Learning term
HTTP 502 — Incident analysis and recovery
HTTP 502 means a gateway did not receive a valid response from its upstream. This card shows its role in “Incident analysis and recovery” and a safe diagnostic path.
Orientation
HTTP 502 means a gateway did not receive a valid response from its upstream. At this level, separate purpose, input, and visible result. Place HTTP 502 within Incident analysis and recovery before changing settings or files.
Practical use
A previously reachable service fails after a change. For HTTP 502, preserve the timeline, task history, exit code, latest logs, and resource state; then test the smallest justified correction and confirm recovery with the same request. Start in a sandbox with neutral examples. Record the expected state, make one controlled change, and compare status output, application behavior, and logs.
Technical understanding
HTTP 502 means a gateway did not receive a valid response from its upstream. Technically, HTTP 502 connects through interfaces, configuration, state, or dependencies. Trace data from input to output and check versions, permissions, networking, storage, and resources separately.
Operations and debugging
A previously reachable service fails after a change. For HTTP 502, preserve the timeline, task history, exit code, latest logs, and resource state; then test the smallest justified correction and confirm recovery with the same request. In production-like operations, use measurable signals, least privilege, reproducible configuration, and a documented rollback. Preserve evidence, isolate the cause, and verify the correction with the same test.
Exercise
Try it safely
A previously reachable service fails after a change. For HTTP 502, preserve the timeline, task history, exit code, latest logs, and resource state; then test the smallest justified correction and confirm recovery with the same request. Open an isolated test environment and run “docker service ps example-service --no-trunc”. Write down the expected output first, do not alter production data, and record one safe next diagnostic step.
docker service ps example-service --no-truncQuick check
Can you explain the purpose, observable state, and most common failure source of HTTP 502 — Incident analysis and recovery in one sentence each? Which evidence would you preserve before changing anything, and which repeated test would prove that the correction actually worked?