azure-app-service-monitoring

When to Apply

Reference these guidelines when:

• Setting up Application Insights for App Service
• Creating alerts for errors, performance, or availability
• Analyzing application logs and metrics
• Building monitoring dashboards
• Troubleshooting performance issues
• Configuring availability tests

Monitoring Stack

Application Insights ─── APM, traces, dependencies, exceptions
        │
Log Analytics ───────── Centralized log queries (KQL)
        │
Azure Monitor ───────── Metrics, alerts, dashboards
        │
Diagnostic Settings ─── Route logs to storage/Event Hubs

Application Insights Setup

Enable via CLI

# Create Application Insights resource
az monitor app-insights component create \
  --app <app-insights-name> \
  --location <region> \
  --resource-group <rg> \
  --application-type web

# Get connection string
az monitor app-insights component show \
  --app <app-insights-name> \
  --resource-group <rg> \
  --query connectionString -o tsv

# Configure App Service with App Insights
az webapp config appsettings set \
  --name <app> --resource-group <rg> \
  --settings APPLICATIONINSIGHTS_CONNECTION_STRING="<connection-string>" \
             ApplicationInsightsAgent_EXTENSION_VERSION="~3"

Auto-Instrumentation (Codeless)

For supported runtimes, enable without code changes:

Runtime	Extension Setting
.NET	ApplicationInsightsAgent_EXTENSION_VERSION=~3
Node.js	ApplicationInsightsAgent_EXTENSION_VERSION=~3
Java	ApplicationInsightsAgent_EXTENSION_VERSION=~3
Python	Requires SDK (no codeless support)

Key Metrics to Monitor

Platform Metrics

Metric	Description	Alert Threshold
Http5xx	Server errors	> 5 per 5 min
Http4xx	Client errors	> 100 per 5 min
ResponseTime	Average response time	> 2000ms
CpuPercentage	CPU usage	> 80% for 5 min
MemoryPercentage	Memory usage	> 80% for 5 min
HealthCheckStatus	Health check failures	< 100%

Application Insights Metrics

Metric	Description	Alert Threshold
requests/failed	Failed requests	> 1% error rate
requests/duration	Request duration	P95 > 3s
exceptions/count	Unhandled exceptions	> 10 per 5 min
dependencies/failed	Failed dependencies	> 5 per 5 min
availabilityResults/availabilityPercentage	Availability	< 99%

Alerts Configuration

Create Metric Alert

# Alert on HTTP 5xx errors
az monitor metrics alert create \
  --name "High-5xx-Errors" \
  --resource-group <rg> \
  --scopes "/subscriptions/<sub>/resourceGroups/<rg>/providers/Microsoft.Web/sites/<app>" \
  --condition "total Http5xx > 5" \
  --window-size 5m \
  --evaluation-frequency 1m \
  --action <action-group-id> \
  --severity 2

# Alert on high response time
az monitor metrics alert create \
  --name "High-Response-Time" \
  --resource-group <rg> \
  --scopes "/subscriptions/<sub>/resourceGroups/<rg>/providers/Microsoft.Web/sites/<app>" \
  --condition "avg ResponseTime > 2000" \
  --window-size 5m \
  --evaluation-frequency 1m \
  --action <action-group-id> \
  --severity 3

# Alert on high CPU
az monitor metrics alert create \
  --name "High-CPU" \
  --resource-group <rg> \
  --scopes "/subscriptions/<sub>/resourceGroups/<rg>/providers/Microsoft.Web/serverfarms/<plan>" \
  --condition "avg CpuPercentage > 80" \
  --window-size 5m \
  --evaluation-frequency 1m \
  --action <action-group-id> \
  --severity 2

Create Action Group

az monitor action-group create \
  --name "AppServiceAlerts" \
  --resource-group <rg> \
  --short-name "AppSvcAlert" \
  --email-receiver name="Team" email="team@example.com" \
  --webhook-receiver name="Slack" uri="https://hooks.slack.com/..."

