mirror of https://github.com/hashicorp/consul
480 lines
12 KiB
Go
480 lines
12 KiB
Go
package pool
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import (
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"container/list"
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"fmt"
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"io"
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"net"
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"net/rpc"
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"sync"
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"sync/atomic"
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"time"
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"github.com/hashicorp/consul/tlsutil"
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"github.com/hashicorp/net-rpc-msgpackrpc"
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"github.com/hashicorp/yamux"
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)
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const defaultDialTimeout = 10 * time.Second
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// muxSession is used to provide an interface for a stream multiplexer.
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type muxSession interface {
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Open() (net.Conn, error)
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Close() error
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}
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// streamClient is used to wrap a stream with an RPC client
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type StreamClient struct {
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stream net.Conn
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codec rpc.ClientCodec
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}
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func (sc *StreamClient) Close() {
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sc.stream.Close()
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sc.codec.Close()
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}
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// Conn is a pooled connection to a Consul server
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type Conn struct {
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refCount int32
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shouldClose int32
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addr net.Addr
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session muxSession
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lastUsed time.Time
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version int
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pool *ConnPool
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clients *list.List
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clientLock sync.Mutex
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}
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func (c *Conn) Close() error {
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return c.session.Close()
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}
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// getClient is used to get a cached or new client
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func (c *Conn) getClient() (*StreamClient, error) {
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// Check for cached client
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c.clientLock.Lock()
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front := c.clients.Front()
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if front != nil {
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c.clients.Remove(front)
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}
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c.clientLock.Unlock()
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if front != nil {
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return front.Value.(*StreamClient), nil
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}
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// Open a new session
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stream, err := c.session.Open()
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if err != nil {
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return nil, err
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}
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// Create the RPC client
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codec := msgpackrpc.NewClientCodec(stream)
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// Return a new stream client
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sc := &StreamClient{
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stream: stream,
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codec: codec,
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}
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return sc, nil
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}
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// returnStream is used when done with a stream
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// to allow re-use by a future RPC
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func (c *Conn) returnClient(client *StreamClient) {
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didSave := false
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c.clientLock.Lock()
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if c.clients.Len() < c.pool.MaxStreams && atomic.LoadInt32(&c.shouldClose) == 0 {
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c.clients.PushFront(client)
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didSave = true
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// If this is a Yamux stream, shrink the internal buffers so that
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// we can GC the idle memory
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if ys, ok := client.stream.(*yamux.Stream); ok {
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ys.Shrink()
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}
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}
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c.clientLock.Unlock()
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if !didSave {
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client.Close()
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}
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}
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// markForUse does all the bookkeeping required to ready a connection for use.
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func (c *Conn) markForUse() {
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c.lastUsed = time.Now()
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atomic.AddInt32(&c.refCount, 1)
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}
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// ConnPool is used to maintain a connection pool to other Consul
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// servers. This is used to reduce the latency of RPC requests between
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// servers. It is only used to pool connections in the rpcConsul mode.
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// Raft connections are pooled separately. Maintain at most one
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// connection per host, for up to MaxTime. When MaxTime connection
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// reaping is disabled. MaxStreams is used to control the number of idle
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// streams allowed. If TLS settings are provided outgoing connections
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// use TLS.
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type ConnPool struct {
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// SrcAddr is the source address for outgoing connections.
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SrcAddr *net.TCPAddr
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// LogOutput is used to control logging
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LogOutput io.Writer
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// The maximum time to keep a connection open
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MaxTime time.Duration
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// The maximum number of open streams to keep
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MaxStreams int
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// TLS wrapper
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TLSWrapper tlsutil.DCWrapper
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// ForceTLS is used to enforce outgoing TLS verification
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ForceTLS bool
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sync.Mutex
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// pool maps an address to a open connection
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pool map[string]*Conn
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// limiter is used to throttle the number of connect attempts
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// to a given address. The first thread will attempt a connection
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// and put a channel in here, which all other threads will wait
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// on to close.
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limiter map[string]chan struct{}
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// Used to indicate the pool is shutdown
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shutdown bool
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shutdownCh chan struct{}
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// once initializes the internal data structures and connection
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// reaping on first use.
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once sync.Once
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}
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// init configures the initial data structures. It should be called
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// by p.once.Do(p.init) in all public methods.
