# Angel3 Production Runner [](https://pub.dev/packages/angel3_production) [](https://dart.dev/null-safety) [](https://gitter.im/angel_dart/discussion) [](https://github.com/dukefirehawk/angel/tree/angel3/packages/production/LICENSE) Helpers for concurrency, message-passing, rotating loggers, and other production functionality in Angel3 framework.  This will become the de-facto way to run Angel3 applications in deployed environments, as it takes 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 your application: ```dart import 'dart:async'; import 'dart:isolate'; import 'package:angel3_framework/angel3_framework.dart'; import 'package:angel3_production/angel3_production.dart'; void main(List<String> args) => Runner('example', configureServer).run(args); Future configureServer(Angel app) async { app.get('/', (req, res) => 'Hello, production world!'); app.get('/crash', (req, res) { // We'll crash this instance deliberately, but the Runner will auto-respawn for us. Timer(const Duration(seconds: 3), Isolate.current.kill); return 'Crashing in 3s...'; }); } ``` `Runner` will automatically re-spawn crashed instances, unless `--no-respawn` is passed. This can prevent your server from entirely going down at the first error, and adds a layer of fault tolerance to your infrastructure. When combined with `systemd`, deploying Angel3 applications on Linux can be very simple. ## Message Passing The `Runner` class uses [`belatuk_pub_sub`](<https://pub.dev/packages/belatuk_pub_sub>) to coordinate message passing between isolates. When one isolate sends a message, all other isolates will receive the same message, except for the isolate that sent it. It is injected into your application's `Container` as `pub_sub.Client`, so you can use it as follows: ```dart // Use the injected `pub_sub.Client` to send messages. var client = app.container.make<pub_sub.Client>(); // We can listen for an event to perform some behavior. // // Here, we use message passing to synchronize some common state. var onGreetingChanged = await client.subscribe('user_upgraded'); onGreetingChanged .cast<User>() .listen((user) { // Do something... }); ``` ## 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 injected into each instance: ```dart var instanceInfo = app.container.make<InstanceInfo>(); print('This is instance #${instanceInfo.id}'); ``` ## Command-line Options The `Runner` class supplies options like the following: ```bash appuser$ dart example/main.dart --help _ _ _ ____ _____ _ _____ / \ | \ | |/ ___| ____| | |___ / / _ \ | \| | | _| _| | | |_ \ / ___ \| |\ | |_| | |___| |___ ___) | /_/ \_\_| \_|\____|_____|_____|____/ A batteries-included, full-featured, full-stack framework in Dart. https://angel3-framework.web.app Options: -h, --help Print this help information. --[no-]respawn Automatically respawn crashed application instances. (defaults to on) --use-zone Create a new Zone for each request. --quiet Completely mute logging. --ssl Listen for HTTPS instead of HTTP. --http2 Listen for HTTP/2 instead of HTTP/1.1. -a, --address The address to listen on. (defaults to "127.0.0.1") -j, --concurrency The number of isolates to spawn. (defaults to "4") -p, --port The port to listen on. (defaults to "3000") --certificate-file The PEM certificate file to read. --certificate-password The PEM certificate file password. --key-file The PEM key file to read. --key-password The PEM key file password. ```