Redis Integration

Redis database server can be used on Entando for cache management in high availability applications. It is a requirement for Entando Applications serving multiple tenants. This tutorial describes the steps to integrate Redis for both high availability and multitenancy.

See Entando Multitenancy for more information.

Prerequisites

• A working instance of Entando based on the default Tomcat server image

• Verify dependencies with the Entando CLI: ent check-env develop

• Helm 3 installed in your local environment

Install Redis Sentinel (opens new window)

1. Clone the project:

git clone https://github.com/entando-ps/redis-sentinel.git

Notes:

• The number of Redis replica is 3; it can be adjusted by modifying the replica.replicaCount in the values.yaml file.
• By default, the Redis Sentinel configuration does not use a password. For an external Redis installation where a password is required, you can define a value for the parameter global.redis.password in values.yaml so that Helm creates a secret for it.

2. Set your Kubernetes context to the proper namespace:

kubectl config set-context --current --namespace=YOUR-NAMESPACE

3. Run the custom script:

./install.sh

Configure the EntandoApp

1. Scale down the EntandoApp deployment to 0:

kubectl scale deploy/YOUR-APP-NAME-deployment --replicas=0 -n YOUR-NAMESPACE

2. Edit the deployment YAML and add the environment variables listed below.
   Note: For REDIS_ADDRESSES, note the Sentinel node's logs that list the domain names of the Redis cluster instances. List the master first, then the replicas as shown in this example.

spec:
  containers:
    - env:
      - name: REDIS_ACTIVE
        value: "true"
      - name: REDIS_ADDRESSES
        value: redis-node-0.redis-headless.YOUR-NAMESPACE.svc.cluster.local:26379,redis-node-1.redis-headless.YOUR-NAMESPACE.svc.cluster.local:26379,redis-node-2.redis-headless.YOUR-NAMESPACE.svc.cluster.local:26379
      - name: REDIS_SESSION_ACTIVE 
        value: "true"

3. Scale the deployment back up to 1 or more replicas:

kubectl scale deploy/YOUR-APP-NAME-deployment --replicas=1 -n YOUR-NAMESPACE

4. To check that your Redis is running as expected, shell into the redis-node-0 pod, then execute redis-cli. Run KEYS * to list all current keys present in the cache.

Additional Settings

1. Use a password for Redis
   If a password was used in your Redis values.yaml file, an additional environment variable is required in the EntandoApp deployment image.

spec:
  containers:
    - env:
      - name: REDIS_PASSWORD
        valueFrom:
          secretKeyRef:
            key: YOUR_REDIS_PASSWORD_KEY
            name: YOUR-REDIS-SECRET-NAME
            optional: false

2. Monitor Redis
   When Redis Sentinel is active, Sentinel monitoring can be utilized to trigger an automatic failover process by using an additional environment variable in the EntandoApp deployment image.

spec:
  containers:
    - env:
      - name: REDIS_USE_SENTINEL_EVENTS
        value: "true" 

If this env variable is set to true, the Sentinel failover process for electing a new master will be used when a master node becomes unreachable.

When the variable is set to false, the application doesn't subscribe to the events but uses a scheduler to periodically check the master IP to detect if the master has changed. This can be useful as a fallback method in case of a problem with events detections.