feat: support for Redis sentinel (#1301)

closes: #925

.env.example

@@ -22,6 +22,11 @@ REDIS_URL=redis://redis:6379
 # which will be the password for the redis service running inside the docker-compose
 # to make it secure
 REDIS_PASSWORD=
+# Redis Sentinel can be used by passing list of sentinel host and ports e,g. sentinel_host1:port1,sentinel_host2:port2
+REDIS_SENTINELS=
+# Redis sentinel master name is required when using sentinel, default value is "mymaster".
+# You can find list of master using "SENTINEL masters" command
+REDIS_SENTINEL_MASTER_NAME=
 
 # Postgres Database config variables
 POSTGRES_HOST=postgres

config/initializers/redis.rb

@@ -2,8 +2,23 @@ app_redis_config = {
   url: URI.parse(ENV.fetch('REDIS_URL', 'redis://127.0.0.1:6379')),
   password: ENV.fetch('REDIS_PASSWORD', nil).presence
 }
-redis = Rails.env.test? ? MockRedis.new : Redis.new(app_redis_config)
 
+if ENV['REDIS_SENTINELS'].presence
+  default_sentinel_port = '26379'
+  # expected format for REDIS_SENTINELS url string is host1:port1, host2:port2
+  sentinels = ENV['REDIS_SENTINELS'].split(',').map do |sentinel_url|
+    host, port = sentinel_url.split(':').map(&:strip)
+    { host: host, port: port || default_sentinel_port, password: app_redis_config[:password] }
+  end
+
+  master_name = ENV.fetch('REDIS_SENTINEL_MASTER_NAME', 'mymaster')
+  # over-write redis url as redis://:<your-redis-password>@<master-name>/ when using sentinel
+  # more at https://github.com/redis/redis-rb/issues/531#issuecomment-263501322
+  app_redis_config[:url] = URI.parse("redis://#{master_name}")
+  app_redis_config[:sentinels] = sentinels
+end
+
+redis = Rails.env.test? ? MockRedis.new : Redis.new(app_redis_config)
 # Alfred
 # Add here as you use it for more features
 # Used for Round Robin, Conversation Emails & Online Presence