Is it possible to restart a process in Google Cloud run

Question

We have multiple Google Cloud Run services running for an API. There is one parent service and multiple child services. When the parent service starts it loads a schema from all the children.

Currently there isn't a way to tell the parent process to reload the schema so when a new child is deployed the parent service needs to be restarted to reload the schema.

We understand there there are 1 or more instances of Google Cloud Run running and have ideas on dealing with this, but are wondering if there is a way to restart the parent process at all. Without a way to achieve it, one or more is irrelevant for now. The only way found it by deploying the parent which seems like overkill.

The containers running in google cloud are Alpine Linux with Nodejs, running an express application/middleware. I can stop the node application running but not restart it. If I stop the service Google Cloud Run may still continue to serve traffic to that instances causing errors.

Perhaps I can stop the express service so Google Cloud run will replace that instance? Is this a possibility? Is there a graceful way to do it so it tries to complete and current requests first (not simply kill express)?

Looking for any approaches to force Google Cloud Run to restart or start new instances. Thoughts?

Answer 1

If it's a Flask app, you can use bellow code,

os._exit(0)

To exit the application, the cloud run will restart your service.

Answer 2

Your design seems, at high level, be a cache system: The parent service get the data from the child service and cache the data.

Therefore, you have all the difficulties of cache management, especially cache invalidation. There is no easy solution for that, but my recommendation will be to use memorystore where all child service publish the latest version number of their schema (at container startup for example). Then, the parent service checks (at each requests, for example) the status in memory store (single digit ms latency) if a new version is available of not. If a new, request the child service, and update the parent service schema cache.

If applicable, you can also set a TTL on your cache and reload it every minute for example.

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EDIT 1

If I focus only on Cloud Run, you can in only one condition, restart your container without deploying a new version: set the max-instance param to 1, and implement an exit endpoint (simply do os.exit() or similar in your code)

Ok, you loose all the scale up capacity, but it's the only case where, with a special exit endpoint, you can exit the container and force Cloud Run to reload it at the next request.

If you have more than 1 instance, you won't be able to restart all the running instances but only this one which handle the "exit" request.

Therefore, the only one solution is to deploy a new revision (simply deploy, without code/config change)