On 06.09.2012 15:10, kharp...@oreillyauto.com wrote:
... This actually didn't surprise me after I
discovered how large the sessions were. Using JMX (VisualVM) I watched the
Heap size on my two servers as I tested 7000 sessions. Heap climbed
approximately 1GB. When I restarted node2, I watched node1's heap usage
nearly double.
This confirmed my suspicion that the replication process is putting a copy
of all sessions into a new object (list I suppose?) before transmitting
them. After replication finished (109 seconds), node1's heap usage went
back to normal.
That's a plausible explanation for your observation. You can split
replication in several chunks using the config items you already
observed. Even in TC 6 the DeltaManager supports:
sendAllSessions (Default: true, means all session send in one
message, false means split in multiple messages)
sendAllSessionsSize (Default: 1000, number of sessions send per
message when switch is false)
sendAllSessionsWaitTime (Default: 2000; sleep pause between sending
consecutive messages)
The aggregation of sessions into a new object to be sent (I presume as part
of the handleGET_ALL_SESSIONS?) seems to work quickly, though I'm not sure
how to test how much of the 109 seconds it took to replicate was Tomcat
gathering up all the sessions to send and how much was network traffic. We
have a low utilization gigabit ethernet fabric connecting all servers, so
transferring 1GB of data shouldn't take more than 10-12 seconds.
Does anyone know if there are ways to time the different steps in the
replication process?
Set log level of org.apache.catalina.ha.session.DeltaManager to DEBUG or
FINE depending whether you are using log4j or juli for Tomcat.
If it is the network send/receive process that's
slow,
Try sniffing both ends for network analysis.
are there transmit/receive settings for the sender/receiver that
could aid in speeding up replication of large data chunks? I see there are
rxBufSize and txBufSize settings on the Receiver and Transport elements,
and they're set to 25/43kb. If those values represents how data is chunked
then larger settings might help (similar to the throughput difference of
transferring 100x 10MB files vs. 10,000x 100kb files on a network).
Regards,
Rainer
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