Added Redis Sentinel support¶

Contributed by
Stephen Clouse
in #31437.

Redis Sentinel is a distributed system that provides high availability for Redis. It allows you to create a Redis deployment that resists certain kinds of failures without human intervention.

In Symfony 4.4, we've added support for it thanks to the new redis_sentinel option that you can add to the Redis connection DSN:

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use Symfony\Component\Cache\Adapter\RedisAdapter;

// set the 'redis_sentinel' parameter to the name of your service group
$client = RedisAdapter::createConnection(
    'redis:?host[redis1:26379]&host[redis2:26379]&host[redis3:26379]&redis_sentinel=mymaster'
);

That's all! The only caveat is that Sentinel also requires the Predis library.

Improved Redis Tag Aware Adapter¶

Contributed by
Andre Rømcke
in #33461.

Tag Aware Adapters are used in Symfony Cache to invalidate caches based on tags instead of expiration time. In Symfony 4.4 we've improved the RedisTagAwareAdapter in several ways:

• We've lowered the Redis requirement to 2.8 and we no longer require certain phpredis versions;
• We've raised the 2 billion keys per tag constraint to 4 billion keys per tag, which is the limit of the Redis Set datatype;
• We've improved the invalidation process to also delete the tag key in order to avoid leaving unused tags that gradually consume more and more memory.