Prerequisite

• You will need to have access to a Redis server. It can be running on your machine or elsewhere. Windows users can use Memurai if desired.

Setup using Docker

1. Install the PHP Redis extension (replace "X" with your server's PHP version, e.g. 8.0)

   sudo apt update && sudo apt install -y phpX-redis

2. Enable the Redis PHP extension.
3. Restart your web server.
4. Confirm the Redis PHP extension is enabled: "php -i | grep redis" - You should see a bunch of lines related to Redis.
5. Install Redis. e.g. using Docker

   docker run --name redis -p 6379:6379 -d redis

6. Setup Redis as the session handler, e.g. copy the following to your config.php:

   $CFG->session_handler_class = '\core\session\redis';

   $CFG->session_redis_host = '127.0.0.1';

   $CFG->session_redis_port = 6379;

7. Configure your MUC cache (via Site administration / Plugins / Caching / Configuration / Cache administration) so that it has a Redis cache:
   1. Add a Redis instance by clicking the Add instance link in the Redis line of the table under Installed cache stores.
   2. Set the store name to whatever you like, the server to wherever you have a Redis server installed (E.g. localhost)
   3. Set the Key prefix' to an easily distinguishable value, eg. 4242_.
   4. Save settings
8. Set the core/coursemodinfo cache to use the Redis cache:
   1. Under Known cache definitions find the line with coursemodinfo and click Edit mappings.
   2. Change the Primary store to your Redis instance (whatever you called it).
   3. Save settings.

Before applying the patch

Manual Testing

1. Checkout to the previous weekly release.
2. To see if Redis is being used, in a prompt on the server type the following command (replace "4242_" with the Key prefix you set earlier):

   redis-cli monitor | grep 4242_

3. Purge the Redis cache by clicking the Purge link in the Redis line of the table under Configured store instances.
4. Select a suitable course id from your test install, keeping an eye on the open terminal.
5. Confirm that you see a SETNX and an EXPIRE command for the created lock, eg.

   1724359413.837901 [0 [::1]:52870] "SETNX" "4242_2-609a980901cad2119e4cc965e0ff2850" "s:32:\"f41b22dea89abd0af0f910da38e2ade2\";"

   1724359413.837980 [0 [::1]:52870] "EXPIRE" "4242_2-609a980901cad2119e4cc965e0ff2850" "600"

After applying the patch

Manual Testing

1. Checkout the the latest main branch.
2. To see if Redis is being used, in a prompt on the server type the following command (replace "4242_" with the Key prefix you set earlier):

   redis-cli monitor | grep 4242_

3. Purge the Redis cache by clicking the Purge link in the Redis line of the table under Configured cache instances.
4. Select a suitable course id from your test install, keeping an eye on the open terminal.
5. Confirm that you see only a SET command for the created lock, eg.

   1724359503.664419 [0 [::1]:46242] "SET" "4242_2-609a980901cad2119e4cc965e0ff2850" "s:32:\"f41b22dea89abd0af0f910da38e2ade2\";" "ex" "600" "nx"

Code verified against automated checks.

Checked MDL-80815 using repository: https://github.com/ziegenberg/moodle

• main (0 errors / 0 warnings) [branch: MDL-80815_simplify-redis-acquire_lock-method | CI Job]

_{More information about this report}

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