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From Waldemar Klein <waldemar.kle...@googlemail.com>
Subject Windows service startup configuration - how to find out the "working" process?
Date Wed, 25 Apr 2012 22:03:36 GMT
Hello.


Looking at the startup procedure of Apache on Windows (as service), I
noticed that the httpd.conf is read and processed (i.e. procedures
ran) in total 4 times. After startup, only one of them is actually
used later to handle requests.

I have a module which has a rather expansive (reading and processing a
few big files into memory) operation on startup. It is a waste of
resources to do this 4 times, when it is used only once.

What I found out so far:
- the first process (pid A), runs as the user who entered the command
httpd -k (re)start. Processes httpd.conf once. This will be terminated
after startup is complete. It would not use and memory later on, but
still it needs the processing time at startup.
- the second (pid B) (runs as "SYSTEM") seems to be the "control"
process and only starts another child process (pid B), processes
httpd.conf once. Writes its pid to logs/http.pid. Stays as process but
doesn't answer requests.
- the third (pid C), processes the http.conf twice, only the second
one is actually used.

I can think of a few quite ugly hacks to solve this:
- writing the pids to files and only doing the configuration work when
I already see my own pid was in the file, this must be the 2nd run on
the process with pid C (can also clean up then). Problemmatic with
crashes during startup.
- only prepare the config (store filenames) and finish (read and
process files) the first time I actually get to work. Problem is,
first request might take some time, because the "work" must be done.
Could be solved by a dummy request right after startup. (it's still an
ugly hack :) )
- since I can identify the first process (different user), I could
start a counter, and only read my files when the counter reaches 4.
Problem: this doesnt work if apache is started with -X. (Also I
haven't checked yet what the user of the 1st process is if it's
started at boot or via a scheduled task)
I can think of a few more problems that might arise, and I am even
more afraid of the problems that I can not think of right now :)

Now my question is, is there a good method to find out if we (the
configuration procedures) are in the "working" configuration? This
would be the third process and the 2nd processing of the httpd.conf,
which will be actually used when the module gets to work.

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