feat(redis): add redis.cluster config and docs

Signed-off-by: Thomas.G <thomas.gallois@murena.com>

.config/redis.config.php

@@ -1,5 +1,27 @@
 <?php
-if (getenv('REDIS_HOST')) {
+if (getenv('REDIS_CLUSTER_SEEDS')) {
+  $redisClusterSeeds = array_values(
+    array_filter(
+      array_map('trim', explode(',', getenv('REDIS_CLUSTER_SEEDS'))),
+      function ($seed) {
+        return $seed !== '';
+      }
+    )
+  );
+
+  $CONFIG = array(
+    'memcache.distributed' => '\OC\Memcache\Redis',
+    'memcache.locking' => '\OC\Memcache\Redis',
+    'redis.cluster' => array(
+      'seeds' => $redisClusterSeeds,
+      'password' => getenv('REDIS_HOST_PASSWORD_FILE') ? trim(file_get_contents(getenv('REDIS_HOST_PASSWORD_FILE'))) : (string) getenv('REDIS_HOST_PASSWORD'),
+    ),
+  );
+
+  if (getenv('REDIS_HOST_USER') !== false) {
+    $CONFIG['redis.cluster']['user'] = (string) getenv('REDIS_HOST_USER');
+  }
+} elseif (getenv('REDIS_HOST')) {
   $CONFIG = array(
     'memcache.distributed' => '\OC\Memcache\Redis',
     'memcache.locking' => '\OC\Memcache\Redis',

README.md

@@ -290,6 +290,10 @@ To use Redis for memory caching as well as PHP session storage, specify the foll
 - `REDIS_HOST_USER` (not set by default) Optional username for Redis, only use for external Redis servers that require a user.
 - `REDIS_HOST_PASSWORD` (not set by default) Redis password
 
+For Redis Cluster, set the seed list as a comma-separated list of host:port pairs. When `REDIS_CLUSTER_SEEDS` is set, Redis Cluster config is used instead of `REDIS_HOST`.
+
+- `REDIS_CLUSTER_SEEDS` (not set by default) Comma-separated list of cluster seeds, e.g. `redis-1:6379,redis-2:6379,redis-3:6379`
+
 Check the [Nextcloud documentation](https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/caching_configuration.html) for more information.
 
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