Redis

Redis is an open-source (BSD-licensed), in-memory data structure store, used as a database, cache, and message broker. It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperlogs, and geospatial indexes with radius queries.

• Super-fast in-memory data structure server
• Pub/Sub
• Rich client libraries
• Zero install and easy to operate
• Connect multiple node.js-servers to 1 redis channel

$ brew info redis
$ brew install redis

$ redis-cli ping
$ redis-cli
$ redis-cli incr mycounter

4. Commands

• add test unit in test/tdd/
• add a tab socket-redis and a component src/socket-redis/PubSubApp.js
• add pub/sub clients

$ redis-cli
> config set stop-writes-on-bgsave-error no

• set smoothie to initialize redis smoothie, to test persistant store.

$ redis-cli
127.0.0.1:6379> hset smoothie field1 'red'
(integer) 1
127.0.0.1:6379> hset smoothie field2 'blue'
(integer) 1
127.0.0.1:6379> hgetall smoothie
1) "field1"
2) "red"
3) "field2"
4) "blue"

• after the set, in server.js, this is available:

  pub.hgetall('smoothie', callback);

• set get loginCounts 10; get, incr, decr, del
• redis-cli> get loginCounts
• redis-cli> INFO

5. Redis-backed Pub/Sub

• 2 clients required: 1 for pub, 1 for sub (or multiple subs)
• use 1 channel, add metadata to your message
• browser: socket.emit
• server: socket.on redis.publish redis.subscribe socket.emit
• browser: socket.on

Q&A

• In order to send chat messages to users across servers we will update our server to use Redis as a PubSub service (along with session store). Redis natively supports pub-sub operations.
• Subscribe channel
• Unsubscribe channel
• Publish channel message
• redis.createClient()

Reference

• Using Redis with Node.js and Socket.IO