feat: add redis liveness probe

[victorgarcia98]

Description

Check the health of redis instance and expose it trough the API endpoint /health/ready

Look & Feel

Request

[GET] http://localhost:5000/api/v3_0/health/ready

Response

{
	"database_redis": false,
	"database_sql": true,
	"status": 503
}

Testing Steps

1. Configure credentials

echo 'FLEXMEASURES_REDIS_PASSWORD="MyPassWord"' >> ~/.flexmeasures.cfg 

2. Run FM Server

flexmeasures run

3. Get and check status

curl localhost:5000/api/v3_0/health/ready

⚙️ Check the response (status=503 and database_redis=false)

{
  "database_redis": false,
  "database_sql": true,
  "status": 503
}

4. Create Redis instance with Docker

sudo docker run --name my-redis -p 6379:6379 -d redis --requirepass "MyPassWord"

5. Get and check status

curl localhost:5000/api/v3_0/health/ready

⚙️ Check the response (status=200 and database_redis=true)

{
  "database_redis": true,
  "database_sql": true,
  "status": 200
}

Clean up

sudo docker stop my-redis && sudo docker rm my-redis

---

Closes #663

[nhoening]

Looks cool!

I tried on our docker compose stack, but the server node is not connecting to redis (only the worker needs it):

± sudo docker ps
CONTAINER ID   IMAGE                 COMMAND                  CREATED         STATUS                     PORTS                                       NAMES
2c366a9a86bc   flexmeasures-server   "/bin/sh -c 'pip ins…"   2 minutes ago   Up 2 minutes (unhealthy)   0.0.0.0:5000->5000/tcp, :::5000->5000/tcp   flexmeasures-server-1
2d385cb8dcd7   flexmeasures-worker   "flexmeasures jobs r…"   2 minutes ago   Up 2 minutes               5000/tcp                                    flexmeasures-worker-1
fb7bfc9c9023   postgres              "docker-entrypoint.s…"   2 minutes ago   Up 2 minutes               5432/tcp                                    flexmeasures-test-db-1
165d2616189d   postgres              "docker-entrypoint.s…"   2 minutes ago   Up 2 minutes               5432/tcp                                    flexmeasures-dev-db-1
feb39978747b   redis                 "docker-entrypoint.s…"   2 minutes ago   Up 2 minutes               6379/tcp                                    flexmeasures-queue-db-1

I don't have the answer right here, but "health" isn't an atomic concept, I'm afraid.

Maybe we should be able to tell the endpoint what we define as health with some GET variables, e.g. http://localhost:5000/api/v3_0/health/ready?expect_redis=no

[victorgarcia98]

Maybe we should be able to tell the endpoint what we define as health with some GET variables, e.g. http://localhost:5000/api/v3_0/health/ready?expect_redis=no

Good idea! Following Issue #663, we could also check if FLEXMEASURES_REDIS_PASSWORD is an empty string, although I like the idea of passing the parameter because we could have a worker and a server working under the same environment.

[nhoening]

For now, checking FLEXMEASURES_REDIS_PASSWORD seems to be the easiest solution. If the environment has a value here, we should be able to find it.

Unless these nodes operate in different access contexts (e.g. in Kubernetes). Of course, that is rather rare probably, and can be solved by not only using one environment configuration for all nodes. (giving a FM instance access to a credential it shall not be using is not a good security approach, either :)

So I'd argue to go ahead with the simple check.
What do you think?

[victorgarcia98]

Unless these nodes operate in different access contexts (e.g. in Kubernetes). Of course, that is rather rare probably, and can be solved by not only using one environment configuration for all nodes. (giving a FM instance access to a credential it shall not be using is not a good security approach, either :)

That's true, we shouldn't have extra env variables if we don't need them.

[nhoening]

@victorgarcia98 Can you add a changelog entry? And then let's merge this PR!

[Flix6x]

Leftover statement, or starting a list of new endpoints?