I am using 8888 for liveness & readiness probes, 8887 for normal HTTP requests, readiness probe is failing and pods are in 0/1, not ready state. ButI still see normal POST requests being served by the pod. Is this expected. should health probes and normal requests be received on the same port?
0
votes
Are you saying port 8887 works? Why is your readiness probe not pointing to 8887? Is anything serving on 8888?
– Serge
it's depends on your application you can run both HTTP request and health checks on same port. sorry here not getting your question ideally it should not have to work since pod is not ready to take request how you are able to get response back ?
– Harsh Manvar
My question is that "Is it mandatory to put the HTTP requests and health probes to be on same port.... so that when readiness fails, the normal HTTP reauests wont be served?"
– sushma kuchipudi
@HarshManvar any further conclusion?
– sushma kuchipudi
i would suggest keeping it same health check and HTTP port so that if health check fails mean HTTP also failing. still required you can use diff port also.
– Harsh Manvar
2 Answers
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Liveness and readyness probes have different purposes. In short the liveness probe controls whether Kubernetes will restart the pod. But the readyness probe controls whether a pod is included in the endpoints of a service. Unless a pod has indicated it's ready through the readyness probe, it should not receive traffic through a service. That doesn't mean it can't be sent requests, it just means it won't be sent traffic through the service. So in your case the question is, where are those POST requests coming from.
0
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@pst and @Harsh are right but I would like to expand on it a bit.
As the official docs say:
If you'd like to start sending traffic to a Pod only when a probe succeeds, specify a readiness probe. In this case, the readiness probe might be the same as the liveness probe, but the existence of the readiness probe in the spec means that the Pod will start without receiving any traffic and only start receiving traffic after the probe starts succeeding.
and:
The kubelet uses readiness probes to know when a container is ready to start accepting traffic. A Pod is considered ready when all of its containers are ready. One use of this signal is to control which Pods are used as backends for Services. When a Pod is not ready, it is removed from Service load balancers.
Answering your question:
So if readiness probe fails, should i still expect traffic on 8887?
No, the pod should not start receiving traffic if the readiness probe fails.
It can also depend on your app. By using a readiness probe, Kubernetes waits until the app is fully started before it allows the service to send traffic to the new copy.
Also, it is very important to make sure your probes are configured properly:
Probes have a number of fields that you can use to more precisely control the behavior of liveness and readiness checks:
initialDelaySeconds: Number of seconds after the container has started before liveness or readiness probes are initiated. Defaults to 0 seconds. Minimum value is 0.
periodSeconds: How often (in seconds) to perform the probe. Default to 10 seconds. Minimum value is 1.
timeoutSeconds: Number of seconds after which the probe times out. Defaults to 1 second. Minimum value is 1.
successThreshold: Minimum consecutive successes for the probe to be considered successful after having failed. Defaults to 1. Must be 1 for liveness. Minimum value is 1.
failureThreshold: When a probe fails, Kubernetes will try failureThreshold times before giving up. Giving up in case of liveness probe means restarting the container. In case of readiness probe the Pod will be marked Unready. Defaults to 3. Minimum value is 1.
If you wish to expand your knowledge regarding the liveness, readiness and startup probes please refer to the official docs. You will wind some examples there that can be compared with your setup in order to see if you understand and configured it right.
