DaprJobsClient usage

Lifetime management

A DaprJobsClient is a version of the Dapr client that is dedicated to interacting with the Dapr Jobs API. It can be registered alongside a DaprClient and other Dapr clients without issue.

It maintains access to networking resources in the form of TCP sockets used to communicate with the Dapr sidecar and implements IDisposable to support the eager cleanup of resources.

For best performance, create a single long-lived instance of DaprJobsClient and provide access to that shared instance throughout your application. DaprJobsClient instances are thread-safe and intended to be shared.

This can be aided by utilizing the dependency injection functionality. The registration method supports registration using as a singleton, a scoped instance or as transient (meaning it’s recreated every time it’s injected), but also enables registration to utilize values from an IConfiguration or other injected service in a way that’s impractical when creating the client from scratch in each of your classes.

Avoid creating a DaprJobsClient for each operation and disposing it when the operation is complete.

Configuring DaprJobsClient via the DaprJobsClientBuilder

A DaprJobsClient can be configured by invoking methods on the DaprJobsClientBuilder class before calling .Build() to create the client itself. The settings for each DaprJobsClient are separate and cannot be changed after calling .Build().

var daprJobsClient = new DaprJobsClientBuilder()
    .UseDaprApiToken("abc123") // Specify the API token used to authenticate to other Dapr sidecars
    .Build();

The DaprJobsClientBuilder contains settings for:

• The HTTP endpoint of the Dapr sidecar
• The gRPC endpoint of the Dapr sidecar
• The JsonSerializerOptions object used to configure JSON serialization
• The GrpcChannelOptions object used to configure gRPC
• The API token used to authenticate requests to the sidecar
• The factory method used to create the HttpClient instance used by the SDK
• The timeout used for the HttpClient instance when making requests to the sidecar

The SDK will read the following environment variables to configure the default values:

• DAPR_HTTP_ENDPOINT: used to find the HTTP endpoint of the Dapr sidecar, example: https://dapr-api.mycompany.com
• DAPR_GRPC_ENDPOINT: used to find the gRPC endpoint of the Dapr sidecar, example: https://dapr-grpc-api.mycompany.com
• DAPR_HTTP_PORT: if DAPR_HTTP_ENDPOINT is not set, this is used to find the HTTP local endpoint of the Dapr sidecar
• DAPR_GRPC_PORT: if DAPR_GRPC_ENDPOINT is not set, this is used to find the gRPC local endpoint of the Dapr sidecar
• DAPR_API_TOKEN: used to set the API token

Configuring gRPC channel options

Dapr’s use of CancellationToken for cancellation relies on the configuration of the gRPC channel options. If you need to configure these options yourself, make sure to enable the ThrowOperationCanceledOnCancellation setting.

var daprJobsClient = new DaprJobsClientBuilder()
    .UseGrpcChannelOptions(new GrpcChannelOptions { ... ThrowOperationCanceledOnCancellation = true })
    .Build();

Using cancellation with DaprJobsClient

The APIs on DaprJobsClient perform asynchronous operations and accept an optional CancellationToken parameter. This follows a standard .NET practice for cancellable operations. Note that when cancellation occurs, there is no guarantee that the remote endpoint stops processing the request, only that the client has stopped waiting for completion.

When an operation is cancelled, it will throw an OperationCancelledException.

Configuring DaprJobsClient via dependency injection

Using the built-in extension methods for registering the DaprJobsClient in a dependency injection container can provide the benefit of registering the long-lived service a single time, centralize complex configuration and improve performance by ensuring similarly long-lived resources are re-purposed when possible (e.g. HttpClient instances).

There are three overloads available to give the developer the greatest flexibility in configuring the client for their scenario. Each of these will register the IHttpClientFactory on your behalf if not already registered, and configure the DaprJobsClientBuilder to use it when creating the HttpClient instance in order to re-use the same instance as much as possible and avoid socket exhaustion and other issues.

In the first approach, there’s no configuration done by the developer and the DaprJobsClient is configured with the default settings.

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddDaprJobsClient(); //Registers the `DaprJobsClient` to be injected as needed
var app = builder.Build();

Sometimes the developer will need to configure the created client using the various configuration options detailed above. This is done through an overload that passes in the DaprJobsClientBuiler and exposes methods for configuring the necessary options.

