bf6001074c
In this commit, we fix a race condition related to the way we attempt to query to see if an outpoint has already been spent by the time it’s registered within the ChainNotifier. If the transaction creating the outpoint hasn’t made it into the mempool by the time we execute the GetTxOut call, then we’ll attempt to query for the transaction itself. In this case, if we query for the transaction, then the block hash field will be empty as it hasn’t yet made it into a block. Under the previous logic, we’d then attempt to force a rescan. This is an issue as the forced rescan will fail since it’ll try to fetch the block hash of all zeroes. In this commit, we fix this issue by only entering this “fallback to rescan” logic iff, the transaction has actually been mined.
685 lines
20 KiB
Go
685 lines
20 KiB
Go
package bitcoindnotify
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import (
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"errors"
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"fmt"
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"sync"
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"sync/atomic"
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"time"
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"github.com/lightningnetwork/lnd/chainntnfs"
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"github.com/roasbeef/btcd/btcjson"
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"github.com/roasbeef/btcd/chaincfg"
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"github.com/roasbeef/btcd/chaincfg/chainhash"
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"github.com/roasbeef/btcd/rpcclient"
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"github.com/roasbeef/btcd/wire"
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"github.com/roasbeef/btcutil"
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"github.com/roasbeef/btcwallet/chain"
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)
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const (
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// notifierType uniquely identifies this concrete implementation of the
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// ChainNotifier interface.
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notifierType = "bitcoind"
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// reorgSafetyLimit is assumed maximum depth of a chain reorganization.
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// After this many confirmation, transaction confirmation info will be
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// pruned.
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reorgSafetyLimit = 100
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)
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var (
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// ErrChainNotifierShuttingDown is used when we are trying to
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// measure a spend notification when notifier is already stopped.
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ErrChainNotifierShuttingDown = errors.New("chainntnfs: system interrupt " +
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"while attempting to register for spend notification.")
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)
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// chainUpdate encapsulates an update to the current main chain. This struct is
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// used as an element within an unbounded queue in order to avoid blocking the
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// main rpc dispatch rule.
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type chainUpdate struct {
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blockHash *chainhash.Hash
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blockHeight int32
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}
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// txUpdate encapsulates a transaction related notification sent from bitcoind
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// to the registered RPC client. This struct is used as an element within an
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// unbounded queue in order to avoid blocking the main rpc dispatch rule.
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type txUpdate struct {
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tx *btcutil.Tx
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details *btcjson.BlockDetails
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}
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// TODO(roasbeef): generalize struct below:
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// * move chans to config, allow outside callers to handle send conditions
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// BitcoindNotifier implements the ChainNotifier interface using a bitcoind
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// chain client. Multiple concurrent clients are supported. All notifications
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// are achieved via non-blocking sends on client channels.
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type BitcoindNotifier struct {
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spendClientCounter uint64 // To be used atomically.
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epochClientCounter uint64 // To be used atomically.
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started int32 // To be used atomically.
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stopped int32 // To be used atomically.
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heightMtx sync.RWMutex
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bestHeight int32
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chainConn *chain.BitcoindClient
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notificationCancels chan interface{}
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notificationRegistry chan interface{}
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spendNotifications map[wire.OutPoint]map[uint64]*spendNotification
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txConfNotifier *chainntnfs.TxConfNotifier
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blockEpochClients map[uint64]*blockEpochRegistration
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wg sync.WaitGroup
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quit chan struct{}
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}
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// Ensure BitcoindNotifier implements the ChainNotifier interface at compile
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// time.
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var _ chainntnfs.ChainNotifier = (*BitcoindNotifier)(nil)
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// New returns a new BitcoindNotifier instance. This function assumes the
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// bitcoind node detailed in the passed configuration is already running, and
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// willing to accept RPC requests and new zmq clients.
