package pool import ( "container/list" "crypto/tls" "fmt" "log" "net" "net/rpc" "sync" "sync/atomic" "time" "github.com/hashicorp/consul/agent/structs" "github.com/hashicorp/consul/lib" "github.com/hashicorp/consul/tlsutil" msgpackrpc "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 nodeName string addr net.Addr session muxSession lastUsed time.Time 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.NewCodecFromHandle(true, true, stream, structs.MsgpackHandle) // 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. Maintain at most one // connection per host, for up to MaxTime. When MaxTime connection // reaping is disabled. MaxStreams is used to control the number of idle // streams allowed. If TLS settings are provided outgoing connections // use TLS. type ConnPool struct { // SrcAddr is the source address for outgoing connections. SrcAddr *net.TCPAddr // Logger passed to yamux // TODO: consider refactoring to accept a full yamux.Config instead of a logger Logger *log.Logger // The maximum time to keep a connection open MaxTime time.Duration // The maximum number of open streams to keep MaxStreams int // TLSConfigurator TLSConfigurator *tlsutil.Configurator // GatewayResolver is a function that returns a suitable random mesh // gateway address for dialing servers in a given DC. This is only // needed if wan federation via mesh gateways is enabled. GatewayResolver func(string) string // Datacenter is the datacenter of the current agent. Datacenter string // Server should be set to true if this connection pool is configured in a // server instead of a client. Server bool sync.Mutex // pool maps a nodeName+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{} // Used to indicate the pool is shutdown shutdown bool shutdownCh chan struct{} // once initializes the internal data structures and connection // reaping on first use. once sync.Once } // init configures the initial data structures. It should be called // by p.once.Do(p.init) in all public methods. func (p *ConnPool) init() { p.pool = make(map[string]*Conn) p.limiter = make(map[string]chan struct{}) p.shutdownCh = make(chan struct{}) if p.MaxTime > 0 { go p.reap() } } // Shutdown is used to close the connection pool func (p *ConnPool) Shutdown() error { p.once.Do(p.init) 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, nodeName string, addr net.Addr) (*Conn, error) { if nodeName == "" { return nil, fmt.Errorf("pool: ConnPool.acquire requires a node name") } addrStr := addr.String() poolKey := nodeName + ":" + addrStr // Check to see if there's a pooled connection available. This is up // here since it should the vastly more common case than the rest // of the code here. p.Lock() c := p.pool[poolKey] 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, nodeName, addr) p.Lock() delete(p.limiter, addrStr) close(wait) if err != nil { p.Unlock() return nil, err } p.pool[poolKey] = 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[poolKey]; 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 without exposing // the underlying TLS or raw TCP connection. type HalfCloser interface { CloseWrite() error } // DialTimeout is used to establish a raw connection to the given server, with // given connection timeout. It also writes RPCTLS as the first byte. func (p *ConnPool) DialTimeout( dc string, nodeName string, addr net.Addr, actualRPCType RPCType, ) (net.Conn, HalfCloser, error) { p.once.Do(p.init) if p.Server && p.GatewayResolver != nil && p.TLSConfigurator != nil && dc != p.Datacenter { // NOTE: TLS is required on this branch. return DialTimeoutWithRPCTypeViaMeshGateway( dc, nodeName, addr, p.SrcAddr, p.TLSConfigurator.OutgoingALPNRPCWrapper(), actualRPCType, RPCTLS, // gateway stuff p.Server, p.TLSConfigurator, p.GatewayResolver, p.Datacenter, ) } return p.dial(dc, addr, actualRPCType, RPCTLS) } func (p *ConnPool) dial( dc string, addr net.Addr, actualRPCType RPCType, tlsRPCType RPCType, ) (net.Conn, HalfCloser, error) { // Try to dial the conn d := &net.Dialer{LocalAddr: p.SrcAddr, Timeout: defaultDialTimeout} conn, err := d.Dial("tcp", addr.String()) if err != nil { return nil, nil, err } var hc HalfCloser if tcp, ok := conn.