khenaidoo | ffe076b | 2019-01-15 16:08:08 -0500 | [diff] [blame^] | 1 | // Copyright 2015 The etcd Authors |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | // you may not use this file except in compliance with the License. |
| 5 | // You may obtain a copy of the License at |
| 6 | // |
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | // See the License for the specific language governing permissions and |
| 13 | // limitations under the License. |
| 14 | |
| 15 | package httpproxy |
| 16 | |
| 17 | import ( |
| 18 | "encoding/json" |
| 19 | "net/http" |
| 20 | "strings" |
| 21 | "time" |
| 22 | |
| 23 | "golang.org/x/net/http2" |
| 24 | ) |
| 25 | |
| 26 | const ( |
| 27 | // DefaultMaxIdleConnsPerHost indicates the default maximum idle connection |
| 28 | // count maintained between proxy and each member. We set it to 128 to |
| 29 | // let proxy handle 128 concurrent requests in long term smoothly. |
| 30 | // If the number of concurrent requests is bigger than this value, |
| 31 | // proxy needs to create one new connection when handling each request in |
| 32 | // the delta, which is bad because the creation consumes resource and |
| 33 | // may eat up ephemeral ports. |
| 34 | DefaultMaxIdleConnsPerHost = 128 |
| 35 | ) |
| 36 | |
| 37 | // GetProxyURLs is a function which should return the current set of URLs to |
| 38 | // which client requests should be proxied. This function will be queried |
| 39 | // periodically by the proxy Handler to refresh the set of available |
| 40 | // backends. |
| 41 | type GetProxyURLs func() []string |
| 42 | |
| 43 | // NewHandler creates a new HTTP handler, listening on the given transport, |
| 44 | // which will proxy requests to an etcd cluster. |
| 45 | // The handler will periodically update its view of the cluster. |
| 46 | func NewHandler(t *http.Transport, urlsFunc GetProxyURLs, failureWait time.Duration, refreshInterval time.Duration) http.Handler { |
| 47 | if t.TLSClientConfig != nil { |
| 48 | // Enable http2, see Issue 5033. |
| 49 | err := http2.ConfigureTransport(t) |
| 50 | if err != nil { |
| 51 | plog.Infof("Error enabling Transport HTTP/2 support: %v", err) |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | p := &reverseProxy{ |
| 56 | director: newDirector(urlsFunc, failureWait, refreshInterval), |
| 57 | transport: t, |
| 58 | } |
| 59 | |
| 60 | mux := http.NewServeMux() |
| 61 | mux.Handle("/", p) |
| 62 | mux.HandleFunc("/v2/config/local/proxy", p.configHandler) |
| 63 | |
| 64 | return mux |
| 65 | } |
| 66 | |
| 67 | // NewReadonlyHandler wraps the given HTTP handler to allow only GET requests |
| 68 | func NewReadonlyHandler(hdlr http.Handler) http.Handler { |
| 69 | readonly := readonlyHandlerFunc(hdlr) |
| 70 | return http.HandlerFunc(readonly) |
| 71 | } |
| 72 | |
| 73 | func readonlyHandlerFunc(next http.Handler) func(http.ResponseWriter, *http.Request) { |
| 74 | return func(w http.ResponseWriter, req *http.Request) { |
| 75 | if req.Method != "GET" { |
| 76 | w.WriteHeader(http.StatusNotImplemented) |
| 77 | return |
| 78 | } |
| 79 | |
| 80 | next.ServeHTTP(w, req) |
| 81 | } |
| 82 | } |
| 83 | |
| 84 | func (p *reverseProxy) configHandler(w http.ResponseWriter, r *http.Request) { |
| 85 | if !allowMethod(w, r.Method, "GET") { |
| 86 | return |
| 87 | } |
| 88 | |
| 89 | eps := p.director.endpoints() |
| 90 | epstr := make([]string, len(eps)) |
| 91 | for i, e := range eps { |
| 92 | epstr[i] = e.URL.String() |
| 93 | } |
| 94 | |
| 95 | proxyConfig := struct { |
| 96 | Endpoints []string `json:"endpoints"` |
| 97 | }{ |
| 98 | Endpoints: epstr, |
| 99 | } |
| 100 | |
| 101 | json.NewEncoder(w).Encode(proxyConfig) |
| 102 | } |
| 103 | |
| 104 | // allowMethod verifies that the given method is one of the allowed methods, |
| 105 | // and if not, it writes an error to w. A boolean is returned indicating |
| 106 | // whether or not the method is allowed. |
| 107 | func allowMethod(w http.ResponseWriter, m string, ms ...string) bool { |
| 108 | for _, meth := range ms { |
| 109 | if m == meth { |
| 110 | return true |
| 111 | } |
| 112 | } |
| 113 | w.Header().Set("Allow", strings.Join(ms, ",")) |
| 114 | http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed) |
| 115 | return false |
| 116 | } |