BANDA ACEH – How directives behave and which directives are mainly available hinges on the loaded MPM. As discussed in our previous series, MPM is short for MultiProcess Modules, and they determine the basis for how Apache addresses multiprocessing. Using our last article on Apache MPM Modules as a springboard, we will use this section to cover the following subsections:
Each part will focus on how the directives affect performance for their respective MPM and some common considerations that should be assessed when optimizing Apache with those specific MPMs.
Be sure to review this article in its entirety as the universal directives operate in the same manner regardless of the MPM chosen.
General Optimization
IfModule
An important directive to learn when working with Apache servers is the IfModule conditional statement. There are two parts to the IfModule statement. A beginning, which also accepts a module name or module source file name, as well as a closing statement. When the provided module is loaded into Apache, then all directives between the beginning IfModule statement and the closing IfModule statement are also read into the Apache running configuration. Please review the provided example below for further clarification:
<ifModule mpm_prefork_module>
MaxSpareServers 16
</ifModule>
Timeout 60
The above example defines the MaxSpareServers directive only when loaded by mpm_prefork_module. The Timeout directive is applied every time due to it being outside of the IfModule closing statement.
IfModule statements are used to maintain compatibility within Apache configuration between module changes. Maintaining compatibility is done by grouping directives into IfModule statements, so they are only used when the required module is loaded. Ensuring a syntactically correct configuration file even when swapping modules.
Remember, as a rule of thumb, appropriately wrapping everything in an IfModule statement is a best practice standard with Apache and should be adhered to for superior compatibility in config files.
Timeout
The numerical value of seconds Apache waits for all common I/O events. Apache will abandon requests fail to complete before the provided Timeout value.
Determining the right Timeout depends on both traffic habits and hosted applications. Ideally, Timeout should be as low as possible while still allowing the vast majority of regular traffic to operate without issue. Large timeouts, those above 1 minute, open the server to SlowLoris style DOS attacks and foster a long wait in the browser when it encounters a problem. Lower timeouts allow Apache to recover from errant stuck connections quickly. It becomes necessary to strike a balance between the two extremes.
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