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routing/chainview: add new light client p2p version of FilteredChainView

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This commit adds a new implementation of the FilteredChainView
interface. This implementation speaks purely to the p2p network and is
backed by a new experimental light client implementation.
This commit is contained in:
Olaoluwa Osuntokun 2017-05-21 18:35:27 -07:00
parent 461d84dd75
commit cc25049684
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GPG Key ID: 9CC5B105D03521A2
1 changed files with 319 additions and 0 deletions
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routing/chainview/neutrino.go Normal file
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package chainview
import (
"fmt"
"sync"
"sync/atomic"
"github.com/roasbeef/btcd/chaincfg/chainhash"
"github.com/roasbeef/btcd/wire"
"github.com/roasbeef/btcrpcclient"
"github.com/roasbeef/btcutil"
"github.com/roasbeef/btcwallet/waddrmgr"
"github.com/lightninglabs/neutrino"
)
// CfFilteredChainView is an implementation of the FilteredChainView interface
// which is supported by an underlying Bitcoin light client which supports
// client side filtering of Golomb Coded Sets. Rather than fetching all the
// blocks, the light client is able to query fitlers locally, to test if an
// item in ablock modifies any of our watched set of UTXOs/
type CfFilteredChainView struct {
started int32
stopped int32
// p2pNode is a pointer to the running GCS-filter supported Bitcoin
// light clientl
p2pNode *neutrino.ChainService
// chainView is the active rescan which only watches our specified
// sub-set of the UTXO set.
chainView neutrino.Rescan
// rescanErrChan is the channel that any errors encountered during the
// rescan will be sent over.
rescanErrChan <-chan error
// newBlocks is the channel in which new filtered blocks are sent over.
newBlocks chan *FilteredBlock
// staleBlocks is the channel in which blocks that have been
// disconnected from the mainchain are sent over.
staleBlocks chan *FilteredBlock
// filterUpdates is a channel in which updates to the utxo filter
// attached to this instance are sent over.
filterUpdates chan filterUpdate
// chainFilter is the
filterMtx sync.RWMutex
chainFilter map[wire.OutPoint]struct{}
quit chan struct{}
wg sync.WaitGroup
}
// A compile time check to ensure CfFilteredChainView implements the
// chainview.FilteredChainView.
var _ FilteredChainView = (*CfFilteredChainView)(nil)
// NewCfFilteredChainView creates a new instance of the CfFilteredChainView
// which is connected to an active neutrino node.
//
// NOTE: The node should already be running an syncing before being passed into
// this function.
func NewCfFilteredChainView(node *neutrino.ChainService) (*CfFilteredChainView, error) {
return &CfFilteredChainView{
newBlocks: make(chan *FilteredBlock),
staleBlocks: make(chan *FilteredBlock),
quit: make(chan struct{}),
rescanErrChan: make(chan error),
filterUpdates: make(chan filterUpdate),
chainFilter: make(map[wire.OutPoint]struct{}),
p2pNode: node,
}, nil
}
// Start kicks off the FilteredChainView implementation. This function must be
// called before any calls to UpdateFilter can be processed.
// j
// NOTE: This is part of the FilteredChainView interface.
func (c *CfFilteredChainView) Start() error {
// Already started?
if atomic.AddInt32(&c.started, 1) != 1 {
return nil
}
log.Infof("FilteredChainView starting")
// First, we'll obtain the latest block height of the p2p node. We'll
// start the auto-rescan from this point. Once a caller actually wishes
// to register a chain view, the rescan state will be rewound
// accordingly.
bestHeader, bestHeight, err := c.p2pNode.LatestBlock()
if err != nil {
return err
}
startingPoint := &waddrmgr.BlockStamp{
Height: int32(bestHeight),
Hash: bestHeader.BlockHash(),
}
// Next, we'll create our set of rescan options. Currently it's
// required that a user MUST set a addr/outpoint/txid when creating a
// rescan. To get around this, we'll add a "zero" outpoint, that won't
// actually be matched.
var zeroPoint wire.OutPoint
rescanOptions := []neutrino.RescanOption{
neutrino.StartBlock(startingPoint),
neutrino.QuitChan(c.quit),
neutrino.NotificationHandlers(
btcrpcclient.NotificationHandlers{
OnFilteredBlockConnected: c.onFilteredBlockConnected,
OnFilteredBlockDisconnected: c.onFilteredBlockDisconnected,
},
),
neutrino.WatchOutPoints(zeroPoint),
}
// Finally, we'll create our rescan struct, start it, and launch all
// the goroutines we need to operate this FilteredChainView instance.
c.chainView = c.p2pNode.NewRescan(rescanOptions...)
c.rescanErrChan = c.chainView.Start()
c.wg.Add(1)
go c.chainFilterer()
return nil
}
// Stop signals all active goroutines for a graceful shutdown.
