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 Topic: problem with custom module |
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scott
Joined: 16 Jun 2009
Posts: 6
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 Posted: Tue 16 Jun '09 9:28 Post subject: problem with custom module |
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Hello,
I have been working on a module for apache (for windows)
when i found that it was calling the register_hooks function
twice.
I copied a tutorial from the net and compiled it to see if I
got the same problem - and I did.
Here is the tutorial code:
| Code: |
/* a very simple module: put a header in the reply with the number of hits this process has received */
#include <httpd.h>
#include <http_config.h>
#include <apr_strings.h>
void __declspec(dllimport) __stdcall ap_hook_fixups(int (*)(request_rec*), int, int, int);
static apr_uint32_t hitCount = 0;
static int myHitsCounter(request_rec *request) {
//if main exists, this is an internal redirect, which means we've already acted on this "hit"
if (!request->main) {
char *hitString;
hitCount++;
hitString = apr_itoa(request->pool, hitCount);
apr_table_set(request->headers_out, "X-Process-Hits", hitString);
}
return OK;
}
static void myRegisterHooks(apr_pool_t *p) {
ap_hook_fixups(myHitsCounter, NULL, NULL, APR_HOOK_MIDDLE);
}
module AP_MODULE_DECLARE_DATA myhits_module = {
STANDARD20_MODULE_STUFF,
NULL, /* create per-directory config structures */
NULL, /* merge per-directory config structures */
NULL, /* create per-server config structures */
NULL, /* merge per-server config structures */
NULL, /* command handlers */
myRegisterHooks /* register hooks */
};
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I find when debugging using gdb and running httpd -X
the registerHooks function is called twice. This is
a problem for my other module. Does anyone know why?
Note that the tutorial does compile and work as expected
and that calling myRegisterHooks twice does not affect
this module.
Any help much appreciated.
--scott |
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scott
Joined: 16 Jun 2009
Posts: 6
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| Posted: Tue 16 Jun '09 9:52 Post subject: |
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On second thoughts i believe that the module is being loaded twice.
Is there any reason why apache would do that?
there is only one entry in the httpd.conf file. |
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tdonovan
Moderator
Joined: 17 Dec 2005
Posts: 611
Location: Milford, MA, USA
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| Posted: Tue 16 Jun '09 13:44 Post subject: |
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This is expected. Apache makes two passes of the configuration at startup.
The first pass is just to check for errors. Then, all modules are unloaded and the whole configuration is processed again for *real*.
You need to make sure that anything you do in your startup functions (like RegisterHooks) can safely be done twice.
-tom- |
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scott
Joined: 16 Jun 2009
Posts: 6
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| Posted: Tue 16 Jun '09 15:27 Post subject: |
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thanks for the reply - in my actual module i was trying to create a thread in the init function, which can not be done twice.
Is there a recommended work around?
I think ill figure something out anyway now that i know the problem!
Thanks again!
--scott |
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James Blond
Moderator
Joined: 19 Jan 2006
Posts: 7294
Location: Germany, Next to Hamburg
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| Posted: Tue 16 Jun '09 20:18 Post subject: |
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Well I'm not used to C coding, but in PHP I would use a singleton function to make sure that in instance runs only once.
But what is the syntax is incorrect? Does your thread unload with apache? Since apache unload all modules after sysntax check I think it would be good to make sure that your module unloads the thread it creates when it is unload by apache. |
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scott
Joined: 16 Jun 2009
Posts: 6
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| Posted: Wed 17 Jun '09 5:22 Post subject: |
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A singleton is no good, since unloading the module destroys all the variables created. It does not destroy the thread tho.
--scott |
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