-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Colin,
On 3/19/13 2:29 PM, Colin Ingarfield wrote: > First of all, thank you this detailed analysis of the situation. > Based on the bug report I suspected the driver, but it now seems > clear it was (at least part of) the problem. > > re: Why was it necessary for the abandoned connection thread to > act? I'm not sure.. I looked into the JDBC Session manager class > and it appeared to be simply reading/deserializing a session from > the database when the deadlock occurred. I would expect that to be > a very fast query -- this is a production system but under very > light load. > > I looked into the pool configuration and 'removed abandoned > timeout' was 60 seconds. That timeout seems a bit short, but if it > takes > 60 sec to load a session from the database then there is a > serious performance issue. I've never observed delays like that in > the application. I would agree that loading a session from the db should take less than 60 seconds. I'm not sure exactly how your session manager works, but I suspect that loading a complete session from the db into memory is a fairly rare event. If it happened a lot, and it took a long time (like more than 10 seconds), I suspect your website would be quite unusable - -- or at least very unpleasant to use. > My guess at this point is perhaps the db (Amazon RDS/MySql) was > unavailable/very slow/down in some way, causing this connection to > be held beyond the timeout. I don't have great visibility into > performance or outage information for RDS, tho I may reach out to > DBAs and try to get it. Consider enabling a performance-monitoring interceptor (I believe there is one included out-of-the-box but as I've never actually used Tomcat's pool I'm not 100% certain): you may get some good information about average and maybe even peak pool usage (e.g. average length of pool check-out). - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEAREIAAYFAlFIwwMACgkQ9CaO5/Lv0PCbMQCfR2IDE4EeyzDel77hg5J+oHxe bzoAoJ/fMSMzGoKrY/Mcbjmj/U8vMqjA =vzRa -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