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddDaprJobsClient((_, daprJobsClientBuilder) => {
   //Set the API token
   daprJobsClientBuilder.UseDaprApiToken("abc123");
   //Specify a non-standard HTTP endpoint
   daprJobsClientBuilder.UseHttpEndpoint("http://dapr.my-company.com");
});

var app = builder.Build();

Finally, it’s possible that the developer may need to retrieve information from another service in order to populate these configuration values. That value may be provided from a DaprClient instance, a vendor-specific SDK or some local service, but as long as it’s also registered in DI, it can be injected into this configuration operation via the last overload:

var builder = WebApplication.CreateBuilder(args);

//Register a fictional service that retrieves secrets from somewhere
builder.Services.AddSingleton<SecretService>();

builder.Services.AddDaprJobsClient((serviceProvider, daprJobsClientBuilder) => {
    //Retrieve an instance of the `SecretService` from the service provider
    var secretService = serviceProvider.GetRequiredService<SecretService>();
    var daprApiToken = secretService.GetSecret("DaprApiToken").Value;

    //Configure the `DaprJobsClientBuilder`
    daprJobsClientBuilder.UseDaprApiToken(daprApiToken);
});

var app = builder.Build();

Understanding payload serialization on DaprJobsClient

While there are many methods on the DaprClient that automatically serialize and deserialize data using the System.Text.Json serializer, this SDK takes a different philosophy. Instead, the relevant methods accept an optional payload of ReadOnlyMemory<byte> meaning that serialization is an exercise left to the developer and is not generally handled by the SDK.

That said, there are some helper extension methods available for each of the scheduling methods. If you know that you want to use a type that’s JSON-serializable, you can use the Schedule*WithPayloadAsync method for each scheduling type that accepts an object as a payload and an optional JsonSerializerOptions to use when serializing the value. This will convert the value to UTF-8 encoded bytes for you as a convenience. Here’s an example of what this might look like when scheduling a Cron expression:

public sealed record Doodad (string Name, int Value);

//...
var doodad = new Doodad("Thing", 100);
await daprJobsClient.ScheduleCronJobWithPayloadAsync("myJob", "5 * * * *", doodad);

In the same vein, if you have a plain string value, you can use an overload of the same method to serialize a string-typed payload and the JSON serialization step will be skipped and it’ll only be encoded to an array of UTF-8 encoded bytes. Here’s an example of what this might look like when scheduling a one-time job:

var now = DateTime.UtcNow;
var oneWeekFromNow = now.AddDays(7);
await daprJobsClient.ScheduleOneTimeJobWithPayloadAsync("myOtherJob", oneWeekFromNow, "This is a test!");

The delegate handling the job invocation expects at least two arguments to be present:

• A string that is populated with the jobName, providing the name of the invoked job
• A ReadOnlyMemory<byte> that is populated with the bytes originally provided during the job registration.

Because the payload is stored as a ReadOnlyMemory<byte>, the developer has the freedom to serialize and deserialize as they wish, but there are again two helper extensions included that can deserialize this to either a JSON-compatible type or a string. Both methods assume that the developer encoded the originally scheduled job (perhaps using the helper serialization methods) as these methods will not force the bytes to represent something they’re not.

To deserialize the bytes to a string, the following helper method can be used:

var payloadAsString = Encoding.UTF8.GetString(jobPayload.Span); //If successful, returns a string with the value

Error handling

Methods on DaprJobsClient will throw a DaprJobsServiceException if an issue is encountered between the SDK and the Jobs API service running on the Dapr sidecar. If a failure is encountered because of a poorly formatted request made to the Jobs API service through this SDK, a DaprMalformedJobException will be thrown. In case of illegal argument values, the appropriate standard exception will be thrown (e.g. ArgumentOutOfRangeException or ArgumentNullException) with the name of the offending argument. And for anything else, a DaprException will be thrown.

The most common cases of failure will be related to:

• Incorrect argument formatting while engaging with the Jobs API
• Transient failures such as a networking problem
• Invalid data, such as a failure to deserialize a value into a type it wasn’t originally serialized from

In any of these cases, you can examine more exception details through the .InnerException property.