appengine-context

Http middleware to create an AppEngine context from the request and make it easy to retrieve it further down the call stack by saving it into the request context.

See this issue for why this is necessary - calls to AppEngine services must be made using a context created using the original request and if you have middleware storing things into the context, this replaces the request with a clone which then interferes with your ability to call AppEngine services.

The code is tiny but I end up needing it in nearly every AppEngine project so decided to package it up.

Installation

Install using go get

go get -i github.com/captaincodeman/appengine-context

Usage

Add the Middleware to your Router package of choice (or wrap the standard http package Mux) and use the Context function whenever you need to retrieve the AppEngine context to call any AppEngine services. The middleware should be added before any other middleware that adds things to the request context.

Example:

package demo

import (
	"fmt"

	"net/http"

	"google.golang.org/appengine"
	"google.golang.org/appengine/log"

	"github.com/captaincodeman/appengine-context"
)

func main() {
	handler := http.HandlerFunc(handle)
	http.Handle("/", gaecontext.Middleware(handler))
	appengine.Main()
}

func handle(w http.ResponseWriter, r *http.Request) {
	ctx := gaecontext.Context(r)

    // simple example just to demonstrate a call to
    // an Appengine Service (stackdriver logging)
    // using the context. This would work even if
    // some other middleware added things into the
    // request context ...
	log.Debugf(ctx, "saying hello")

	fmt.Fprint(w, "hello world!")
}