Incident response runbook and diagnostic scripts

                  #!/usr/bin/env bash
set -euo pipefail

# ==========================================================
# Production Incident Response Runbook
# ==========================================================
# Usage: ./incident-runbook.sh [triage|cpu|memory|disk|network|k8s]
# ==========================================================

NAMESPACE="${NAMESPACE:-production}"
APP="${APP:-myapp}"

# Colors for output
RED='\033[0;31m'
YELLOW='\033[1;33m'
GREEN='\033[0;32m'
NC='\033[0m'

header() { echo -e "\n${YELLOW}=== $1 ===${NC}\n"; }
ok()     { echo -e "${GREEN}[OK]${NC} $1"; }
warn()   { echo -e "${YELLOW}[WARN]${NC} $1"; }
fail()   { echo -e "${RED}[FAIL]${NC} $1"; }

# ==========================================================
# TRIAGE: Quick health overview
# ==========================================================
triage() {
  header "System Overview"
  echo "Timestamp: $(date -u +%Y-%m-%dT%H:%M:%SZ)"
  echo "Hostname:  $(hostname)"
  echo "Uptime:    $(uptime)"

  header "Resource Usage"
  echo "--- CPU ---"
  top -bn1 | head -5

  echo -e "\n--- Memory ---"
  free -h

  echo -e "\n--- Disk ---"
  df -h / /var /tmp 2>/dev/null

  echo -e "\n--- Load Average ---"
  cat /proc/loadavg

  header "Top Processes (CPU)"
  ps aux --sort=-%cpu | head -10

  header "Top Processes (Memory)"
  ps aux --sort=-%mem | head -10

  header "Recent OOM Kills"
  dmesg -T 2>/dev/null | grep -i "oom\|killed" | tail -5 || echo "None found"

  header "Failed Services"
  systemctl --failed 2>/dev/null || echo "systemctl not available"

  header "Listening Ports"
  ss -tlnp | head -20

  header "Recent Errors in syslog"
  journalctl -p err --since "1 hour ago" --no-pager 2>/dev/null | tail -20
}

# ==========================================================
# CPU Investigation
# ==========================================================
investigate_cpu() {
  header "CPU Investigation"

  echo "Load averages (1/5/15 min):"
  cat /proc/loadavg
  echo "CPU cores: $(nproc)"
  echo ""

  local load_1m=$(cat /proc/loadavg | awk '{print $1}')
  local cores=$(nproc)
  echo "Load per core: $(echo "$load_1m $cores" | awk '{printf "%.2f", $1/$2}')"

  header "CPU-hungry processes"
  ps -eo pid,user,%cpu,%mem,comm --sort=-%cpu | head -15

  header "Per-CPU usage"
  mpstat -P ALL 1 3 2>/dev/null || sar -u 1 3 2>/dev/null || echo "Install sysstat"

  header "Thread count by process"
  ps -eo nlwp,pid,user,comm --sort=-nlwp | head -10
}

# ==========================================================
# Memory Investigation
# ==========================================================
investigate_memory() {
  header "Memory Investigation"

  free -h
  echo ""

  header "Memory-hungry processes"
  ps -eo pid,user,%mem,rss,vsz,comm --sort=-%mem | head -15

  header "Memory details from /proc/meminfo"
  grep -E "^(MemTotal|MemFree|MemAvailable|Buffers|Cached|SwapTotal|SwapFree)" /proc/meminfo

  header "OOM score (higher = more likely to be killed)"
  for pid in $(ps -eo pid --sort=-%mem --no-headers | head -5); do
    name=$(cat /proc/$pid/comm 2>/dev/null || echo "unknown")
    score=$(cat /proc/$pid/oom_score 2>/dev/null || echo "N/A")
    echo "  PID $pid ($name): OOM score = $score"
  done

  header "Swap usage by process"
  for f in /proc/[0-9]*/status; do
    awk '/VmSwap/ {if ($2 > 0) print FILENAME, $0}' "$f" 2>/dev/null
  done | sort -k3 -rn | head -10
}

