Middleware

Configuration

Defaults

There are two middlewares that are added to the message handling pipeline by default: HandlerInvocationMiddleware and StopwatchMiddleware.

The handler invocation middleware is always the innermost middleware in a pipeline, and is responsible for resolving a handler and calling it.

The stopwatch middleware wraps the handler invocation one, and ensures that the IMessageMonitor.HandlerExecutionTime method is called correctly.

If no custom middleware configuration is provided, the above middlewares will be added.

Adding additional middleware

Middleware pipelines are configured on a per-subscription basis, using the SqsReadConfiguration.WithMiddlewareConfiguration API:

c.WithReadConfiguration(rc =>
    rc.WithMiddlewareConfiguration(m =>
    {
        m.Use<MyMiddleware>();
        m.UseExactlyOnce<SimpleMessage>("simple-message-lock");
        m.UseDefaults<SimpleMessage>(typeof(SimpleMessageHandler));   // Add default middleware pipeline
    }))

This will produce the following pipeline, where before/after refer to when code executes before or after the call to the next middleware.

Before - MyMiddleware Before - ExactlyOnceMiddleware Before - StopwatchMiddleware Before - HandlerInvocationMiddleware After - HandlerInvocationMiddleware After - StopwatchMiddleware After - ExactlyOnceMiddleware After - MyMiddleware

If you don't call UseDefaults<T>(...) then messages won't pass through your handler, nor will they be deleted from their queues, so it's strongly recommended to use it.

An example of using custom middleware can be found in the sample