How to: Author middleware components

Learn how to develop middleware components

Dapr allows custom processing pipelines to be defined by chaining a series of middleware components. In this guide, you’ll learn how to create a middleware component. To learn how to configure an existing middleware component, see Configure middleware components

Writing a custom HTTP middleware

HTTP middlewares in Dapr wrap standard Go net/http handler functions.

Your middleware needs to implement a middleware interface, which defines a GetHandler method that returns a http.Handler callback and an error:

  1. type Middleware interface {
  2.   GetHandler(metadata middleware.Metadata) (func(next http.Handler) http.Handler, error)
  3. }

The handler receives a next callback that should be invoked to continue processing the request.

Your handler implementation can include an inbound logic, outbound logic, or both:

  2. func (m *customMiddleware) GetHandler(metadata middleware.Metadata) (func(next http.Handler) http.Handler, error) {
  3.   var err error
  4.   return func(next http.Handler) http.Handler {
  5.     return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  6.       // Inbound logic
  7.       // ...
  9.       // Call the next handler
  10.       next.ServeHTTP(w, r)
  12.       // Outbound logic
  13.       // ...
  14.     }
  15.   }, err
  16. }

Last modified February 1, 2023: Updated docs for authoring middleware components in 1.10 (6415f00c)