hangs under MySQL

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: ManifoldCF 1.8
• Fix Version/s: ManifoldCF 1.8, ManifoldCF 2.0
• Component/s: Framework agents process
• Assignee: Karl Wright
• Reporter: Karl Wright
• Created: 14/Nov/14 01:48
• Updated: 14/Nov/14 10:14
• Resolved: 14/Nov/14 10:14

Description

A ^C of the agents process using the MySQL database driver hung and had the following in its thread dump:

"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)

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().