lnd.xprv/chainntfs/btcdnotify/btcd.go

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package btcdnotify
import (
"container/heap"
"fmt"
"sync"
"sync/atomic"
"time"
"github.com/btcsuite/btcd/btcjson"
"github.com/btcsuite/btcd/wire"
"github.com/btcsuite/btcrpcclient"
"github.com/btcsuite/btcutil"
2016-01-16 21:45:54 +03:00
"github.com/lightningnetwork/lnd/chainntfs"
)
// BtcdNotifier implements the ChainNotifier interface using btcd's websockets
// notifications. Multiple concurrent clients are supported. All notifications
// are achieved via non-blocking sends on client channels.
type BtcdNotifier struct {
started int32 // To be used atomically.
stopped int32 // To be used atomically.
chainConn *btcrpcclient.Client
notificationRegistry chan interface{}
// TODO(roasbeef): make map point to slices? Would allow for multiple
// clients to listen for same spend. Would we ever need this?
spendNotifications map[wire.OutPoint]*spendNotification
confNotifications map[wire.ShaHash]*confirmationsNotification
confHeap *confirmationHeap
connectedBlockHashes chan *blockNtfn
disconnectedBlockHashes chan *blockNtfn
relevantTxs chan *btcutil.Tx
wg sync.WaitGroup
quit chan struct{}
}
// Ensure BtcdNotifier implements the ChainNotifier interface at compile time.
var _ chainntnfs.ChainNotifier = (*BtcdNotifier)(nil)
// NewBtcdNotifier returns a new BtcdNotifier instance. This function assumes
// the btcd node detailed in the passed configuration is already running, and
// willing to accept new websockets clients.
func NewBtcdNotifier(config *btcrpcclient.ConnConfig) (*BtcdNotifier, error) {
notifier := &BtcdNotifier{
notificationRegistry: make(chan interface{}),
spendNotifications: make(map[wire.OutPoint]*spendNotification),
confNotifications: make(map[wire.ShaHash]*confirmationsNotification),
confHeap: newConfirmationHeap(),
connectedBlockHashes: make(chan *blockNtfn, 20),
disconnectedBlockHashes: make(chan *blockNtfn, 20),
relevantTxs: make(chan *btcutil.Tx, 100),
quit: make(chan struct{}),
}
ntfnCallbacks := &btcrpcclient.NotificationHandlers{
OnBlockConnected: notifier.onBlockConnected,
OnBlockDisconnected: notifier.onBlockDisconnected,
OnRedeemingTx: notifier.onRedeemingTx,
}
// Disable connecting to btcd within the btcrpcclient.New method. We defer
// establishing the connection to our .Start() method.
config.DisableConnectOnNew = true
config.DisableAutoReconnect = false
chainConn, err := btcrpcclient.New(config, ntfnCallbacks)
if err != nil {
return nil, err
}
notifier.chainConn = chainConn
return notifier, nil
}
// Start connects to the running btcd node over websockets, registers for block
// notifications, and finally launches all related helper goroutines.
func (b *BtcdNotifier) Start() error {
// Already started?
if atomic.AddInt32(&b.started, 1) != 1 {
return nil
}
// Connect to btcd, and register for notifications on connected, and
// disconnected blocks.
if err := b.chainConn.Connect(20); err != nil {
return err
}
if err := b.chainConn.NotifyBlocks(); err != nil {
return err
}
b.wg.Add(1)
go b.notificationDispatcher()
return nil
}
// Stop shutsdown the BtcdNotifier.
func (b *BtcdNotifier) Stop() error {
// Already shutting down?
if atomic.AddInt32(&b.stopped, 1) != 1 {
return nil
}
// Shutdown the rpc client, this gracefully disconnects from btcd, and
// cleans up all related resources.
b.chainConn.Shutdown()
close(b.quit)
b.wg.Wait()
// Notify all pending clients of our shutdown by closing the related
// notification channels.
