# Azure Diagnostics

Systematic guidance for debugging Azure production issues using AppLens, Azure Monitor, and resource health checks.

## When to Use

Activate this skill when troubleshooting:

- Production failures in Container Apps, Function Apps, or AKS
- Application errors requiring log or metric analysis
- Infrastructure issues like image pull errors or cold start problems
- Kubernetes connectivity or pod scheduling issues

## Core Diagnostic Approach (5 Steps)

1. **Identify symptoms** — Determine what's failing and when
2. **Check resource health** — Verify Azure service status for the affected region
3. **Review logs** — Examine diagnostic information via AppLens or Monitor
4. **Analyze metrics** — Identify performance patterns and anomalies
5. **Investigate changes** — Assess recent deployments, configuration changes

## Service-Specific Guidance

### Container Apps

Common issues and investigation paths:
- **Image pull failures** — Check registry access, credential rotation
- **Cold starts** — Review min replicas, scaling rules
- **Health probe failures** — Verify probe endpoints and response times

### Function Apps

Common issues and investigation paths:
- **Invocation failures** — Check function logs and exception details
- **Timeouts** — Review function duration vs. host timeout setting
- **Binding errors** — Verify connection strings and managed identity permissions
- **Cold start delays** — Consider Premium plan or Always Ready instances

### AKS

Common issues and investigation paths:
- **Cluster access** — Verify kubeconfig and RBAC permissions
- **Node problems** — Check node status, resource pressure, kubelet logs
- **DNS failures** — Review CoreDNS pods, network policies
- **Upgrade complications** — Check node pool upgrade status, PDB violations

## Diagnostic Tools

| Tool | Capability |
|------|-----------|
| **AppLens** | Automated issue detection and root cause analysis |
| **Azure Monitor** | KQL queries against logs and metrics |

### Sample KQL Queries

```kql
// Container App failures in the last hour
ContainerAppConsoleLogs
| where TimeGenerated > ago(1h)
| where Log contains "error" or Log contains "exception"
| project TimeGenerated, ContainerAppName, Log

// Function App exceptions
FunctionAppLogs
| where TimeGenerated > ago(1h)
| where Level == "Error"
| project TimeGenerated, FunctionName, Message, ExceptionDetails
```

## CLI Commands

```bash
# Container Apps
az containerapp logs show --name <app> --resource-group <rg> --follow

# Function Apps
az functionapp log deployment show --name <app> --resource-group <rg>

# AKS
kubectl logs <pod-name> --previous
kubectl describe pod <pod-name>
kubectl get events --sort-by='.lastTimestamp'
```

## Installation

```bash
npx skills add https://github.com/microsoft/azure-skills --skill azure-diagnostics
```

---

*Mirrored from [https://github.com/microsoft/azure-skills](https://github.com/microsoft/azure-skills) — original author: **microsoft**, license: **MIT**.*
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