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func New(config *rpcclient.ConnConfig, zmqConnect string,
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params chaincfg.Params) (*BitcoindNotifier, error) {
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notifier := &BitcoindNotifier{
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notificationCancels: make(chan interface{}),
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notificationRegistry: make(chan interface{}),
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blockEpochClients: make(map[uint64]*blockEpochRegistration),
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spendNotifications: make(map[wire.OutPoint]map[uint64]*spendNotification),
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quit: make(chan struct{}),
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}
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// Disable connecting to bitcoind within the rpcclient.New method. We
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// defer establishing the connection to our .Start() method.
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config.DisableConnectOnNew = true
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config.DisableAutoReconnect = false
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chainConn, err := chain.NewBitcoindClient(¶ms, config.Host,
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config.User, config.Pass, zmqConnect, 100*time.Millisecond)
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if err != nil {
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return nil, err
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}
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notifier.chainConn = chainConn
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return notifier, nil
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}
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// Start connects to the running bitcoind node over websockets, registers for
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// block notifications, and finally launches all related helper goroutines.
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func (b *BitcoindNotifier) Start() error {
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// Already started?
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if atomic.AddInt32(&b.started, 1) != 1 {
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return nil
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}
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// Connect to bitcoind, and register for notifications on connected,
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// and disconnected blocks.
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if err := b.chainConn.Start(); err != nil {
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return err
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}
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if err := b.chainConn.NotifyBlocks(); err != nil {
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return err
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}
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_, currentHeight, err := b.chainConn.GetBestBlock()
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if err != nil {
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return err
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}
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b.heightMtx.Lock()
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b.bestHeight = currentHeight
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b.heightMtx.Unlock()
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b.txConfNotifier = chainntnfs.NewTxConfNotifier(
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uint32(currentHeight), reorgSafetyLimit)
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b.wg.Add(1)
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go b.notificationDispatcher()
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return nil
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}
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// Stop shutsdown the BitcoindNotifier.
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func (b *BitcoindNotifier) Stop() error {
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// Already shutting down?
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if atomic.AddInt32(&b.stopped, 1) != 1 {
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return nil
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}
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// Shutdown the rpc client, this gracefully disconnects from bitcoind,
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// and cleans up all related resources.
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b.chainConn.Stop()
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close(b.quit)
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b.wg.Wait()
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// Notify all pending clients of our shutdown by closing the related
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// notification channels.
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for _, spendClients := range b.spendNotifications {
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for _, spendClient := range spendClients {
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close(spendClient.spendChan)
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}
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}
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for _, epochClient := range b.blockEpochClients {
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close(epochClient.epochChan)
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}
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b.txConfNotifier.TearDown()
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return nil
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}
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// blockNtfn packages a notification of a connected/disconnected block along
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// with its height at the time.
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type blockNtfn struct {
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sha *chainhash.Hash
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height int32
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}
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// notificationDispatcher is the primary goroutine which handles client
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// notification registrations, as well as notification dispatches.
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func (b *BitcoindNotifier) notificationDispatcher() {
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out:
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for {
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select {
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case cancelMsg := <-b.notificationCancels:
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switch msg := cancelMsg.(type) {
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case *spendCancel:
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chainntnfs.Log.Infof("Cancelling spend "+
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"notification for out_point=%v, "+
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"spend_id=%v", msg.op, msg.spendID)
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// Before we attempt to close the spendChan,
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// ensure that the notification hasn't already
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// yet been dispatched.
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if outPointClients, ok := b.spendNotifications[msg.op]; ok {
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close(outPointClients[msg.spendID].spendChan)
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delete(b.spendNotifications[msg.op], msg.spendID)
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}
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case *epochCancel:
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chainntnfs.Log.Infof("Cancelling epoch "+
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"notification, epoch_id=%v", msg.epochID)
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// First, close the cancel channel for this
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// specific client, and wait for the client to
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// exit.
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close(b.blockEpochClients[msg.epochID].cancelChan)
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b.blockEpochClients[msg.epochID].wg.Wait()
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// Once the client has exited, we can then
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// safely close the channel used to send epoch
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// notifications, in order to notify any
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// listeners that the intent has been
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// cancelled.
