Check Logs

Check Logs Skill

This skill helps you query and analyze logs from the Kagenti platform using Loki via Grafana.

When to Use

• User asks "show me logs for X"
• Investigating errors or failures
• After deployments to check for issues
• Debugging pod crashes or restarts
• Analyzing application behavior

What This Skill Does

1. Query Logs: Search logs by namespace, pod, container, or log level
2. Error Detection: Find errors and warnings in logs
3. Log Aggregation: View logs across multiple pods
4. Time-based Queries: Query logs for specific time ranges
5. Log Patterns: Detect common issues from log patterns

Examples

Query Logs in Grafana UI

Access Grafana: https://grafana.localtest.me:9443 Navigate: Explore → Select Loki datasource

Log Dashboard: https://grafana.localtest.me:9443/d/loki-logs/loki-logs

Query Examples in Grafana Explore:

# All logs from observability namespace
{kubernetes_namespace_name="observability"}

# Logs from specific pod
{kubernetes_pod_name=~"prometheus.*"}

# Logs with errors
{kubernetes_namespace_name="observability"} |= "error"

# Logs from last 5 minutes with level=error
{kubernetes_namespace_name="observability"} | json | level="error"

# Count errors per namespace
sum by (kubernetes_namespace_name) (count_over_time({kubernetes_namespace_name=~".+"} |= "error" [5m]))

Query Logs via CLI (Promtail/Loki)

# Query Loki for recent errors in observability namespace
kubectl exec -n observability deployment/grafana -- \
  curl -s -G 'http://loki.observability.svc:3100/loki/api/v1/query_range' \
  --data-urlencode 'query={kubernetes_namespace_name="observability"} |= "error"' \
  --data-urlencode 'limit=100' \
  --data-urlencode 'start='$(date -u -v-5M +%s)000000000 \
  --data-urlencode 'end='$(date -u +%s)000000000 | python3 -m json.tool

Check Logs for Specific Pod

# Get logs for a specific pod using kubectl
kubectl logs -n observability deployment/prometheus --tail=100

# Get logs from previous container (if crashed)
kubectl logs -n observability pod/prometheus-xxx --previous

# Follow logs in real-time
kubectl logs -n observability deployment/grafana -f --tail=20

# Get logs from specific container in pod
kubectl logs -n observability pod/alertmanager-xxx -c alertmanager --tail=50

Search for Errors Across Platform

# Get recent error logs from all namespaces
for ns in observability keycloak oauth2-proxy istio-system kiali-system; do
  echo "=== Errors in $ns ==="
  kubectl logs -n $ns --all-containers=true --tail=50 2>&1 | grep -i "error\|fatal\|exception" | head -5
  echo
done

Check Logs for Failed Pods

# Find pods with issues and check their logs
kubectl get pods -A | grep -E "Error|CrashLoop|ImagePull" | while read ns pod rest; do
  echo "=== Logs for $pod in $ns ==="
  kubectl logs -n $ns $pod --tail=30 --previous 2>/dev/null || kubectl logs -n $ns $pod --tail=30
  echo
done

Query Log Volume by Namespace

# In Grafana Explore (Loki datasource)
sum by (kubernetes_namespace_name) (
  rate({kubernetes_namespace_name=~".+"}[5m])
)

Search for Specific Error Pattern

# Find connection errors
{kubernetes_namespace_name="observability"} |~ "connection (refused|timeout|reset)"

# Find authentication failures
{kubernetes_namespace_name=~"keycloak|oauth2-proxy"} |~ "auth.*fail|unauthorized|forbidden"

# Find OOM kills
{kubernetes_namespace_name=~".+"} |~ "OOM|out of memory|oom.*kill"

Log Levels and Filtering

Standard Log Levels

• error: Critical errors requiring attention
• warn/warning: Warnings that may indicate issues
• info: Informational messages
• debug: Detailed debugging information
• trace: Very detailed trace information

