production

Helpers for concurrency, message-passing, rotating loggers, and other production functionality in Angel.

This will become the de-facto way to run Angel applications in deployed environments, as ittakes care of inter-isolate communication, respawning dead processes, and other housekeeping for you automatically.

Most users will want to use the Runner class.

Runner

Runner is a utility, powered by package:args, that is intended to be the entry point of your application.

Instantiate it as follows, and your file will become a command-line executable that spawns multiple instances of yourapplication:

1. import 'dart:async';
2. import 'dart:isolate';
3. import 'package:angel_framework/angel_framework.dart';
4. import 'package:angel_production/angel_production.dart';

6. main(List<String> args) => Runner('example', configureServer).run(args);

8. Future configureServer(Angel app) async {
9. app.get('/', (req, res) => 'Hello, production world!');

11. app.get('/crash', (req, res) {
12. // We'll crash this instance deliberately, but the Runner will auto-respawn for us.
13. Timer(const Duration(seconds: 3), Isolate.current.kill);
14. return 'Crashing in 3s...';
15. });
16. }

Runner will automatically re-spawn crashed instances, unless —no-respawn is passed. This can preventyour server from entirely going down at the first error, and adds a layer of fault tolerance to yourinfrastructure.

When combined with systemd, deploying Angel applications on Linux can be very simple.

Message Passing

The Runner class uses package:pub_sub to coordinatemessage passing between isolates.

When one isolate sends a message, all other isolates willreceive the same message, except for the isolate that sent it.

It is injected into your application's Container aspub_sub.Client, so you can use it as follows:

1. // Use the injected `pub_sub.Client` to send messages.
2. var client = app.container.make<pub_sub.Client>();

4. // We can listen for an event to perform some behavior.
5. //
6. // Here, we use message passing to synchronize some common state.
7. var onGreetingChanged = await client.subscribe('user_upgraded');
8. onGreetingChanged
9. .cast<User>()
10. .listen((user) {
11. // Do something...
12. });

Run-time Metadata

At run-time, you may want to know information about the currently-running instance,for example, which number instance. For this, the InstanceInfo class is injectedinto each instance:

1. var instanceInfo = app.container.make<InstanceInfo>();
2. print('This is instance #${instanceInfo.id}');

Command-line Options

The Runner class supplies options like the following:

1. Tobes-MacBook-Air:production thosakwe$ dart example/main.dart --help
2. ____________   ________________________
3. ___    |__  | / /_  ____/__  ____/__  /
4. __  /| |_   |/ /_  / __ __  __/  __  /
5. _  ___ |  /|  / / /_/ / _  /___  _  /___
6. /_/  |_/_/ |_/  ____/  /_____/  /_____/

8. A batteries-included, full-featured, full-stack framework in Dart.

10. https://angel-dart.github.io

12. Options:
13. -h, --help                    Print this help information.
14. --[no-]respawn            Automatically respawn crashed application instances.
15. (defaults to on)

17. --use-zone                Create a new Zone for each request.
18. --quiet                   Completely mute logging.
19. --ssl                     Listen for HTTPS instead of HTTP.
20. --http2                   Listen for HTTP/2 instead of HTTP/1.1.
21. -a, --address                 The address to listen on.
22. (defaults to "127.0.0.1")

24. -j, --concurrency             The number of isolates to spawn.
25. (defaults to "4")

27. -p, --port                    The port to listen on.
28. (defaults to "3000")

30. --certificate-file        The PEM certificate file to read.
31. --certificate-password    The PEM certificate file password.
32. --key-file                The PEM key file to read.
33. --key-password            The PEM key file password.