Temporalio.Extensions.Hosting 0.1.0-alpha6

Hosting and Dependency Injection Support

This extension adds support for worker Generic Hosts and activity Dependency Injection to the Temporal .NET SDK.

⚠️ UNDER ACTIVE DEVELOPMENT

This SDK is under active development and has not released a stable version yet. APIs may change in incompatible ways until the SDK is marked stable.

Quick Start

Add the Temporalio.Extensions.Hosting package from NuGet. For example, using the dotnet CLI:

dotnet add package Temporalio.Extensions.Hosting --prerelease

To create a worker service, you can do the following:

using Temporalio.Extensions.Hosting;

var builder = Host.CreateApplicationBuilder(args);
// Add a hosted Temporal worker which returns a builder to add activities and workflows
builder.Services.
    AddHostedTemporalWorker(
        "my-temporal-host:7233",
        "my-namespace",
        "my-task-queue").
    AddScopedActivities<MyActivityClass>().
    AddWorkflow<MyWorkflow>();

// Run
var host = builder.Build();
host.Run();

This creates a hosted Temporal worker which returns a builder. Then MyActivityClass is added to the service collection as scoped (via TryAddScoped) and registered on the worker. Also MyWorkflow is registered as a workflow on the worker.

This means that for every activity invocation, a new scope is created and the the activity is obtained via the service provider. So if it is registered as scoped the activity is created each time but if it registered as singleton it is created only once and reused. The activity's constructor can be used to accept injected dependencies.

Workflows are inherently self-contained, deterministic units of work and therefore should never call anything external. Therefore, there is no such thing as dependency injection for workflows, their construction and lifetime is managed by Temporal.

Worker Services

When this extension is depended upon, two overloads for AddHostedTemporalWorker are added as extension methods on IServiceCollection in the Microsoft.Extensions.DependencyInjection.

One overload of AddHostedTemporalWorker, used in the quick start sample above, accepts the client target host, the client namespace, and the worker task queue. This form will connect to a client for the worker. The other overload of AddHostedTemporalWorker only accepts the worker task queue. In the latter, an ITemporalClient can either be set on the services container and therefore reused across workers, or the resulting builder can have client options set.

When called, these register a TemporalWorkerServiceOptions options class with the container and return a ITemporalWorkerServiceOptionsBuilder for configuring the worker service options.

For adding activity classes to the service collection and registering activities with the worker, the following extension methods exist on the builder each accepting activity type:

• AddSingletonActivities - TryAddSingleton + register activities on worker
• AddScopedActivities - TryAddScoped + register activities on worker
• AddTransientActivities - TryAddTransient + register activities on worker
• AddStaticActivities - register activities on worker that all must be static
• AddActivitiesInstance - register activities on worker via an existing instance

These all expect the activity methods to have the [Activity] attribute on them. If an activity type is already added to the service collection, ApplyTemporalActivities can be used to just register the activities on the worker.

For registering workflows on the worker, AddWorkflow extension method is available. This does nothing to the service collection because the construction and lifecycle of workflows is managed by Temporal. Dependency injection for workflows is intentionally not supported.

Other worker and client options can be configured on the builder via the ConfigureOptions extension method. With no parameters, this returns an OptionsBuilder<TemporalWorkerServiceOptions> to use. When provided an action, the options are available as parameters that can be configured. TemporalWorkerServiceOptions simply extends TemporalWorkerOptions with an added property for optional client options that can be set to connect a client on worker start instead of expecting a ITemporalClient to be present on the service collection.

Activity Dependency Injection without Worker Services

Some users may prefer to manually create the TemporalWorker without using host support, but still make their activities created via the service provider. CreateTemporalActivityDefinitions extension methods are present on IServiceProvider that will return a collection of ActivityDefinition instances for each activity on the type. These can be added to the TemporalWorkerOptions directly.