# ==========================================================
# Disk Investigation
# ==========================================================
investigate_disk() {
  header "Disk Investigation"

  df -h
  echo ""

  header "Disk I/O"
  iostat -x 1 3 2>/dev/null || echo "Install sysstat"

  header "Large files (>100MB)"
  find / -type f -size +100M -exec ls -lh {} \; 2>/dev/null | sort -k5 -rh | head -10

  header "Large directories"
  du -sh /var/log/* 2>/dev/null | sort -rh | head -10
  echo "---"
  du -sh /tmp/* 2>/dev/null | sort -rh | head -10

  header "Inode usage"
  df -i / /var /tmp 2>/dev/null

  header "Open files (top consumers)"
  lsof 2>/dev/null | awk '{print $1}' | sort | uniq -c | sort -rn | head -10
}

# ==========================================================
# Kubernetes Investigation
# ==========================================================
investigate_k8s() {
  header "Kubernetes Cluster Health"

  echo "--- Node Status ---"
  kubectl get nodes -o wide

  echo -e "\n--- Pod Status (${NAMESPACE}) ---"
  kubectl get pods -n "$NAMESPACE" -o wide

  header "Unhealthy Pods"
  kubectl get pods -n "$NAMESPACE" --field-selector='status.phase!=Running,status.phase!=Succeeded'

  header "Pod Restart Counts (top 10)"
  kubectl get pods -n "$NAMESPACE" -o json | \
    jq -r '.items[] | select(.status.containerStatuses != null) |
      .status.containerStatuses[] |
      select(.restartCount > 0) |
      "\(.restartCount)\t\(.name)"' | \
    sort -rn | head -10

  header "Recent Events (warnings)"
  kubectl get events -n "$NAMESPACE" \
    --field-selector type=Warning \
    --sort-by='.lastTimestamp' | tail -20

  header "Resource Usage"
  kubectl top pods -n "$NAMESPACE" --sort-by=cpu 2>/dev/null | head -15
  echo "---"
  kubectl top nodes 2>/dev/null

  header "Recent Pod Logs (crashed/restarting)"
  for pod in $(kubectl get pods -n "$NAMESPACE" --no-headers | \
    awk '$3 ~ /CrashLoop|Error|OOM/ {print $1}' | head -3); do
    echo "--- Logs: $pod ---"
    kubectl logs -n "$NAMESPACE" "$pod" --tail=30 --previous 2>/dev/null || \
      kubectl logs -n "$NAMESPACE" "$pod" --tail=30 2>/dev/null
  done

  header "HPA Status"
  kubectl get hpa -n "$NAMESPACE" 2>/dev/null

  header "PVC Status"
  kubectl get pvc -n "$NAMESPACE" 2>/dev/null
}

# ==========================================================
# Network Investigation
# ==========================================================
investigate_network() {
  header "Network Investigation"

  echo "--- Active connections ---"
  ss -s

  header "Listening services"
  ss -tlnp

  header "Connection states"
  ss -tan | awk '{print $1}' | sort | uniq -c | sort -rn

  header "Established connections per IP (top 10)"
  ss -tn state established | awk '{print $5}' | \
    cut -d: -f1 | sort | uniq -c | sort -rn | head -10

  header "DNS resolution test"
  for domain in api.example.com db.internal redis.internal; do
    if dig +short "$domain" A 2>/dev/null | head -1; then
      ok "$domain resolves"
    else
      fail "$domain FAILED to resolve"
    fi
  done

  header "TCP connectivity test"
  for target in "db.internal:5432" "redis.internal:6379"; do
    host=$(echo "$target" | cut -d: -f1)
    port=$(echo "$target" | cut -d: -f2)
    if timeout 3 bash -c "cat < /dev/null > /dev/tcp/$host/$port" 2>/dev/null; then
      ok "$target reachable"
    else
      fail "$target UNREACHABLE"
    fi
  done
}

# ==========================================================
# Main dispatcher
# ==========================================================
case "${1:-triage}" in
  triage)   triage ;;
  cpu)      investigate_cpu ;;
  memory)   investigate_memory ;;
  disk)     investigate_disk ;;
  network)  investigate_network ;;
  k8s)      investigate_k8s ;;
  all)
    triage
    investigate_cpu
    investigate_memory
    investigate_disk
    investigate_network
    ;;
  *)
    echo "Usage: $0 [triage|cpu|memory|disk|network|k8s|all]"
    exit 1
    ;;
esac

echo -e "\n${GREEN}=== Diagnostics complete: $(date -u +%Y-%m-%dT%H:%M:%SZ) ===${NC}"