for _, spendClient := range b.spendNotifications {
close(spendClient.spendChan)
}
for _, confClient := range b.confNotifications {
close(confClient.finConf)
close(confClient.negativeConf)
}
return nil
}
// blockNtfn packages a notification of a connected/disconnected block along
// with its height at the time.
type blockNtfn struct {
sha *wire.ShaHash
height int32
}
// onBlockConnected implements on OnBlockConnected callback for btcrpcclient.
func (b *BtcdNotifier) onBlockConnected(hash *wire.ShaHash, height int32, t time.Time) {
select {
case b.connectedBlockHashes <- &blockNtfn{hash, height}:
case <-b.quit:
}
}
// onBlockDisconnected implements on OnBlockDisconnected callback for btcrpcclient.
func (b *BtcdNotifier) onBlockDisconnected(hash *wire.ShaHash, height int32, t time.Time) {
b.onBlockDisconnected(hash, height, t)
}
// onRedeemingTx implements on OnRedeemingTx callback for btcrpcclient.
func (b *BtcdNotifier) onRedeemingTx(transaction *btcutil.Tx, details *btcjson.BlockDetails) {
select {
case b.relevantTxs <- transaction:
case <-b.quit:
}
}
// notificationDispatcher is the primary goroutine which handles client
// notification registrations, as well as notification dispatches.
func (b *BtcdNotifier) notificationDispatcher() {
out:
for {
select {
case registerMsg := <-b.notificationRegistry:
switch msg := registerMsg.(type) {
case *spendNotification:
b.spendNotifications[*msg.targetOutpoint] = msg
case *confirmationsNotification:
b.confNotifications[*msg.txid] = msg
}
case staleBlockHash := <-b.disconnectedBlockHashes:
// TODO(roasbeef): re-orgs
// * second channel to notify of confirmation decrementing
// re-org?
// * notify of negative confirmations
fmt.Println(staleBlockHash)
case connectedBlock := <-b.connectedBlockHashes:
newBlock, err := b.chainConn.GetBlock(connectedBlock.sha)
if err != nil {
continue
}
newHeight := connectedBlock.height
for _, tx := range newBlock.Transactions() {
// Check if the inclusion of this transaction
// within a block by itself triggers a block
// confirmation threshold, if so send a
// notification. Otherwise, place the notification
// on a heap to be triggered in the future once
// additional confirmations are attained.
txSha := tx.Sha()
b.checkConfirmationTrigger(txSha, newHeight)
}
// A new block has been connected to the main
// chain. Send out any N confirmation notifications
// which may have been triggered by this new block.
b.notifyConfs(newHeight)
case newSpend := <-b.relevantTxs:
// First, check if this transaction spends an output
// that has an existing spend notification for it.
for i, txIn := range newSpend.MsgTx().TxIn {
prevOut := txIn.PreviousOutPoint
// If this transaction indeed does spend an
// output which we have a registered notification
// for, then create a spend summary, finally
// sending off the details to the notification
// subscriber.
if ntfn, ok := b.spendNotifications[prevOut]; ok {
spenderSha := newSpend.Sha()
spendDetails := &chainntnfs.SpendDetail{
SpentOutPoint: ntfn.targetOutpoint,
SpenderTxHash: spenderSha,
// TODO(roasbeef): copy tx?
SpendingTx: newSpend.MsgTx(),
SpenderInputIndex: uint32(i),
}
ntfn.spendChan <- spendDetails
delete(b.spendNotifications, prevOut)
}
}
case <-b.quit:
break out
}
}
b.wg.Done()
}
// notifyConfs examines the current confirmation heap, sending off any
// notifications which have been triggered by the connection of a new block at
// newBlockHeight.
func (b *BtcdNotifier) notifyConfs(newBlockHeight int32) {
// If the heap is empty, we have nothing to do.