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close(b.blockEpochClients[msg.epochID].epochChan)
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delete(b.blockEpochClients, msg.epochID)
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}
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case registerMsg := <-b.notificationRegistry:
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switch msg := registerMsg.(type) {
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case *spendNotification:
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chainntnfs.Log.Infof("New spend subscription: "+
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"utxo=%v", msg.targetOutpoint)
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op := *msg.targetOutpoint
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if _, ok := b.spendNotifications[op]; !ok {
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b.spendNotifications[op] = make(map[uint64]*spendNotification)
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}
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b.spendNotifications[op][msg.spendID] = msg
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b.chainConn.NotifySpent([]*wire.OutPoint{&op})
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case *confirmationsNotification:
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chainntnfs.Log.Infof("New confirmations "+
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"subscription: txid=%v, numconfs=%v",
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msg.TxID, msg.NumConfirmations)
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// Lookup whether the transaction is already included in the
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// active chain.
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txConf, err := b.historicalConfDetails(msg.TxID)
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if err != nil {
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chainntnfs.Log.Error(err)
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}
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b.heightMtx.RLock()
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err = b.txConfNotifier.Register(&msg.ConfNtfn, txConf)
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if err != nil {
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chainntnfs.Log.Error(err)
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}
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b.heightMtx.RUnlock()
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case *blockEpochRegistration:
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chainntnfs.Log.Infof("New block epoch subscription")
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b.blockEpochClients[msg.epochID] = msg
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}
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case ntfn := <-b.chainConn.Notifications():
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switch item := ntfn.(type) {
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case chain.BlockConnected:
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b.heightMtx.Lock()
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if item.Height != b.bestHeight+1 {
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chainntnfs.Log.Warnf("Received blocks out of order: "+
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"current height=%d, new height=%d",
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b.bestHeight, item.Height)
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b.heightMtx.Unlock()
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continue
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}
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b.bestHeight = item.Height
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rawBlock, err := b.chainConn.GetBlock(&item.Hash)
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if err != nil {
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chainntnfs.Log.Errorf("Unable to get block: %v", err)
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b.heightMtx.Unlock()
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continue
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}
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chainntnfs.Log.Infof("New block: height=%v, sha=%v",
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item.Height, item.Hash)
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b.notifyBlockEpochs(item.Height, &item.Hash)
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txns := btcutil.NewBlock(rawBlock).Transactions()
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err = b.txConfNotifier.ConnectTip(&item.Hash,
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uint32(item.Height), txns)
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if err != nil {
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chainntnfs.Log.Error(err)
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}
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b.heightMtx.Unlock()
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continue
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case chain.BlockDisconnected:
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b.heightMtx.Lock()
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if item.Height != b.bestHeight {
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chainntnfs.Log.Warnf("Received blocks "+
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"out of order: current height="+
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"%d, disconnected height=%d",
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b.bestHeight, item.Height)
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b.heightMtx.Unlock()
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continue
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}
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b.bestHeight = item.Height - 1
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chainntnfs.Log.Infof("Block disconnected from "+
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"main chain: height=%v, sha=%v",
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item.Height, item.Hash)
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err := b.txConfNotifier.DisconnectTip(
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uint32(item.Height))
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if err != nil {
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chainntnfs.Log.Error(err)
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}
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b.heightMtx.Unlock()
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case chain.RelevantTx:
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tx := item.TxRecord.MsgTx
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// First, check if this transaction spends an output
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// that has an existing spend notification for it.
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for i, txIn := range tx.TxIn {
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prevOut := txIn.PreviousOutPoint
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// If this transaction indeed does spend an
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// output which we have a registered
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// notification for, then create a spend
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// summary, finally sending off the details to
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// the notification subscriber.
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if clients, ok := b.spendNotifications[prevOut]; ok {
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spenderSha := tx.TxHash()
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spendDetails := &chainntnfs.SpendDetail{
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SpentOutPoint: &prevOut,
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SpenderTxHash: &spenderSha,
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SpendingTx: &tx,
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SpenderInputIndex: uint32(i),
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}
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// TODO(roasbeef): after change to
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// loadfilter, only notify on block
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// inclusion?