Filter by Log Level

# Only errors
{kubernetes_namespace_name="observability"} | json | level="error"

# Errors and warnings
{kubernetes_namespace_name="observability"} | json | level=~"error|warn"

# Everything except debug
{kubernetes_namespace_name="observability"} | json | level!="debug"

Common Log Queries for Platform Components

Prometheus Logs

kubectl logs -n observability deployment/prometheus --tail=100

# Check for scrape errors
kubectl logs -n observability deployment/prometheus | grep -i "scrape\|error"

Grafana Logs

kubectl logs -n observability deployment/grafana --tail=100

# Check for datasource errors
kubectl logs -n observability deployment/grafana | grep -i "datasource\|error"

Keycloak Logs

kubectl logs -n keycloak statefulset/keycloak --tail=100

# Check for authentication errors
kubectl logs -n keycloak statefulset/keycloak | grep -i "auth\|login\|error"

Istio Proxy (Sidecar) Logs

# Check sidecar logs for a specific pod
POD=$(kubectl get pod -n observability -l app=alertmanager -o jsonpath='{.items[0].metadata.name}')
kubectl logs -n observability $POD -c istio-proxy --tail=50

AlertManager Logs

kubectl logs -n observability deployment/alertmanager -c alertmanager --tail=100

# Check for notification errors
kubectl logs -n observability deployment/alertmanager -c alertmanager | grep -i "notif\|error\|fail"

Log Analysis Patterns

Detect Crash Loops

# Find pods restarting frequently
kubectl get pods -A | awk '{if ($4 > 5) print $0}'

# Check logs before crash
kubectl logs -n <namespace> <pod-name> --previous | tail -50

Find HTTP Errors

{kubernetes_namespace_name=~".+"} |~ "HTTP.*[45]\\d{2}"

Find Timeout Errors

{kubernetes_namespace_name=~".+"} |~ "timeout|timed out|deadline exceeded"

Find Database Connection Issues

{kubernetes_namespace_name=~".+"} |~ "database.*error|connection.*refused|SQL.*error"

Troubleshooting with Logs

Issue: Service Not Starting

1. Check pod events: kubectl describe pod <pod-name> -n <namespace>
2. Check container logs: kubectl logs <pod-name> -n <namespace>
3. Check init container logs: kubectl logs <pod-name> -n <namespace> -c <init-container>

Issue: High Error Rate

1. Query error logs: {kubernetes_namespace_name="X"} |= "error" [5m]
2. Group by component: sum by (kubernetes_pod_name) (count_over_time({...} |= "error" [5m]))
3. Identify pattern in error messages

Issue: Performance Degradation

1. Check for warnings: {kubernetes_namespace_name="X"} |= "warn"
2. Look for timeout messages
3. Check for resource exhaustion messages

Grafana Loki Dashboard Features

Loki Logs Dashboard: https://grafana.localtest.me:9443/d/loki-logs/loki-logs

Features:

• Namespace filter: Select specific namespace
• Pod filter: Filter by pod name
• Log level: Filter by error/warn/info/debug
• Time range: Select time window
• Log volume graphs: See log rate over time
• Log table: Browse actual log lines

Panels:

1. Log Volume by Level: See errors vs warnings over time
2. Log Volume by Namespace: Compare activity across namespaces
3. Logs per Second: Current log ingestion rate
4. Log Lines: Actual log content with search

Related Documentation

• Loki Documentation
• LogQL Query Language
• CLAUDE.md Troubleshooting
• Alert Runbooks - Many reference logs

Pro Tips

1. Use time ranges: Always specify time range to limit data
2. Filter early: Add namespace/pod filters before log level filters (more efficient)
3. Use regex carefully: Complex regex can be slow on large log volumes
4. Check both current and previous: For crashed pods, use --previous
5. Tail first: Use --tail=N to limit output, then increase if needed

🤖 Generated with Claude Code