[MDL-68696] Read only sessions option throw exception with tool_mobile_get_public_config mobile when using redis sessions - Moodle Tracker

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Details

Type: Bug
Status: Closed
Priority: Minor
Resolution: Fixed
Affects Version/s: 3.9
Fix Version/s: 3.9
Component/s: Authentication, Performance
Labels:
- CatalystIT
- ci
- partner
- triaged

Affected Branches:
MOODLE_39_STABLE
Fixed Branches:
MOODLE_39_STABLE
Pull from Repository:
https://github.com/Agilicus/moodle
Pull Main Branch:
read-only-session
Pull Main Diff URL:
https://github.com/moodle/moodle/compare/master...Agilicus:read-only-session

Testing Instructions:

Hide

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

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);

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image-2020-05-19-11-09-35-737.png
174 kB
19/May/20 11:09 AM

Issue Links

has a non-specific relationship to

MDL-58018 Reduce session lock contention with opt-in READ_ONLY_SESSION

Closed

Activity

People

Assignee:: Don Bowman

Reporter:: Don Bowman

Peer reviewer:: Brendan Heywood

Integrator:: Sara Arjona (@sarjona)

Tester:: Janelle Barcega

Participants:: Brendan Heywood, CiBoT, Don Bowman, Eloy Lafuente (stronk7), Janelle Barcega, Matteo Scaramuccia, Sara Arjona (@sarjona)

Votes:: 3 Vote for this issue

Watchers:: 6 Start watching this issue

Dates

Created:: 13/May/20 7:29 AM

Updated:: 20/May/20 12:43 AM

Resolved:: 20/May/20 12:43 AM

Fix Release Date:: 15/Jun/20

Time Tracking

Estimated:

Not Specified

Remaining:

Logged:

2h 20m