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if item.Block != nil {
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spendDetails.SpendingHeight = item.Block.Height
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} else {
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b.heightMtx.RLock()
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spendDetails.SpendingHeight = b.bestHeight + 1
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b.heightMtx.RUnlock()
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}
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for _, ntfn := range clients {
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chainntnfs.Log.Infof("Dispatching "+
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"spend notification for "+
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"outpoint=%v", ntfn.targetOutpoint)
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ntfn.spendChan <- spendDetails
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// Close spendChan to ensure that any calls to Cancel will not
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// block. This is safe to do since the channel is buffered, and the
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// message can still be read by the receiver.
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close(ntfn.spendChan)
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}
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delete(b.spendNotifications, prevOut)
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}
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}
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}
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case <-b.quit:
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break out
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}
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}
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b.wg.Done()
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}
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// historicalConfDetails looks up whether a transaction is already included in a
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// block in the active chain and, if so, returns details about the confirmation.
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func (b *BitcoindNotifier) historicalConfDetails(txid *chainhash.Hash,
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) (*chainntnfs.TxConfirmation, error) {
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// If the transaction already has some or all of the confirmations,
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// then we may be able to dispatch it immediately.
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// TODO: fall back to scanning blocks if txindex isn't on.
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tx, err := b.chainConn.GetRawTransactionVerbose(txid)
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if err != nil || tx == nil || tx.BlockHash == "" {
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if err == nil {
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return nil, nil
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}
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// Do not return an error if the transaction was not found.
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if jsonErr, ok := err.(*btcjson.RPCError); ok {
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if jsonErr.Code == btcjson.ErrRPCNoTxInfo {
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return nil, nil
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}
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}
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return nil, fmt.Errorf("unable to query for txid(%v): %v", txid, err)
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}
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// As we need to fully populate the returned TxConfirmation struct,
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// grab the block in which the transaction was confirmed so we can
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// locate its exact index within the block.
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blockHash, err := chainhash.NewHashFromStr(tx.BlockHash)
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if err != nil {
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return nil, fmt.Errorf("unable to get block hash %v for historical "+
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"dispatch: %v", tx.BlockHash, err)
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}
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block, err := b.chainConn.GetBlockVerbose(blockHash)
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if err != nil {
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return nil, fmt.Errorf("unable to get block hash: %v", err)
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}
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// If the block obtained, locate the transaction's index within the
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// block so we can give the subscriber full confirmation details.
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txIndex := -1
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targetTxidStr := txid.String()
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for i, txHash := range block.Tx {
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if txHash == targetTxidStr {
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txIndex = i
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break
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}
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}
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if txIndex == -1 {
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return nil, fmt.Errorf("unable to locate tx %v in block %v",
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txid, blockHash)
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}
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txConf := chainntnfs.TxConfirmation{
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BlockHash: blockHash,
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BlockHeight: uint32(block.Height),
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TxIndex: uint32(txIndex),
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}
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return &txConf, nil
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}
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// notifyBlockEpochs notifies all registered block epoch clients of the newly
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// connected block to the main chain.
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func (b *BitcoindNotifier) notifyBlockEpochs(newHeight int32, newSha *chainhash.Hash) {
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epoch := &chainntnfs.BlockEpoch{
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Height: newHeight,
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Hash: newSha,
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}
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for _, epochClient := range b.blockEpochClients {
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b.wg.Add(1)
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epochClient.wg.Add(1)
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go func(ntfnChan chan *chainntnfs.BlockEpoch, cancelChan chan struct{},
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clientWg *sync.WaitGroup) {
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// TODO(roasbeef): move to goroutine per client, use sync queue
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defer clientWg.Done()
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defer b.wg.Done()
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select {
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case ntfnChan <- epoch:
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case <-cancelChan:
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return
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case <-b.quit:
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return
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}
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}(epochClient.epochChan, epochClient.cancelChan, &epochClient.wg)
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}
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}
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// spendNotification couples a target outpoint along with the channel used for
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// notifications once a spend of the outpoint has been detected.