(*net.TCPConn); ok { tcp.SetKeepAlive(true) tcp.SetNoDelay(true) // Expose TCPConn CloseWrite method on HalfCloser hc = tcp } // Check if TLS is enabled if p.TLSConfigurator.UseTLS(dc) { wrapper := p.TLSConfigurator.OutgoingRPCWrapper() // Switch the connection into TLS mode if _, err := conn.Write([]byte{byte(tlsRPCType)}); err != nil { conn.Close() return nil, nil, err } // Wrap the connection in a TLS client tlsConn, err := wrapper(dc, conn) if err != nil { conn.Close() return nil, nil, err } conn = tlsConn // If this is a tls.Conn, expose HalfCloser to caller if tlsConn, ok := conn.(*tls.Conn); ok { hc = tlsConn } } // Send the type-byte for the protocol if one is required. // // When using insecure TLS there is no inner type-byte as these connections // aren't wrapped like the standard TLS ones are. if tlsRPCType != RPCTLSInsecure { if _, err := conn.Write([]byte{byte(actualRPCType)}); err != nil { conn.Close() return nil, nil, err } } return conn, hc, nil } // DialTimeoutWithRPCTypeViaMeshGateway dials the destination node and sets up // the connection to be the correct RPC type using ALPN. This currently is // exclusively used to dial other servers in foreign datacenters via mesh // gateways. // // NOTE: There is a close mirror of this method in agent/consul/wanfed/wanfed.go:dial func DialTimeoutWithRPCTypeViaMeshGateway( dc string, nodeName string, addr net.Addr, src *net.TCPAddr, wrapper tlsutil.ALPNWrapper, actualRPCType RPCType, tlsRPCType RPCType, // gateway stuff dialingFromServer bool, tlsConfigurator *tlsutil.Configurator, gatewayResolver func(string) string, thisDatacenter string, ) (net.Conn, HalfCloser, error) { if !dialingFromServer { return nil, nil, fmt.Errorf("must dial via mesh gateways from a server agent") } else if gatewayResolver == nil { return nil, nil, fmt.Errorf("gatewayResolver is nil") } else if tlsConfigurator == nil { return nil, nil, fmt.Errorf("tlsConfigurator is nil") } else if dc == thisDatacenter { return nil, nil, fmt.Errorf("cannot dial servers in the same datacenter via a mesh gateway") } else if wrapper == nil { return nil, nil, fmt.Errorf("cannot dial via a mesh gateway when outgoing TLS is disabled") } nextProto := actualRPCType.ALPNString() if nextProto == "" { return nil, nil, fmt.Errorf("rpc type %d cannot be routed through a mesh gateway", actualRPCType) } gwAddr := gatewayResolver(dc) if gwAddr == "" { return nil, nil, structs.ErrDCNotAvailable } dialer := &net.Dialer{LocalAddr: src, Timeout: defaultDialTimeout} rawConn, err := dialer.Dial("tcp", gwAddr) if err != nil { return nil, nil, err } if tcp, ok := rawConn.(*net.TCPConn); ok { _ = tcp.SetKeepAlive(true) _ = tcp.SetNoDelay(true) } // NOTE: now we wrap the connection in a TLS client. tlsConn, err := wrapper(dc, nodeName, nextProto, rawConn) if err != nil { return nil, nil, err } var conn net.Conn = tlsConn var hc HalfCloser if tlsConn, ok := conn.(*tls.Conn); ok { // Expose *tls.Conn CloseWrite method on HalfCloser hc = tlsConn } return conn, hc, nil } // getNewConn is used to return a new connection func (p *ConnPool) getNewConn(dc string, nodeName string, addr net.Addr) (*Conn, error) { if nodeName == "" { return nil, fmt.Errorf("pool: ConnPool.getNewConn requires a node name") } // Get a new, raw connection and write the Consul multiplex byte to set the mode conn, _, err := p.DialTimeout(dc, nodeName, addr, RPCMultiplexV2) if err != nil { return nil, err } conf := yamux.DefaultConfig() // override the default because LogOutput conflicts with Logger. conf.LogOutput = nil conf.Logger = p.Logger // Create a multiplexed session session, err := yamux.Client(conn, conf) if