Scheduled Job Missed Lab¶

Reproduce a missed scheduled execution by using the wrong timezone assumption, then validate the fix by correcting the UTC schedule.

Lab Metadata¶

flowchart TD
    A[Author local-time cron assumption] --> B[Deploy scheduled job]
    B --> C[Wait for expected local-time window]
    C --> D[Observe no execution]
    D --> E[Check configured UTC schedule]
    E --> F[Manually start job]
    F --> G[Correct cron to UTC]
    G --> H[Observe next expected execution]

1. Question¶

Does scheduled job missed reproduce when the documented trigger condition is present, and does applying the documented resolution fully restore service?

2. Setup¶

Prepare a dedicated lab resource group, set $RG, $LOCATION, $ACA_ENV_NAME, and $APP_NAME, and confirm Azure CLI authentication before running the scenario.

3. Hypothesis¶

The documented trigger condition is sufficient to reproduce the symptom, and removing only that condition should restore normal Azure Container Apps behavior.

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¶

Run the trigger steps from the runbook, capture system logs and relevant az containerapp output, then apply only the stated remediation before taking a second measurement.

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¶

Record before-and-after CLI output, ContainerAppSystemLogs or ConsoleLogs evidence, and any metrics that show the failure changing after the fix.

8. Measurement¶

• A before-and-after record of the cron expression.
• Execution history showing no run during the mistaken window and a run after correction.
• Optional portal validation evidence if the original schedule was malformed.

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¶

• A before-and-after record of the cron expression.
• Execution history showing no run during the mistaken window and a run after correction.
• Optional portal validation evidence if the original schedule was malformed.

Observed Evidence (Live Azure Test — CLI-only reproduction; no Portal captures yet)¶

# Baseline: * * * * * — executions run every minute
az containerapp job execution list --name job-cron-lab5 --resource-group rg-aca-lab-test5 \
  --query "[].{status:properties.status, start:properties.startTime}"
→ Status=Failed  StartTime=2026-05-01T03:50:00+00:00
→ Status=Failed  StartTime=2026-05-01T03:49:00+00:00

# Execution count before impossible schedule: 2

# Trigger: switch to 0 0 31 2 * (Feb 31 — impossible date)
az containerapp job update --name job-cron-lab5 --resource-group rg-aca-lab-test5 \
  --cron-expression "0 0 31 2 *"

# Wait 3 minutes
Execution count after 3 min: 2   ← unchanged
New executions during impossible schedule: 0

# Fix: restore * * * * *
az containerapp job update --name job-cron-lab5 --resource-group rg-aca-lab-test5 \
  --cron-expression "* * * * *"

# 75 seconds later
Execution count: 3   ← 1 new execution

• [Observed] * * * * *: executions fire every minute (confirmed from job execution list).
• [Measured] 0 0 31 2 * (Feb 31): 0 new executions in 3 minutes (count: 2 → 2). No error or alert surfaced.
• [Observed] After restoring * * * * *: new execution within 75 seconds.
• [Inferred] An impossible cron date silently suppresses job execution — the platform accepts the expression without error, but the schedule never fires.

Environment: koreacentral, rg-aca-lab-test5, cae-lab5.

13. Solution¶

Apply the remediation in the Runbook section for this lab, then verify the corrected Container Apps resource reaches a healthy state and 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¶

Scheduled Job Missed 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.

Clean Up¶

• Keep the corrected UTC schedule if the job is real.
• If this was a disposable lab job, remove it through your normal IaC or platform teardown process.

Related Playbook¶

• Scheduled Job Missed

See Also¶

• Event Job Storm Lab
• Container App Job Execution Failure

Sources¶

• Azure Container Apps jobs
• Create a job with the Azure CLI