if b.confHeap.Len() == 0 {
return
}
// Traverse our confirmation heap. The heap is a
// min-heap, so the confirmation notification which requires
// the smallest block-height will always be at the top
// of the heap. If a confirmation notification is eligible
// for triggering, then fire it off, and check if another
// is eligible until there are no more eligible entries.
nextConf := heap.Pop(b.confHeap).(*confEntry)
for nextConf.triggerHeight <= uint32(newBlockHeight) {
nextConf.finConf <- struct{}{}
if b.confHeap.Len() == 0 {
return
}
nextConf = heap.Pop(b.confHeap).(*confEntry)
}
heap.Push(b.confHeap, nextConf)
}
// checkConfirmationTrigger determines if the passed txSha included at blockHeight
// triggers any single confirmation notifications. In the event that the txid
// matches, yet needs additional confirmations, it is added to the confirmation
// heap to be triggered at a later time.
// TODO(roasbeef): perhaps lookup, then track by inputs instead?
func (b *BtcdNotifier) checkConfirmationTrigger(txSha *wire.ShaHash, blockHeight int32) {
// If a confirmation notification has been registered
// for this txid, then either trigger a notification
// event if only a single confirmation notification was
// requested, or place the notification on the
// confirmation heap for future usage.
if confNtfn, ok := b.confNotifications[*txSha]; ok {
delete(b.confNotifications, *txSha)
if confNtfn.numConfirmations == 1 {
confNtfn.finConf <- struct{}{}
return
}
// The registered notification requires more
// than one confirmation before triggering. So
// we create a heapConf entry for this notification.
// The heapConf allows us to easily keep track of
// which notification(s) we should fire off with
// each incoming block.
confNtfn.initialConfirmHeight = uint32(blockHeight)
finalConfHeight := uint32(confNtfn.initialConfirmHeight + confNtfn.numConfirmations - 1)
heapEntry := &confEntry{
confNtfn,
finalConfHeight,
}
heap.Push(b.confHeap, heapEntry)
}
}
// spendNotification couples a target outpoint along with the channel used for
// notifications once a spend of the outpoint has been detected.
type spendNotification struct {
targetOutpoint *wire.OutPoint
spendChan chan *chainntnfs.SpendDetail
}
// RegisterSpendNotification registers an intent to be notified once the target
// outpoint has been spent by a transaction on-chain. Once a spend of the target
// outpoint has been detected, the details of the spending event will be sent
// across the 'Spend' channel.
func (b *BtcdNotifier) RegisterSpendNtfn(outpoint *wire.OutPoint) (*chainntnfs.SpendEvent, error) {
if err := b.chainConn.NotifySpent([]*wire.OutPoint{outpoint}); err != nil {
return nil, err
}
ntfn := &spendNotification{
targetOutpoint: outpoint,
spendChan: make(chan *chainntnfs.SpendDetail, 1),
}
b.notificationRegistry <- ntfn
return &chainntnfs.SpendEvent{ntfn.spendChan}, nil
}
// confirmationNotification represents a client's intent to receive a
// notification once the target txid reaches numConfirmations confirmations.
type confirmationsNotification struct {
txid *wire.ShaHash
initialConfirmHeight uint32
numConfirmations uint32
finConf chan struct{}
negativeConf chan int32 // TODO(roasbeef): re-org funny business
}
// RegisterConfirmationsNotification registers a notification with BtcdNotifier
// which will be triggered once the txid reaches numConfs number of
// confirmations.
func (b *BtcdNotifier) RegisterConfirmationsNtfn(txid *wire.ShaHash,
numConfs uint32) (*chainntnfs.ConfirmationEvent, error) {
ntfn := &confirmationsNotification{
txid: txid,
numConfirmations: numConfs,
finConf: make(chan struct{}, 1),
negativeConf: make(chan int32, 1),
}
b.notificationRegistry <- ntfn
return &chainntnfs.ConfirmationEvent{
Confirmed: ntfn.finConf,
NegativeConf: ntfn.negativeConf,
}, nil
}