d7d2f14d61
`bitcoind` notifies transactions once they're accepted into the mempool and once they're confirmed in a block. Previously, reading a message from ZMQ would allocate a buffer with the size of the message. This can cause nodes to perform a large number of allocations within a small amount periodically (3000 300B allocations every 10 mins on average), which can cause a lot of GC pressure on lower resourced nodes. To remedy this, we introduce two static buffers, one for blocks and another for transactions, that will be reused for every message read. Each is constrained by its maximum expected size.
460 lines
13 KiB
Go
460 lines
13 KiB
Go
package chain
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import (
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"bytes"
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"fmt"
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"io"
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"net"
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"sync"
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"sync/atomic"
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"time"
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"github.com/btcsuite/btcd/chaincfg"
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"github.com/btcsuite/btcd/chaincfg/chainhash"
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"github.com/btcsuite/btcd/rpcclient"
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"github.com/btcsuite/btcd/wire"
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"github.com/lightninglabs/gozmq"
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)
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const (
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// rawBlockZMQCommand is the command used to receive raw block
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// notifications from bitcoind through ZMQ.
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rawBlockZMQCommand = "rawblock"
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// rawTxZMQCommand is the command used to receive raw transaction
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// notifications from bitcoind through ZMQ.
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rawTxZMQCommand = "rawtx"
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// maxRawBlockSize is the maximum size in bytes for a raw block received
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// from bitcoind through ZMQ.
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maxRawBlockSize = 4e6
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// maxRawTxSize is the maximum size in bytes for a raw transaction
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// received from bitcoind through ZMQ.
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maxRawTxSize = maxRawBlockSize
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// seqNumLen is the length of the sequence number of a message sent from
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// bitcoind through ZMQ.
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seqNumLen = 4
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)
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// BitcoindConn represents a persistent client connection to a bitcoind node
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// that listens for events read from a ZMQ connection.
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type BitcoindConn struct {
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started int32 // To be used atomically.
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stopped int32 // To be used atomically.
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// rescanClientCounter is an atomic counter that assigns a unique ID to
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// each new bitcoind rescan client using the current bitcoind
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// connection.
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rescanClientCounter uint64
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// chainParams identifies the current network the bitcoind node is
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// running on.
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chainParams *chaincfg.Params
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// client is the RPC client to the bitcoind node.
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client *rpcclient.Client
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// zmqBlockConn is the ZMQ connection we'll use to read raw block
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// events.
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zmqBlockConn *gozmq.Conn
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// zmqTxConn is the ZMQ connection we'll use to read raw transaction
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// events.
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zmqTxConn *gozmq.Conn
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// rescanClients is the set of active bitcoind rescan clients to which
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// ZMQ event notfications will be sent to.
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rescanClientsMtx sync.Mutex
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rescanClients map[uint64]*BitcoindClient
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quit chan struct{}
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wg sync.WaitGroup
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}
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// NewBitcoindConn creates a client connection to the node described by the host
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// string. The ZMQ connections are established immediately to ensure liveness.
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// If the remote node does not operate on the same bitcoin network as described
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// by the passed chain parameters, the connection will be disconnected.
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func NewBitcoindConn(chainParams *chaincfg.Params,
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host, user, pass, zmqBlockHost, zmqTxHost string,
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zmqPollInterval time.Duration) (*BitcoindConn, error) {
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clientCfg := &rpcclient.ConnConfig{
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Host: host,
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User: user,
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Pass: pass,
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DisableAutoReconnect: false,
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DisableConnectOnNew: true,
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DisableTLS: true,
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HTTPPostMode: true,
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}
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client, err := rpcclient.New(clientCfg, nil)
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if err != nil {
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return nil, err
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}
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// Establish two different ZMQ connections to bitcoind to retrieve block
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// and transaction event notifications. We'll use two as a separation of
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// concern to ensure one type of event isn't dropped from the connection
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// queue due to another type of event filling it up.
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zmqBlockConn, err := gozmq.Subscribe(
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zmqBlockHost, []string{rawBlockZMQCommand}, zmqPollInterval,
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)
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if err != nil {
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return nil, fmt.Errorf("unable to subscribe for zmq block "+
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"events: %v", err)
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}
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zmqTxConn, err := gozmq.Subscribe(
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zmqTxHost, []string{rawTxZMQCommand}, zmqPollInterval,
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)
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if err != nil {
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zmqBlockConn.Close()
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return nil, fmt.Errorf("unable to subscribe for zmq tx "+
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"events: %v", err)
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}
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conn := &BitcoindConn{
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chainParams: chainParams,
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client: client,
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zmqBlockConn: zmqBlockConn,
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zmqTxConn: zmqTxConn,
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rescanClients: make(map[uint64]*BitcoindClient),
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quit: make(chan struct{}),
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}
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return conn, nil
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}
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// Start attempts to establish a RPC and ZMQ connection to a bitcoind node. If
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// successful, a goroutine is spawned to read events from the ZMQ connection.
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// It's possible for this function to fail due to a limited number of connection
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// attempts. This is done to prevent waiting forever on the connection to be
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// established in the case that the node is down.
