Red Hat ENTERPRISE LINUX 3 Reference Manual

Also see for ENTERPRISE LINUX 3 - SECURITY GUIDE: Tuning guide Installation guide Installation guide Installation guide Manual

Contents

140 Chapter 10. Apache HTTP ServerBy default, Apache HTTP Server 2.0 defines the server-pool for both the prefork and workerMPMs.The following a list of directives found within the MPM-specific server-pool containers.10.5.9.1. StartServersStartServers sets how many server processes are created upon startup. Since the Web server dy-namically kills and creates server processes based on traffic load, it is not necessary to change thisparameter. The Web server is set to start 8 server processes at startup for the prefork MPM and 2for the worker MPM.10.5.9.2. MaxRequestsPerChildMaxRequestsPerChild sets the total number of requests each child server process serves beforethe child dies. The main reason for setting MaxRequestsPerChild is to avoid long-lived processinduced memory leaks. The default MaxRequestsPerChild for the prefork MPM is 1000 and forthe worker MPM is 0.10.5.9.3. MaxClientsMaxClients sets a limit on the total number of server processes, or simultaneously connected clients,that can run at one time. The main purpose of this directive is to keep a runaway Apache HTTP Serverfrom crashing the operating system. For busy servers this value should be set to a high value. Theserver’s default is set to 150 regardless of the MPM in use. However, it is not recommended that thevalue for MaxClients exceeds 256 when using the prefork MPM.10.5.9.4. MinSpareServers and MaxSpareServersThese values are only used with the prefork MPM. They adjust how the Apache HTTP Serverdynamically adapts to the perceived load by maintaining an appropriate number of spare server pro-cesses based on the number of incoming requests. The server checks the number of servers waitingfor a request and kills some if there are more than MaxSpareServers or creates some if the numberof servers is less than MinSpareServers.The default MinSpareServers value is 5; the default MaxSpareServers value is 20. These defaultsettings should be appropriate for most situations. Be careful not to increase the MinSpareServersto a large number as doing so creates a heavy processing load on the server even when traffic is light.10.5.9.5. MinSpareThreads and MaxSpareThreadsThese values are only used with the worker MPM. They adjust how the Apache HTTP Server dy-namically adapts to the perceived load by maintaining an appropriate number of spare server threadsbased on the number of incoming requests. The server checks the number of server threads waitingfor a request and kills some if there are more than MaxSpareThreads or creates some if the numberof servers is less than MinSpareThreads.The default MinSpareThreads value is 25; the default MaxSpareThreads value is 75. These de-fault settings should be appropriate for most situations. The value for MaxSpareThreads is must begreater than or equal to the sum of MinSpareThreads and ThreadsPerChild or Apache HTTPServer automatically corrects it.