Connection Draining

📅2026-02-12 작성·🔄2026-09-17 수정·⏱2분 읽기

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Connection Draining 패턴

Connection Draining은 종료 시 기존 연결을 안전하게 정리하는 패턴입니다.

HTTP Keep-Alive 연결 처리

// Node.js Express with Connection Draining
const express = require('express');
const app = express();
const server = app.listen(8080);

let isShuttingDown = false;
const activeConnections = new Set();

// 연결 추적
server.on('connection', (conn) => {
  activeConnections.add(conn);
  conn.on('close', () => {
    activeConnections.delete(conn);
  });
});

function gracefulShutdown(signal) {
  console.log(`${signal} received`);
  isShuttingDown = true;

  // 새 연결 거부
  server.close(() => {
    console.log('Server closed, no new connections');
  });

  // 기존 연결 종료
  console.log(`Closing ${activeConnections.size} active connections`);
  activeConnections.forEach((conn) => {
    conn.destroy(); // 강제 종료 (또는 conn.end()로 graceful)
  });

  // 정리 작업 후 종료
  setTimeout(() => {
    console.log('Graceful shutdown complete');
    process.exit(0);
  }, 5000);
}

process.on('SIGTERM', () => gracefulShutdown('SIGTERM'));

WebSocket 연결 정리

// WebSocket graceful shutdown
const WebSocket = require('ws');
const wss = new WebSocket.Server({ port: 8080 });

const clients = new Set();

wss.on('connection', (ws) => {
  clients.add(ws);

  ws.on('close', () => {
    clients.delete(ws);
  });

  ws.on('message', (message) => {
    // 메시지 처리
  });
});

function gracefulShutdown() {
  console.log(`Closing ${clients.size} WebSocket connections`);

  clients.forEach((ws) => {
    // 클라이언트에게 종료 알림
    ws.send(JSON.stringify({ type: 'server_shutdown' }));
    ws.close(1001, 'Server shutting down');
  });

  wss.close(() => {
    console.log('WebSocket server closed');
    process.exit(0);
  });
}

process.on('SIGTERM', gracefulShutdown);

gRPC Graceful Shutdown

package main

import (
    "context"
    "log"
    "net"
    "os"
    "os/signal"
    "syscall"
    "time"

    "google.golang.org/grpc"
    pb "myapp/proto"
)

type server struct {
    pb.UnimplementedMyServiceServer
}

func main() {
    lis, err := net.Listen("tcp", ":9090")
    if err != nil {
        log.Fatalf("Failed to listen: %v", err)
    }

    s := grpc.NewServer()
    pb.RegisterMyServiceServer(s, &server{})

    go func() {
        log.Println("gRPC server starting on :9090")
        if err := s.Serve(lis); err != nil {
            log.Fatalf("Failed to serve: %v", err)
        }
    }()

    // SIGTERM 대기
    quit := make(chan os.Signal, 1)
    signal.Notify(quit, syscall.SIGTERM, syscall.SIGINT)
    <-quit

    log.Println("Graceful shutdown initiated")

    // GracefulStop: 진행 중인 RPC 완료 대기
    done := make(chan struct{})
    go func() {
        s.GracefulStop()
        close(done)
    }()

    // Timeout 처리
    select {
    case <-done:
        log.Println("gRPC server stopped gracefully")
    case <-time.After(50 * time.Second):
        log.Println("Graceful stop timeout, forcing stop")
        s.Stop() // 강제 종료
    }
}

데이터베이스 연결 풀 정리

# Python with psycopg2 connection pool
import psycopg2
from psycopg2 import pool
import signal
import sys

# Connection pool
db_pool = psycopg2.pool.SimpleConnectionPool(
    minconn=1,
    maxconn=10,
    host='db.example.com',
    database='mydb',
    user='user',
    password='password'
)

def graceful_shutdown(signum, frame):
    print("Closing database connections...")

    # 모든 연결 종료
    db_pool.closeall()

    print("Database connections closed")
    sys.exit(0)

signal.signal(signal.SIGTERM, graceful_shutdown)

# 애플리케이션 로직
def query_database():
    conn = db_pool.getconn()
    try:
        cur = conn.cursor()
        cur.execute("SELECT * FROM users")
        return cur.fetchall()
    finally:
        db_pool.putconn(conn)