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func (p *ConnPool) init() {
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p.pool = make(map[string]*Conn)
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p.limiter = make(map[string]chan struct{})
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p.shutdownCh = make(chan struct{})
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if p.MaxTime > 0 {
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go p.reap()
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}
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}
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// Shutdown is used to close the connection pool
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func (p *ConnPool) Shutdown() error {
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p.once.Do(p.init)
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p.Lock()
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defer p.Unlock()
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for _, conn := range p.pool {
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conn.Close()
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}
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p.pool = make(map[string]*Conn)
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if p.shutdown {
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return nil
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}
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p.shutdown = true
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close(p.shutdownCh)
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return nil
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}
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// acquire will return a pooled connection, if available. Otherwise it will
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// wait for an existing connection attempt to finish, if one if in progress,
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// and will return that one if it succeeds. If all else fails, it will return a
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// newly-created connection and add it to the pool.
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func (p *ConnPool) acquire(dc string, addr net.Addr, version int, useTLS bool) (*Conn, error) {
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addrStr := addr.String()
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// Check to see if there's a pooled connection available. This is up
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// here since it should the the vastly more common case than the rest
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// of the code here.
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p.Lock()
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c := p.pool[addrStr]
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if c != nil {
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c.markForUse()
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p.Unlock()
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return c, nil
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}
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// If not (while we are still locked), set up the throttling structure
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// for this address, which will make everyone else wait until our
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// attempt is done.
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var wait chan struct{}
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var ok bool
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if wait, ok = p.limiter[addrStr]; !ok {
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wait = make(chan struct{})
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p.limiter[addrStr] = wait
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}
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isLeadThread := !ok
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p.Unlock()
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// If we are the lead thread, make the new connection and then wake
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// everybody else up to see if we got it.
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if isLeadThread {
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c, err := p.getNewConn(dc, addr, version, useTLS)
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p.Lock()
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delete(p.limiter, addrStr)
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close(wait)
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if err != nil {
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p.Unlock()
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return nil, err
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}
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p.pool[addrStr] = c
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p.Unlock()
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return c, nil
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}
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// Otherwise, wait for the lead thread to attempt the connection
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// and use what's in the pool at that point.
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select {
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case <-p.shutdownCh:
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return nil, fmt.Errorf("rpc error: shutdown")
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case <-wait:
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}
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// See if the lead thread was able to get us a connection.
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p.Lock()
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if c := p.pool[addrStr]; c != nil {
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c.markForUse()
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p.Unlock()
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return c, nil
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}
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p.Unlock()
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return nil, fmt.Errorf("rpc error: lead thread didn't get connection")
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}
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// HalfCloser is an interface that exposes a TCP half-close. We need this
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// because we want to expose the raw TCP connection underlying a TLS one in a
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// way that's hard to screw up and use for anything else. There's a change
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// brewing that will allow us to use the TLS connection for this instead -
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// https://go-review.googlesource.com/#/c/25159/.
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type HalfCloser interface {
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CloseWrite() error
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}
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// DialTimeout is used to establish a raw connection to the given server, with a
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// given connection timeout.
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func (p *ConnPool) DialTimeout(dc string, addr net.Addr, timeout time.Duration, useTLS bool) (net.Conn, HalfCloser, error) {
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p.once.Do(p.init)
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// Try to dial the conn
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d := &net.Dialer{LocalAddr: p.SrcAddr, Timeout: timeout}
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conn, err := d.Dial("tcp", addr.String())
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if err != nil {
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return nil, nil, err
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}
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// Cast to TCPConn
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var hc HalfCloser
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if tcp, ok := conn.(*net.TCPConn); ok {
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tcp.SetKeepAlive(true)
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tcp.SetNoDelay(true)
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hc = tcp
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}
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// Check if TLS is enabled
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if (useTLS || p.ForceTLS) && p.TLSWrapper != nil {
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// Switch the connection into TLS mode
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if _, err := conn.Write([]byte{byte(RPCTLS)}); err != nil {
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conn.Close()
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return nil, nil, err
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}
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// Wrap the connection in a TLS client
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tlsConn, err := p.TLSWrapper(dc, conn)
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if err != nil {
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conn.Close()
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return nil, nil, err
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}
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conn = tlsConn
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}
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return conn, hc, nil
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}
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// getNewConn is used to return a new connection
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func (p *ConnPool) getNewConn(dc string, addr net.Addr, version int, useTLS bool) (*Conn, error) {
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// Get a new, raw connection.
