fix e2e producer

[bachmanity1]

I've noticed that when working with clusters having several controller and broker nodes, retrieving cluster metadata may occasionally return stale data. This issue is evident when, for example, an end-to-end test topic is created, and the topic metadata is retrieved immediately afterward. In this case, the metadata request may return error code 3, which corresponds to the UNKNOWN_TOPIC_OR_PARTITION error. This error likely occurs when a client connects to a broker that is not yet aware of the new topic because it hasn't consumed the latest data from the __cluster_metadata topic.

In summary, when the end-to-end code attempts to populate the value of s.partitionCount, it might encounter the UNKNOWN_TOPIC_OR_PARTITION error, even if the topic actually exists. This results in a partition count of zero, preventing the producer from sending any data.

[bachmanity1]

even if the err above is nil the topicMetadata.Topics[0].ErrorCode is not guaranteed to be zero.

[bachmanity1]

Hi @weeco. Can you please have a look?

[weeco]

@bachmanity1 I'll try to look at your PR soon, but I'm currently very busy with other things that have higher priority. Even though this change is just a few lines, I'll have to dig deeper to see if this could cause other sort of issues before approving & merging the PR.

[bachmanity1]

Hi @weeco,

I wanted to let you know that I've updated this PR. I've realized that my previous approach didn't account for scenarios where the broker count is updated.

I also wanted to discuss the partitionsPerBroker config. I believe it should be clarified that this configuration is only applied when a topic is created and does not take effect when the broker count changes. If the original intent was for this setting to apply even when the broker count changes, we’d need to adjust the topic reconciliation logic accordingly. However, I think that handling cases where the broker count decreases could be quite tricky.

By the way, it seems there’s a bug preventing new partitions from being created when new brokers are added, as reported in #257. Could you take a look at that PR too? Thanks!