Log Analytics Queries (KQL)

Enable Diagnostic Settings

# Send App Service logs to Log Analytics
az monitor diagnostic-settings create \
  --name "app-diagnostics" \
  --resource "/subscriptions/<sub>/resourceGroups/<rg>/providers/Microsoft.Web/sites/<app>" \
  --workspace <log-analytics-workspace-id> \
  --logs '[
    {"category": "AppServiceHTTPLogs", "enabled": true},
    {"category": "AppServiceConsoleLogs", "enabled": true},
    {"category": "AppServiceAppLogs", "enabled": true},
    {"category": "AppServicePlatformLogs", "enabled": true}
  ]'

Common KQL Queries

HTTP Errors Analysis

AppServiceHTTPLogs
| where TimeGenerated > ago(24h)
| where ScStatus >= 500
| summarize ErrorCount = count() by bin(TimeGenerated, 1h), CsUriStem
| order by ErrorCount desc

Slow Requests

AppServiceHTTPLogs
| where TimeGenerated > ago(1h)
| where TimeTaken > 5000
| project TimeGenerated, CsUriStem, TimeTaken, ScStatus, CIp
| order by TimeTaken desc
| take 100

Exception Analysis (Application Insights)

exceptions
| where timestamp > ago(24h)
| summarize Count = count() by type, outerMessage
| order by Count desc
| take 20

Request Performance Percentiles

requests
| where timestamp > ago(1h)
| summarize 
    P50 = percentile(duration, 50),
    P90 = percentile(duration, 90),
    P95 = percentile(duration, 95),
    P99 = percentile(duration, 99)
    by bin(timestamp, 5m)
| render timechart

Dependency Failures

dependencies
| where timestamp > ago(1h)
| where success == false
| summarize FailureCount = count() by target, type, resultCode
| order by FailureCount desc

App Service Instance Health

AppServiceHTTPLogs
| where TimeGenerated > ago(1h)
| summarize 
    RequestCount = count(),
    ErrorCount = countif(ScStatus >= 500),
    AvgDuration = avg(TimeTaken)
    by ComputerName
| extend ErrorRate = round(100.0 * ErrorCount / RequestCount, 2)

Availability Tests

Create URL Ping Test

# Create availability test
az monitor app-insights web-test create \
  --resource-group <rg> \
  --app-insights <app-insights-name> \
  --name "Homepage-Availability" \
  --web-test-kind "ping" \
  --locations "us-va-ash-azr" "emea-nl-ams-azr" "apac-sg-sin-azr" \
  --frequency 300 \
  --timeout 120 \
  --enabled true \
  --defined-web-test-name "Homepage" \
  --request-url "https://<app>.azurewebsites.net/health"

Multi-Step Test (Standard Test)

# Create standard test with multiple validations
az monitor app-insights web-test create \
  --resource-group <rg> \
  --app-insights <app-insights-name> \
  --name "API-Health-Check" \
  --web-test-kind "standard" \
  --locations "us-va-ash-azr" "emea-nl-ams-azr" \
  --frequency 300 \
  --timeout 30 \
  --enabled true \
  --http-verb "GET" \
  --request-url "https://<app>.azurewebsites.net/api/health" \
  --expected-status-code 200 \
  --content-match "healthy"

Health Check Configuration

# Configure health check path
az webapp config set \
  --name <app> --resource-group <rg> \
  --generic-configurations '{"healthCheckPath": "/health"}'

# View health check status
az webapp show \
  --name <app> --resource-group <rg> \
  --query "siteConfig.healthCheckPath"

Health Check Behavior:

• Probed every 1 minute per instance
• Instance marked unhealthy after 10 consecutive failures
• Unhealthy instances removed from load balancer (2+ instances)
• 1 hour before unhealthy instance replaced

Live Metrics & Debugging

# Stream live logs
az webapp log tail --name <app> --resource-group <rg>

# Enable application logging
az webapp log config \
  --name <app> --resource-group <rg> \
  --application-logging filesystem \
  --level verbose

# Download logs
az webapp log download \
  --name <app> --resource-group <rg> \
  --log-file ./logs.zip

Recommended Alert Set

Alert	Condition	Severity
High Error Rate	Http5xx > 5 in 5 min	Sev 2
High Latency	ResponseTime avg > 3s	Sev 3
Health Check Failed	HealthCheckStatus < 100%	Sev 1
High CPU	CpuPercentage > 85% for 5 min	Sev 2
High Memory	MemoryPercentage > 85% for 5 min	Sev 2
Availability Down	availabilityPercentage < 99%	Sev 1

References

• KQL Queries: See references/kql-queries.md for comprehensive query examples
• Alert Templates: See references/alert-templates.md for alert configuration