CGI Push and Apache memory consumption

["Kiss, John (GE Infra, Energy, Non-GE)" <john.kiss@xxxxxx>]

 

Hello I'm having an issue with long running CGI push scripts causing Apache to consume all available free memory over a period of several days.

 

The scenario : System free memory at 220 Megs, browser connects to cgi push script. Within 3 days system free memory goes down and hovers at 5 megs but now other browsers cannot connect because of a lack of system resources. Let the system run for two more days and Apache kills/restarts it's threads and free memory returns to 220Megs and other browser can connect to web pages again. Without ever resetting Apache I let this cycle repeat over a 2 week period.

 

I've tested on a custom Linux system running Apache 2.0.55 under Linux 2.6.13 and on Ubuntu Feisty  which uses Apache 2.2.3 (using default apache config). The same problem appears on both. Nothing special with configuration and loading of modules.

 

I have attached a simple CGI script that replicates the issue (See below) where Apache's memory grows linearly at a rate of ~19.6kB/min (typically in 4kB increments depending on your Linux/MMU page size).. If anyone has any insight on why this is happening and what I can do resolve it, I would very be much appreciated it.

 

BTW, I have looked into this issue (http://marc.info/?l=apache-httpd-users&m=112307824726606&w=2) already discussed on this list and have found my issue is not related to range headers since Apache 2.0.55 contains the patch (fix).

 

Cheers

John

 

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Steps to reproduce:
-------------------
1. Build CGI script (see below cgi script)

2. Restart Apache.

3. Point a browser at the CGI script.

4. Monitor system free memory using 'free' and apache processes using 'ps'. Over a period of 10 minutes you'll witness free memory going down and apache thread memory going up.

1. cgi script:
------------------------
#include <time.h>
#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

/*
main.
*/
int main(int argc, char *argv[])
{
    runPlain();
}

/*
Run a text/plain test.
*/
int runPlain()
{
    int i,j;
    printf("Content-type: text/plain; charset=us-ascii\n\n");
    for (i=0; ; i++)
    {
        for (j=0; j<5; j++)
        {
            printf("%d,%d: wakka wakka wakka wakka wakka wakka wakka\n",i,j);
        }
        printf("\n");
        usleep(5000);
    }
}