Database Connection Cleanup

Hook Content

The main content for this hook.

stop.json

json

{
  "hookConfig": {
    "hooks": {
      "stop": {
        "script": "./.claude/hooks/database-connection-cleanup.sh"
      }
    }
  },
  "scriptContent": "#!/usr/bin/env bash\n\necho \"🗄️ Starting database connection cleanup...\" >&2\n\n# PostgreSQL cleanup\nif pgrep postgres >/dev/null 2>&1; then\n  echo \"🐘 PostgreSQL: Checking connections...\" >&2\n  \n  # Check if psql is available and we can connect\n  if command -v psql &> /dev/null; then\n    # Count active connections\n    ACTIVE_CONNECTIONS=$(psql -t -c \"SELECT count(*) FROM pg_stat_activity WHERE state = 'active' AND pid <> pg_backend_pid();\" 2>/dev/null | xargs || echo \"0\")\n    IDLE_CONNECTIONS=$(psql -t -c \"SELECT count(*) FROM pg_stat_activity WHERE state = 'idle' AND pid <> pg_backend_pid();\" 2>/dev/null | xargs || echo \"0\")\n    \n    echo \"📊 PostgreSQL: $ACTIVE_CONNECTIONS active, $IDLE_CONNECTIONS idle connections\" >&2\n    \n    # Terminate long-running idle connections (older than 5 minutes)\n    if [ \"$IDLE_CONNECTIONS\" -gt 0 ]; then\n      TERMINATED=$(psql -t -c \"SELECT count(*) FROM (SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE state = 'idle' AND state_change < now() - interval '5 minutes' AND pid <> pg_backend_pid()) t;\" 2>/dev/null | xargs || echo \"0\")\n      if [ \"$TERMINATED\" -gt 0 ]; then\n        echo \"✅ PostgreSQL: Terminated $TERMINATED idle connections\" >&2\n      fi\n    fi\n  else\n    echo \"⚠️ PostgreSQL running but psql not available\" >&2\n  fi\nfi\n\n# MySQL cleanup\nif pgrep mysql >/dev/null 2>&1 || pgrep mysqld >/dev/null 2>&1; then\n  echo \"🐬 MySQL: Checking connections...\" >&2\n  \n  if command -v mysql &> /dev/null; then\n    PROCESSLIST=$(mysql -e \"SHOW PROCESSLIST;\" 2>/dev/null | grep -c \"Sleep\" || echo \"0\")\n    TOTAL_CONNECTIONS=$(mysql -e \"SHOW PROCESSLIST;\" 2>/dev/null | wc -l || echo \"0\")\n    echo \"📊 MySQL: $TOTAL_CONNECTIONS total connections, $PROCESSLIST sleeping\" >&2\n    \n    # Kill long-running sleeping connections (optional, requires PROCESS privilege)\n    # mysql -e \"KILL CONNECTION_ID;\" 2>/dev/null || true\n  else\n    echo \"⚠️ MySQL running but mysql client not available\" >&2\n  fi\nfi\n\n# MongoDB cleanup\nif pgrep mongod >/dev/null 2>&1; then\n  echo \"🍃 MongoDB: Checking connections...\" >&2\n  \n  if command -v mongosh &> /dev/null; then\n    CONNECTIONS=$(mongosh --quiet --eval \"db.currentOp().inprog.length\" 2>/dev/null || echo \"0\")\n    echo \"📊 MongoDB: $CONNECTIONS active operations\" >&2\n  elif command -v mongo &> /dev/null; then\n    CONNECTIONS=$(mongo --quiet --eval \"db.currentOp().inprog.length\" 2>/dev/null || echo \"0\")\n    echo \"📊 MongoDB: $CONNECTIONS active operations\" >&2\n  else\n    echo \"⚠️ MongoDB running but mongo client not available\" >&2\n  fi\nfi\n\n# Redis cleanup\nif pgrep redis-server >/dev/null 2>&1; then\n  echo \"📮 Redis: Checking connections...\" >&2\n  \n  if command -v redis-cli &> /dev/null; then\n    CLIENT_COUNT=$(redis-cli CLIENT LIST 2>/dev/null | wc -l || echo \"0\")\n    echo \"📊 Redis: $CLIENT_COUNT connected clients\" >&2\n    \n    # Optionally close idle clients\n    # redis-cli CLIENT KILL TYPE normal SKIPME yes 2>/dev/null || true\n  else\n    echo \"⚠️ Redis running but redis-cli not available\" >&2\n  fi\nfi\n\n# Check for database connection strings in environment\nif [ -f \".env\" ]; then\n  DB_VARS=$(grep -E \"(DATABASE_URL|MONGODB_URI|REDIS_URL|POSTGRES|MYSQL)\" .env 2>/dev/null | wc -l || echo \"0\")\n  if [ \"$DB_VARS\" -gt 0 ]; then\n    echo \"📋 Found $DB_VARS database configuration variables in .env\" >&2\n  fi\nfi\n\necho \"✅ Database connection cleanup completed\" >&2\nexit 0"
}

