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From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DBCP-244) Connection socket hangs sporadically in DBCP 1.2.2 but not 1.2.1
Date Mon, 07 Feb 2011 12:00:32 GMT

    [ https://issues.apache.org/jira/browse/DBCP-244?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12991345#comment-12991345
] 

Phil Steitz commented on DBCP-244:
----------------------------------

@tangile:  What exactly do you mean by "procedural paralysis?"  Do you mean that the thread
waiting on the hung socket stalls, or other threads as well are blocked?  If the latter, can
you attach a thread dump?

> Connection socket hangs sporadically in DBCP 1.2.2 but not 1.2.1
> ----------------------------------------------------------------
>
>                 Key: DBCP-244
>                 URL: https://issues.apache.org/jira/browse/DBCP-244
>             Project: Commons Dbcp
>          Issue Type: Bug
>    Affects Versions: 1.2.2
>         Environment: Fedora Core 3, MySQL 4.1.22. with the latest driver (5.07). Exceptions
only occur in the "job processing" JVM, which sits idle for long periods of time and occasionally
wakes up to interact with the database.
>            Reporter: ori
>             Fix For: 1.3
>
>
> I think I've traced an exception to DBCP's code.
> Communication with the database is hanging sporadically in a production environment.
If I don't set the socketTimeout property on the underlying connection, it will hang forever.
With the socketTimeout property, I get the following exception:
> -------
> com.mysql.jdbc.CommunicationsException: Communications link failure due to underlying
exception:
> ** BEGIN NESTED EXCEPTION **
> java.net.SocketTimeoutException
> MESSAGE: Read timed out
> STACKTRACE:
> java.net.SocketTimeoutException: Read timed out
>        at java.net.SocketInputStream.socketRead0(Native Method)
>        at java.net.SocketInputStream.read(SocketInputStream.java:129)
>        at com.mysql.jdbc.util.ReadAheadInputStream.fill(ReadAheadInputStream.java:113)
>        at com.mysql.jdbc.util.ReadAheadInputStream.readFromUnderlyingStreamIfNecessary(ReadAheadInputStream.java:160)
>        at com.mysql.jdbc.util.ReadAheadInputStream.read(ReadAheadInputStream.java:188)
>        at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:1994)
>        at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2411)
>        at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2916)
>        at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1631)
>        at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1723)
>        at com.mysql.jdbc.Connection.execSQL(Connection.java:3250)
>        at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1355)
>        at com.mysql.jdbc.Statement.executeUpdate(Statement.java:1270)
>        at org.apache.commons.dbcp.DelegatingStatement.executeUpdate(DelegatingStatement.java:228)
> ...
> -------
> It always happens in an infrequently used JVM (not an app server handling frequent connections).
So it's likely the offending connection was asleep for a long time before the exception occurs.

> I've confirmed that this issue only occurs using 1.2.2 and not 1.2.1. I've been looking
through the changelogs but can't find anything that would cause this behavior.
> Does somebody familiar with the codebase have any idea what change (1.2.1->1.2.2)
could be causing this behavior? 
> Thanks

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