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func (c *BitcoindConn) Start() error {
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if !atomic.CompareAndSwapInt32(&c.started, 0, 1) {
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return nil
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}
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// Verify that the node is running on the expected network.
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net, err := c.getCurrentNet()
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if err != nil {
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return err
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}
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if net != c.chainParams.Net {
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return fmt.Errorf("expected network %v, got %v",
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c.chainParams.Net, net)
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}
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c.wg.Add(2)
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go c.blockEventHandler()
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go c.txEventHandler()
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return nil
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}
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// Stop terminates the RPC and ZMQ connection to a bitcoind node and removes any
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// active rescan clients.
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func (c *BitcoindConn) Stop() {
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if !atomic.CompareAndSwapInt32(&c.stopped, 0, 1) {
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return
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}
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for _, client := range c.rescanClients {
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client.Stop()
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}
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close(c.quit)
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c.client.Shutdown()
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c.zmqBlockConn.Close()
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c.zmqTxConn.Close()
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c.client.WaitForShutdown()
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c.wg.Wait()
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}
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// blockEventHandler reads raw blocks events from the ZMQ block socket and
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// forwards them along to the current rescan clients.
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//
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// NOTE: This must be run as a goroutine.
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func (c *BitcoindConn) blockEventHandler() {
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defer c.wg.Done()
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log.Info("Started listening for bitcoind block notifications via ZMQ "+
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"on", c.zmqBlockConn.RemoteAddr())
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// Set up the buffers we expect our messages to consume. ZMQ
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// messages from bitcoind include three parts: the command, the
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// data, and the sequence number.
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//
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// We'll allocate a fixed data slice that we'll reuse when reading
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// blocks from bitcoind through ZMQ. There's no need to recycle this
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// slice (zero out) after using it, as further reads will overwrite the
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// slice and we'll only be deserializing the bytes needed.
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var (
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command [len(rawBlockZMQCommand)]byte
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seqNum [seqNumLen]byte
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data = make([]byte, maxRawBlockSize)
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)
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for {
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// Before attempting to read from the ZMQ socket, we'll make
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// sure to check if we've been requested to shut down.
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select {
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case <-c.quit:
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return
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default:
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}
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// Poll an event from the ZMQ socket.
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var (
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bufs = [][]byte{command[:], data, seqNum[:]}
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err error
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)
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bufs, err = c.zmqBlockConn.Receive(bufs)
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if err != nil {
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// EOF should only be returned if the connection was
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// explicitly closed, so we can exit at this point.
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if err == io.EOF {
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return
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}
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// It's possible that the connection to the socket
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// continuously times out, so we'll prevent logging this
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// error to prevent spamming the logs.
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netErr, ok := err.(net.Error)
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if ok && netErr.Timeout() {
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log.Trace("Re-establishing timed out ZMQ " +
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"block connection")
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continue
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}
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log.Errorf("Unable to receive ZMQ %v message: %v",
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rawBlockZMQCommand, err)
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continue
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}
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// We have an event! We'll now ensure it is a block event,
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// deserialize it, and report it to the different rescan
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// clients.
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eventType := string(bufs[0])
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switch eventType {
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case rawBlockZMQCommand:
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block := &wire.MsgBlock{}
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r := bytes.NewReader(bufs[1])
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if err := block.Deserialize(r); err != nil {
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log.Errorf("Unable to deserialize block: %v",
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err)
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continue
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}
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c.rescanClientsMtx.Lock()
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for _, client := range c.rescanClients {
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select {
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case client.zmqBlockNtfns <- block:
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case <-client.quit:
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case <-c.quit:
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c.rescanClientsMtx.Unlock()
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return
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}
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}
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c.rescanClientsMtx.Unlock()
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default:
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// It's possible that the message wasn't fully read if
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// bitcoind shuts down, which will produce an unreadable
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// event type. To prevent from logging it, we'll make
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// sure it conforms to the ASCII standard.
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if eventType == "" || !isASCII(eventType) {
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continue
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}
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log.Warnf("Received unexpected event type from %v "+
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"subscription: %v", rawBlockZMQCommand,
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eventType)
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}
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}
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}
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// txEventHandler reads raw blocks events from the ZMQ block socket and forwards
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// them along to the current rescan clients.
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//
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// NOTE: This must be run as a goroutine.
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func (c *BitcoindConn) txEventHandler() {
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defer c.wg.Done()
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log.Info("Started listening for bitcoind transaction notifications "+
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"via ZMQ on", c.zmqTxConn.RemoteAddr())
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// Set up the buffers we expect our messages to consume. ZMQ
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// messages from bitcoind include three parts: the command, the
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// data, and the sequence number.
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//
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// We'll allocate a fixed data slice that we'll reuse when reading
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// transactions from bitcoind through ZMQ. There's no need to recycle
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// this slice (zero out) after using it, as further reads will overwrite
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// the slice and we'll only be deserializing the bytes needed.
