khenaidoo | d948f77 | 2021-08-11 17:49:24 -0400 | [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 srv looks up DNS SRV records. |
| 16 | package srv |
| 17 | |
| 18 | import ( |
| 19 | "fmt" |
| 20 | "net" |
| 21 | "net/url" |
| 22 | "strings" |
| 23 | |
| 24 | "github.com/coreos/etcd/pkg/types" |
| 25 | ) |
| 26 | |
| 27 | var ( |
| 28 | // indirection for testing |
| 29 | lookupSRV = net.LookupSRV // net.DefaultResolver.LookupSRV when ctxs don't conflict |
| 30 | resolveTCPAddr = net.ResolveTCPAddr |
| 31 | ) |
| 32 | |
| 33 | // GetCluster gets the cluster information via DNS discovery. |
| 34 | // Also sees each entry as a separate instance. |
| 35 | func GetCluster(service, name, dns string, apurls types.URLs) ([]string, error) { |
| 36 | tempName := int(0) |
| 37 | tcp2ap := make(map[string]url.URL) |
| 38 | |
| 39 | // First, resolve the apurls |
| 40 | for _, url := range apurls { |
| 41 | tcpAddr, err := resolveTCPAddr("tcp", url.Host) |
| 42 | if err != nil { |
| 43 | return nil, err |
| 44 | } |
| 45 | tcp2ap[tcpAddr.String()] = url |
| 46 | } |
| 47 | |
| 48 | stringParts := []string{} |
| 49 | updateNodeMap := func(service, scheme string) error { |
| 50 | _, addrs, err := lookupSRV(service, "tcp", dns) |
| 51 | if err != nil { |
| 52 | return err |
| 53 | } |
| 54 | for _, srv := range addrs { |
| 55 | port := fmt.Sprintf("%d", srv.Port) |
| 56 | host := net.JoinHostPort(srv.Target, port) |
| 57 | tcpAddr, terr := resolveTCPAddr("tcp", host) |
| 58 | if terr != nil { |
| 59 | err = terr |
| 60 | continue |
| 61 | } |
| 62 | n := "" |
| 63 | url, ok := tcp2ap[tcpAddr.String()] |
| 64 | if ok { |
| 65 | n = name |
| 66 | } |
| 67 | if n == "" { |
| 68 | n = fmt.Sprintf("%d", tempName) |
| 69 | tempName++ |
| 70 | } |
| 71 | // SRV records have a trailing dot but URL shouldn't. |
| 72 | shortHost := strings.TrimSuffix(srv.Target, ".") |
| 73 | urlHost := net.JoinHostPort(shortHost, port) |
| 74 | if ok && url.Scheme != scheme { |
| 75 | err = fmt.Errorf("bootstrap at %s from DNS for %s has scheme mismatch with expected peer %s", scheme+"://"+urlHost, service, url.String()) |
| 76 | } else { |
| 77 | stringParts = append(stringParts, fmt.Sprintf("%s=%s://%s", n, scheme, urlHost)) |
| 78 | } |
| 79 | } |
| 80 | if len(stringParts) == 0 { |
| 81 | return err |
| 82 | } |
| 83 | return nil |
| 84 | } |
| 85 | |
| 86 | failCount := 0 |
| 87 | err := updateNodeMap(service+"-ssl", "https") |
| 88 | srvErr := make([]string, 2) |
| 89 | if err != nil { |
| 90 | srvErr[0] = fmt.Sprintf("error querying DNS SRV records for _%s-ssl %s", service, err) |
| 91 | failCount++ |
| 92 | } |
| 93 | err = updateNodeMap(service, "http") |
| 94 | if err != nil { |
| 95 | srvErr[1] = fmt.Sprintf("error querying DNS SRV records for _%s %s", service, err) |
| 96 | failCount++ |
| 97 | } |
| 98 | if failCount == 2 { |
| 99 | return nil, fmt.Errorf("srv: too many errors querying DNS SRV records (%q, %q)", srvErr[0], srvErr[1]) |
| 100 | } |
| 101 | return stringParts, nil |
| 102 | } |
| 103 | |
| 104 | type SRVClients struct { |
| 105 | Endpoints []string |
| 106 | SRVs []*net.SRV |
| 107 | } |
| 108 | |
| 109 | // GetClient looks up the client endpoints for a service and domain. |
| 110 | func GetClient(service, domain string) (*SRVClients, error) { |
| 111 | var urls []*url.URL |
| 112 | var srvs []*net.SRV |
| 113 | |
| 114 | updateURLs := func(service, scheme string) error { |
| 115 | _, addrs, err := lookupSRV(service, "tcp", domain) |
| 116 | if err != nil { |
| 117 | return err |
| 118 | } |
| 119 | for _, srv := range addrs { |
| 120 | urls = append(urls, &url.URL{ |
| 121 | Scheme: scheme, |
| 122 | Host: net.JoinHostPort(srv.Target, fmt.Sprintf("%d", srv.Port)), |
| 123 | }) |
| 124 | } |
| 125 | srvs = append(srvs, addrs...) |
| 126 | return nil |
| 127 | } |
| 128 | |
| 129 | errHTTPS := updateURLs(service+"-ssl", "https") |
| 130 | errHTTP := updateURLs(service, "http") |
| 131 | |
| 132 | if errHTTPS != nil && errHTTP != nil { |
| 133 | return nil, fmt.Errorf("dns lookup errors: %s and %s", errHTTPS, errHTTP) |
| 134 | } |
| 135 | |
| 136 | endpoints := make([]string, len(urls)) |
| 137 | for i := range urls { |
| 138 | endpoints[i] = urls[i].String() |
| 139 | } |
| 140 | return &SRVClients{Endpoints: endpoints, SRVs: srvs}, nil |
| 141 | } |