package consul import ( "container/list" "fmt" "io" "net" "net/rpc" "sync" "sync/atomic" "time" "github.com/hashicorp/consul/consul/agent" "github.com/hashicorp/consul/tlsutil" "github.com/hashicorp/net-rpc-msgpackrpc" "github.com/hashicorp/yamux" ) const defaultDialTimeout = 10 * time.Second // muxSession is used to provide an interface for a stream multiplexer. type muxSession interface { Open() (net.Conn, error) Close() error } // streamClient is used to wrap a stream with an RPC client type StreamClient struct { stream net.Conn codec rpc.ClientCodec } func (sc *StreamClient) Close() { sc.stream.Close() sc.codec.Close() } // Conn is a pooled connection to a Consul server type Conn struct { refCount int32 shouldClose int32 addr net.Addr session muxSession lastUsed time.Time version int pool *ConnPool clients *list.List clientLock sync.Mutex } func (c *Conn) Close() error { return c.session.Close() } // getClient is used to get a cached or new client func (c *Conn) getClient() (*StreamClient, error) { // Check for cached client c.clientLock.Lock() front := c.clients.Front() if front != nil { c.clients.Remove(front) } c.clientLock.Unlock() if front != nil { return front.Value.(*StreamClient), nil } // Open a new session stream, err := c.session.Open() if err != nil { return nil, err } // Create the RPC client codec := msgpackrpc.NewClientCodec(stream) // Return a new stream client sc := &StreamClient{ stream: stream, codec: codec, } return sc, nil } // returnStream is used when done with a stream // to allow re-use by a future RPC func (c *Conn) returnClient(client *StreamClient) { didSave := false c.clientLock.Lock() if c.clients.Len() < c.pool.maxStreams && atomic.LoadInt32(&c.shouldClose) == 0 { c.clients.PushFront(client) didSave = true // If this is a Yamux stream, shrink the internal buffers so that // we can GC the idle memory if ys, ok := client.stream.(*yamux.Stream); ok { ys.Shrink() } } c.clientLock.Unlock() if !didSave { client.Close() } } // markForUse does all the bookkeeping required to ready a connection for use. func (c *Conn) markForUse() { c.lastUsed = time.Now() atomic.AddInt32(&c.refCount, 1) } // ConnPool is used to maintain a connection pool to other // Consul servers. This is used to reduce the latency of // RPC requests between servers. It is only used to pool // connections in the rpcConsul mode. Raft connections // are pooled separately. type ConnPool struct { sync.Mutex // src is the source address for outgoing connections. src *net.TCPAddr // LogOutput is used to control logging logOutput io.Writer // The maximum time to keep a connection open maxTime time.Duration // The maximum number of open streams to keep maxStreams int // pool maps an address to a open connection pool map[string]*Conn // limiter is used to throttle the number of connect attempts // to a given address. The first thread will attempt a connection // and put a channel in here, which all other threads will wait // on to close. limiter map[string]chan struct{} // TLS wrapper tlsWrap tlsutil.DCWrapper // forceTLS is used to enforce outgoing TLS verification forceTLS bool // Used to indicate the pool is shutdown shutdown bool shutdownCh chan struct{} } // NewPool is used to make a new connection pool // Maintain at most one connection per host, for up to maxTime. // Set maxTime to 0 to disable reaping. maxStreams is used to control // the number of idle streams allowed. // If TLS settings are provided outgoing connections use TLS. func NewPool(src *net.TCPAddr, logOutput io.Writer, maxTime time.Duration, maxStreams int, tlsWrap tlsutil.DCWrapper, forceTLS bool) *ConnPool { pool := &ConnPool{ src: src, logOutput: logOutput, maxTime: maxTime, maxStreams: maxStreams, pool: make(map[string]*Conn), limiter: make(map[string]chan