Delegate RunLogsService.TailLogs to DataProxyService to remove duplicate implementation #7252

[Carina-TzuHsuan]

Remove the duplicate K8sLogStreamer from the runs service and replace it
with a thin forwarding shim that calls DataProxyService.TailLogs. The
/RunLogsService/TailLogs endpoint is kept registered for backward
compatibility — clients see no change.

Tracking issue

Closes #7252

Why are the changes needed?

RunLogsService and DataProxyService both maintained their own
K8sLogStreamer with nearly identical logic for streaming pod logs.
This duplicated maintenance burden — any fix to log streaming had to be
applied in two places.

What changes were proposed in this pull request?

• runs/service/run_logs_service.go: Replaced the repo + K8sLogStreamer implementation with a DataProxyServiceClient field.
  TailLogs now validates the request, acquires a semaphore slot, then
  forwards to DataProxyService.TailLogs and relays responses back to
  the caller.
• runs/service/k8s_log_streamer.go: Deleted (duplicate removed).
• runs/config/config.go: Added DataProxyServiceURL config field
  (default: http://localhost:8088).
• runs/setup.go: Replaced K8s streamer wiring with a
  DataProxyServiceClient injection. RunLogsService is now always
  mounted unconditionally (K8s access is DataProxy's concern).

Net result: −531 lines.

How was this patch tested?

Rewrote run_logs_service_test.go with five test cases using a real
httptest.Server backed by a fakeDataProxyHandler:

• TestTailLogs_HappyPath — response lines forwarded correctly from DataProxy to caller
• TestTailLogs_MissingActionID — returns CodeInvalidArgument
• TestTailLogs_DataProxyError — DataProxy error propagated to caller
• TestTailLogs_ConcurrencyLimit — semaphore rejects at 100 concurrent streams with CodeResourceExhausted
• TestTailLogs_RequestForwardedToDataProxy — action_id and attempt forwarded unchanged

Labels

• removed: duplicate K8sLogStreamer deleted from runs service
• changed: RunLogsService now delegates to DataProxyService

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

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• main
  • Flyte 2: Cut over to Flyte 2 new backend implementation #6583
    • Delegate RunLogsService.TailLogs to DataProxyService to remove duplicate implementation Delegate RunLogsService.TailLogs to DataProxyService to remove duplicate implementation #7252 👈

[pingsutw]

thank you, lgtm, could you resolve the merge conflict

[Carina-TzuHsuan]

@pingsutw Please review it. Thank you!