Redis HA environment with docker-compose and ioredis client
docker-compose up --build
Check in the logs how the replicas sync with the master and how the sentinels monitor the master.
- Check master and slaves from a sentinel (either connect to the container to run commands on it or use shorcut commands)
npm run show:master
npm run show:slaves
- Pause master container
docker-compose pause redis-ha-server1
Wait 10s and watch sentinels promote a replica as new master (quorum is 2 so after 2 replicas have agreed upon a sdown event it will trigger the failover)
- Check master and slaves again.
You should see a new master and the old master as slave.
- Add master back to the cluster
docker-compose unpause redis-ha-server1
This container has now become a replica and you should see in the logs how it syncs to the new master.
- Set server1 as master again
server2 and 3 have priority as slaves (check docker-compose), so if you force a failover when ther server1 is backup, it will be set as the master again
npm run failover
Double check it worked: npm run show:master
There are 4 commands that will trigger the app.js script and will connect to the node or cluster usnig ioredis client. These are the examples:
npm run single_master will directly connect to server1(master), write a key and read it back again.
npm run single_replica will directly connect to server2(replica) nad try to write a key which will fail.
npm run sentinels_use_master will connect to sentinels to ask for the master node, write a key and read it back again.
npm run sentinels_use_replicas will connect to sentinels to ask for a replica node and try to write a key which will fail.