Debugging Production Issues

Quick Diagnosis Flow

•Identify symptoms - What's failing?
•Check resource health - Is Azure healthy?
•Review logs - What do logs show?
•Analyze metrics - Performance patterns?
•Investigate recent changes - What changed?

Container Apps Troubleshooting

Common Issues Matrix

Symptom	Likely Cause	Quick Fix
Image pull failure	ACR credentials missing	`az containerapp registry set --identity system`
ACR build fails	ACR Tasks disabled (free sub)	Build locally with Docker
Cold start timeout	min-replicas=0	`az containerapp update --min-replicas 1`
Port mismatch	Wrong target port	Check Dockerfile EXPOSE matches ingress
App keeps restarting	Health probe failing	Verify `/health` endpoint

Image Pull Failures

Diagnose:

bash

# Check registry configuration
az containerapp show --name APP -g RG --query "properties.configuration.registries"

# Check revision status
az containerapp revision list --name APP -g RG --output table

Fix:

bash

az containerapp registry set \
  --name APP -g RG \
  --server ACR.azurecr.io \
  --identity system

ACR Tasks Disabled (Free Subscriptions)

Symptom: az acr build fails with "ACR Tasks is not supported"

Fix: Build locally instead:

bash

docker build -t ACR.azurecr.io/myapp:v1 .
az acr login --name ACR
docker push ACR.azurecr.io/myapp:v1

Cold Start Issues

Symptom: First request very slow or times out

Fix:

bash

az containerapp update --name APP -g RG --min-replicas 1

Health Probe Failures

Symptom: Container keeps restarting

Check:

bash

# View health probe config
az containerapp show --name APP -g RG --query "properties.configuration.ingress"

# Check if /health endpoint responds
curl https://APP.REGION.azurecontainerapps.io/health

Fix: Ensure app has health endpoint returning 200:

javascript

app.get('/health', (req, res) => res.sendStatus(200));

Port Mismatch

Symptom: App starts but returns 502/503

Check:

bash

az containerapp show --name APP -g RG --query "properties.configuration.ingress.targetPort"

Verify: App must listen on this exact port. Check:

•Dockerfile EXPOSE statement
•process.env.PORT or hardcoded port in app

View Logs

bash

# Stream logs (wait for replicas if scale-to-zero)
az containerapp logs show --name APP -g RG --follow

# Recent logs
az containerapp logs show --name APP -g RG --tail 100

# System logs (startup issues)
az containerapp logs show --name APP -g RG --type system

Get All Diagnostic Info

bash

# Combined diagnostic command
echo "=== Container App Diagnostics ===" && \
echo "Revisions:" && az containerapp revision list --name APP -g RG -o table && \
echo "Registry Config:" && az containerapp show --name APP -g RG --query "properties.configuration.registries" && \
echo "Ingress Config:" && az containerapp show --name APP -g RG --query "properties.configuration.ingress" && \
echo "Recent Logs:" && az containerapp logs show --name APP -g RG --tail 20

Check Azure Resource Health

Using MCP

code

Use azure_resourcehealth_* tools to check resource availability status.

Using CLI

bash

# Check specific resource health
az resource show --ids RESOURCE_ID

# Check recent activity
az monitor activity-log list -g RG --max-events 20

Application Logs

App Service

bash

az webapp log tail --name APP -g RG

Functions

bash

func azure functionapp logstream FUNCTIONAPP

Log Analytics (KQL)

Common diagnostic queries:

kql

// Recent errors
AppExceptions
| where TimeGenerated > ago(1h)
| project TimeGenerated, Message, StackTrace
| order by TimeGenerated desc

// Failed requests
AppRequests
| where Success == false
| where TimeGenerated > ago(1h)
| summarize count() by Name, ResultCode
| order by count_ desc

// Slow requests
AppRequests
| where TimeGenerated > ago(1h)
| where DurationMs > 5000
| project TimeGenerated, Name, DurationMs
| order by DurationMs desc

// Dependency failures
AppDependencies
| where Success == false
| where TimeGenerated > ago(1h)
| summarize count() by Name, ResultCode, Target

Common Issues by Service

App Service

Symptom	Check
503 Service Unavailable	App logs, memory/CPU usage
Slow cold start	Always On setting, app startup
Deployment failures	Deployment logs, slot swap

Azure Functions

Symptom	Check
Not triggering	Trigger configuration, host.json
Timeout errors	Execution time, plan limits
Cold starts	Premium plan, package size

Database Issues

Symptom	Check
Connection failures	Firewall rules, connection limits
Slow queries	Query Performance Insights
Throttling	DTU/RU usage, tier limits

Using AppLens (MCP)

For comprehensive AI-powered diagnostics:

code

Use azure_applens tools to get:
- Automated issue detection
- Root cause analysis
- Remediation recommendations

Escalation Checklist

Before escalating:

• Checked resource health status
• Reviewed application logs
• Analyzed recent deployments
• Checked for Azure service issues (status.azure.com)
• Reviewed metric dashboards
• Attempted basic remediation