httpware

Package httpware is a collection of middleware (net/http.Handler wrapper) and tripperware (net/http.RoundTripper wrapper)

• CorrelationId gets or creates a correlation_id and adds it to the http.request Context and in the http.response header (in order to propagate this ID throught all microservices)
• Metrics will use a given Recorder to collect inflight request(current parrallel request count), request duration and response size.

Name	Middleware	Tripperware
CorrelationId	X	X
Metrics	X	X

Installation

go get -u github.com/gol4ng/httpware

Quick Start

Client side

package main

import (
	"net/http"
	"os"
	"runtime"
	
	"github.com/gol4ng/httpware/v2"
	"github.com/gol4ng/httpware/v2/tripperware"
)

func main(){
    // create http client with correlationId activated
    client := &http.Client{
        Transport: tripperware.CorrelationId(),
    }
    
    _, _ = client.Get("fake-address.foo")
    // request will have Header "Correlation-Id: <randomID(10)>"
}

Server side

package main

import (
	"fmt"
	"net/http"
	"os"
	"runtime"
	
	"github.com/gol4ng/httpware/v2"
	"github.com/gol4ng/httpware/v2/correlation_id"
	"github.com/gol4ng/httpware/v2/middleware"
)

func main(){
    port:= ":8001"
    srv := http.NewServeMux()
    srv.HandleFunc("/", func(writer http.ResponseWriter, request *http.Request) {
        // Correlation-Id come directly from the client or was generated by the middleware
        fmt.Println(request.Header.Get(correlation_id.HeaderName))
        writer.WriteHeader(http.StatusOK)
    })
    
    go func() {
        if err := http.ListenAndServe(port, middleware.CorrelationId()(srv)); err != nil {
            panic(err)
        }
    }()
}

Middlewares

A middleware is an http.Handler decorator, its role is to wrap arround http.Handler or another middleware

A middleware stack is a collection of middleware ([]Middleware) that acts has a single Middleware (Append/Prepend).

A stack allows you to DecorateHandler and DecorateHandlerFunc

Tripperwares

A tripperware is an http.RoundTripper decorator, its role is to wrap arround http.RoundTripper or another tripperware

A tripperware stack is a collection of tripperware ([]Tripperware) that acts has a single Tripperware (RoundTrip/DecorateClient/Append/Prepend).

A stack allows you to DecorateRoundTripper and DecorateRoundTripFunc.

Decorate existing client

You can decorate an existing http.Client

client := &http.Client{}
   
// when you decorate client you can set second arg to true if you want a copy
tripperware.CorrelationId().DecorateClient(client, false)
    
_, _ = client.Get("fake-address.foo")
// request will have Header "Correlation-Id: <randomID(10)>"

Act has http.RoundTripper

A tripperware can be use has an http.RoundTripper

tripperware.CorrelationId() == tripperware.CorrelationId()(http.DefaultTransport)

client := &http.Client{
    Transport:tripperware.CorrelationId(),
}
    
_, _ = client.Get("fake-address.foo")
// request will have Header "Correlation-Id: <randomID(10)>"

Become a tripperware stack

The Append and Prepend functions will convert a tripperware into a []Tripperware

roundTripper := tripperware.CorrelationId()
roundTripper.Prepend(func(t http.RoundTripper) http.RoundTripper {
    return httpware.RoundTripFunc(func(req *http.Request) (*http.Response, error) {
        fmt.Println("http request headers :", req.Header)
        return t.RoundTrip(req)
    })
})

client := &http.Client{
    Transport:roundTripper,
}

_, _ = client.Get("fake-address.foo")
// request will have Header "Correlation-Id: <randomID(10)>"

Stack computation

The stack is gonna be computed when you decorate the final round tripper.

m1, m2, m3 are middlewares

[m1, m2, m3].DecorateHandler(<yourHandler>) == m1( m2( m3( <yourHandler> ) ) )

t1 t2 t3 are tripperwares

[t1, t2, t3].DecorateRoundTripper(<yourTripper>) == t1( t2( t3( <yourTripper> ) ) )

	tripperware := func(before, after string) httpware.Tripperware {
		return func(t http.RoundTripper) http.RoundTripper {
			return httpware.RoundTripFunc(func(req *http.Request) (*http.Response, error) {
				defer fmt.Println(after) // will print string AFTER child round trip executed
				fmt.Println(before) // will print string BEFORE child round trip executed
				return t.RoundTrip(req)
			})
		}
	}

	stack := httpware.TripperwareStack(
		tripperware("A before", "A after"),
		tripperware("B before", "B after"),
		tripperware("C before", "C after"),
		tripperware("D before", "D after"),
	)
	// A( B( C( D( http.DefaultTransport ) ) ) )

	client := &http.Client{
		Transport: stack,
	}
	_, _ = client.Get("http://localhost/")
	//Output:
	//A before
	//B before
	//C before
	//D before
	//D after
	//C after
	//B after
	//A after