package kv // import "github.com/docker/docker/pkg/discovery/kv" import ( "fmt" "path" "strings" "time" "github.com/docker/docker/pkg/discovery" "github.com/docker/go-connections/tlsconfig" "github.com/docker/libkv" "github.com/docker/libkv/store" "github.com/docker/libkv/store/consul" "github.com/docker/libkv/store/etcd" "github.com/docker/libkv/store/zookeeper" "github.com/sirupsen/logrus" ) const ( defaultDiscoveryPath = "docker/nodes" ) // Discovery is exported type Discovery struct { backend store.Backend store store.Store heartbeat time.Duration ttl time.Duration prefix string path string } func init() { Init() } // Init is exported func Init() { // Register to libkv zookeeper.Register() consul.Register() etcd.Register() // Register to internal discovery service discovery.Register("zk", &Discovery{backend: store.ZK}) discovery.Register("consul", &Discovery{backend: store.CONSUL}) discovery.Register("etcd", &Discovery{backend: store.ETCD}) } // Initialize is exported func (s *Discovery) Initialize(uris string, heartbeat time.Duration, ttl time.Duration, clusterOpts map[string]string) error { var ( parts = strings.SplitN(uris, "/", 2) addrs = strings.Split(parts[0], ",") err error ) // A custom prefix to the path can be optionally used. if len(parts) == 2 { s.prefix = parts[1] } s.heartbeat = heartbeat s.ttl = ttl // Use a custom path if specified in discovery options dpath := defaultDiscoveryPath if clusterOpts["kv.path"] != "" { dpath = clusterOpts["kv.path"] } s.path = path.Join(s.prefix, dpath) var config *store.Config if clusterOpts["kv.cacertfile"] != "" && clusterOpts["kv.certfile"] != "" && clusterOpts["kv.keyfile"] != "" { logrus.Info("Initializing discovery with TLS") tlsConfig, err := tlsconfig.Client(tlsconfig.Options{ CAFile: clusterOpts["kv.cacertfile"], CertFile: clusterOpts["kv.certfile"], KeyFile: clusterOpts["kv.keyfile"], }) if err != nil { return err } config = &store.Config{ // Set ClientTLS to trigger https (bug in libkv/etcd) ClientTLS: &store.ClientTLSConfig{ CACertFile: clusterOpts["kv.cacertfile"], CertFile: clusterOpts["kv.certfile"], KeyFile: clusterOpts["kv.keyfile"], }, // The actual TLS config that will be used TLS: tlsConfig, } } else { logrus.Info("Initializing discovery without TLS") } // Creates a new store, will ignore options given // if not supported by the chosen store s.store, err = libkv.NewStore(s.backend, addrs, config) return err } // Watch the store until either there's a store error or we receive a stop request. // Returns false if we shouldn't attempt watching the store anymore (stop request received). func (s *Discovery) watchOnce(stopCh <-chan struct{}, watchCh <-chan []*store.KVPair, discoveryCh chan discovery.Entries, errCh chan error) bool { for { select { case pairs := <-watchCh: if pairs == nil { return true } logrus.WithField("discovery", s.backend).Debugf("Watch triggered with %d nodes", len(pairs)) // Convert `KVPair` into `discovery.Entry`. addrs := make([]string, len(pairs)) for _, pair := range pairs { addrs = append(addrs, string(pair.Value)) } entries, err := discovery.CreateEntries(addrs) if err != nil { errCh <- err } else { discoveryCh <- entries } case <-stopCh: // We were requested to stop watching. return false } } } // Watch is exported func (s *Discovery) Watch(stopCh <-chan struct{}) (<-chan discovery.Entries, <-chan error) { ch := make(chan discovery.Entries) errCh := make(chan error) go func() { defer close(ch) defer close(errCh) // Forever: Create a store watch, watch until we get an error and then try again. // Will only stop if we receive a stopCh request. for { // Create the path to watch if it does not exist yet exists, err := s.store.Exists(s.path) if err != nil { errCh <- err } if !exists { if err := s.store.Put(s.path, []byte(""), &store.WriteOptions{IsDir: true}); err != nil { errCh <- err } } // Set up a watch. watchCh, err := s.store.WatchTree(s.path, stopCh) if err != nil { errCh <- err } else { if !s.watchOnce(stopCh, watchCh, ch, errCh) { return } } // If we get here it means the store watch channel was closed. This // is unexpected so let's retry later. errCh <- fmt.Errorf("Unexpected watch error") time.Sleep(s.heartbeat) } }() return ch, errCh } // Register is exported func (s *Discovery) Register(addr string) error { opts := &store.WriteOptions{TTL: s.ttl} return s.store.Put(path.Join(s.path, addr), []byte(addr), opts) } // Store returns the underlying store used by KV discovery. func (s *Discovery) Store() store.Store { return s.store } // Prefix returns the store prefix func (s *Discovery) Prefix() string { return s.prefix }