struct{}), tlsWrap: tlsWrap, forceTLS: forceTLS, shutdownCh: make(chan struct{}), } if maxTime > 0 { go pool.reap() } return pool } // Shutdown is used to close the connection pool func (p *ConnPool) Shutdown() error { p.Lock() defer p.Unlock() for _, conn := range p.pool { conn.Close() } p.pool = make(map[string]*Conn) if p.shutdown { return nil } p.shutdown = true close(p.shutdownCh) return nil } // acquire will return a pooled connection, if available. Otherwise it will // wait for an existing connection attempt to finish, if one if in progress, // and will return that one if it succeeds. If all else fails, it will return a // newly-created connection and add it to the pool. func (p *ConnPool) acquire(dc string, addr net.Addr, version int, useTLS bool) (*Conn, error) { addrStr := addr.String() // Check to see if there's a pooled connection available. This is up // here since it should the the vastly more common case than the rest // of the code here. p.Lock() c := p.pool[addrStr] if c != nil { c.markForUse() p.Unlock() return c, nil } // If not (while we are still locked), set up the throttling structure // for this address, which will make everyone else wait until our // attempt is done. var wait chan struct{} var ok bool if wait, ok = p.limiter[addrStr]; !ok { wait = make(chan struct{}) p.limiter[addrStr] = wait } isLeadThread := !ok p.Unlock() // If we are the lead thread, make the new connection and then wake // everybody else up to see if we got it. if isLeadThread { c, err := p.getNewConn(dc, addr, version, useTLS) p.Lock() delete(p.limiter, addrStr) close(wait) if err != nil { p.Unlock() return nil, err } p.pool[addrStr] = c p.Unlock() return c, nil } // Otherwise, wait for the lead thread to attempt the connection // and use what's in the pool at that point. select { case <-p.shutdownCh: return nil, fmt.Errorf("rpc error: shutdown") case <-wait: } // See if the lead thread was able to get us a connection. p.Lock() if c := p.pool[addrStr]; c != nil { c.markForUse() p.Unlock() return c, nil } p.Unlock() return nil, fmt.Errorf("rpc error: lead thread didn't get connection") } // HalfCloser is an interface that exposes a TCP half-close. We need this // because we want to expose the raw TCP connection underlying a TLS one in a // way that's hard to screw up and use for anything else. There's a change // brewing that will allow us to use the TLS connection for this instead - // https://go-review.googlesource.com/#/c/25159/. type HalfCloser interface { CloseWrite() error } // DialTimeout is used to establish a raw connection to the given server, with a // given connection timeout. func (p *ConnPool) DialTimeout(dc string, addr net.Addr, timeout time.Duration, useTLS bool) (net.Conn, HalfCloser, error) { // Try to dial the conn d := &net.Dialer{LocalAddr: p.src, Timeout: timeout} conn, err := d.Dial("tcp", addr.String()) if err != nil { return nil, nil, err } // Cast to TCPConn var hc HalfCloser if tcp, ok := conn.(*net.TCPConn); ok { tcp.SetKeepAlive(true) tcp.SetNoDelay(true) hc = tcp } // Check if TLS is enabled if (useTLS || p.forceTLS) && p.tlsWrap != nil { // Switch the connection into TLS mode if _, err := conn.Write([]byte{byte(rpcTLS)}); err != nil { conn.Close() return nil, nil, err } // Wrap the connection in a TLS client tlsConn, err := p.tlsWrap(dc, conn) if err != nil { conn.Close() return nil, nil, err } conn = tlsConn } return conn, hc, nil } // getNewConn is used to return a new connection func (p *ConnPool) getNewConn(dc string, addr net.Addr, version int, useTLS bool) (*Conn, error) { // Get a new, raw connection. conn, _, err := p.DialTimeout(dc, addr, defaultDialTimeout, useTLS) if err != nil { return nil, err } // Switch the multiplexing based on version var session muxSession