Feature: #93436 - Introduce cache:warmup console command

See forge#93436

Description

It is now possible to warmup TYPO3 caches using the command line.

The administrator can use the following CLI command:

./typo3/sysext/core/bin/typo3 cache:warmup

Specific cache groups can be defined via the group option. The usage is described as:

cache:warmup [--group <all|system|di|pages|…>]

All available cache groups can be supplied as option. The command defaults to warm all available cache groups.

Extensions that register custom caches are encouraged to implement cache warmers via TYPO3\CMS\Core\Cache\Event\CacheWarmupEvent.

Note: TYPO3 frontend caches will not be warmed by TYPO3 core, such functionality could be added by third party extensions with the help of TYPO3\CMS\Core\Cache\Event\CacheWarmupEvent.

Impact

It is common practice to clear all caches during deployment of TYPO3 instance updates. This means that the first request after a deployment usually takes a major amount of time and blocks other requests due to cache-locks.

TYPO3 caches can now be warmed during deployment in release preparatory steps in symlink based deployment/release procedures. This enables fast first requests with all (or at least system) caches being prepared and warmed.

Caches are often filesystem relevant (filepaths are calculated into cache hashes), therefore cache warmup should only be performed on the the live system, in the final folder of a new release, and ideally before switching to that new release (via symlink switch). Note that caches that have be pre-created in CI will likely be useless as cache hashes will not match.

To summarize: Cache warmup is to be used during deployment, on the live system server, inside the new release folder and before switching the new release live.

Deployment steps are:

  • Release preparation:

    • git-checkout/rsync your codebase (on CI or on live system)

    • composer install (on CI or on live system)

    • vendor/bin/typo3 cache:warmup --group system (only on the live system)

  • Change release symlink to the new release folder

  • Release postparation

    • Clear only the page related caches (e.g. via database truncate or an upcoming cache:flush command)

The conceptional idea is to warmup all file-related caches before (symlink) switching to a new release and to only flush database and frontend (shared) caches after the symlink switch. Database warmup could be implemented with the help of the TYPO3\CMS\Core\Cache\Event\CacheWarmupEvent as an additionally functionality by third party extensions.

Note that file-related caches (summarized into the group "system") can safely be cleared before doing a release switch, as it is recommended to keep file caches per release. In other words, share var/session, var/log, var/lock and var/charset between releases, but keep var/cache be associated only with one release.