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etcd.go
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etcd.go
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// Package etcd provides the etcd backend plugin.
package etcd
import (
"encoding/json"
"fmt"
"strings"
"time"
"github.com/coredns/coredns/plugin"
"github.com/coredns/coredns/plugin/etcd/msg"
"github.com/coredns/coredns/plugin/pkg/fall"
"github.com/coredns/coredns/plugin/proxy"
"github.com/coredns/coredns/request"
etcdc "github.com/coreos/etcd/client"
"github.com/miekg/dns"
"golang.org/x/net/context"
)
// Etcd is a plugin talks to an etcd cluster.
type Etcd struct {
Next plugin.Handler
Fall fall.F
Zones []string
PathPrefix string
Proxy proxy.Proxy // Proxy for looking up names during the resolution process
Client etcdc.KeysAPI
Ctx context.Context
Stubmap *map[string]proxy.Proxy // list of proxies for stub resolving.
endpoints []string // Stored here as well, to aid in testing.
}
// Services implements the ServiceBackend interface.
func (e *Etcd) Services(state request.Request, exact bool, opt plugin.Options) (services []msg.Service, err error) {
services, err = e.Records(state, exact)
if err != nil {
return
}
services = msg.Group(services)
return
}
// Reverse implements the ServiceBackend interface.
func (e *Etcd) Reverse(state request.Request, exact bool, opt plugin.Options) (services []msg.Service, err error) {
return e.Services(state, exact, opt)
}
// Lookup implements the ServiceBackend interface.
func (e *Etcd) Lookup(state request.Request, name string, typ uint16) (*dns.Msg, error) {
return e.Proxy.Lookup(state, name, typ)
}
// IsNameError implements the ServiceBackend interface.
func (e *Etcd) IsNameError(err error) bool {
if ee, ok := err.(etcdc.Error); ok && ee.Code == etcdc.ErrorCodeKeyNotFound {
return true
}
return false
}
// Records looks up records in etcd. If exact is true, it will lookup just this
// name. This is used when find matches when completing SRV lookups for instance.
func (e *Etcd) Records(state request.Request, exact bool) ([]msg.Service, error) {
name := state.Name()
path, star := msg.PathWithWildcard(name, e.PathPrefix)
r, err := e.get(path, true)
if err != nil {
return nil, err
}
segments := strings.Split(msg.Path(name, e.PathPrefix), "/")
switch {
case exact && r.Node.Dir:
return nil, nil
case r.Node.Dir:
return e.loopNodes(r.Node.Nodes, segments, star, nil)
default:
return e.loopNodes([]*etcdc.Node{r.Node}, segments, false, nil)
}
}
// get is a wrapper for client.Get
func (e *Etcd) get(path string, recursive bool) (*etcdc.Response, error) {
ctx, cancel := context.WithTimeout(e.Ctx, etcdTimeout)
defer cancel()
r, err := e.Client.Get(ctx, path, &etcdc.GetOptions{Sort: false, Recursive: recursive})
if err != nil {
return nil, err
}
return r, nil
}
// skydns/local/skydns/east/staging/web
// skydns/local/skydns/west/production/web
//
// skydns/local/skydns/*/*/web
// skydns/local/skydns/*/web
// loopNodes recursively loops through the nodes and returns all the values. The nodes' keyname
// will be match against any wildcards when star is true.
func (e *Etcd) loopNodes(ns []*etcdc.Node, nameParts []string, star bool, bx map[msg.Service]bool) (sx []msg.Service, err error) {
if bx == nil {
bx = make(map[msg.Service]bool)
}
Nodes:
for _, n := range ns {
if n.Dir {
nodes, err := e.loopNodes(n.Nodes, nameParts, star, bx)
if err != nil {
return nil, err
}
sx = append(sx, nodes...)
continue
}
if star {
keyParts := strings.Split(n.Key, "/")
for i, n := range nameParts {
if i > len(keyParts)-1 {
// name is longer than key
continue Nodes
}
if n == "*" || n == "any" {
continue
}
if keyParts[i] != n {
continue Nodes
}
}
}
serv := new(msg.Service)
if err := json.Unmarshal([]byte(n.Value), serv); err != nil {
return nil, fmt.Errorf("%s: %s", n.Key, err.Error())
}
b := msg.Service{Host: serv.Host, Port: serv.Port, Priority: serv.Priority, Weight: serv.Weight, Text: serv.Text, Key: n.Key}
if _, ok := bx[b]; ok {
continue
}
bx[b] = true
serv.Key = n.Key
serv.TTL = e.TTL(n, serv)
if serv.Priority == 0 {
serv.Priority = priority
}
sx = append(sx, *serv)
}
return sx, nil
}
// TTL returns the smaller of the etcd TTL and the service's
// TTL. If neither of these are set (have a zero value), a default is used.
func (e *Etcd) TTL(node *etcdc.Node, serv *msg.Service) uint32 {
etcdTTL := uint32(node.TTL)
if etcdTTL == 0 && serv.TTL == 0 {
return ttl
}
if etcdTTL == 0 {
return serv.TTL
}
if serv.TTL == 0 {
return etcdTTL
}
if etcdTTL < serv.TTL {
return etcdTTL
}
return serv.TTL
}
const (
priority = 10 // default priority when nothing is set
ttl = 300 // default ttl when nothing is set
etcdTimeout = 5 * time.Second
)