Features

Key capabilities and functionality

Automatic database connection cleanup on session end
Multi-database support (PostgreSQL, MySQL, MongoDB, Redis)
Idle connection termination for PostgreSQL
Connection monitoring and reporting
Safe cleanup with error handling
Resource leak prevention

Installation

Setup instructions and requirements

Claude Code Setup

Create hooks directory: mkdir -p .claude/hooks
Create hook script: .claude/hooks/database-connection-cleanup.sh
Add hook configuration to your Claude Code config
Make script executable: chmod +x .claude/hooks/database-connection-cleanup.sh
Restart Claude Code to activate the hook

Configuration Paths

project

.claude/hooks/

user

~/.claude/hooks/

Requirements

Claude Code CLI
Bash shell
Hook-specific dependencies (e.g., jq, prettier)

Hook Configuration

Hook setup and script content

stop-config.json

json

{
  "hooks": {
    "stop": {
      "script": "./.claude/hooks/database-connection-cleanup.sh"
    }
  }
}

stop-script.sh

bash

#!/usr/bin/env bash

echo "🗄️ Starting database connection cleanup..." >&2

# PostgreSQL cleanup
if pgrep postgres >/dev/null 2>&1; then
  echo "🐘 PostgreSQL: Checking connections..." >&2
  
  # Check if psql is available and we can connect
  if command -v psql &> /dev/null; then
    # Count active connections
    ACTIVE_CONNECTIONS=$(psql -t -c "SELECT count(*) FROM pg_stat_activity WHERE state = 'active' AND pid <> pg_backend_pid();" 2>/dev/null | xargs || echo "0")
    IDLE_CONNECTIONS=$(psql -t -c "SELECT count(*) FROM pg_stat_activity WHERE state = 'idle' AND pid <> pg_backend_pid();" 2>/dev/null | xargs || echo "0")
    
    echo "📊 PostgreSQL: $ACTIVE_CONNECTIONS active, $IDLE_CONNECTIONS idle connections" >&2
    
    # Terminate long-running idle connections (older than 5 minutes)
    if [ "$IDLE_CONNECTIONS" -gt 0 ]; then
      TERMINATED=$(psql -t -c "SELECT count(*) FROM (SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE state = 'idle' AND state_change < now() - interval '5 minutes' AND pid <> pg_backend_pid()) t;" 2>/dev/null | xargs || echo "0")
      if [ "$TERMINATED" -gt 0 ]; then
        echo "✅ PostgreSQL: Terminated $TERMINATED idle connections" >&2
      fi
    fi
  else
    echo "⚠️ PostgreSQL running but psql not available" >&2
  fi
fi

