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From "Dimitry Declercq (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LOG4J2-407) JDBCAppender cannot recover from loss of database connectivity
Date Wed, 20 Nov 2013 13:57:37 GMT

    [ https://issues.apache.org/jira/browse/LOG4J2-407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13827669#comment-13827669

Dimitry Declercq commented on LOG4J2-407:

Now the first check will fail because 'this.connection.isClosed()' returns true, so it throws
the AppenderLoggingException. I might be missing it, but placing code after that throw would
result in the reconnect not being executed, so I placed it before the throw (but I might be
overlooking something).

For your complete fix, special attention should be given to cases in which the database or
network is down, as to not end-up in a endless loop of reconnects and retries. This can offcourse
be resolved as simple as by adding a counter that only tries x times. 
Also, the SQLException is never thrown at this moment, the check on the connection returns
with a AppenderLoggingException.
Offcourse, these are all small things that when programming a complete fix would probably
be dealt with anyway

PS: I wouldn't want to do a ping every time a logevent occurs, so always executing a  this.connection.isValid(t)
seems a bit overkill. I think (although not tested) that this would decimate performance for
both the application and the DB server.

> JDBCAppender cannot recover from loss of database connectivity
> --------------------------------------------------------------
>                 Key: LOG4J2-407
>                 URL: https://issues.apache.org/jira/browse/LOG4J2-407
>             Project: Log4j 2
>          Issue Type: Bug
>          Components: Appenders
>    Affects Versions: 2.0-beta9
>            Reporter: Michael Kloster
>            Assignee: Nick Williams
> The JDBCAppender holds a single database connection for all its logging. If that database
connection is closed, it does not attempt to make a new connection.
> Many connection pools automatically close connections after a certain amount of inactivity.
(This can be worked around by properly configuring a pool).
> Database connectivity issues are also common enough that a long running application may
experience temporary network issues. When the network comes back online, the logging will
not resume.
> I've been meaning to submit a patch for this, but I haven't gotten to it. Since I saw
that you are looking to come out of beta soon, I thought I would log this issue in case someone
else has time to write the patch before I get to it.

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