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type spendNotification struct {
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targetOutpoint *wire.OutPoint
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spendChan chan *chainntnfs.SpendDetail
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spendID uint64
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}
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// spendCancel is a message sent to the BitcoindNotifier when a client wishes
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// to cancel an outstanding spend notification that has yet to be dispatched.
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type spendCancel struct {
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// op is the target outpoint of the notification to be cancelled.
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op wire.OutPoint
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// spendID the ID of the notification to cancel.
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spendID uint64
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}
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// RegisterSpendNtfn registers an intent to be notified once the target
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// outpoint has been spent by a transaction on-chain. Once a spend of the target
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// outpoint has been detected, the details of the spending event will be sent
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// across the 'Spend' channel.
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func (b *BitcoindNotifier) RegisterSpendNtfn(outpoint *wire.OutPoint,
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_ uint32) (*chainntnfs.SpendEvent, error) {
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if err := b.chainConn.NotifySpent([]*wire.OutPoint{outpoint}); err != nil {
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return nil, err
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}
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ntfn := &spendNotification{
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targetOutpoint: outpoint,
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spendChan: make(chan *chainntnfs.SpendDetail, 1),
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spendID: atomic.AddUint64(&b.spendClientCounter, 1),
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}
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select {
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case <-b.quit:
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return nil, ErrChainNotifierShuttingDown
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case b.notificationRegistry <- ntfn:
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}
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// The following conditional checks to ensure that when a spend notification
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// is registered, the output hasn't already been spent. If the output
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// is no longer in the UTXO set, the chain will be rescanned from the point
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// where the output was added. The rescan will dispatch the notification.
|
|
txout, err := b.chainConn.GetTxOut(&outpoint.Hash, outpoint.Index, true)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
if txout == nil {
|
|
// TODO: fall back to scanning blocks if txindex isn't on.
|
|
transaction, err := b.chainConn.GetRawTransactionVerbose(&outpoint.Hash)
|
|
if err != nil {
|
|
jsonErr, ok := err.(*btcjson.RPCError)
|
|
if !ok || jsonErr.Code != btcjson.ErrRPCNoTxInfo {
|
|
return nil, err
|
|
}
|
|
}
|
|
|
|
// We'll only request a rescan if the transaction has actually
|
|
// been included within a block. Otherwise, we'll encounter an
|
|
// error when scanning for blocks. This can happens in the case
|
|
// of a race condition, wherein the output itself is unspent,
|
|
// and only arrives in the mempool after the getxout call.
|
|
if transaction != nil && transaction.BlockHash != "" {
|
|
blockhash, err := chainhash.NewHashFromStr(transaction.BlockHash)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Rewind the rescan, since the btcwallet bitcoind
|
|
// back-end doesn't support that.
|
|
blockHeight, err := b.chainConn.GetBlockHeight(blockhash)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
b.heightMtx.Lock()
|
|
currentHeight := b.bestHeight
|
|
b.bestHeight = blockHeight
|
|
for i := currentHeight; i > blockHeight; i-- {
|
|
err = b.txConfNotifier.DisconnectTip(uint32(i))
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
b.heightMtx.Unlock()
|
|
|
|
ops := []*wire.OutPoint{outpoint}
|
|
if err := b.chainConn.Rescan(blockhash, nil, ops); err != nil {
|
|
chainntnfs.Log.Errorf("Rescan for spend "+
|
|
"notification txout failed: %v", err)
|
|
return nil, err
|
|
}
|
|
}
|
|
}
|
|
|
|
return &chainntnfs.SpendEvent{
|
|
Spend: ntfn.spendChan,
|
|
Cancel: func() {
|
|
cancel := &spendCancel{
|
|
op: *outpoint,
|
|
spendID: ntfn.spendID,
|
|
}
|
|
|
|
// Submit spend cancellation to notification dispatcher.