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var (
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command [len(rawTxZMQCommand)]byte
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seqNum [seqNumLen]byte
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data = make([]byte, maxRawTxSize)
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)
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for {
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// Before attempting to read from the ZMQ socket, we'll make
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// sure to check if we've been requested to shut down.
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select {
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case <-c.quit:
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return
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default:
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}
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// Poll an event from the ZMQ socket.
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var (
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bufs = [][]byte{command[:], data, seqNum[:]}
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err error
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)
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bufs, err = c.zmqTxConn.Receive(bufs)
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if err != nil {
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// EOF should only be returned if the connection was
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// explicitly closed, so we can exit at this point.
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if err == io.EOF {
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return
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}
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// It's possible that the connection to the socket
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// continuously times out, so we'll prevent logging this
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// error to prevent spamming the logs.
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netErr, ok := err.(net.Error)
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if ok && netErr.Timeout() {
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log.Trace("Re-establishing timed out ZMQ " +
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"transaction connection")
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continue
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}
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log.Errorf("Unable to receive ZMQ %v message: %v",
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rawTxZMQCommand, err)
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continue
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}
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// We have an event! We'll now ensure it is a transaction event,
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// deserialize it, and report it to the different rescan
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// clients.
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eventType := string(bufs[0])
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switch eventType {
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case rawTxZMQCommand:
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tx := &wire.MsgTx{}
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r := bytes.NewReader(bufs[1])
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if err := tx.Deserialize(r); err != nil {
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log.Errorf("Unable to deserialize "+
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"transaction: %v", err)
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continue
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}
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c.rescanClientsMtx.Lock()
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for _, client := range c.rescanClients {
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select {
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case client.zmqTxNtfns <- tx:
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case <-client.quit:
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case <-c.quit:
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c.rescanClientsMtx.Unlock()
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return
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}
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}
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c.rescanClientsMtx.Unlock()
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default:
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// It's possible that the message wasn't fully read if
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// bitcoind shuts down, which will produce an unreadable
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// event type. To prevent from logging it, we'll make
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// sure it conforms to the ASCII standard.
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if eventType == "" || !isASCII(eventType) {
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continue
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}
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log.Warnf("Received unexpected event type from %v "+
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"subscription: %v", rawTxZMQCommand, eventType)
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}
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}
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}
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// getCurrentNet returns the network on which the bitcoind node is running.
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func (c *BitcoindConn) getCurrentNet() (wire.BitcoinNet, error) {
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hash, err := c.client.GetBlockHash(0)
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if err != nil {
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return 0, err
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}
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switch *hash {
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case *chaincfg.TestNet3Params.GenesisHash:
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return chaincfg.TestNet3Params.Net, nil
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case *chaincfg.RegressionNetParams.GenesisHash:
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return chaincfg.RegressionNetParams.Net, nil
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case *chaincfg.MainNetParams.GenesisHash:
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return chaincfg.MainNetParams.Net, nil
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default:
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return 0, fmt.Errorf("unknown network with genesis hash %v", hash)
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}
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}
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// NewBitcoindClient returns a bitcoind client using the current bitcoind
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// connection. This allows us to share the same connection using multiple
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// clients.
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func (c *BitcoindConn) NewBitcoindClient() *BitcoindClient {
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return &BitcoindClient{
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quit: make(chan struct{}),
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id: atomic.AddUint64(&c.rescanClientCounter, 1),
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chainParams: c.chainParams,
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chainConn: c,
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rescanUpdate: make(chan interface{}),
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watchedAddresses: make(map[string]struct{}),
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watchedOutPoints: make(map[wire.OutPoint]struct{}),
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watchedTxs: make(map[chainhash.Hash]struct{}),
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notificationQueue: NewConcurrentQueue(20),
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zmqTxNtfns: make(chan *wire.MsgTx),
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zmqBlockNtfns: make(chan *wire.MsgBlock),
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mempool: make(map[chainhash.Hash]struct{}),
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expiredMempool: make(map[int32]map[chainhash.Hash]struct{}),
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}
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}
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// AddClient adds a client to the set of active rescan clients of the current
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// chain connection. This allows the connection to include the specified client
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// in its notification delivery.
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//
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// NOTE: This function is safe for concurrent access.
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func (c *BitcoindConn) AddClient(client *BitcoindClient) {
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c.rescanClientsMtx.Lock()
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defer c.rescanClientsMtx.Unlock()
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c.rescanClients[client.id] = client
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}
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// RemoveClient removes the client with the given ID from the set of active
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// rescan clients. Once removed, the client will no longer receive block and
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// transaction notifications from the chain connection.
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//
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// NOTE: This function is safe for concurrent access.
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func (c *BitcoindConn) RemoveClient(id uint64) {
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c.rescanClientsMtx.Lock()
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defer c.rescanClientsMtx.Unlock()
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delete(c.rescanClients, id)
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}
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// isASCII is a helper method that checks whether all bytes in `data` would be
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// printable ASCII characters if interpreted as a string.
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func isASCII(s string) bool {
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for _, c := range s {
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if c < 32 || c > 126 {
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return false
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}
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}
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return true
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}
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