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  1. Moodle
  2. MDL-68696

Read only sessions option throw exception with tool_mobile_get_public_config mobile when using redis sessions

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Details

    • MOODLE_39_STABLE
    • MOODLE_39_STABLE
    • read-only-session
    • Hide
      1. Setup Redis server: https://docs.moodle.org/en/Redis_cache_store 
        • Install redis-server
        • Install Redis PHP driver
        • Configure Redis in Moodle
      2. Configure Redis as the session handler:  

        $CFG->session_redis_host = '127.0.0.1';
        		 
        $CFG->session_redis_port = 6379;
        		 
        $CFG->session_redis_acquire_lock_timeout = 5;
        		 
        $CFG->session_handler_class = '\core\session\redis';

      3. Turn on read only sessions: 

        $CFG->enable_read_only_sessions = true;

      4. Run this web service (you'll need to replace moodle.local by your local Moodle URL): 

        curl -v -X POST 'http://moodle.local/lib/ajax/service.php?info=tool_mobile_get_public_config' -d '[{"siteUrl": "http://moodle.local", "index": 0, "methodname":"tool_mobile_get_public_config", "args":{}}]'

      5. Confirm you don't get an exception
      Show
      Setup Redis server: https://docs.moodle.org/en/Redis_cache_store   Install redis-server Install Redis PHP driver Configure Redis in Moodle Configure Redis as the session handler:  $CFG->session_redis_host = '127.0.0.1'; $CFG->session_redis_port = 6379; $CFG->session_redis_acquire_lock_timeout = 5; $CFG->session_handler_class = '\core\session\redis'; Turn on read only sessions: $CFG->enable_read_only_sessions = true; Run this web service (you'll need to replace moodle.local by your local Moodle URL): curl -v -X POST 'http://moodle.local/lib/ajax/service.php?info=tool_mobile_get_public_config' -d '[{"siteUrl": "http://moodle.local", "index": 0, "methodname":"tool_mobile_get_public_config", "args":{}}]' Confirm you don't get an exception

    Description

      I'm not too sure on this as a patch, but it resolves the issue.

      On startup, the mobile app does a POST as:

      curl -X POST 'http://localhost/lib/ajax/service.php?info=tool_mobile_get_public_config&XDEBUG_SESSION_START=VSCODE' -d '[\{"siteUrl": "http://localhost", "index": 0, "methodname":"tool_mobile_get_public_config", "args":{}}]'

      If read-only sessions and redis are enabled, this hits the handler_read() function.

      In there, if finds there is not yet a session in redis, then, if write-lock is needed, returns '' else returns false.

      Since false is returned, we throw later on.

      diff --git a/lib/classes/session/redis.php b/lib/classes/session/redis.php
      		 
      index ff11a66129..f2da4525b0 100644
      		 
      --- a/lib/classes/session/redis.php
      		 
      +++ b/lib/classes/session/redis.php
      		 
      @@ -257,8 +257,10 @@ class redis extends handler {
      		 
                       $this->lock_session($id);
      		 
                   }
      		 
                   $sessiondata = $this->connection->get($id);
      		 
      -            if ($sessiondata === false && $this->requires_write_lock()) {
      		 
      -                $this->unlock_session($id);
      		 
      +            if ($sessiondata === false) {
      		 
      +                if ($this->requires_write_lock()) {
      		 
      +                    $this->unlock_session($id);
      		 
      +                }
      		 
                       return '';
      		 
                   }
      		 
                   $this->connection->expire($id, $this->timeout);

      Attachments

        Issue Links

          has a non-specific relationship to

          Improvement - An enhancement to an existing Moodle feature. MDL-58018 Reduce session lock contention with opt-in READ_ONLY_SESSION

          • Major - Major loss of function, incorrect output
          • Closed

          Activity

            People

              donbowman Don Bowman
              donbowman Don Bowman
              Brendan Heywood Brendan Heywood
              Sara Arjona (@sarjona) Sara Arjona (@sarjona)
              Janelle Barcega Janelle Barcega
              David Woloszyn, Huong Nguyen, Jake Dallimore, Meirza, Michael Hawkins, Raquel Ortega, Safat Shahin, Stevani Andolo, Matteo Scaramuccia, David Woloszyn, Huong Nguyen, Jake Dallimore, Meirza, Michael Hawkins, Raquel Ortega, Safat Shahin, Stevani Andolo
              Votes:
              3 Vote for this issue
              Watchers:
              6 Start watching this issue

              Dates

                Created:
                Updated:
                Resolved:
                15/Jun/20

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