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This error message returned by the Apache log (
$HOME/admin/logs/apache/) indicates that the limit on the number of PHP processes (20) at a given time has been reached and that new connections are waiting for a PHP process to become available.
To quickly restart the site you can do it in Web > Sites. This will however only “artificially” and temporarily fix the problem. You can analyze the processes or use PHP profiling services such as New Relic, Tideways or Blackfire to find the source.
There can be many reasons: lack of optimization, unreachable external resource, session problem…
Every time a PHP session is started, a file is created (
session.save_path) comprising all of its information and allocating it an ID. When a user returns, they provide this ID so that
session_start() can retrieve the session data. Every time
session_start() is started, the session file is locked using
This may cause problems when two PHP processes attempt to simultaneously access the same PHP session: the second has to wait until the first one ends before it can run to avoid competitive incidents. Consequently, this causes slowdowns or unavailabilities.
The analysis of your HTTP processes returns:
$ strace -f -p1821543 -p1822026 Process 1821543 attached Process 1822026 attached [pid 1821543] flock(8, LOCK_EX <unfinished ...> [pid 1822026] flock(8, LOCK_EX
This documentation will provide you with more information and solutions for correcting these problem sessions.
You have reached the 256 Mbyte limit, the default value for
memory_limit in PHP. You can increase this value in Environment > PHP or from the site itself in Web > Sites > Details for the relevant site.
To use in SSH another PHP version and/or configuration than the one indicated in Environment > PHP, it is possible to use the following commands:
$ export PHP_VERSION=<version> $ export PHPRC=/path/to/php.ini
or else for the
$ php -c /path/to/php.ini