redis

Example: Redis Migration

This example demonstrates the migration of a Redis instance across different hosts. We will use three hosts and several containers to illustrate this process.

Setup

Host 1

• Containers:
  1. redis-app: Exposes the value of the key counter via an HTTP GET endpoint.
  2. redis-producer: Fetches the value of the key counter from a Redis instance (accessed via a load balancer), increments it by 1, and updates the key counter in the Redis instance every second.
  3. redis-client: Simulates a frontend client that fetches data (the counter) from the backend (redis-app) every second.

Host 2

• Container:
  1. redis-instance: Runs the initial Redis instance.

Host 3

• Host 3 initially has no containers running. We will migrate the Redis instance from Host 2 to Host 3.

Running the example

To build the topology, start containers and run the controller, run:

make

To start the redis-client, run:

make client

You should see the counter value being fetched every second.

To migrate the container from the source host to the target host, and update the switch accordingly, run:

make migrate SOURCE=2 TARGET=3

You should see no change in the counter value being fetched every second. However, the Redis instance is now running on Host 3. You can verify this by running:

sudo podman ps

and

sudo podman logs -f h2 # Nothing should be printed
sudo podman logs -f h3 # You should see the Redis logs

To cleanup the topology, networks, pods, and containers, run:

make clean

To show logs of the switch, run:

sudo podman logs -f s1