106 lines
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3.5 KiB
Markdown
106 lines
No EOL
3.5 KiB
Markdown
# production
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Helpers for concurrency, message-passing, rotating loggers, and other production functionality in Angel.
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This will become the de-facto way to run Angel applications in deployed environments, as it
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takes care of inter-isolate communication, respawning dead processes, and other housekeeping for you automatically.
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Most users will want to use the `Runner` class.
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## `Runner`
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`Runner` is a utility, powered by `package:args`, that is intended to be the entry point of your application.
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Instantiate it as follows, and your file will become a command-line executable that spawns multiple instances of your
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application:
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```dart
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import 'dart:async';
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import 'dart:isolate';
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import 'package:angel_framework/angel_framework.dart';
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import 'package:angel_production/angel_production.dart';
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main(List<String> args) => new Runner('example', configureServer).run(args);
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Future configureServer(Angel app) async {
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app.get('/', (req, res) => 'Hello, production world!');
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app.get('/crash', (req, res) {
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// We'll crash this instance deliberately, but the Runner will auto-respawn for us.
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new Timer(const Duration(seconds: 3), Isolate.current.kill);
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return 'Crashing in 3s...';
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});
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}
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```
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`Runner` will automatically re-spawn crashed instances, unless `--no-respawn` is passed. This can prevent
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your server from entirely going down at the first error, and adds a layer of fault tolerance to your
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infrastructure.
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When combined with `systemd`, deploying Angel applications on Linux can be very simple.
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## Message Passing
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The `Runner` class uses [`package:pub_sub`](https://github.com/thosakwe/pub_sub) to coordinate
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message passing between isolates.
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When one isolate sends a message, all other isolates will
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receive the same message, except for the isolate that sent it.
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It is injected into your application's `Container` as
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`pub_sub.Client`, so you can use it as follows:
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```dart
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// Use the injected `pub_sub.Client` to send messages.
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var client = app.container.make<pub_sub.Client>();
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// We can listen for an event to perform some behavior.
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//
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// Here, we use message passing to synchronize some common state.
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var onGreetingChanged = await client.subscribe('user_upgraded');
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onGreetingChanged
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.cast<User>()
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.listen((user) {
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// Do something...
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});
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```
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## Run-time Metadata
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At run-time, you may want to know information about the currently-running instance,
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for example, which number instance. For this, the `InstanceInfo` class is injected
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into each instance:
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```dart
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var instanceInfo = app.container.make<InstanceInfo>();
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print('This is instance #${instanceInfo.id}');
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```
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## Command-line Options
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The `Runner` class supplies options like the following:
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```
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wg-dhcp201d194d221:production thosakwe$ dart example/main.dart --help
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____________ ________________________
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___ |__ | / /_ ____/__ ____/__ /
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__ /| |_ |/ /_ / __ __ __/ __ /
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_ ___ | /| / / /_/ / _ /___ _ /___
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/_/ |_/_/ |_/ ____/ /_____/ /_____/
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A batteries-included, full-featured, full-stack framework in Dart.
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https://angel-dart.github.io
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Options:
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-h, --help Print this help information.
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--[no-]respawn Automatically respawn crashed application instances.
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(defaults to on)
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--use-zone Create a new Zone for each request.
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-a, --address The address to listen on.
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(defaults to "127.0.0.1")
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-j, --concurrency The number of isolates to spawn.
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(defaults to "4")
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-p, --port The port to listen on.
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(defaults to "3000")
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``` |