Description
- When saving or exporting certain Katalyst experiments, users experience:
- Very long export times, followed by a stack trace in the UI.
- Experiments remaining locked in export_start state.
- The error stack trace includes a 502 Proxy Error similar to:
- com.google.gwt.user.client.rpc.StatusCodeException: 502
- <title>502 Proxy Error</title>
Reason: Error reading from remote server
- Multiple experiments may be affected (e.g., several KAT IDs).
Solution
- Identify the layer producing the 502:
- Typically, a reverse proxy or load balancer in front of Katalyst.
- Check its logs around the time exports occur.
- Likely root causes:
- Long‑running export operations combined with insufficient proxy timeout settings.
- Backend performance issues causing slow responses from the Katalyst application server.
- Remediation steps:
- Proxy configuration
- Increase request and backend timeouts so that longer exports do not result in 502 errors.
- Confirm that the proxy correctly routes long‑running requests to the Katalyst server.
- Katalyst/export performance
- Review Katalyst server logs and metrics during export.
- Identify if particular export types or very large experiments consistently cause timeouts.
- Optimize database queries, indexing, or export logic where necessary (with Technical Support help).
- Unlocking affected experiments
- Use admin tools or scripts to transition experiments out of the export_start state to a usable state (following internal procedures).
- Proxy configuration
- After adjustments, test:
- Export of problematic experiments in a controlled environment.
- Monitor for stability and absence of new 502 errors.
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