What is the proper way to gracefully shutdown a Grizzly server? (Embedded with Jersey)

Question

I have the following piece of code to start a basic Embedded Grizzly server running with Jersey.

  private static void startServer() {
    ServerResourceConfiguration configuration = new ServerResourceConfiguration();

    HttpServer server = GrizzlyHttpServerFactory.createHttpServer(
            URI.create(BASE_URI),
            configuration,
            false,
            null,
            false);

    server.start();

    if (System.in.read() > -2) {
      server.shutdownNow();
    }
  }

This does not look like production level way to stop a server. What is the best practice to gracefully shut it down ? I guess a terminal command of some sort. Killing the process would work but it is not very graceful.

I am using Gradle on this project and runs the server with the gradle run command. Could a Gradle task do the job?

Also I have seen this about gracefully terminating a grizzly transport: http://grizzly-nio.net/2013/08/gracefully-terminating-a-grizzly-transport/ But I am not sure if I would need to use it. I don't understand how to use it.

EDIT: I came across this post: https://stackoverflow.com/a/15391081/3982755 Is that an acceptable way to terminate an Http server in a production environment?

Answer 1

There is no answer so I will post my own, I implemented it with a Shutdown Hook and it works very well.

• The server will wait for all connections to terminate before shutting down.
• To avoid getting blocked for ever if a connection never terminates, we set a grace period(60 seconds)
• After the grace period the server will force termination of all connections

Here is the code for the hook to be run when the server receives a SIGINT or SIGTERM signal.

public class GrizzlyServerShutdownHookThread extends Thread {

  public static final String THREAD_NAME = "Grizzly Server Shutdown Hook";

  public static final int GRACE_PERIOD = 60;
  public static final TimeUnit GRACE_PERIOD_TIME_UNIT = TimeUnit.SECONDS;

  private final HttpServer server;

  /**
   * @param server The server to shut down
   */
  public GrizzlyServerShutdownHookThread(HttpServer server) {
    this.server = server;
    setName(THREAD_NAME);
  }

  @Override
  public void run() {
    LOG.info("Running Grizzly Server Shutdown Hook.");
    LOG.info("Shutting down server.");
    GrizzlyFuture<HttpServer> future = server.shutdown(GRACE_PERIOD, GRACE_PERIOD_TIME_UNIT);

    try {
      LOG.info(format("Waiting for server to shut down... Grace period is %s %s", GRACE_PERIOD, GRACE_PERIOD_TIME_UNIT));
      future.get();
    } catch(InterruptedException | ExecutionException e) {
      LOG.error("Error while shutting down server.", e);
    }

    LOG.info("Server stopped.");
  }
}

Then I register the Hook into the RunTime object this way when I setup the server:

Runtime.getRuntime().addShutdownHook(
    new GrizzlyServerShutdownHookThread(server)
);

And finally, I start the server this way:

try {
  server.start();
} catch (IOException e) {
  throw new RuntimeException(e);
}
// wait for a SIGINT (Ctrl+c) signal to shut down
try {
  LOG.info("Press CTRL^C to exit..");
  Thread.currentThread().join();
} catch(InterruptedException e) {
  throw new RuntimeException(e);
}