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| -rw-r--r-- | user_guide_src/source/libraries/sessions.rst | 35 |
1 files changed, 34 insertions, 1 deletions
diff --git a/user_guide_src/source/libraries/sessions.rst b/user_guide_src/source/libraries/sessions.rst index ac0ca27f5..e2780683f 100644 --- a/user_guide_src/source/libraries/sessions.rst +++ b/user_guide_src/source/libraries/sessions.rst @@ -72,6 +72,39 @@ automatic. .. note:: Under CLI, the Session library will automatically halt itself, as this is a concept based entirely on the HTTP protocol. +A note about concurrency +------------------------ + +Unless you're developing a website with heavy AJAX usage, you can skip this +section. If you are, however, and if you're experiencing performance +issues, then this note is exactly what you're looking for. + +Sessions in previous versions of CodeIgniter didn't implement locking, +which meant that two HTTP requests using the same session could run exactly +at the same time. To use a more appropriate technical term - requests were +non-blocking. + +However, non-blocking requests in the context of sessions also means +unsafe, because modifications to session data (or session ID regeneration) +in one request can interfere with the execution of a second, concurrent +request. This detail was at the root of many issues and the main reason why +CodeIgniter 3.0 has a completely re-written Session library. + +Why are we telling you this? Because it is likely that after trying to +find the reason for your performance issues, you may conclude that locking +is the issue and therefore look into how to remove the locks ... + +DO NOT DO THAT! Removing locks would be **wrong** and it will cause you +more problems! + +Locking is not the issue, it is a solution. Your issue is that you still +have the session open, while you've already processed it and therefore no +longer need it. So, what you need is to close the session for the +current request after you no longer need it. + +Long story short - call ``session_write_close()`` once you no longer need +anything to do with session variables. + What is Session Data? ===================== @@ -542,7 +575,7 @@ In order to use the 'database' session driver, you must also create this table that we already mentioned and then set it as your ``$config['sess_save_path']`` value. For example, if you would like to use 'ci_sessions' as your table name, -you would do this: +you would do this:: $config['sess_driver'] = 'database'; $config['sess_save_path'] = 'ci_sessions'; |