[GitHub] [kafka] C0urante commented on pull request #10530: KAFKA-10231 fail bootstrap of Rest server if the host name in the adv…

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C0urante commented on pull request #10530:
URL: https://github.com/apache/kafka/pull/10530#issuecomment-824847306


   I've just realized--this may not be a safe change to make. Although we should fail fast on startup if a worker tries to join an existing cluster with a bad hostname, it's still possible right now to run a single worker in that scenario. Although running a single worker in distributed mode may sound like an anti-pattern, there are still benefits to such a setup, such as persistent storage of configurations in a Kafka topic. It's also possible that there are Dockerized quickstarts and demos that use a single Connect worker and may have a bad hostname; these would suddenly break on upgrade if we merge this change.
   
   At the very least, I think we should be more explicit about _why_ we're failing workers on startup with our error message, try to give users a better picture of how workers with a bad hostname can be dangerous (since right now they don't fail on startup but instead begin to fail silently when forwarding user requests or task configs to the leader), and even call out Dockerized setups with instructions on how to fix the worker config in that case by changing the advertised URL to use a valid hostname and, if running a multi-node cluster, making sure that the worker is reachable from other workers with that advertised URL.
   
   But I think at this point we're doing a fair bit of work to try to circumvent this issue instead of addressing it head-on. Using a different HTTP client has already been discussed as an option but punted on in favor of a smaller, simpler change; given that this change seems less simple now, I wonder if it's worth reconsidering.


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