//
// NOTE: This is part of the FilteredChainView interface.
func (c *CfFilteredChainView) Stop() error {
// Already shutting down?
if atomic.AddInt32(&c.stopped, 1) != 1 {
return nil
}
log.Infof("FilteredChainView stopping")
close(c.quit)
c.wg.Wait()
return nil
}
// onFilteredBlockConnected is called for each block that's connected to the
// end of the main chain. Based on our current chain filter, the block may or
// may not include any relevant transactions.
func (c *CfFilteredChainView) onFilteredBlockConnected(height int32,
header *wire.BlockHeader, txns []*btcutil.Tx) {
mtxs := make([]*wire.MsgTx, len(txns))
for i, tx := range txns {
mtx := tx.MsgTx()
mtxs[i] = mtx
for _, txIn := range mtx.TxIn {
c.filterMtx.Lock()
delete(c.chainFilter, txIn.PreviousOutPoint)
c.filterMtx.Unlock()
}
}
go func() {
c.newBlocks <- &FilteredBlock{
Hash: header.BlockHash(),
Height: uint32(height),
Transactions: mtxs,
}
}()
}
// onFilteredBlockDisconnected is a callback which is executed once a block is
// disconnected from the end of the main chain.
func (c *CfFilteredChainView) onFilteredBlockDisconnected(height int32,
header *wire.BlockHeader) {
go func() {
c.staleBlocks <- &FilteredBlock{
Hash: header.BlockHash(),
Height: uint32(height),
}
}()
}
// chainFilterer is the primary coordination goroutine within the
// CfFilteredChainView. This goroutine handles errors from the running rescan,
// and also filter updates.
func (c *CfFilteredChainView) chainFilterer() {
defer c.wg.Done()
for {
select {
case err := <-c.rescanErrChan:
log.Errorf("Error encountered during rescan: %v", err)
// We've received a new update to the filter from the caller to
// mutate their established chain view.
case update := <-c.filterUpdates:
log.Debugf("Updating chain filter with new UTXO's: %v",
update.newUtxos)
// First, we'll update the current chain view, by
// adding any new UTXO's, ignoring duplicates int he
// process.
c.filterMtx.Lock()
for _, op := range update.newUtxos {
c.chainFilter[op] = struct{}{}
}
c.filterMtx.Unlock()
// With our internal chain view update, we'll craft a
// new update to the chainView which includes our new
// UTOX's, and current update height.
rescanUpdate := []neutrino.UpdateOption{
neutrino.AddOutPoints(update.newUtxos...),
neutrino.Rewind(update.updateHeight),
}
err := c.chainView.Update(rescanUpdate...)
if err != nil {
log.Errorf("unable to update rescan: %v", err)
}
case <-c.quit:
return
}
}
}
// FilterBlock takes a block hash, and returns a FilteredBlocks which is the
// result of applying the current registered UTXO sub-set on the block
// corresponding to that block hash. If any watched UTOX's are spent by the
// selected lock, then the internal chainFilter will also be updated.
//
// NOTE: This is part of the FilteredChainView interface.
func (c *CfFilteredChainView) FilterBlock(blockHash *chainhash.Hash) (*FilteredBlock, error) {
// As we need to manually filter a block, we'll first fetch the block
// form the network.
block, err := c.p2pNode.GetBlockFromNetwork(*blockHash)
if err != nil {
return nil, err
}
// Along with the block, we'll also need the height of the block in
// order to complete the notification.
_, blockHeight, err := c.p2pNode.GetBlockByHash(*blockHash)
if err != nil {
return nil, err
}
// Finally, we'll step through the block, input by input, to see if any
// transactions spend any outputs from our watched sub-set of the UTXO
// set.
var filteredTxns []*wire.MsgTx
for _, tx := range block.Transactions() {
for _, txIn := range tx.MsgTx().TxIn {
prevOp := txIn.PreviousOutPoint
if _, ok := c.chainFilter[prevOp]; ok {
filteredTxns = append(filteredTxns, tx.MsgTx())
c.filterMtx.Lock()
delete(c.chainFilter, prevOp)
c.filterMtx.Unlock()
break
}
}
}
return &FilteredBlock{
Hash: *blockHash,
Height: blockHeight,
Transactions: filteredTxns,
}, nil
}
// UpdateFilter updates the UTXO filter which is to be consulted when creating
// FilteredBlocks to be sent to subscribed clients. This method is cumulative
// meaning repeated calls to this method should _expand_ the size of the UTXO
// sub-set currently being watched. If the set updateHeight is _lower_ than
// the best known height of the implementation, then the state should be
// rewound to ensure all relevant notifications are dispatched.
//
// NOTE: This is part of the FilteredChainView interface.
func (c *CfFilteredChainView) UpdateFilter(ops []wire.OutPoint, updateHeight uint32) error {
select {
case c.filterUpdates <- filterUpdate{
newUtxos: ops,
updateHeight: updateHeight,
}:
return nil
case <-c.quit:
return fmt.Errorf("chain filter shutting down")
}
}
// FilteredBlocks returns the channel that filtered blocks are to be sent over.
// Each time a block is connected to the end of a main chain, and appropriate
// FilteredBlock which contains the transactions which mutate our watched UTXO
// set is to be returned.
//
// NOTE: This is part of the FilteredChainView interface.
func (c *CfFilteredChainView) FilteredBlocks() <-chan *FilteredBlock {
return c.newBlocks
}
// DisconnectedBlocks returns a receive only channel which will be sent upon
// with the empty filtered blocks of blocks which are disconnected from the
// main chain in the case of a re-org.
//
// NOTE: This is part of the FilteredChainView interface.
func (c *CfFilteredChainView) DisconnectedBlocks() <-chan *FilteredBlock {
return c.staleBlocks
}