Invocation pipeline with DI

Invocation pipeline with a DI container

Unlike the dispatch pipeline, the invocation pipeline is pretty much the same with or without a DI container. That's because there is no natural DI scope for an invocation: if an invocation executes within a DI scope, this scope comes from another enclosing activity, such as a dispatch that makes this invocation.

Building an invocation pipeline with Microsoft's DI container

You can call AddIceRpcInvoker to add a new invoker (invocation pipeline) singleton to your DI container.

For example:

// Construct an invocation pipeline using Microsoft's DI container.

using IceRpc.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection;
...

// Add a new IInvoker singleton configured with an action.
services
    .AddIceRpcClientConnection()
    .AddIceRpcInvoker(builder => builder.Into<ClientConnection>())

You must specify a final invoker with the Into method. With this example, the new invoker flows into the ClientConnection singleton we configured earlier.

Installing an interceptor in an IInvokerBuilder

All the interceptors that ship with IceRPC can be used with or without DI, and use features for communications within an invocation. For instance, the retry interceptor communicates with a connection cache using an IServerAddressFeature to coordinate retries over replicated servers.

These interceptors can be installed into a Pipeline or an IInvokerBuilder.

For example:

// Construct an invocation pipeline using Microsoft's DI container.

using IceRpc.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection;
...

// Add a new IInvoker singleton configured with an action.
services
    .AddIceRpcClientConnection()
    .AddIceRpcInvoker(builder =>
        builder
            .UseLogger()
            .Into<ClientConnection>())

Here, UseLogger is an extension method provided by the IceRpc.Logger assembly. This extension method works with any DI container that implements IServiceProvider, such as Microsoft's DI container and Simple Injector's container.

The implementation of the UseLogger method simply retrieves a logger instance from the DI container and then create a new interceptor with this instance:

public static IInvokerBuilder UseLogger(this IInvokerBuilder builder) =>
    builder.ServiceProvider.GetService(typeof(ILogger<LoggerInterceptor>)) is ILogger logger ?
        builder.Use(next => new LoggerInterceptor(next, logger)) :
        throw new InvalidOperationException(
            $"Could not find service of type '{nameof(ILogger<LoggerInterceptor>)}' in the service container.");

We recommend you follow the same pattern when you create your own interceptor and provide Use extension methods for both Pipeline and IInvokerBuilder.