package consul import ( "fmt" "io" "log" "os" "path/filepath" "strconv" "strings" "sync" "time" "github.com/hashicorp/consul/consul/agent" "github.com/hashicorp/consul/consul/servers" "github.com/hashicorp/consul/consul/structs" "github.com/hashicorp/serf/coordinate" "github.com/hashicorp/serf/serf" ) const ( // clientRPCConnMaxIdle controls how long we keep an idle connection // open to a server. 127s was chosen as the first prime above 120s // (arbitrarily chose to use a prime) with the intent of reusing // connections who are used by once-a-minute cron(8) jobs *and* who // use a 60s jitter window (e.g. in vixie cron job execution can // drift by up to 59s per job, or 119s for a once-a-minute cron job). clientRPCConnMaxIdle = 127 * time.Second // clientMaxStreams controls how many idle streams we keep // open to a server clientMaxStreams = 32 // serfEventBacklog is the maximum number of unprocessed Serf Events // that will be held in queue before new serf events block. A // blocking serf event queue is a bad thing. serfEventBacklog = 256 // serfEventBacklogWarning is the threshold at which point log // warnings will be emitted indicating a problem when processing serf // events. serfEventBacklogWarning = 200 ) // Interface is used to provide either a Client or Server, // both of which can be used to perform certain common // Consul methods type Interface interface { RPC(method string, args interface{}, reply interface{}) error LANMembers() []serf.Member LocalMember() serf.Member } // Client is Consul client which uses RPC to communicate with the // services for service discovery, health checking, and DC forwarding. type Client struct { config *Config // Connection pool to consul servers connPool *ConnPool // servers is responsible for the selection and maintenance of // Consul servers this agent uses for RPC requests servers *servers.Manager // eventCh is used to receive events from the // serf cluster in the datacenter eventCh chan serf.Event // Logger uses the provided LogOutput logger *log.Logger // serf is the Serf cluster maintained inside the DC // which contains all the DC nodes serf *serf.Serf shutdown bool shutdownCh chan struct{} shutdownLock sync.Mutex } // NewClient is used to construct a new Consul client from the // configuration, potentially returning an error func NewClient(config *Config) (*Client, error) { // Check the protocol version if err := config.CheckVersion(); err != nil { return nil, err } // Check for a data directory! if config.DataDir == "" { return nil, fmt.Errorf("Config must provide a DataDir") } // Sanity check the ACLs if err := config.CheckACL(); err != nil { return nil, err } // Ensure we have a log output if config.LogOutput == nil { config.LogOutput = os.Stderr } // Create the tls Wrapper tlsWrap, err := config.tlsConfig().OutgoingTLSWrapper() if err != nil { return nil, err } // Create a logger logger := log.New(config.LogOutput, "", log.LstdFlags) // Create server c := &Client{ config: config, connPool: NewPool(config.LogOutput, clientRPCConnMaxIdle, clientMaxStreams, tlsWrap), eventCh: make(chan serf.Event, serfEventBacklog), logger: logger, shutdownCh: make(chan struct{}), } // Start lan event handlers before lan Serf setup to prevent deadlock go c.lanEventHandler() // Initialize the lan Serf c.serf, err = c.setupSerf(config.SerfLANConfig, c.eventCh, serfLANSnapshot) if err != nil { c.Shutdown() return nil, fmt.Errorf("Failed to start lan serf: %v", err) } // Start maintenance task for servers c.servers = servers.New(c.logger, c.shutdownCh, c.serf, c.connPool) go c.servers.Start() return c, nil } // setupSerf is used to setup and initialize a Serf func (c *Client) setupSerf(conf *serf.Config, ch chan serf.Event, path string) (*serf.Serf, error) { conf.Init() conf.NodeName = c.config.NodeName conf.Tags["role"] = "node" conf.Tags["dc"] = c.config.Datacenter conf.Tags["vsn"] = fmt.Sprintf("%d", c.config.ProtocolVersion) conf.Tags["vsn_min"] = fmt.Sprintf("%d", ProtocolVersionMin) conf.Tags["vsn_max"] = fmt.Sprintf("%d", ProtocolVersionMax) conf.Tags["build"] = c.config.Build conf.MemberlistConfig.LogOutput = c.config.LogOutput conf.LogOutput = c.config.LogOutput conf.EventCh = ch conf.SnapshotPath = filepath.Join(c.config.DataDir, path) conf.ProtocolVersion = protocolVersionMap[c.config.ProtocolVersion] conf.RejoinAfterLeave = c.config.RejoinAfterLeave conf.Merge = &lanMergeDelegate{dc: c.config.Datacenter} conf.DisableCoordinates = c.config.DisableCoordinates if err := ensurePath(conf.SnapshotPath, false); err != nil { return nil, err } return serf.Create(conf) } // Shutdown is used to shutdown the client func (c *Client) Shutdown() error { c.logger.Printf("[INFO] consul: shutting down client") c.shutdownLock.Lock() defer c.shutdownLock.Unlock() if c.shutdown { return nil } c.shutdown = true close(c.shutdownCh) if c.serf != nil { c.serf.Shutdown() } // Close the connection pool c.connPool.Shutdown() return nil } // Leave is used to prepare for a graceful shutdown func (c *Client) Leave() error { c.logger.Printf("[INFO] consul: client starting leave") // Leave the LAN pool if c.serf != nil { if err := c.serf.Leave(); err != nil { c.logger.Printf("[ERR] consul: Failed to leave LAN Serf cluster: %v", err) } } return nil } // JoinLAN is used to have Consul client join the inner-DC pool // The target address should be another node inside the DC // listening on the Serf LAN address func (c *Client) JoinLAN(addrs []string) (int, error) { return c.serf.Join(addrs, true) } // LocalMember is used to return the local node func (c *Client) LocalMember() serf.Member { return c.serf.LocalMember() } // LANMembers is used to return the members of the LAN cluster func (c *Client) LANMembers() []serf.Member { return c.serf.Members() } // RemoveFailedNode is used to remove a failed node from the cluster func (c *Client) RemoveFailedNode(node string) error { return c.serf.RemoveFailedNode(node) } // KeyManagerLAN returns the LAN Serf keyring manager func (c *Client) KeyManagerLAN() *serf.KeyManager { return c.serf.KeyManager() } // Encrypted determines if gossip is encrypted func (c *Client) Encrypted() bool { return c.serf.EncryptionEnabled() } // lanEventHandler is used to handle events from the lan Serf cluster func (c *Client) lanEventHandler() { var numQueuedEvents int for { numQueuedEvents = len(c.eventCh) if numQueuedEvents > serfEventBacklogWarning { c.logger.Printf("[WARN] consul: number of queued serf events above warning threshold: %d/%d", numQueuedEvents, serfEventBacklogWarning) } select { case e := <-c.eventCh: switch e.EventType() { case serf.EventMemberJoin: c.nodeJoin(e.(serf.MemberEvent)) case serf.EventMemberLeave, serf.EventMemberFailed: c.nodeFail(e.(serf.MemberEvent)) case serf.EventUser: c.localEvent(e.(serf.UserEvent)) case serf.EventMemberUpdate: // Ignore case serf.EventMemberReap: // Ignore case serf.EventQuery: // Ignore default: c.logger.Printf("[WARN] consul: unhandled LAN Serf Event: %#v", e) } case <-c.shutdownCh: return } } } // nodeJoin is used to handle join events on the serf cluster func (c *Client) nodeJoin(me serf.MemberEvent) { for _, m := range me.Members { ok, parts := agent.IsConsulServer(m) if !ok { continue } if parts.Datacenter != c.config.Datacenter { c.logger.Printf("[WARN] consul: server %s for datacenter %s has joined wrong cluster", m.Name, parts.Datacenter) continue } c.logger.Printf("[INFO] consul: adding server %s", parts) c.servers.AddServer(parts) // Trigger the callback if c.config.ServerUp != nil { c.config.ServerUp() } } } // nodeFail is used to handle fail events on the serf cluster func (c *Client) nodeFail(me serf.MemberEvent) { for _, m := range me.Members { ok, parts := agent.IsConsulServer(m) if !ok { continue } c.logger.Printf("[INFO] consul: removing server %s", parts) c.servers.RemoveServer(parts) } } // localEvent is called when we receive an event on the local Serf func (c *Client) localEvent(event serf.UserEvent) { // Handle only consul events if !strings.HasPrefix(event.Name, "consul:") { return } switch name := event.Name; { case name == newLeaderEvent: c.logger.Printf("[INFO] consul: New leader elected: %s", event.Payload) // Trigger the callback if c.config.ServerUp != nil { c.config.ServerUp() } case isUserEvent(name): event.Name = rawUserEventName(name) c.logger.Printf("[DEBUG] consul: user event: %s", event.Name) // Trigger the callback if c.config.UserEventHandler != nil { c.config.UserEventHandler(event) } default: c.logger.Printf("[WARN] consul: Unhandled local event: %v", event) } } // RPC is used to forward an RPC call to a consul server, or fail if no servers func (c *Client) RPC(method string, args interface{}, reply interface{}) error { server := c.servers.FindServer() if server == nil { return structs.ErrNoServers } // Forward to remote Consul if err := c.connPool.RPC(c.config.Datacenter, server.Addr, server.Version, method, args, reply); err != nil { c.servers.NotifyFailedServer(server) c.logger.Printf("[ERR] consul: RPC failed to server %s: %v", server.Addr, err) return err } return nil } // SnapshotReplyFn gets a peek at the reply before the snapshot streams, which // is useful for setting headers. type SnapshotReplyFn func(reply *structs.SnapshotResponse) error // SnapshotRPC sends the snapshot request to one of the servers, reading from // the streaming input and writing to the streaming output depending on the // operation. func (c *Client) SnapshotRPC(args *structs.SnapshotRequest, in io.Reader, out io.Writer, replyFn SnapshotReplyFn) error { // Locate a server to make the request to. server := c.servers.FindServer() if server == nil { return structs.ErrNoServers } // Request the operation. var reply structs.SnapshotResponse snap, err := SnapshotRPC(c.connPool, c.config.Datacenter, server.Addr, args, in, &reply) if err != nil { return err } defer func() { if err := snap.Close(); err != nil { c.logger.Printf("[WARN] consul: Failed closing snapshot stream: %v", err) } }() // Let the caller peek at the reply. if replyFn != nil { if err := replyFn(&reply); err != nil { return nil } } // Stream the snapshot. if out != nil { if _, err := io.Copy(out, snap); err != nil { return fmt.Errorf("failed to stream snapshot: %v", err) } } return nil } // Stats is used to return statistics for debugging and insight // for various sub-systems func (c *Client) Stats() map[string]map[string]string { numServers := c.servers.NumServers() toString := func(v uint64) string { return strconv.FormatUint(v, 10) } stats := map[string]map[string]string{ "consul": map[string]string{ "server": "false", "known_servers": toString(uint64(numServers)), }, "serf_lan": c.serf.Stats(), "runtime": runtimeStats(), } return stats } // GetCoordinate returns the network coordinate of the current node, as // maintained by Serf. func (c *Client) GetCoordinate() (*coordinate.Coordinate, error) { return c.serf.GetCoordinate() }