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forwarding_proxy.go
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/
forwarding_proxy.go
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// Copyright (c) OpenFaaS Author(s). All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
package handlers
import (
"context"
"fmt"
"io"
"log"
"net/http"
"os"
"regexp"
"strings"
"time"
"github.com/openfaas/faas/gateway/pkg/middleware"
"github.com/openfaas/faas/gateway/types"
)
// functionMatcher parses out the service name (group 1) and rest of path (group 2).
var functionMatcher = regexp.MustCompile("^/?(?:async-)?function/([^/?]+)([^?]*)")
// Indices and meta-data for functionMatcher regex parts
const (
hasPathCount = 3
routeIndex = 0 // routeIndex corresponds to /function/ or /async-function/
nameIndex = 1 // nameIndex is the function name
pathIndex = 2 // pathIndex is the path i.e. /employee/:id/
)
// BaseURLResolver URL resolver for upstream requests
type BaseURLResolver interface {
Resolve(r *http.Request) string
}
// URLPathTransformer Transform the incoming URL path for upstream requests
type URLPathTransformer interface {
Transform(r *http.Request) string
}
// MakeForwardingProxyHandler create a handler which forwards HTTP requests
func MakeForwardingProxyHandler(proxy *types.HTTPClientReverseProxy,
notifiers []HTTPNotifier,
baseURLResolver BaseURLResolver,
urlPathTransformer URLPathTransformer,
serviceAuthInjector middleware.AuthInjector) http.HandlerFunc {
writeRequestURI := false
if _, exists := os.LookupEnv("write_request_uri"); exists {
writeRequestURI = exists
}
return func(w http.ResponseWriter, r *http.Request) {
baseURL := baseURLResolver.Resolve(r)
originalURL := r.URL.String()
requestURL := urlPathTransformer.Transform(r)
for _, notifier := range notifiers {
notifier.Notify(r.Method, requestURL, originalURL, http.StatusProcessing, "started", time.Second*0)
}
start := time.Now()
statusCode, err := forwardRequest(w, r, proxy.Client, baseURL, requestURL, proxy.Timeout, writeRequestURI, serviceAuthInjector)
seconds := time.Since(start)
if err != nil {
log.Printf("error with upstream request to: %s, %s\n", requestURL, err.Error())
}
for _, notifier := range notifiers {
notifier.Notify(r.Method, requestURL, originalURL, statusCode, "completed", seconds)
}
}
}
func buildUpstreamRequest(r *http.Request, baseURL string, requestURL string) *http.Request {
url := baseURL + requestURL
if len(r.URL.RawQuery) > 0 {
url = fmt.Sprintf("%s?%s", url, r.URL.RawQuery)
}
upstreamReq, _ := http.NewRequest(r.Method, url, nil)
copyHeaders(upstreamReq.Header, &r.Header)
deleteHeaders(&upstreamReq.Header, &hopHeaders)
if len(r.Host) > 0 && upstreamReq.Header.Get("X-Forwarded-Host") == "" {
upstreamReq.Header["X-Forwarded-Host"] = []string{r.Host}
}
if upstreamReq.Header.Get("X-Forwarded-For") == "" {
upstreamReq.Header["X-Forwarded-For"] = []string{r.RemoteAddr}
}
if r.Body != nil {
upstreamReq.Body = r.Body
}
return upstreamReq
}
func forwardRequest(w http.ResponseWriter,
r *http.Request,
proxyClient *http.Client,
baseURL string,
requestURL string,
timeout time.Duration,
writeRequestURI bool,
serviceAuthInjector middleware.AuthInjector) (int, error) {
upstreamReq := buildUpstreamRequest(r, baseURL, requestURL)
if upstreamReq.Body != nil {
defer upstreamReq.Body.Close()
}
if serviceAuthInjector != nil {
serviceAuthInjector.Inject(upstreamReq)
}
if writeRequestURI {
log.Printf("forwardRequest: %s %s\n", upstreamReq.Host, upstreamReq.URL.String())
}
ctx, cancel := context.WithTimeout(r.Context(), timeout)
defer cancel()
