tree eb05a887290ebc288a24cf4e1ff76dde44d37c86
parent 4eb88f21fde3de089e314ff94f6d39c292f1e84f
author Marcin Czech <maczech@gmail.com> 1642639790 +0100
committer Marcin Czech <maczech@gmail.com> 1643055980 +0000

Use Kafka REST Proxy id to subscribe to the correct instance

When using a Kafka REST Proxy with multiple instances behind a
workload balancer, the consumers are allocated on one of the
allocated instances. The Kafka REST client needs to understand
which one is the instance that the client should talk to.

For deployments that can use workload balancers with sticky
sessions, there isn't any logic needed on the client side, because
the cookies allocated and stored on the client would do the job.
However, when using a standard K8s deployment[1], the sticky
session allocation isn't an option and any of the incoming
traffic may reach any of the pods.

Kafka REST Proxy allows with this change to specify the REST_PROXY_ID
with the placeholder ${rest_proxy_id} in the API URL, to help
redirecting the calls to the correct instance.

Example:
[plugin "events-kafka"]
  restApiUri = http://kafka-rest:8080/${kafka_rest_id}

[1] https://kubernetes.io/docs/concepts/workloads/controllers/deployment/

Change-Id: I396c3bc759ee05547e8c16cb4806b4fea63b833c