Backend process handles graceful shutdown

A backend process that ignores SIGTERM drops in-flight requests immediately when the orchestrator (Kubernetes, Railway, Fly.io, Heroku) restarts or redeploys it. Users mid-checkout, mid-upload, or mid-auth flow receive hard errors with no recovery path. CWE-460 (improper cleanup on thrown exception) encompasses improper shutdown handling. Platforms send SIGTERM and wait a grace period (typically 30 seconds) before SIGKILL; failing to handle it means every deploy causes unannounced request failures that are invisible in your error tracking.

Register SIGTERM and SIGINT handlers in your server entry point. Stop accepting new connections immediately, let in-flight requests finish, then close the database pool and exit.

// src/server.ts
const server = app.listen(3000)

async function shutdown(signal: string) {
  console.log(`${signal} received — shutting down`)
  server.close(async () => {
    await pool.end()
    process.exit(0)
  })
  // Force exit if drain takes too long
  setTimeout(() => process.exit(1), 30_000)
}

process.on('SIGTERM', () => shutdown('SIGTERM'))
process.on('SIGINT', () => shutdown('SIGINT'))

Test graceful shutdown locally: run your server, send kill -SIGTERM <pid>, and verify in-flight requests complete before the process exits.

• ID: error-resilience.graceful-degradation-shutdown.graceful-shutdown

• Severity: low

• What to look for: Count all signal handlers (SIGINT, SIGTERM) and cleanup routines. Enumerate whether the server completes in-flight requests and closes database connections before shutting down. Look for signal handlers (SIGTERM, SIGINT) in the backend entry point. Check whether the application waits for in-flight requests to complete and closes the connection pool before exiting.

• Pass criteria: Backend listens for SIGTERM and SIGINT; in-flight requests are completed before shutdown; connection pool is drained. At least 1 signal handler must be registered for SIGTERM with cleanup of at least 2 resources (DB connections, HTTP server).

• Fail criteria: No signal handlers configured, or shutdown immediately kills connections without draining.

• Skip (N/A) when: The application has no backend or is running in a serverless environment (AWS Lambda, Vercel Functions, etc.) that manages shutdown.

• Cross-reference: For database connection pool cleanup, see database-connection-pool.

• Detail on fail: "No graceful shutdown handler. Server stops abruptly, killing in-flight requests" or "Signal handler exists but doesn't wait for requests to complete"

• Remediation: Add graceful shutdown:

  // src/server.ts — graceful shutdown
  process.on('SIGTERM', async () => { await pool.end(); server.close(() => process.exit(0)) })
  

  // server.ts
  import express from 'express'
  import http from 'http'
  
  const app = express()
  const server = http.createServer(app)
  
  let isShuttingDown = false
  
  process.on('SIGTERM', () => {
    console.log('SIGTERM received, shutting down gracefully')
    isShuttingDown = true
  
    server.close(() => {
      console.log('Server closed')
      process.exit(0)
    })
  
    // Force exit after 30 seconds
    setTimeout(() => {
      console.error('Forced shutdown')
      process.exit(1)
    }, 30000)
  })
  
  server.listen(3000, () => {
    console.log('Server running')
  })