I am setting up an apache configuration to check for the existence of a file. If the file exists, then the server will redirect to a maintenance page. If not, the application will get served up normally.
I'm concerned that with a large number of requests, that the file check has to happen on each individual request and could end up causing a large amount of unnecessary IO.
Is there IO overhead for checking the existence of a file?
If so, are there any alternatives to checking for the existence of a file?
I need to be able to modify something outside of apache that won't require a restart or graceful. For example, is there a module that allows querying a memcached instance for the presence of a key? or is there any other type of memory based cache that could be used?