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// Copyright 2015 The etcd Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package srv looks up DNS SRV records.
package srv
import (
"fmt"
"net"
"net/url"
"strings"
"go.etcd.io/etcd/client/pkg/v3/types"
)
var (
// indirection for testing
lookupSRV = net.LookupSRV // net.DefaultResolver.LookupSRV when ctxs don't conflict
resolveTCPAddr = net.ResolveTCPAddr
)
// GetCluster gets the cluster information via DNS discovery.
// Also sees each entry as a separate instance.
func GetCluster(serviceScheme, service, name, dns string, apurls types.URLs) ([]string, error) {
tempName := int(0)
tcp2ap := make(map[string]url.URL)
// First, resolve the apurls
for _, url := range apurls {
tcpAddr, err := resolveTCPAddr("tcp", url.Host)
if err != nil {
return nil, err
}
tcp2ap[tcpAddr.String()] = url
}
stringParts := []string{}
updateNodeMap := func(service, scheme string) error {
_, addrs, err := lookupSRV(service, "tcp", dns)
if err != nil {
return err
}
for _, srv := range addrs {
port := fmt.Sprintf("%d", srv.Port)
host := net.JoinHostPort(srv.Target, port)
tcpAddr, terr := resolveTCPAddr("tcp", host)
if terr != nil {
err = terr
continue
}
n := ""
url, ok := tcp2ap[tcpAddr.String()]
if ok {
n = name
}
if n == "" {
n = fmt.Sprintf("%d", tempName)
tempName++
}
// SRV records have a trailing dot but URL shouldn't.
shortHost := strings.TrimSuffix(srv.Target, ".")
urlHost := net.JoinHostPort(shortHost, port)
if ok && url.Scheme != scheme {
err = fmt.Errorf("bootstrap at %s from DNS for %s has scheme mismatch with expected peer %s", scheme+"://"+urlHost, service, url.String())
} else {
stringParts = append(stringParts, fmt.Sprintf("%s=%s://%s", n, scheme, urlHost))
}
}
if len(stringParts) == 0 {
return err
}
return nil
}
err := updateNodeMap(service, serviceScheme)
if err != nil {
return nil, fmt.Errorf("error querying DNS SRV records for _%s %s", service, err)
}
return stringParts, nil
}
type SRVClients struct {
Endpoints []string
SRVs []*net.SRV
}
// GetClient looks up the client endpoints for a service and domain.
func GetClient(service, domain string, serviceName string) (*SRVClients, error) {
var urls []*url.URL
var srvs []*net.SRV
updateURLs := func(service, scheme string) error {
_, addrs, err := lookupSRV(service, "tcp", domain)
if err != nil {
return err
}
for _, srv := range addrs {
urls = append(urls, &url.URL{
Scheme: scheme,
Host: net.JoinHostPort(srv.Target, fmt.Sprintf("%d", srv.Port)),
})
}
srvs = append(srvs, addrs...)
return nil
}
errHTTPS := updateURLs(GetSRVService(service, serviceName, "https"), "https")
errHTTP := updateURLs(GetSRVService(service, serviceName, "http"), "http")
if errHTTPS != nil && errHTTP != nil {
return nil, fmt.Errorf("dns lookup errors: %s and %s", errHTTPS, errHTTP)
}
endpoints := make([]string, len(urls))
for i := range urls {
endpoints[i] = urls[i].String()
}
return &SRVClients{Endpoints: endpoints, SRVs: srvs}, nil
}
// GetSRVService generates a SRV service including an optional suffix.
func GetSRVService(service, serviceName string, scheme string) (SRVService string) {
if scheme == "https" {
service = fmt.Sprintf("%s-ssl", service)
}
if serviceName != "" {
return fmt.Sprintf("%s-%s", service, serviceName)
}
return service
}
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