[Streams] Improve processor error handling

[LucaWintergerst]

Today we don't validate or at least don't enforce the correctness of a processor. This can lead to issues when saving them.

In the latest version, the UI is showing that the processor could not be simulated, but we let the user save it regardless.

The same is also true for some other processors, such as GROK

An incorrect pattern like:
%{ASDFASDFASF:foo}

Would throw:

Failed to change state: Failed to execute Elasticsearch actions: parse_exception Root causes: parse_exception: [patterns] Invalid regex pattern found in: [%{ASDFASDFASF:foo}]. Unable to find pattern [ASDFASDFASF] in Grok's pattern dictionary. The cluster state may be inconsistent. If you experience issues, please use the resync API to restore a consistent state.

CleanShot.2025-07-24.at.10.14.25.mp4

[elasticmachine]

Pinging @elastic/obs-ux-logs-team (Team:obs-ux-logs)

[tonyghiani]

@LucaWintergerst validation is a bit tricky since the user might not have sample documents and wants to create processors anyway. We are not restricting this behavior, but it's more difficult to validate client-side if a processor is in a full compatible state. The server-side error notified with the toast gives back what would happen if the config is invalid, is this about finding a better way to provide feedback in case of misconfigured processors?

[LucaWintergerst]

ok, I see, that makes a lot of sense that preventing a user from saving would actually be pretty bad.

@tonyghiani When this was reported, we didn't have the outcome per processor yet, so it was much easier to miss this.

Now it's much better with the red X, but I think still not ideal.

Thinking out loud here, maybe instead we need to find an even better way to bubble up the true failures to the user. Right now the processor gets the red X, but the exception is still hidden below the scroll.

[tonyghiani]

Agree, would be great to have another round of design review on the processor panels since they can easily get very crowded.
cc @patpscal @boriskirov