if version < 2 { conn.Close() return nil, fmt.Errorf("cannot make client connection, unsupported protocol version %d", version) } // Write the Consul multiplex byte to set the mode if _, err := conn.Write([]byte{byte(rpcMultiplexV2)}); err != nil { conn.Close() return nil, err } // Setup the logger conf := yamux.DefaultConfig() conf.LogOutput = p.logOutput // Create a multiplexed session session, _ = yamux.Client(conn, conf) // Wrap the connection c := &Conn{ refCount: 1, addr: addr, session: session, clients: list.New(), lastUsed: time.Now(), version: version, pool: p, } return c, nil } // clearConn is used to clear any cached connection, potentially in response to an error func (p *ConnPool) clearConn(conn *Conn) { // Ensure returned streams are closed atomic.StoreInt32(&conn.shouldClose, 1) // Clear from the cache addrStr := conn.addr.String() p.Lock() if c, ok := p.pool[addrStr]; ok && c == conn { delete(p.pool, addrStr) } p.Unlock() // Close down immediately if idle if refCount := atomic.LoadInt32(&conn.refCount); refCount == 0 { conn.Close() } } // releaseConn is invoked when we are done with a conn to reduce the ref count func (p *ConnPool) releaseConn(conn *Conn) { refCount := atomic.AddInt32(&conn.refCount, -1) if refCount == 0 && atomic.LoadInt32(&conn.shouldClose) == 1 { conn.Close() } } // getClient is used to get a usable client for an address and protocol version func (p *ConnPool) getClient(dc string, addr net.Addr, version int, useTLS bool) (*Conn, *StreamClient, error) { retries := 0 START: // Try to get a conn first conn, err := p.acquire(dc, addr, version, useTLS) if err != nil { return nil, nil, fmt.Errorf("failed to get conn: %v", err) } // Get a client client, err := conn.getClient() if err != nil { p.clearConn(conn) p.releaseConn(conn) // Try to redial, possible that the TCP session closed due to timeout if retries == 0 { retries++ goto START } return nil, nil, fmt.Errorf("failed to start stream: %v", err) } return conn, client, nil } // RPC is used to make an RPC call to a remote host func (p *ConnPool) RPC(dc string, addr net.Addr, version int, method string, useTLS bool, args interface{}, reply interface{}) error { // Get a usable client conn, sc, err := p.getClient(dc, addr, version, useTLS) if err != nil { return fmt.Errorf("rpc error: %v", err) } // Make the RPC call err = msgpackrpc.CallWithCodec(sc.codec, method, args, reply) if err != nil { sc.Close() p.releaseConn(conn) return fmt.Errorf("rpc error: %v", err) } // Done with the connection conn.returnClient(sc) p.releaseConn(conn) return nil } // PingConsulServer sends a Status.Ping message to the specified server and // returns true if healthy, false if an error occurred func (p *ConnPool) PingConsulServer(s *agent.Server) (bool, error) { // Get a usable client conn, sc, err := p.getClient(s.Datacenter, s.Addr, s.Version, s.UseTLS) if err != nil { return false, err } // Make the RPC call var out struct{} err = msgpackrpc.CallWithCodec(sc.codec, "Status.Ping", struct{}{}, &out) if err != nil { sc.Close() p.releaseConn(conn) return false, err } // Done with the connection conn.returnClient(sc) p.releaseConn(conn) return true, nil } // Reap is used to close conns open over maxTime func (p *ConnPool) reap() { for { // Sleep for a while select { case <-p.shutdownCh: return case <-time.After(time.Second): } // Reap all old conns p.Lock() var removed []string now := time.Now() for host, conn := range p.pool { // Skip recently used connections if now.Sub(conn.lastUsed) < p.maxTime { continue } // Skip connections with active streams if atomic.LoadInt32(&conn.refCount) > 0 { continue } // Close the conn conn.Close() // Remove from pool removed = append(removed, host) } for _, host := range removed { delete(p.pool, host) } p.Unlock() } }