res, resErr := proxyClient.Do(upstreamReq.WithContext(ctx))
if resErr != nil {
badStatus := http.StatusBadGateway
w.WriteHeader(badStatus)
return badStatus, resErr
}
if res.Body != nil {
defer res.Body.Close()
}
copyHeaders(w.Header(), &res.Header)
// Write status code
w.WriteHeader(res.StatusCode)
if res.Body != nil {
// Copy the body over
io.CopyBuffer(w, res.Body, nil)
}
return res.StatusCode, nil
}
func copyHeaders(destination http.Header, source *http.Header) {
for k, v := range *source {
vClone := make([]string, len(v))
copy(vClone, v)
(destination)[k] = vClone
}
}
func deleteHeaders(target *http.Header, exclude *[]string) {
for _, h := range *exclude {
target.Del(h)
}
}
// SingleHostBaseURLResolver resolves URLs against a single BaseURL
type SingleHostBaseURLResolver struct {
BaseURL string
}
// Resolve the base URL for a request
func (s SingleHostBaseURLResolver) Resolve(r *http.Request) string {
baseURL := s.BaseURL
if strings.HasSuffix(baseURL, "/") {
baseURL = baseURL[0 : len(baseURL)-1]
}
return baseURL
}
// FunctionAsHostBaseURLResolver resolves URLs using a function from the URL as a host
type FunctionAsHostBaseURLResolver struct {
FunctionSuffix string
FunctionNamespace string
}
// Resolve the base URL for a request
func (f FunctionAsHostBaseURLResolver) Resolve(r *http.Request) string {
svcName := getServiceName(r.URL.Path)
const watchdogPort = 8080
var suffix string
if len(f.FunctionSuffix) > 0 {
if index := strings.LastIndex(svcName, "."); index > -1 && len(svcName) > index+1 {
suffix = strings.Replace(f.FunctionSuffix, f.FunctionNamespace, "", -1)
} else {
suffix = "." + f.FunctionSuffix
}
}
return fmt.Sprintf("http://%s%s:%d", svcName, suffix, watchdogPort)
}
// TransparentURLPathTransformer passes the requested URL path through untouched.
type TransparentURLPathTransformer struct {
}
// Transform returns the URL path unchanged.
func (f TransparentURLPathTransformer) Transform(r *http.Request) string {
return r.URL.Path
}
// FunctionPrefixTrimmingURLPathTransformer removes the "/function/servicename/" prefix from the URL path.
type FunctionPrefixTrimmingURLPathTransformer struct {
}
// Transform removes the "/function/servicename/" prefix from the URL path.
func (f FunctionPrefixTrimmingURLPathTransformer) Transform(r *http.Request) string {
ret := r.URL.Path
if ret != "" {
// When forwarding to a function, since the `/function/xyz` portion
// of a path like `/function/xyz/rest/of/path` is only used or needed
// by the Gateway, we want to trim it down to `/rest/of/path` for the
// upstream request. In the following regex, in the case of a match
// the r.URL.Path will be at `0`, the function name at `1` and the
// rest of the path (the part we are interested in) at `2`.
matcher := functionMatcher.Copy()
parts := matcher.FindStringSubmatch(ret)
if len(parts) == hasPathCount {
ret = parts[pathIndex]
}
}
return ret
}
// Hop-by-hop headers. These are removed when sent to the backend.
// As of RFC 7230, hop-by-hop headers are required to appear in the
// Connection header field. These are the headers defined by the
// obsoleted RFC 2616 (section 13.5.1) and are used for backward
// compatibility.
// Copied from: https://golang.org/src/net/http/httputil/reverseproxy.go
var hopHeaders = []string{
"Connection",
"Proxy-Connection", // non-standard but still sent by libcurl and rejected by e.g. google
"Keep-Alive",
"Proxy-Authenticate",
"Proxy-Authorization",
"Te", // canonicalized version of "TE"
"Trailer", // not Trailers per URL above; https://www.rfc-editor.org/errata_search.php?eid=4522
"Transfer-Encoding",
"Upgrade",
}