Graceful Shutdown

Concept

Graceful Shutdown refers to the orderly termination of a program or service, ensuring that all resources are properly closed, ongoing tasks are completed, and data consistency and integrity are maintained. Unlike a forced exit (such as killing a process directly), a graceful shutdown prevents data loss, resource leaks, or inconsistent system states.

Steps

1. Receive Exit Signals:

   The program needs to listen for system signals (e.g., SIGINT, SIGTERM) or custom exit requests to trigger the graceful shutdown process.

   Special Note: The SIGKILL signal triggered by kill -9 pid cannot be handled, as the process is forcibly terminated by the system. Therefore, avoid using this command to terminate the program; instead, use kill pid, which triggers SIGTERM.

2. Stop Accepting New Requests:

   During the shutdown process, the program should stop accepting new requests or tasks to avoid processing incomplete work.

3. Complete Ongoing Tasks:

   Ensure that all tasks or requests currently being processed are completed. For example, an HTTP server should wait for the current request to finish before shutting down.

4. Release Resources:

   Close database connections, file handles, network connections, and other resources to ensure no resource leaks.

5. Clean Up Temporary States:

   Clear caches, temporary files, or intermediate states to ensure system consistency.

6. Timeout Mechanism:

   Set a timeout period. If the shutdown process cannot be completed within the specified time, force an exit to avoid the program hanging.

7. Logging:

   Record key information during the shutdown process for troubleshooting purposes.

Implementation

 1func main() {
 2    go server.ListenAndServe()
 3    
 4    // Listen for exit signals
 5	sig := make(chan os.Signal, 1)
 6	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
 7    // Execute graceful shutdown upon receiving the signal
 8	<-sig
 9	logger.Info("Stopping the service...")
10    // Create a context with a 5-second timeout
11	shutdownCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
12	defer cancel()
13	
14    if err := server.Shutdown(shutdownCtx); err != nil {
15        logger.Info("shutdown err: %v", err)
16    }
17
18    logger.Info("Server gracefully shut down")
19}