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middleware.go
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middleware.go
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// Copyright 2015, 2016, 2017 Ed Marshall. All rights reserved.
// Use of this source code is governed by a GPL-style
// license that can be found in the COPYING file.
package main
import (
"context"
"fmt"
"log"
"net/http"
"sync/atomic"
)
const requestIDKey uint64 = 0
var currentID uint64
// NewContext creates a context with a request ID attached to it.
func NewContext(ctx context.Context, req *http.Request) context.Context {
id := atomic.AddUint64(¤tID, 1)
return context.WithValue(ctx, requestIDKey, id)
}
// RequestID retrieves a request ID from a context.
func RequestID(ctx context.Context) uint64 {
return ctx.Value(requestIDKey).(uint64)
}
// RequestIDMiddleware adds a request id context to the request.
func RequestIDMiddleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
ctx := NewContext(req.Context(), req)
next.ServeHTTP(rw, req.WithContext(ctx))
})
}
// Error extends the error interface to add HTTP status information.
type Error interface {
error
Status() int
}
// StatusError implements Error, storing both an error and an HTTP status code.
type StatusError struct {
Code int
Err error
}
// Error returns the text of the returned error.
func (se StatusError) Error() string { return se.Err.Error() }
// Status returns the HTTP error code of our raised error.
func (se StatusError) Status() int { return se.Code }
// ErrorHandler extended the Handler interface to include an error return value.
type ErrorHandler func(http.ResponseWriter, *http.Request) error
// ErrorHandler.ServeHTTP adds logging and error handling to a standard Handler
func (h ErrorHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
addr := req.Header.Get("X-Real-IP")
if addr == "" {
addr = req.Header.Get("X-Forwarded-For")
}
if addr == "" {
addr = req.RemoteAddr
} else {
addr = fmt.Sprintf("%s (%s)", addr, req.RemoteAddr)
}
rid := RequestID(req.Context())
log.Printf("[%d] %s - %s %s %s", rid, addr, req.Method,
req.URL.RequestURI(), req.Proto)
if err := h(w, req); err != nil {
switch e := err.(type) {
case Error:
log.Printf("[%d] %s", rid, e)
http.Error(w, e.Error(), e.Status())
default:
msg := fmt.Sprintf("%s - %s",
http.StatusText(http.StatusInternalServerError),
err.Error())
log.Printf("[%d] %s", rid, msg)
http.Error(w, msg, http.StatusInternalServerError)
}
}
}