On 16/11/2011 16:52, Christopher Schultz wrote: > Pid, > > On 11/16/11 8:47 AM, Pid * wrote: >> Tomcat 6.0.32, HTTPD (worker mpm) 2.2.19, mod_jk 1.2.31. > >> If ThreadsPerChild is 60 and ServerLimit is 10, MaxClients is 600, >> how many connections, at peak, will be made to 20 Tomcat >> instances? > > - From httpd docs: > > MaxClients: For threaded and hybrid servers (e.g. beos or worker) > MaxClients restricts the total number of threads that will be > available to serve clients. The default value for beos is 50. For > hybrid MPMs the default value is 16 (ServerLimit) multiplied by the > value of 25 (ThreadsPerChild). Therefore, to increase MaxClients to a > value that requires more than 16 processes, you must also raise > ServerLimit. > > ServerLimit: With worker use this directive only if your MaxClients > and ThreadsPerChild settings require more than 16 server processes > (default). Do not set the value of this directive any higher than the > number of server processes required by what you may want for > MaxClients and ThreadsPerChild. > > So if MaxClients is 600 and ThreadsPerChild is 60 then you can't have > more than 10 processes each with 60 threads. If you want more than 16 > server processes (which it looks like you don't need), then you'll > need to set ServerLimit to something higher than it's default for > worker which appears to be 16. > > I'm not sure you need ServerLimit at all. > > If you have 20 TCs on the back end, then mod_jk will have to open 20 * > 600 = 12000 connections at peak, if my math is correct. That's only > 600 connections per TC, or course, but you may have trouble with > creating that many connections from the proxy.
What I'm not clear on is whether the mod_jk worker connection_pool_size is 60 per Server child, or 60 * 10 Server children. If MaxClients is still 600 and there is one Tomcat, one might assume that allowing all 600 to go to that Tomcat is sensible - but if there are two Tomcats, what is the behaviour? NB 600 to each Tomcat would be more than MaxClients. > If you have more than one worker, then the number of Tomcat instances > is essentially multiplied. So, if you have 20 TC backends each with 2 > workers assigned to them, then you'll 24000 connections instead. > >> Will this change If Tomcat instances start failing? > > Probably not -- mod_jk will just retire the connection and create a > new one. If you are having load problems, you might make things worse > with all this connection churn. Agreed. p > -chris > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org > For additional commands, e-mail: users-h...@tomcat.apache.org > -- [key:62590808]
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