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conn, _, err := p.DialTimeout(dc, addr, defaultDialTimeout, useTLS)
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if err != nil {
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return nil, err
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}
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// Switch the multiplexing based on version
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var session muxSession
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if version < 2 {
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conn.Close()
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return nil, fmt.Errorf("cannot make client connection, unsupported protocol version %d", version)
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}
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// Write the Consul multiplex byte to set the mode
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if _, err := conn.Write([]byte{byte(RPCMultiplexV2)}); err != nil {
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conn.Close()
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return nil, err
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}
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// Setup the logger
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conf := yamux.DefaultConfig()
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conf.LogOutput = p.LogOutput
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// Create a multiplexed session
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session, _ = yamux.Client(conn, conf)
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// Wrap the connection
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c := &Conn{
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refCount: 1,
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addr: addr,
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session: session,
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clients: list.New(),
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lastUsed: time.Now(),
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version: version,
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pool: p,
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}
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return c, nil
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}
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// clearConn is used to clear any cached connection, potentially in response to an error
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func (p *ConnPool) clearConn(conn *Conn) {
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// Ensure returned streams are closed
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atomic.StoreInt32(&conn.shouldClose, 1)
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// Clear from the cache
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addrStr := conn.addr.String()
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p.Lock()
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if c, ok := p.pool[addrStr]; ok && c == conn {
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delete(p.pool, addrStr)
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}
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p.Unlock()
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// Close down immediately if idle
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if refCount := atomic.LoadInt32(&conn.refCount); refCount == 0 {
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conn.Close()
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}
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}
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// releaseConn is invoked when we are done with a conn to reduce the ref count
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func (p *ConnPool) releaseConn(conn *Conn) {
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refCount := atomic.AddInt32(&conn.refCount, -1)
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if refCount == 0 && atomic.LoadInt32(&conn.shouldClose) == 1 {
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conn.Close()
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}
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}
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// getClient is used to get a usable client for an address and protocol version
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func (p *ConnPool) getClient(dc string, addr net.Addr, version int, useTLS bool) (*Conn, *StreamClient, error) {
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retries := 0
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START:
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// Try to get a conn first
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conn, err := p.acquire(dc, addr, version, useTLS)
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if err != nil {
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return nil, nil, fmt.Errorf("failed to get conn: %v", err)
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}
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// Get a client
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client, err := conn.getClient()
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if err != nil {
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p.clearConn(conn)
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p.releaseConn(conn)
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// Try to redial, possible that the TCP session closed due to timeout
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if retries == 0 {
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retries++
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goto START
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}
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return nil, nil, fmt.Errorf("failed to start stream: %v", err)
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}
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return conn, client, nil
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}
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// RPC is used to make an RPC call to a remote host
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func (p *ConnPool) RPC(dc string, addr net.Addr, version int, method string, useTLS bool, args interface{}, reply interface{}) error {
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p.once.Do(p.init)
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// Get a usable client
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conn, sc, err := p.getClient(dc, addr, version, useTLS)
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if err != nil {
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return fmt.Errorf("rpc error: %v", err)
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}
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// Make the RPC call
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err = msgpackrpc.CallWithCodec(sc.codec, method, args, reply)
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if err != nil {
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sc.Close()
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// See the comment in leader_test.go TestLeader_ChangeServerID
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// about how we found this. The tldr is that if we see this
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// error, we know this connection is toast, so we should clear
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// it and make a new one on the next attempt.
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if err == io.EOF {
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p.clearConn(conn)
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}
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p.releaseConn(conn)
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return fmt.Errorf("rpc error: %v", err)
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}
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// Done with the connection
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conn.returnClient(sc)
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p.releaseConn(conn)
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return nil
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}
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// Ping sends a Status.Ping message to the specified server and
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// returns true if healthy, false if an error occurred
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func (p *ConnPool) Ping(dc string, addr net.Addr, version int, useTLS bool) (bool, error) {
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var out struct{}
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err := p.RPC(dc, addr, version, "Status.Ping", useTLS, struct{}{}, &out)
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return err == nil, err
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}
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// Reap is used to close conns open over maxTime
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func (p *ConnPool) reap() {
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for {
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// Sleep for a while
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select {
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case <-p.shutdownCh:
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return
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case <-time.After(time.Second):
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}
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// Reap all old conns
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p.Lock()
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var removed []string
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now := time.Now()
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for host, conn := range p.pool {
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// Skip recently used connections
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if now.Sub(conn.lastUsed) < p.MaxTime {
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continue
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}
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// Skip connections with active streams
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if atomic.LoadInt32(&conn.refCount) > 0 {
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continue
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}
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// Close the conn
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conn.Close()
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// Remove from pool
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removed = append(removed, host)
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}
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for _, host := range removed {
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delete(p.pool, host)
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}
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p.Unlock()
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}
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}
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