Configure middleware components

Dapr allows custom processing pipelines to be defined by chaining a series of middleware components. There are two places that you can use a middleware pipeline:

1. Building block APIs - HTTP middleware components are executed when invoking any Dapr HTTP APIs.
2. Service-to-Service invocation - HTTP middleware components are applied to service-to-service invocation calls.

Configure API middleware pipelines

When launched, a Dapr sidecar constructs a middleware processing pipeline for incoming HTTP calls. By default, the pipeline consists of the tracing and CORS middlewares. Additional middlewares, configured by a Dapr Configuration, can be added to the pipeline in the order they are defined. The pipeline applies to all Dapr API endpoints, including state, pub/sub, service invocation, bindings, secrets, configuration, distributed lock, etc.

A request goes through all the defined middleware components before it’s routed to user code, and then goes through the defined middleware, in reverse order, before it’s returned to the client, as shown in the following diagram.

HTTP middleware components are executed when invoking Dapr HTTP APIs using the httpPipeline configuration.

The following configuration example defines a custom pipeline that uses an OAuth 2.0 middleware and an uppercase middleware component. In this case, all requests are authorized through the OAuth 2.0 protocol, and transformed to uppercase text, before they are forwarded to user code.

apiVersion: dapr.io/v1alpha1
kind: Configuration
metadata:
  name: pipeline
  namespace: default
spec:
  httpPipeline:
    handlers:
      - name: oauth2
        type: middleware.http.oauth2
      - name: uppercase
        type: middleware.http.uppercase

As with other components, middleware components can be found in the supported Middleware reference and in the dapr/components-contrib repo.

Configure app middleware pipelines

You can also use any middleware component when making service-to-service invocation calls. For example, to add token validation in a zero-trust environment, to transform a request for a specific app endpoint, or to apply OAuth policies.

Service-to-service invocation middleware components apply to all outgoing calls from a Dapr sidecar to the receiving application (service), as shown in the diagram below.

Any middleware component that can be used as HTTP middleware can also be applied to service-to-service invocation calls as a middleware component using the appHttpPipeline configuration. The example below adds the uppercase middleware component for all outgoing calls from the Dapr sidecar (target of service invocation) to the application that this configuration is applied to.

apiVersion: dapr.io/v1alpha1
kind: Configuration
metadata:
  name: pipeline
  namespace: default
spec:
  appHttpPipeline:
    handlers:
      - name: uppercase
        type: middleware.http.uppercase

Related links

• Learn how to author middleware components
• Component schema
• Configuration overview
• API middleware sample