Allow REDIS_CLUSTER environment variable to use Redis in cluster mode

Author: n1mmy

README.md

@@ -238,6 +238,10 @@ To use Redis for memory caching as well as PHP session storage, specify the foll
 - `REDIS_HOST_PORT` (default: `6379`) Optional port for Redis, only use for external Redis servers that run on non-standard ports.
 - `REDIS_HOST_PASSWORD` (not set by default) Redis password
 
+To use Redis in cluster mode, you can use
+
+- `REDIS_CLUSTER` (not set by default) Name and port number of a redis host.
+
 Check the [Nextcloud documentation](https://docs.nextcloud.com/server/latest/admin_manual/configuration_server/caching_configuration.html) for more information.
 
 ### E-mail (SMTP) Configuration

docker-entrypoint.sh

@@ -132,6 +132,26 @@ if expr "$1" : "apache" 1>/dev/null || [ "$1" = "php-fpm" ] || [ "${NEXTCLOUD_UP
         } > /usr/local/etc/php/conf.d/redis-session.ini
     fi
 
+    if [ -n "${REDIS_CLUSTER+x}" ]; then
+
+        echo "Configuring Rediscluster as session handler"
+        {
+            file_env REDIS_HOST_PASSWORD
+            echo 'session.save_handler = rediscluster'
+            # check if redis password has been set
+            if [ -n "${REDIS_HOST_PASSWORD+x}" ]; then
+                echo "session.save_path = \"seed[]=${REDIS_CLUSTER}&auth=${REDIS_HOST_PASSWORD}\""
+            else
+                echo "session.save_path = \"seed[]=${REDIS_CLUSTER}\""
+            fi
+            echo "redis.session.locking_enabled = 1"
+            echo "redis.session.lock_retries = -1"
+            # redis.session.lock_wait_time is specified in microseconds.
+            # Wait 10ms before retrying the lock rather than the default 2ms.
+            echo "redis.session.lock_wait_time = 10000"
+        } > /usr/local/etc/php/conf.d/redis-session.ini
+    fi
+
     # If another process is syncing the html folder, wait for
     # it to be done, then escape initalization.
     (