|
| 1 | +--- |
| 2 | +type: docs |
| 3 | +title: "Virtual Actors" |
| 4 | +linkTitle: "Actors" |
| 5 | +weight: 1000 |
| 6 | +description: How to build actors |
| 7 | +no_list: true |
| 8 | +--- |
| 9 | + |
| 10 | +If you're new to the actor pattern, the best place to learn about the actor pattern is in |
| 11 | +the [Actor Overview.]({{% ref actors-overview.md %}}) |
| 12 | + |
| 13 | +In the PHP SDK, there are two sides to an actor, the Client, and the Actor (aka, the Runtime). As a client of an actor, |
| 14 | +you'll interact with a remote actor via the `ActorProxy` class. This class generates a proxy class on-the-fly using one |
| 15 | +of several configured strategies. |
| 16 | + |
| 17 | +When writing an actor, state can be managed for you. You can hook into the actor lifecycle, and define reminders and |
| 18 | +timers. This gives you considerable power for handling all types of problems that the actor pattern is suited for. |
| 19 | + |
| 20 | +## The Actor Proxy |
| 21 | + |
| 22 | +Whenever you want to communicate with an actor, you'll need to get a proxy object to do so. The proxy is responsible for |
| 23 | +serializing your request, deserializing the response, and returning it to you, all while obeying the contract defined by |
| 24 | +the specified interface. |
| 25 | + |
| 26 | +In order to create the proxy, you'll first need an interface to define how and what you send and receive from an actor. |
| 27 | +For example, if you want to communicate with a counting actor that solely keeps track of counts, you might define the |
| 28 | +interface as follows: |
| 29 | + |
| 30 | +```php |
| 31 | +<?php |
| 32 | +#[\Dapr\Actors\Attributes\DaprType('Counter')] |
| 33 | +interface ICount { |
| 34 | + function increment(int $amount = 1): void; |
| 35 | + function get_count(): int; |
| 36 | +} |
| 37 | +``` |
| 38 | + |
| 39 | +It's a good idea to put this interface in a shared library that the actor and clients can both access (if both are written in PHP). The `DaprType` |
| 40 | +attribute tells the DaprClient the name of the actor to send to. It should match the implementation's `DaprType`, though |
| 41 | +you can override the type if needed. |
| 42 | + |
| 43 | +```php |
| 44 | +<?php |
| 45 | +$app->run(function(\Dapr\Actors\ActorProxy $actorProxy) { |
| 46 | + $actor = $actorProxy->get(ICount::class, 'actor-id'); |
| 47 | + $actor->increment(10); |
| 48 | +}); |
| 49 | +``` |
| 50 | + |
| 51 | +## Writing Actors |
| 52 | + |
| 53 | +To create an actor, you need to implement the interface you defined earlier and also add the `DaprType` attribute. All |
| 54 | +actors *must* implement `IActor`, however there's an `Actor` base class that implements the boilerplate making your |
| 55 | +implementation much simpler. |
| 56 | + |
| 57 | +Here's the counter actor: |
| 58 | + |
| 59 | +```php |
| 60 | +<?php |
| 61 | +#[\Dapr\Actors\Attributes\DaprType('Count')] |
| 62 | +class Counter extends \Dapr\Actors\Actor implements ICount { |
| 63 | + function __construct(string $id, private CountState $state) { |
| 64 | + parent::__construct($id); |
| 65 | + } |
| 66 | + |
| 67 | + function increment(int $amount = 1): void { |
| 68 | + $this->state->count += $amount; |
| 69 | + } |
| 70 | + |
| 71 | + function get_count(): int { |
| 72 | + return $this->state->count; |
| 73 | + } |
| 74 | +} |
| 75 | +``` |
| 76 | + |
| 77 | +The most important bit is the constructor. It takes at least one argument with the name of `id` which is the id of the |
| 78 | +actor. Any additional arguments are injected by the DI container, including any `ActorState` you want to use. |
| 79 | + |
| 80 | +### Actor Lifecycle |
| 81 | + |
| 82 | +An actor is instantiated via the constructor on every request targeting that actor type. You can use it to calculate |
| 83 | +ephemeral state or handle any kind of request-specific startup you require, such as setting up other clients or |
| 84 | +connections. |
| 85 | + |
| 86 | +After the actor is instantiated, the `on_activation()` method may be called. The `on_activation()` method is called any |
| 87 | +time the actor "wakes up" or when it is created for the first time. It is not called on every request. |
| 88 | + |
| 89 | +Next, the actor method is called. This may be from a timer, reminder, or from a client. You may perform any work that |
| 90 | +needs to be done and/or throw an exception. |
| 91 | + |
| 92 | +Finally, the result of the work is returned to the caller. After some time (depending on how you've configured the |
| 93 | +service), the actor will be deactivated and `on_deactivation()` will be called. This may not be called if the host dies, |
| 94 | +daprd crashes, or some other error occurs which prevents it from being called successfully. |
| 95 | + |
| 96 | +## Actor State |
| 97 | + |
| 98 | +Actor state is a "Plain Old PHP Object" (POPO) that extends `ActorState`. The `ActorState` base class provides a couple |
| 99 | +of useful methods. Here's an example implementation: |
| 100 | + |
| 101 | +```php |
| 102 | +<?php |
| 103 | +class CountState extends \Dapr\Actors\ActorState { |
| 104 | + public int $count = 0; |
| 105 | +} |
| 106 | +``` |
| 107 | + |
| 108 | +## Registering an Actor |
| 109 | + |
| 110 | +Dapr expects to know what actors a service may host at startup. You need to add it to the configuration: |
| 111 | + |
| 112 | +{{< tabpane text=true >}} |
| 113 | + |
| 114 | +{{% tab header="Production" %}} |
| 115 | + |
| 116 | +If you want to take advantage of pre-compiled dependency injection, you need to use a factory: |
| 117 | + |
| 118 | +```php |
| 119 | +<?php |
| 120 | +// in config.php |
| 121 | + |
| 122 | +return [ |
| 123 | + 'dapr.actors' => fn() => [Counter::class], |
| 124 | +]; |
| 125 | +``` |
| 126 | + |
| 127 | +All that is required to start the app: |
| 128 | + |
| 129 | +```php |
| 130 | +<?php |
| 131 | + |
| 132 | +require_once __DIR__ . '/vendor/autoload.php'; |
| 133 | + |
| 134 | +$app = \Dapr\App::create( |
| 135 | + configure: fn(\DI\ContainerBuilder $builder) => $builder->addDefinitions('config.php')->enableCompilation(__DIR__) |
| 136 | +); |
| 137 | +$app->start(); |
| 138 | +``` |
| 139 | + |
| 140 | +{{% /tab %}} |
| 141 | +{{% tab header="Development" %}} |
| 142 | + |
| 143 | +```php |
| 144 | +<?php |
| 145 | +// in config.php |
| 146 | + |
| 147 | +return [ |
| 148 | + 'dapr.actors' => [Counter::class] |
| 149 | +]; |
| 150 | +``` |
| 151 | + |
| 152 | +All that is required to start the app: |
| 153 | + |
| 154 | +```php |
| 155 | +<?php |
| 156 | + |
| 157 | +require_once __DIR__ . '/vendor/autoload.php'; |
| 158 | + |
| 159 | +$app = \Dapr\App::create(configure: fn(\DI\ContainerBuilder $builder) => $builder->addDefinitions('config.php')); |
| 160 | +$app->start(); |
| 161 | +``` |
| 162 | + |
| 163 | +{{% /tab %}} |
| 164 | +{{< /tabpane >}} |
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