ISSUE-424: Docker Image Healthchecks

[sijie]

Original Issue: apache#424

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We deploy Pulsar Manager as a Docker container in ECS. To avoid having to use the DNS of the specific instance it's running on to access the front end (port 9527) and back end (port 7750), I'm trying to put an ALB in front of it. ALB has two listeners, each of which has a target group defined, but the ALB target group requires a health check path.

Manager backend (7750) has the standard Spring health check exposed at /actuator/health. I can call this from the host, but it fails when run inside the container by the target group/ECS - I suspect because the image doesn't have curl installed/available.

The frontend (9527) doesn't appear to have any health check endpoint at all? I could probably get away with just using \ as the "health check" path, but again I believe the lack of curl in the image means this doesn't work. I've never really considered that every other Docker image we've deployed in this manner has curl installed, they appear to.

So, my request is

• please add an explicit health check endpoint for the front-end app
• please add details of both health check endpoints to the documentation (apologies if I've missed it, but I couldn't find anything)
• please include curl in the Docker image (I did assume I could make a custom image which extended the current one, but I equally don't seem to have access to the package manager - though that may be me doing something wrong)