endpoint

Documentation

Index

• func Chain(mw ...endpoint.Middleware) func(endpoint.Endpoint) endpoint.Endpoint
• func Combine(mw ...endpoint.Middleware) func(endpoint.Endpoint) endpoint.Endpoint
• func FailerMiddleware(errorMatcher ErrorMatcher) endpoint.Middleware
• func OperationName(ctx context.Context) (string, bool)
• func OperationNameMiddleware(name string) endpoint.Middleware
• type ErrorMatcher
• type Factory
  • func NewFactory(middlewareFactories ...MiddlewareFactory) Factory
• type MiddlewareFactory
  • func Middleware(middleware endpoint.Middleware) MiddlewareFactory

Examples

• Chain
• Combine

Functions

func Chain

func Chain(mw ...endpoint.Middleware) func(endpoint.Endpoint) endpoint.Endpoint

Chain composes a single middleware from a list. Compared to endpoint.Chain, this function accepts a variadic list. Deprecated: use Combine instead.

Example

annotate := func(pos string) endpoint.Middleware {
	return func(e endpoint.Endpoint) endpoint.Endpoint {
		return func(ctx context.Context, req interface{}) (response interface{}, err error) {
			fmt.Println(pos + " pre")

			response, err = e(ctx, req)

			fmt.Println(pos + " post")

			return
		}
	}
}
e := Chain(
	annotate("first"),
	annotate("second"),
	annotate("third"),
)(
	func(context.Context, interface{}) (interface{}, error) {
		fmt.Println("endpoint")

		return nil, nil
	},
)

if _, err := e(ctx, req); err != nil {
	panic(err)
}

Output:

first pre
second pre
third pre
endpoint
third post
second post
first post

func Combine

func Combine(mw ...endpoint.Middleware) func(endpoint.Endpoint) endpoint.Endpoint

Combine composes a single middleware from a list. Compared to endpoint.Chain, this function accepts a variadic list.

Example

annotate := func(pos string) endpoint.Middleware {
	return func(e endpoint.Endpoint) endpoint.Endpoint {
		return func(ctx context.Context, req interface{}) (response interface{}, err error) {
			fmt.Println(pos + " pre")

			response, err = e(ctx, req)

			fmt.Println(pos + " post")

			return
		}
	}
}
e := Combine(
	annotate("first"),
	annotate("second"),
	annotate("third"),
)(
	func(context.Context, interface{}) (interface{}, error) {
		fmt.Println("endpoint")

		return nil, nil
	},
)

if _, err := e(ctx, req); err != nil {
	panic(err)
}

Output:

first pre
second pre
third pre
endpoint
third post
second post
first post

func FailerMiddleware

func FailerMiddleware(errorMatcher ErrorMatcher) endpoint.Middleware

FailerMiddleware checks if a returned error matches a predicate and wraps it in a failer response if it does.

func OperationName

func OperationName(ctx context.Context) (string, bool)

OperationName fetches the endpoint operation name from the context (if any). If an endpoint name is not found or it isn't string, the second return argument is false.

func OperationNameMiddleware

func OperationNameMiddleware(name string) endpoint.Middleware

OperationNameMiddleware populates the context with a common name for the endpoint. It can be used in subsequent endpoints in the chain to identify the operation.

Types

type ErrorMatcher

type ErrorMatcher func(err error) bool

ErrorMatcher is a predicate for errors. It can be used in middleware to decide whether to take action or not.

type Factory

type Factory interface {
	// NewEndpoint returns an endpoint wrapped with preconfigured middleware.
	// It also accepts an operation name for per operation middleware (eg. logging or tracing middleware).
	NewEndpoint(name string, e endpoint.Endpoint) endpoint.Endpoint
}

Factory returns an endpoint wrapped with preconfigured middleware.

func NewFactory

func NewFactory(middlewareFactories ...MiddlewareFactory) Factory

NewFactory returns a new Factory.

type MiddlewareFactory

type MiddlewareFactory func(name string) endpoint.Middleware

MiddlewareFactory creates a middleware per operation.

func Middleware

func Middleware(middleware endpoint.Middleware) MiddlewareFactory

Middleware wraps singleton middleware and wraps them in a MiddlewareFactory.