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Graceful Shutdown in Java using ShutdownSignalBarrier

This document explains how to use ShutdownSignalBarrier and SigInt.register for graceful shutdown in Java applications.

Purpose

To handle shutdown signals (like Ctrl+C) gracefully and ensure that the main thread does not terminate unexpectedly. This is commonly used in systems like Aeron, Netty, or long-running microservices.

Code Example

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import org.agrona.concurrent.ShutdownSignalBarrier;
import org.agrona.concurrent.SigInt;

ShutdownSignalBarrier barrier = new ShutdownSignalBarrier();
SigInt.register(() -> {
    barrier.signal();
    System.out.println("Signal received");
});

barrier.await();
System.out.println("Main thread terminated");

Explanation

Component Purpose
ShutdownSignalBarrier Blocks the main thread until a shutdown signal is received
SigInt.register(...) Registers a signal handler for SIGINT (Ctrl+C)
barrier.signal() Unblocks the main thread
barrier.await() Waits for the shutdown signal

Use Cases

  • Aeron applications
  • Long-running agents or daemons
  • Console-based servers
  • Microservices that require proper cleanup

Summary

This mechanism is essential to:

  • Keep the application running until explicitly terminated
  • Ensure clean resource release
  • Avoid ungraceful shutdowns that might corrupt state or leave ports open