>-----Ursprüngliche Nachricht----- >Von: André Warnier [mailto:a...@ice-sa.com] >Gesendet: Freitag, 2. März 2012 18:53 >An: Tomcat Users List >Betreff: Re: AW: Too many connections in keepalive state in jk >threadpool > >Hi. > >The recommended way of replying to messages on this list, is >to write your replies below >the comment/question to which it relates. >It makes it much easier to follow the flow of the conversation. > > >> >> -----Ursprüngliche Nachricht----- >> Von: André Warnier [mailto:a...@ice-sa.com] >> Gesendet: Freitag, 2. März 2012 13:01 >> An: Tomcat Users List >> Betreff: Re: Too many connections in keepalive state in jk threadpool >> >> Beier Michael wrote: >>> Hi all, >>> >>> we're running tomcat 7.0.23 on sun jdk 1.6.0_29, connected >via ajp to httpd 2.2.21 using mod_jk 1.2.32. >>> >>> I observed the behavior, that tomcat keeps threads in its >ajp pool in keepalive state, regardless of which timeouts >(connectionTimeout and keepAliveTimeout) are configured in tomcat. >>> I tested three connector configurations and with all I see >connections in tomcat server status where the "Time" value >amounts up to several million milliseconds, which is more than >configured in connectionTimeout/keepAliveTimeout. >>> This results in having 60-80 percent of the thread pool >being in state "keepAlive". >>> >>> 1) >>> <Connector port="8309" protocol="AJP/1.3" >>> maxThreads="200" redirectPort="8343" >tomcatAuthentication="false" >>> keepAliveTimeout="300000" >connectionTimeout="300000" /> >>> 2) >>> <Connector port="8309" protocol="AJP/1.3" >>> maxThreads="200" redirectPort="8343" >tomcatAuthentication="false" >>> keepAliveTimeout="300000" /> >>> 3) >>> <Connector port="8309" protocol="AJP/1.3" >>> maxThreads="200" redirectPort="8343" >>> tomcatAuthentication="false" /> >>> >>> In mod_jk the connection_pool_timeout is set to the same >value as connectionTimeout (only in seconds, not milliseconds). >>> I verified that the values are set correctly querying the >parameters via JMX. >>> >>> How can I avoid having so many threads in keepalive state - >I don't have any idea at the moment and can't see that there >is an error in my configuration. >> >> Before discussing this, I find it useful to review the >basics, such as in : >> >> http://en.wikipedia.org/wiki/HTTP_persistent_connection >> and >> http://tomcat.apache.org/connectors-doc/generic_howto/timeouts.html >> >> In other words, at the level of your front-end webserver >(which I suppose you have, since you are talking about mod_jk >and AJP), do you really need a long KeepAliveTimeout ? >> (and similarly at the level of your Tomcat <Connector>'s above). >> >> As per the documentation : >> >> connectionTimeout >> >> The number of milliseconds this Connector will wait, after >accepting a connection, for the request URI line to be >presented. The default value is 60000 (i.e. 60 seconds). >> >> keepAliveTimeout >> >> The number of milliseconds this Connector will wait for >another AJP request before closing the connection. The default >value is to use the value that has been set for the >connectionTimeout attribute. >> >> In other words, >> - connectionTimeout defaults to 60 seconds >> - if you do not specify either one of them, then they both >default to 60 seconds. >> - if you do specify connectionTimeout and not >KeepAliveTimeout, then KeepAliveTimeout defaults to the same >value as connectionTimeout. >> - your value above for KeepAliveTimeout (300000) means 5 minutes >> >> Do you really want one Tomcat thread to wait for 5 minutes >doing nothing, just in case the browser would decide to send >another request on the same connection ? >> And do you really want, when a browser creates its initial >TCP connection to your webserver, to give it 60 seconds (or 5 >mintes !) before it even starts sending its HTTP request on >that connection ? >> >Beier Michael wrote: >> Hi, >> >> all the points you've mentioned are important and have been >> considered. 5 minutes >> timeout for connection / keepAlive is a very long time, but >> this is OK for our web apps >> running in our intranet. > > >It may be ok for you, but it may also be the reason why you >have processes/threads which >remain alive and are blocking connections.
That's a very sophisticated thesis. I configured a 300 second KeepAliveTimeout and find threads in keepalive state that are more than 1000 seconds old. Why should this behaviour change, if I reduce the configured timeout? But .. I'll try .. >I do not know the deep details of how mod_jk works, but : >- the browser make a connection to the front-end server >- Apache httpd accepts the connection and passes it to a httpd >child process, for request >processing >- the browser sends a HTTP request over that connection, >requesting Keep-Alive >- the front-end server's child processes the request. In the >process of doing this, >mod_jk establishes a connection to the back-end Tomcat, and >passes the request to Tomcat >over that connection >- in Tomcat, a thread starts to process the request >- in Tomcat, the thread sends the response and finishes to >process that request >- but because the connection is Keep-Alive, it does not close >the connection (from >mod_jk), and keeps waiting for more requests >- in the meantime, the Apache child who processed the request >(sending it through mod_jk >to Tomcat) will not close its connection to the browser >either, and will probably keep its >connection to Tomcat open also >- in the meantime, another browser connects to the server, >which will also result in an >Apache front-end child waiting for 5 minutes doing nothing, >and blocking a connection to >Tomcat and a thread in Tomcat.. >And so on. > >It is probably more complex than that, since mod_jk will use a >pool of connections to >Tomcat, and try to keep them alive and re-use them, for >efficiency reasons. >So it is a bit complicated to determine which KeepAlive "wins" >here, and what in the end >is causing these Tomcat threads to remain when they shouldn't. > >> But at the moment I'd be quite happy, if tomcat would make >> use of the defined timeouts >> and terminate the threads, that have been in keepalive state >> for more than 5 minutes. >> >> But this does not happen! >> >> So my first goal is, to make tomcat respect the timeouts I define. >> The second goal then might be fine tuning the timeouts. > >My point was : first set your timeouts to a reasonable value >(2-3 seconds for example), >and then check if you still have a bunch of threads in Tomcat >doing nothing. >If you still do, then you may have a problem worth >investigating further. >But if you don't, then why make your life complicated and look >for problems where there >aren't any ? As I wrote above - I'll try and get back to you. Best regards, Michael Michael Beier Team SIS OIOAW (Web Basis) EnBW Systeme Infrastruktur Support GmbH Durlacher Allee 93 76131 Karlsruhe Tel.: +49 (7 21) 63 - 14545 Fax: +49 (7 21) 63 - 15099 mailto:m.be...@enbw.com EnBW Systeme Infrastruktur Support GmbH Sitz der Gesellschaft: Karlsruhe Handelsregister: Amtsgericht Mannheim HRB 108550 Vorsitzender des Aufsichtsrats: Dr. Bernhard Beck Geschäftsführer: Jochen Adenau, Hans-Günther Meier --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
