Monitoring CPU alert specific path failure response

When this happens

Use this when only one page, endpoint, static asset, or api route fails. Do not stop at the screen message; validate the route, rewrite rule, API path, host header, and upstream mapping first.

Symptom checklist

• CPU alert appears repeatedly in the Monitoring UI or logs.
• metrics, log spikes, traces, SLO, synthetic checks differs between successful and failed requests.
• The issue appears only after separating alert noise from real incident signal.
• It often follows deploys, permission changes, configuration edits, or data refreshes.

Likely causes

• CPU alert specifically changes the investigation surface for Monitoring: verify the exact failing object, route, user, and timestamp before applying the broader pattern.
• The process exceeds memory or heap limits under real data size.
• Disk space, inode count, or mounted volume state fails before byte usage looks obvious.
• File descriptors leak across repeated requests.
• Logs, cache, or build artifacts grow without retention.
• A workload runs synchronously instead of being chunked.
• For the specific path failure case, the first useful clue is the route, rewrite rule, API path, host header, and upstream mapping.

First 1-minute checks

1. Write down the first failure time, latest change, affected user, path, and object ID.
2. Compare metrics, log spikes, traces, SLO, synthetic checks for success and failure in the same window.
3. Test the hypothesis: resource exhaustion caused by memory pressure, disk or inode shortage, descriptor limits, cache growth, volume state, or oversized workload.
4. Classify this as specific path failure: the route, rewrite rule, API path, host header, and upstream mapping.
5. Capture current values before changing configuration.

First evidence

Treat CPU alert as a specific path failure case. First collect evidence for the route, rewrite rule, API path, host header, and upstream mapping.

Output examples

Normal output

Working and failing paths use the intended host, status, and upstream.

Failing output

Only one route changes status, redirect target, content type, or upstream.

Output-to-action branches

• Only one page, endpoint, static asset, or API route fails.
  Compare a working path and failing path, then fix routing, rewrite, upload limit, or upstream mapping.
• The working and failing outputs differ.
  Act on the differing layer first: For CPU alert, apply the fix only after reproducing the same condition and saving the before/after evidence for this exact code.
• Command output is normal but users still fail.
  Separate browser cache, cookies, permissions, and network location before declaring it fixed.

Do not do this

• Do not clear every cache before proving the route mapping.
• Do not change multiple layers before identifying the failing layer.
• Do not delete production data, grant broad permissions, or disable security controls as a first response.

Evidence quality

Auto-generated operator draft: includes issue-specific causes, commands, output branches, and unsafe-action warnings. Official-source links and real incident validation are queued for enrichment.

Commands to run first

grep -R "CPU alert" ./logs

curl -s https://status.example.com

grep -R "CPU alert" ./logs | tail

promtool query instant http_requests_total

date -u

df -h && df -i

ulimit -n

ps aux --sort=-%mem | head

du -sh ./* | sort -h | tail

curl -I https://example.com/failing-path && curl -I https://example.com/working-path

Fix order

1. Record the full CPU alert message, failing URL, user, object ID, and latest change.
2. Collect issue-specific evidence for resource exhaustion caused by memory pressure, disk or inode shortage, descriptor limits, cache growth, volume state, or oversized workload.
3. Compare the failing case with a successful case before editing settings.
4. If this is the specific path failure branch, Compare a working path and failing path, then fix routing, rewrite, upload limit, or upstream mapping.
5. Re-check with the same command and URL, then record the normal output.

Actions by cause

• For CPU alert, apply the fix only after reproducing the same condition and saving the before/after evidence for this exact code.
• Measure memory, disk, inode, descriptor, and mounted volume state at failure time.
• Clean generated artifacts and add retention policies.
• Raise limits only after removing leaks or oversized batches.
• Chunk large jobs and stream outputs where possible.
• Add alerts before hard exhaustion.
• For the specific path failure branch, Compare a working path and failing path, then fix routing, rewrite, upload limit, or upstream mapping.

Evidence links

• Prometheus alerting rules official
• Grafana alerting official

Verification metadata

• operator-draft
• official-reference-linked
• 2026-07-23

Update queue

• Review cadence
  weekly-source-review
• Next enrichment
  Add one official-source check and one real output example for Monitoring CPU alert.

Environment-specific checks

• Shared hosting, proxies, VPNs, or CDN layers can change alert noise from real incident signal results.
• Do not trust only the Monitoring UI; compare command output.
• Japanese hosting panels may show completion before DNS or SSL fully propagates.
• Test from both office and external networks.

Prevent it next time

• Store normal examples for metrics, log spikes, traces, SLO, synthetic checks.
• Add alert thresholds, burn rate, trace sampling, runbook to the release checklist.
• Keep recurring errors in the same note format.
• Split alerts by error rate, latency, certificates, disk, and permission changes.

Related notes

• Monitoring High latency fix note
• Monitoring High latency fix note 2
• Monitoring High latency fix note 3
• Monitoring High latency fix note 4
• Monitoring High latency fix note 5
• Monitoring High latency fix note 6
• Monitoring high latency first triage response
• Monitoring error budget first triage response