Re: [Jrtg-users] insert() error - NullPointerException

[Leech, J. <jl...@vi...>]

Laurent,
 
Very good question. The RTGDBDriver has the commitAllTransactions(), and
reconnectAll() methods exposed through JMX to do extactly that
externally. This would help in scenarios of a planned maintenance, or an
outage that is detected quickly. Also you should call pauseDBInserts()
on the DBBuffer first. So the steps would be
1) pauseDBInserts()
2) commitAllTransactions()
3) perform database maintenance
4) reconnectAll()
5) resumeDBInserts().
 
JRTG has not yet been instrumented to automatically reconnect to the
database after certain fatal errors. The place to do this would be
either the DBDriver class or in the ConnectionWrapper class. I intended
to do so in the ConnectionWrapper class, there is even a comment at the
top: // TODO: attempt to reconnect to the database after certain SQL
errors. This recquires some knowledge of which errors should result in a
reconnection and which shouldn't. A good place to find this kind of
information might be JBoss connection pool logic, or a similar
connection pooling library.
 
The NPE is a bug. Line 193 of JRTGDBDriver should be modified to read:
if (ps != null) ps.close(); It is masking the real SQLExceptions caused
by the database restart.
 
Also, if you have a firewall or some other evil device in between your
poller and database, you should probably also add a call to
setQueryTimeout() on the PreparedStatement prior to ps.execute() on line
178. I don't know specifically how the mySQL JDBC driver would react to
a connection dropped by a firewall, or if it implements
setQueryTimeout(), but I can attest to the fact that the Oracle JDBC
driver will hang indefinitely on the execute() method if the connection
is dropped, unless a timeout is provided.
 
-Jonathan

________________________________

From: Laurent Geyer [mailto:lg...@gm...] 
Sent: Friday, December 05, 2008 1:52 PM
To: jrt...@li...
Subject: [Jrtg-users] insert() error - NullPointerException


Hi,

So far so good. Have had jrtg running little over a month now and it's
been solid.

Unfortunately today I noticed I lost about two days worth of data. The
date it stopped collecting coincided with a MySQL server restart
following a MySQL upgrade.

Dec 5, 2008 3:44:34 PM com.virtela.poller.DBDriver insert
WARNING: insert() error.
java.lang.NullPointerException
        at com.virtela.poller.RTGDBDriver.insert(RTGDBDriver.java:193)
        at com.virtela.poller.DBDriver.insert(DBDriver.java:220)
        at com.virtela.poller.DBDriver.insert(DBDriver.java:200)
        at com.virtela.poller.DBBuffer$3.call(DBBuffer.java:253)
        at com.virtela.poller.DBBuffer$3.call(DBBuffer.java:250)
        at
java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecuto
r.java:885)
        at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.ja
va:907)
        at java.lang.Thread.run(Thread.java:619)

Is there any way I can reconnect the MySQL session and commit the
inserts following a restart or loss of connectivity?

Thanks,

Laurent