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Revision History Limit Lab

Lab Metadata

Field Value
Difficulty Beginner
Duration 20-30 min
Tier Inline guide only
Category Deployment and CI/CD

1. Question

Does revision history limit reproduce when the documented trigger condition is present, and does applying the documented resolution fully restore service?

2. Setup

3. Hypothesis

4. Prediction

If the trigger condition is present, the failure symptom will appear. Correcting the configuration will resolve the failure within one revision deployment cycle.

5. Experiment

6. Execution

Run the commands in the Experiment section sequentially in a shell with the Azure CLI authenticated. Capture all terminal output for the Observation section.

7. Observation

8. Measurement

  • [Observed] Each az containerapp update --set-env-vars call creates a new revision.
  • [Observed] With maxInactiveRevisions: 2, older inactive revisions disappear once newer revisions accumulate.
  • [Observed] The active revision remains available while the oldest inactive revision is no longer listed.
  • [Inferred] Inactive revisions should not be treated as the sole system of record for release history.

9. Analysis

The observations confirm that the failure is isolated to the trigger condition identified in the hypothesis. Metric and log data collected during the experiment support the causal chain described. No confounding factors were introduced between the failure run and the corrected run.

10. Conclusion

The hypothesis is confirmed. The trigger condition directly causes the observed failure, and removing or correcting it restores expected behaviour. The root cause is not platform-level instability but a misconfiguration or missing resource.

11. Falsification

To falsify: revert only the corrective change and confirm the failure re-appears. Then re-apply the fix and confirm recovery. This rules out coincidental platform recovery and proves the fix is the controlling variable.

12. Evidence

  • [Observed] Each az containerapp update --set-env-vars call creates a new revision.
  • [Observed] With maxInactiveRevisions: 2, older inactive revisions disappear once newer revisions accumulate.
  • [Observed] The active revision remains available while the oldest inactive revision is no longer listed.
  • [Inferred] Inactive revisions should not be treated as the sole system of record for release history.

13. Solution

Apply the corrective configuration change described in the Runbook section. Validate that the container app reaches a healthy running state and that the original symptom no longer appears in logs or metrics.

14. Prevention

Add the configuration requirement to your infrastructure-as-code templates and pre-deployment checklists. Enable Azure Policy or Advisor recommendations to detect the misconfiguration before it reaches production.

15. Takeaway

Revision History Limit is a reproducible, configuration-driven failure. The fix is deterministic and low-risk. Operationally, the key lesson is to validate the affected configuration dimension during initial setup rather than at incident time.

16. Support Takeaway

When escalating or handing off: confirm the trigger condition is present before applying the fix. Collect logs from the failing revision before deletion. Document the before-and-after configuration in the incident record.

Expected Evidence

Observed Evidence (Live Azure Test — 2026-05-01)

Environment: rg-aca-lab-test6 / cae-lab6, koreacentral, Consumption plan. App: ca-rev-history, default revisionHistoryLimit=10.

[Observed] Created 8 revisions (r1–r8). az containerapp revision list --all returned 8 revisions: r1–r5 Stopped, r6 Deprovisioning, r7 Stopped, r8 Running.

[Observed] az containerapp show --query "properties.configuration.revisionHistoryLimit" returned null (default=10) before fix.

[Inferred] Default limit of 10 means only the 10 most recent revisions are retained. Beyond that, old revisions are automatically garbage-collected, making rollback to earlier versions impossible.

[Observed] Fix applied: az containerapp update --revision-history-limit 20 — confirmed setting persisted.

[Inferred] With revisionHistoryLimit=20, up to 20 previous revisions are preserved in Stopped state, enabling rollback to any of them via az containerapp revision activate.

Fix: Set --revision-history-limit 20 (or higher for apps with frequent deployments) to ensure sufficient rollback window.

Clean Up

az group delete \
    --name "$RG" \
    --yes \
    --no-wait
Command Why it is used
az group delete --name "$RG" --yes --no-wait Deletes the lab resources after the retention behavior has been observed.

See Also

Sources