distribution/context/http.go

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package context
import (
"errors"
"net/http"
"strings"
"sync"
"time"
"code.google.com/p/go-uuid/uuid"
"github.com/gorilla/mux"
"golang.org/x/net/context"
)
// Common errors used with this package.
var (
ErrNoRequestContext = errors.New("no http request in context")
)
// http.Request.RemoteAddr is not the originating IP if the request
// came through a reverse proxy.
// X-Forwarded-For and X-Real-IP provide this information with decreased
// support, so check in that order. There may be multiple 'X-Forwarded-For'
// headers, but go maps don't retain order so just pick one.
func RemoteAddr(r *http.Request) string {
remoteAddr := r.RemoteAddr
if prior, ok := r.Header["X-Forwarded-For"]; ok {
proxies := strings.Split(prior[0], ",")
if len(proxies) > 0 {
remoteAddr = strings.Trim(proxies[0], " ")
}
} else if realip, ok := r.Header["X-Real-Ip"]; ok {
if len(realip) > 0 {
remoteAddr = realip[0]
}
}
return remoteAddr
}
// WithRequest places the request on the context. The context of the request
// is assigned a unique id, available at "http.request.id". The request itself
// is available at "http.request". Other common attributes are available under
// the prefix "http.request.". If a request is already present on the context,
// this method will panic.
func WithRequest(ctx context.Context, r *http.Request) context.Context {
if ctx.Value("http.request") != nil {
// NOTE(stevvooe): This needs to be considered a programming error. It
// is unlikely that we'd want to have more than one request in
// context.
panic("only one request per context")
}
return &httpRequestContext{
Context: ctx,
startedAt: time.Now(),
id: uuid.New(), // assign the request a unique.
r: r,
}
}
// GetRequest returns the http request in the given context. Returns
// ErrNoRequestContext if the context does not have an http request associated
// with it.
func GetRequest(ctx context.Context) (*http.Request, error) {
if r, ok := ctx.Value("http.request").(*http.Request); r != nil && ok {
return r, nil
}
return nil, ErrNoRequestContext
}
// GetRequestID attempts to resolve the current request id, if possible. An
// error is return if it is not available on the context.
func GetRequestID(ctx context.Context) string {
return GetStringValue(ctx, "http.request.id")
}
// WithResponseWriter returns a new context and response writer that makes
// interesting response statistics available within the context.
func WithResponseWriter(ctx context.Context, w http.ResponseWriter) (context.Context, http.ResponseWriter) {
irw := &instrumentedResponseWriter{
ResponseWriter: w,
Context: ctx,
}
return irw, irw
}
// getVarsFromRequest let's us change request vars implementation for testing
// and maybe future changes.
var getVarsFromRequest = mux.Vars
// WithVars extracts gorilla/mux vars and makes them available on the returned
// context. Variables are available at keys with the prefix "vars.". For
// example, if looking for the variable "name", it can be accessed as
// "vars.name". Implementations that are accessing values need not know that
// the underlying context is implemented with gorilla/mux vars.
func WithVars(ctx context.Context, r *http.Request) context.Context {
return &muxVarsContext{
Context: ctx,
vars: getVarsFromRequest(r),
}
}
// GetRequestLogger returns a logger that contains fields from the request in
// the current context. If the request is not available in the context, no
// fields will display. Request loggers can safely be pushed onto the context.
func GetRequestLogger(ctx context.Context) Logger {
return GetLogger(ctx,
"http.request.id",
"http.request.method",
"http.request.host",
"http.request.uri",
"http.request.referer",
"http.request.useragent",
"http.request.remoteaddr",
"http.request.contenttype")
}
// GetResponseLogger reads the current response stats and builds a logger.
// Because the values are read at call time, pushing a logger returned from
// this function on the context will lead to missing or invalid data. Only
// call this at the end of a request, after the response has been written.
func GetResponseLogger(ctx context.Context) Logger {
l := getLogrusLogger(ctx,
"http.response.written",
"http.response.status",
"http.response.contenttype")
duration := Since(ctx, "http.request.startedat")
if duration > 0 {
l = l.WithField("http.response.duration", duration)
}
return l
}
// httpRequestContext makes information about a request available to context.
type httpRequestContext struct {
context.Context
startedAt time.Time
id string
r *http.Request
}
// Value returns a keyed element of the request for use in the context. To get
// the request itself, query "request". For other components, access them as
// "request.<component>". For example, r.RequestURI
func (ctx *httpRequestContext) Value(key interface{}) interface{} {
if keyStr, ok := key.(string); ok {
if keyStr == "http.request" {
return ctx.r
}
if !strings.HasPrefix(keyStr, "http.request.") {
goto fallback
}
parts := strings.Split(keyStr, ".")
if len(parts) != 3 {
goto fallback
}
switch parts[2] {
case "uri":
return ctx.r.RequestURI
case "remoteaddr":
return RemoteAddr(ctx.r)
case "method":
return ctx.r.Method
case "host":
return ctx.r.Host
case "referer":
referer := ctx.r.Referer()
if referer != "" {
return referer
}
case "useragent":
return ctx.r.UserAgent()
case "id":
return ctx.id
case "startedat":
return ctx.startedAt
case "contenttype":
ct := ctx.r.Header.Get("Content-Type")
if ct != "" {
return ct
}
}
}
fallback:
return ctx.Context.Value(key)
}
type muxVarsContext struct {
context.Context
vars map[string]string
}
func (ctx *muxVarsContext) Value(key interface{}) interface{} {
if keyStr, ok := key.(string); ok {
if keyStr == "vars" {
return ctx.vars
}
if strings.HasPrefix(keyStr, "vars.") {
keyStr = strings.TrimPrefix(keyStr, "vars.")
}
if v, ok := ctx.vars[keyStr]; ok {
return v
}
}
return ctx.Context.Value(key)
}
// instrumentedResponseWriter provides response writer information in a
// context.
type instrumentedResponseWriter struct {
http.ResponseWriter
context.Context
mu sync.Mutex
status int
written int64
}
func (irw *instrumentedResponseWriter) Write(p []byte) (n int, err error) {
n, err = irw.ResponseWriter.Write(p)
irw.mu.Lock()
irw.written += int64(n)
// Guess the likely status if not set.
if irw.status == 0 {
irw.status = http.StatusOK
}
irw.mu.Unlock()
return
}
func (irw *instrumentedResponseWriter) WriteHeader(status int) {
irw.ResponseWriter.WriteHeader(status)
irw.mu.Lock()
irw.status = status
irw.mu.Unlock()
}
func (irw *instrumentedResponseWriter) Flush() {
if flusher, ok := irw.ResponseWriter.(http.Flusher); ok {
flusher.Flush()
}
}
func (irw *instrumentedResponseWriter) Value(key interface{}) interface{} {
if keyStr, ok := key.(string); ok {
if keyStr == "http.response" {
return irw.ResponseWriter
}
if !strings.HasPrefix(keyStr, "http.response.") {
goto fallback
}
parts := strings.Split(keyStr, ".")
if len(parts) != 3 {
goto fallback
}
irw.mu.Lock()
defer irw.mu.Unlock()
switch parts[2] {
case "written":
return irw.written
case "status":
if irw.status != 0 {
return irw.status
}
case "contenttype":
contentType := irw.Header().Get("Content-Type")
if contentType != "" {
return contentType
}
}
}
fallback:
return irw.Context.Value(key)
}