|
|
select {
|
|
case b.notificationCancels <- cancel:
|
|
// Cancellation is being handled, drain the spend chan until it is
|
|
// closed before yielding to the caller.
|
|
for {
|
|
select {
|
|
case _, ok := <-ntfn.spendChan:
|
|
if !ok {
|
|
return
|
|
}
|
|
case <-b.quit:
|
|
return
|
|
}
|
|
}
|
|
case <-b.quit:
|
|
}
|
|
},
|
|
}, nil
|
|
}
|
|
|
|
// confirmationNotification represents a client's intent to receive a
|
|
// notification once the target txid reaches numConfirmations confirmations.
|
|
type confirmationsNotification struct {
|
|
chainntnfs.ConfNtfn
|
|
}
|
|
|
|
// RegisterConfirmationsNtfn registers a notification with BitcoindNotifier
|
|
// which will be triggered once the txid reaches numConfs number of
|
|
// confirmations.
|
|
func (b *BitcoindNotifier) RegisterConfirmationsNtfn(txid *chainhash.Hash,
|
|
numConfs, _ uint32) (*chainntnfs.ConfirmationEvent, error) {
|
|
|
|
ntfn := &confirmationsNotification{
|
|
chainntnfs.ConfNtfn{
|
|
TxID: txid,
|
|
NumConfirmations: numConfs,
|
|
Event: chainntnfs.NewConfirmationEvent(),
|
|
},
|
|
}
|
|
|
|
select {
|
|
case <-b.quit:
|
|
return nil, ErrChainNotifierShuttingDown
|
|
case b.notificationRegistry <- ntfn:
|
|
return ntfn.Event, nil
|
|
}
|
|
}
|
|
|
|
// blockEpochRegistration represents a client's intent to receive a
|
|
// notification with each newly connected block.
|
|
type blockEpochRegistration struct {
|
|
epochID uint64
|
|
|
|
epochChan chan *chainntnfs.BlockEpoch
|
|
|
|
cancelChan chan struct{}
|
|
|
|
wg sync.WaitGroup
|
|
}
|
|
|
|
// epochCancel is a message sent to the BitcoindNotifier when a client wishes
|
|
// to cancel an outstanding epoch notification that has yet to be dispatched.
|
|
type epochCancel struct {
|
|
epochID uint64
|
|
}
|
|
|
|
// RegisterBlockEpochNtfn returns a BlockEpochEvent which subscribes the
|
|
// caller to receive notifications, of each new block connected to the main
|
|
// chain.
|
|
func (b *BitcoindNotifier) RegisterBlockEpochNtfn() (*chainntnfs.BlockEpochEvent, error) {
|
|
registration := &blockEpochRegistration{
|
|
epochChan: make(chan *chainntnfs.BlockEpoch, 20),
|
|
cancelChan: make(chan struct{}),
|
|
epochID: atomic.AddUint64(&b.epochClientCounter, 1),
|
|
}
|
|
|
|
select {
|
|
case <-b.quit:
|
|
return nil, errors.New("chainntnfs: system interrupt while " +
|
|
"attempting to register for block epoch notification.")
|
|
case b.notificationRegistry <- registration:
|
|
return &chainntnfs.BlockEpochEvent{
|
|
Epochs: registration.epochChan,
|
|
Cancel: func() {
|
|
cancel := &epochCancel{
|
|
epochID: registration.epochID,
|
|
}
|
|
|
|
// Submit epoch cancellation to notification dispatcher.
|
|
select {
|
|
case b.notificationCancels <- cancel:
|
|
// Cancellation is being handled, drain the epoch channel until it is
|
|
// closed before yielding to caller.
|
|
for {
|
|
select {
|
|
case _, ok := <-registration.epochChan:
|
|
if !ok {
|
|
return
|
|
}
|
|
case <-b.quit:
|
|
return
|
|
}
|
|
}
|
|
case <-b.quit:
|
|
}
|
|
},
|
|
}, nil
|
|
}
|
|
}
|