# MySQL cleanup
if pgrep mysql >/dev/null 2>&1 || pgrep mysqld >/dev/null 2>&1; then
  echo "🐬 MySQL: Checking connections..." >&2
  
  if command -v mysql &> /dev/null; then
    PROCESSLIST=$(mysql -e "SHOW PROCESSLIST;" 2>/dev/null | grep -c "Sleep" || echo "0")
    TOTAL_CONNECTIONS=$(mysql -e "SHOW PROCESSLIST;" 2>/dev/null | wc -l || echo "0")
    echo "📊 MySQL: $TOTAL_CONNECTIONS total connections, $PROCESSLIST sleeping" >&2
    
    # Kill long-running sleeping connections (optional, requires PROCESS privilege)
    # mysql -e "KILL CONNECTION_ID;" 2>/dev/null || true
  else
    echo "⚠️ MySQL running but mysql client not available" >&2
  fi
fi

# MongoDB cleanup
if pgrep mongod >/dev/null 2>&1; then
  echo "🍃 MongoDB: Checking connections..." >&2
  
  if command -v mongosh &> /dev/null; then
    CONNECTIONS=$(mongosh --quiet --eval "db.currentOp().inprog.length" 2>/dev/null || echo "0")
    echo "📊 MongoDB: $CONNECTIONS active operations" >&2
  elif command -v mongo &> /dev/null; then
    CONNECTIONS=$(mongo --quiet --eval "db.currentOp().inprog.length" 2>/dev/null || echo "0")
    echo "📊 MongoDB: $CONNECTIONS active operations" >&2
  else
    echo "⚠️ MongoDB running but mongo client not available" >&2
  fi
fi

# Redis cleanup
if pgrep redis-server >/dev/null 2>&1; then
  echo "📮 Redis: Checking connections..." >&2
  
  if command -v redis-cli &> /dev/null; then
    CLIENT_COUNT=$(redis-cli CLIENT LIST 2>/dev/null | wc -l || echo "0")
    echo "📊 Redis: $CLIENT_COUNT connected clients" >&2
    
    # Optionally close idle clients
    # redis-cli CLIENT KILL TYPE normal SKIPME yes 2>/dev/null || true
  else
    echo "⚠️ Redis running but redis-cli not available" >&2
  fi
fi

# Check for database connection strings in environment
if [ -f ".env" ]; then
  DB_VARS=$(grep -E "(DATABASE_URL|MONGODB_URI|REDIS_URL|POSTGRES|MYSQL)" .env 2>/dev/null | wc -l || echo "0")
  if [ "$DB_VARS" -gt 0 ]; then
    echo "📋 Found $DB_VARS database configuration variables in .env" >&2
  fi
fi

echo "✅ Database connection cleanup completed" >&2
exit 0

Use Cases

Common scenarios and applications

Automatic resource cleanup in development environments
Prevention of database connection leaks
Clean session termination for database applications
Resource monitoring and management
Multi-database environment cleanup

Troubleshooting

Common issues and solutions

PostgreSQL connections not terminated despite hook execution
Verify psql client is in PATH and can connect without password. Check pg_hba.conf allows local connections. Ensure user has permission to query pg_stat_activity and call pg_terminate_backend.
Stop hook runs but database processes still detected
Hook reports connections but doesn't stop database servers. Use pgrep to verify process detection works. Check connection cleanup SQL executes successfully. Monitor stderr for command errors.
Idle connection count shows zero despite active sessions
Check state filter in pg_stat_activity query matches your PostgreSQL version. Verify 5-minute threshold is appropriate for your workflow. Use psql directly to debug query results.
MySQL processlist command fails with access denied
Grant PROCESS privilege to MySQL user. Run GRANT PROCESS ON *.* TO 'user'@'localhost'. Verify mysql client connects with correct credentials from .env or environment variables.
MongoDB connection check fails with authentication error
Use mongosh for MongoDB 5+ or mongo for older versions. Configure connection string with credentials. Check authentication database matches user creation. Verify network access if using remote MongoDB.

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