err != nil { conn.Close() return nil, fmt.Errorf("Failed to create yamux client: %w", err) } // Wrap the connection c := &Conn{ refCount: 1, nodeName: nodeName, addr: addr, session: session, clients: list.New(), lastUsed: time.Now(), 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) { if conn.nodeName == "" { panic("pool: ConnPool.acquire requires a node name") } // Ensure returned streams are closed atomic.StoreInt32(&conn.shouldClose, 1) // Clear from the cache addrStr := conn.addr.String() poolKey := conn.nodeName + ":" + addrStr p.Lock() if c, ok := p.pool[poolKey]; ok && c == conn { delete(p.pool, poolKey) } 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 func (p *ConnPool) getClient(dc string, nodeName string, addr net.Addr) (*Conn, *StreamClient, error) { retries := 0 START: // Try to get a conn first conn, err := p.acquire(dc, nodeName, addr) if err != nil { return nil, nil, fmt.Errorf("failed to get conn: %w", 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: %w", err) } return conn, client, nil } // RPC is used to make an RPC call to a remote host func (p *ConnPool) RPC( dc string, nodeName string, addr net.Addr, method string, args interface{}, reply interface{}, ) error { if nodeName == "" { return fmt.Errorf("pool: ConnPool.RPC requires a node name") } // TODO (autoconf) probably will want to have a way to invoke the // secure or insecure variant depending on whether its an ongoing // or first time config request. For now though this is fine until // those ongoing requests are implemented. if method == "AutoEncrypt.Sign" || method == "AutoConfig.InitialConfiguration" { return p.rpcInsecure(dc, addr, method, args, reply) } else { return p.rpc(dc, nodeName, addr, method, args, reply) } } // rpcInsecure is used to make an RPC call to a remote host. // It doesn't actually use any of the pooling, it is here so that it is // transparent for the consumer. The pool cannot be used because // AutoEncrypt.Sign is a one-off call and it doesn't make sense to pool that // connection if it is not being reused. func (p *ConnPool) rpcInsecure(dc string, addr net.Addr, method string, args interface{}, reply interface{}) error { if dc != p.Datacenter { return fmt.Errorf("insecure dialing prohibited between datacenters") } var codec rpc.ClientCodec conn, _, err := p.dial(dc, addr, 0, RPCTLSInsecure) if err != nil { return fmt.Errorf("rpcinsecure error establishing connection: %w", err) } codec = msgpackrpc.NewCodecFromHandle(true, true, conn, structs.MsgpackHandle) // Make the RPC call err = msgpackrpc.CallWithCodec(codec, method, args, reply) if err != nil { return fmt.Errorf("rpcinsecure error making call: %w", err) } return nil } func (p *ConnPool) rpc(dc string, nodeName string, addr net.Addr, method string, args interface{}, reply interface{}) error { p.once.Do(p.init) // Get a usable client conn, sc, err := p.getClient(dc, nodeName, addr) if err != nil { return fmt.Errorf("rpc error getting client: %w", err) } // Make the RPC call err = msgpackrpc.CallWithCodec(sc.codec, method, args, reply) if err != nil { sc.Close() // See the comment in leader_test.go TestLeader_ChangeServerID // about how we found this. The tldr is that if we see this // error, we know this connection is toast, so we should clear // it and make a new one on the next attempt. if lib.IsErrEOF(err) { p.clearConn(conn) } p.releaseConn(conn) return fmt.Errorf("rpc error making call: %w", err) } // Done with the connection conn.returnClient(sc) p.releaseConn(conn) return nil } // Ping sends a Status.Ping message to the specified server and // returns true if healthy, false if an error occurred func (p *ConnPool) Ping(dc string, nodeName string, addr net.Addr) (bool, error) { var out struct{} err := p.RPC(dc, nodeName, addr, "Status.Ping", struct{}{}, &out) return err == nil, err } // 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() } }