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How to configure Redis high availability

This guide explains how to create a highly available Redis cluster from the Hikube console. The service uses Redis Sentinel to provide automatic failover as soon as the cluster has at least 2 replicas. Three sentinels are always deployed, whatever the number of replicas.

Prerequisites​

  • A Hikube project with sufficient quotas: CPU, memory and storage consumption is multiplied by the number of replicas, and the three sentinels also count in CPU and memory, at the size of the preset
  • Knowledge of Redis basics (see the quick start)
warning

High availability is decided at creation: the number of replicas cannot be changed afterwards. To convert an existing cluster, contact support or create a new cluster.

Steps​

1. Open the wizard​

Open DB & Messaging → Redis, then click Create a cluster. Fill in the Cluster Name and click Next.

2. Configure at least 3 replicas​

At the Configuration step:

FieldRecommended value in production
Number of replicas3 (or 5 to tolerate two failures)
PresetA size whose memory exceeds the dataset; the m1 series offers the most memory per vCPU
Volume size (GB)Greater than the expected data volume
Enable authenticationEnabled
Public networkDisabled, unless you need access from the Internet
tip

The quorum relies on the three sentinels, not on the number of replicas: 2 replicas are enough for failover, 3 or more let you tolerate more failures.

3. Create the cluster​

At the Summary step, check the Replicas line and the estimated cost, then click Create. Copy the password displayed at the Done step.

4. Understanding automatic failover​

When the master becomes unavailable:

  1. The Sentinels detect the failure and agree by quorum.
  2. A replica is promoted to new master.
  3. The other replicas are reconfigured to follow it.

With the public network enabled, the address displayed in the Host field points to the current master: your clients do not have to change address after a failover, but open connections are dropped and must be re-established.

note

Configure your Redis clients with automatic reconnection and retry delays to absorb the switchover.

Verification​

  • On the cluster page, General section, the Replicas field shows the chosen number.
  • The Connection section shows the Status Ready.
  • From a client, check the role of the node you reached:
redis-cli -h <host> -p 6379 INFO replication

Expected result: role:master and connected_slaves equal to the number of replicas minus one.

Further reading​