Thanks to Sander & André, I clearly understood why it happened and how I can get it over. Now I am looking at an example,.mod_example_ipc.c, to use a shared memory space. Thanks again. On Wed, Jun 24, 2009 at 5:31 PM, André Warnier<aw@xxxxxxxxxx> wrote: > Brian Kim wrote: >> >> Hi. All. >> >> In mod_proxy_http.c, I globally declared a variable, like unsiged int >> count = 0; >> >> And I make it increase whenever the proxy gets a new http request. >> >> I expect it increases like 1, 2, 3, 4,... but it is always same 1. >> >> Does anydoby know why this happens? How can I use a global variable in >> mod_proxy_http? >> > Not a simple answer, but read this : > http://marc.info/?l=apache-httpd-users&m=124467015611975&w=2 > > The basic point is : when it starts, Apache is a single process. That one > loads mod_proxy, with your variable initialised to 0. > Then that main Apache forks into children. Each child is an exact copy, > thus also with the variable = 0. > The main Apache does not serve requests, so its copy always remains 0. > But it distributes requests, 1 per child, as they come in. > So probably your first request gets handled by child #1. It serves the > request, and increments the variable, which for this child is now 1. > Then your next request comes in, and is handled by child #2. > Its variable is still 0. So it serves the request and increments the > variable. > Then your next request comes in and is served by child #3. > And so on. > Until... enough requests have come in, that a child that has been used > before, gets re-used. Then the variable is at 1, and now becomes 2. > But only in that child. > And so on. > > Got it ? > > If you start your Apache with a maximum of 3 children e.g., then after 4 > requests you are guaranteed to see a 2. > > Morality : you have to find a place to store your counter, that is common to > all children (or threads). And of course synchronise access to it. > > > --------------------------------------------------------------------- > The official User-To-User support forum of the Apache HTTP Server Project. > See <URL:http://httpd.apache.org/userslist.html> for more info. > To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx > " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx > For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx > > --------------------------------------------------------------------- The official User-To-User support forum of the Apache HTTP Server Project. See <URL:http://httpd.apache.org/userslist.html> for more info. To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx
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