141 lines
3.8 KiB
Go
141 lines
3.8 KiB
Go
// Copyright 2015 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package srv looks up DNS SRV records.
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package srv
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import (
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"fmt"
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"net"
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"net/url"
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"strings"
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"github.com/coreos/etcd/pkg/types"
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)
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var (
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// indirection for testing
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lookupSRV = net.LookupSRV // net.DefaultResolver.LookupSRV when ctxs don't conflict
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resolveTCPAddr = net.ResolveTCPAddr
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)
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// GetCluster gets the cluster information via DNS discovery.
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// Also sees each entry as a separate instance.
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func GetCluster(service, name, dns string, apurls types.URLs) ([]string, error) {
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tempName := int(0)
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tcp2ap := make(map[string]url.URL)
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// First, resolve the apurls
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for _, url := range apurls {
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tcpAddr, err := resolveTCPAddr("tcp", url.Host)
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if err != nil {
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return nil, err
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}
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tcp2ap[tcpAddr.String()] = url
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}
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stringParts := []string{}
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updateNodeMap := func(service, scheme string) error {
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_, addrs, err := lookupSRV(service, "tcp", dns)
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if err != nil {
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return err
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}
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for _, srv := range addrs {
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port := fmt.Sprintf("%d", srv.Port)
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host := net.JoinHostPort(srv.Target, port)
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tcpAddr, terr := resolveTCPAddr("tcp", host)
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if terr != nil {
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err = terr
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continue
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}
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n := ""
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url, ok := tcp2ap[tcpAddr.String()]
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if ok {
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n = name
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}
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if n == "" {
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n = fmt.Sprintf("%d", tempName)
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tempName++
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}
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// SRV records have a trailing dot but URL shouldn't.
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shortHost := strings.TrimSuffix(srv.Target, ".")
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urlHost := net.JoinHostPort(shortHost, port)
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stringParts = append(stringParts, fmt.Sprintf("%s=%s://%s", n, scheme, urlHost))
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if ok && url.Scheme != scheme {
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err = fmt.Errorf("bootstrap at %s from DNS for %s has scheme mismatch with expected peer %s", scheme+"://"+urlHost, service, url.String())
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}
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}
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if len(stringParts) == 0 {
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return err
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}
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return nil
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}
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failCount := 0
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err := updateNodeMap(service+"-ssl", "https")
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srvErr := make([]string, 2)
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if err != nil {
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srvErr[0] = fmt.Sprintf("error querying DNS SRV records for _%s-ssl %s", service, err)
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failCount++
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}
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err = updateNodeMap(service, "http")
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if err != nil {
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srvErr[1] = fmt.Sprintf("error querying DNS SRV records for _%s %s", service, err)
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failCount++
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}
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if failCount == 2 {
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return nil, fmt.Errorf("srv: too many errors querying DNS SRV records (%q, %q)", srvErr[0], srvErr[1])
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}
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return stringParts, nil
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}
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type SRVClients struct {
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Endpoints []string
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SRVs []*net.SRV
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}
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// GetClient looks up the client endpoints for a service and domain.
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func GetClient(service, domain string) (*SRVClients, error) {
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var urls []*url.URL
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var srvs []*net.SRV
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updateURLs := func(service, scheme string) error {
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_, addrs, err := lookupSRV(service, "tcp", domain)
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if err != nil {
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return err
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}
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for _, srv := range addrs {
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urls = append(urls, &url.URL{
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Scheme: scheme,
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Host: net.JoinHostPort(srv.Target, fmt.Sprintf("%d", srv.Port)),
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})
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}
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srvs = append(srvs, addrs...)
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return nil
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}
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errHTTPS := updateURLs(service+"-ssl", "https")
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errHTTP := updateURLs(service, "http")
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if errHTTPS != nil && errHTTP != nil {
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return nil, fmt.Errorf("dns lookup errors: %s and %s", errHTTPS, errHTTP)
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}
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endpoints := make([]string, len(urls))
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for i := range urls {
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endpoints[i] = urls[i].String()
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}
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return &SRVClients{Endpoints: endpoints, SRVs: srvs}, nil
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}
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