Issue when implementing graceful shutdown

[janianttonen]

Issue when implementing graceful shutdown

[JoHuang]

@JaniAnttonen I added close method for manually send the remaining log data after receiving signals.
Now you can call logger.close() or logger.end() to trigger LokiTransport's close method.

const gracefullyShutdown = () => {
    Log.info(`SIGTERM / SIGINT signal received.`);
    Log.info('Closing http server.');
    server.close(() => {
        Log.info('The final log.');
        Log.close();
        // wait for few secs to let transport send data to remote server
        setTimeout(()=> {
            process.exist(0);
        }, 5000);
    });
};

[JaniAnttonen]

Thanks again for your contribution! I might've done a whoopsie (albeit not direct) with this. As of my latest knowledge, this library may now shut down gracefully, but only by itself. This means that it only waits for its own internal state (any unsent batches or unfinished requests) to finish. I don't have a fast answer for this but to make a patch to disable graceful shutdown with a configuration flag.

[JaniAnttonen]

And you're right, there's a dependency that is used to handle the graceful shutdown. It's called async-exit-hook

[JaniAnttonen]

Then again, it only does this:

exitHook(callback => {
      this.sendBatchToLoki()
        .then(() => callback())
        .catch(() => callback())
    })

That shouldn't trigger exit by itself on first glance, since the promised behavior is "Run some code when the process exits" but there's a part in async-exit-hook that does something with process.exit that might be the culprit:

function doExit() {
	if (doExitDone) {
		return;
	}
	doExitDone = true;

	if (exit === true) {
		// All handlers should be called even if the exit-hook handler was registered first
		process.nextTick(process.exit.bind(null, code));
	}
}

[JaniAnttonen]

@JoHuang, I published a new version, 5.1.1 on npm that has a hotfix described here: https://github.com/JaniAnttonen/winston-loki/releases/tag/v5.1.1