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Accepted
Jorge Bernal
Asked: 2009-09-19 04:20:12 +0800 CST

Apache gives empty reply

  • 772

It happens randomly, and only on moodle installations. Apache don't add a line in the logs when this happens, and I don't know where to look.

koke@escher:~/Code/eboxhq/moodle[master]$ curl -I http://training.ebox-technologies.com/login/signup.php?course=WNA001 
curl: (52) Empty reply from server
koke@escher:~/Code/eboxhq/moodle[master]$ curl -I http://training.ebox-technologies.com/login/signup.php?course=WNA001 
HTTP/1.1 200 OK

The apache conf is quite straightforward and works perfectly in the other vhosts

<VirtualHost *:80>
    ServerAdmin [email protected]
    DocumentRoot /srv/apache/training.ebox-technologies.com/htdocs
    ServerName training.eboxhq.com
    ErrorLog /var/log/apache2/training.ebox-technologies.com-error.log
    CustomLog /var/log/apache2/training.ebox-technologies.com-access.log combined

        <FilesMatch "\.(ico|gif|jpe?g|png|js|css)$">
                ExpiresActive On
                ExpiresDefault "access plus 1 week"
                Header add Cache-Control public
        </FilesMatch>
</VirtualHost>

Using apache 2.2.9 php 5.2.6 and moodle 1.9.5+ (Build: 20090722)

Any ideas welcome :)

php

3 Answers

  1. Look at the main server error log, it should have some Child Segfault Error (11).

    This is probably given by a PHP engine fault, often given by a buggy php module, unicode chars handling, gettext corrupted DB, and so on.

    It is very difficult to debug.

    You can enable xdebug tracing and look at what line it is segfaulting:

    pecl install xdebug

    php.ini:

    [xdebug]
xdebug.profiler_enable=1
xdebug.profiler_output_dir="/tmp/xdebug"
xdebug.auto_trace=1            ; enable tracing
xdebug.trace_format=0
xdebug.show_mem_delta=1        ; memory difference
xdebug.show_local_vars=1
xdebug.max_nesting_level=100
    • 1
  2. Best Answer

    Finally solved by adding to /etc/apache2/envvars:

    export USE_ZEND_ALLOC=0
    • 1

  3. Is there nothing in error_log either?

    You could set MaxServers to 1, and then strace that apache thread while requesting the page. It could be that PHP is segfaulting, or the apache child is dying for other reasons.

    Also, tcpdump the request at both ends to see what data is being sent on the wire.

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