How to prevent session locks?

[Martijn Geerts]

PHP writes its session data to a file by default, so does ProcessWire. So when ProcessWire starts executing a process the session starts and the session gets locked. After the process is completed the session unlocks and we are able to use ProcessWire again. For normal scripts this is oké. But when you have long running processes like importing big data or you want to create a responsive AJAX API, this can be a real bottleneck. You see this 'issue' for example with ImportPagesCSV where the admin 'freezes' while importing.

1 Dirty way to avoid session lock for big data import is to remove all sessions after you have started the import script. But this will log you out from the admin. An other way could be to use exec() and send the output to /dev/null. (Running the script in background)

How do you guys deal with these session locks ?

[Craig]

As a first step, you could try using the SessionHandlerDatabase module to see if that makes a difference. It's included in core, but not installed by default.

[horst]

There is also an example layer class on SO that provides none blocking concurent session writes: http://stackoverflow.com/questions/10046570/php-save-session-when-using-session-write-close/27993746#27993746

But you need to implement this yourself before you start the long running tasks and switch back to PWs regular behave after you have finished them.

You can use everything you want to handle sessions with http://php.net/manual/en/function.session-set-save-handler.php.

Edited January 4, 2016 by horst

[Jonathan Lahijani]

Reviving this thread.

Let's say I quickly opened 3 different pages in new browser tabs to edit in the admin that each take 10 seconds to load (assume they are pages with a lot of related data and repeater items).  Because of session locking, it must load the first page, then after that is completed loading, it will load the second page, and so on.  This means there is considerable lag.

I believe this is not an issue with ProcessWire itself (regardless if using SessionHandlerDB or file-based sessions), but how PHP does session locking in general to prevent issues.

So there's no problem-free way around this... is that still correct?