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author | Jeffrey Wilcke <geffobscura@gmail.com> | 2015-06-24 01:19:33 +0800 |
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committer | Jeffrey Wilcke <geffobscura@gmail.com> | 2015-06-24 01:19:33 +0800 |
commit | 72e2613a9fe3205fa5a67b72b832e03b2357ee88 (patch) | |
tree | bbc987510d279d9e174ff8f684158d668131661e /eth/fetcher/fetcher.go | |
parent | 5daf8729be88eca87b302ebf7a46fc69cad0f6d0 (diff) | |
parent | 67e6f74e9af00ff011a6a02f18644804eb18cdaa (diff) | |
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Merge branch 'release/0.9.32'v0.9.32
Diffstat (limited to 'eth/fetcher/fetcher.go')
-rw-r--r-- | eth/fetcher/fetcher.go | 456 |
1 files changed, 456 insertions, 0 deletions
diff --git a/eth/fetcher/fetcher.go b/eth/fetcher/fetcher.go new file mode 100644 index 000000000..90a202235 --- /dev/null +++ b/eth/fetcher/fetcher.go @@ -0,0 +1,456 @@ +// Package fetcher contains the block announcement based synchonisation. +package fetcher + +import ( + "errors" + "fmt" + "math/rand" + "time" + + "github.com/ethereum/go-ethereum/common" + "github.com/ethereum/go-ethereum/core/types" + "github.com/ethereum/go-ethereum/logger" + "github.com/ethereum/go-ethereum/logger/glog" + "gopkg.in/karalabe/cookiejar.v2/collections/prque" +) + +const ( + arriveTimeout = 500 * time.Millisecond // Time allowance before an announced block is explicitly requested + gatherSlack = 100 * time.Millisecond // Interval used to collate almost-expired announces with fetches + fetchTimeout = 5 * time.Second // Maximum alloted time to return an explicitly requested block + maxUncleDist = 7 // Maximum allowed backward distance from the chain head + maxQueueDist = 32 // Maximum allowed distance from the chain head to queue + hashLimit = 256 // Maximum number of unique blocks a peer may have announced + blockLimit = 64 // Maximum number of unique blocks a per may have delivered +) + +var ( + errTerminated = errors.New("terminated") +) + +// blockRetrievalFn is a callback type for retrieving a block from the local chain. +type blockRetrievalFn func(common.Hash) *types.Block + +// blockRequesterFn is a callback type for sending a block retrieval request. +type blockRequesterFn func([]common.Hash) error + +// blockValidatorFn is a callback type to verify a block's header for fast propagation. +type blockValidatorFn func(block *types.Block, parent *types.Block) error + +// blockBroadcasterFn is a callback type for broadcasting a block to connected peers. +type blockBroadcasterFn func(block *types.Block, propagate bool) + +// chainHeightFn is a callback type to retrieve the current chain height. +type chainHeightFn func() uint64 + +// chainInsertFn is a callback type to insert a batch of blocks into the local chain. +type chainInsertFn func(types.Blocks) (int, error) + +// peerDropFn is a callback type for dropping a peer detected as malicious. +type peerDropFn func(id string) + +// announce is the hash notification of the availability of a new block in the +// network. +type announce struct { + hash common.Hash // Hash of the block being announced + time time.Time // Timestamp of the announcement + + origin string // Identifier of the peer originating the notification + fetch blockRequesterFn // Fetcher function to retrieve +} + +// inject represents a schedules import operation. +type inject struct { + origin string + block *types.Block +} + +// Fetcher is responsible for accumulating block announcements from various peers +// and scheduling them for retrieval. +type Fetcher struct { + // Various event channels + notify chan *announce + inject chan *inject + filter chan chan []*types.Block + done chan common.Hash + quit chan struct{} + + // Announce states + announces map[string]int // Per peer announce counts to prevent memory exhaustion + announced map[common.Hash][]*announce // Announced blocks, scheduled for fetching + fetching map[common.Hash]*announce // Announced blocks, currently fetching + + // Block cache + queue *prque.Prque // Queue containing the import operations (block number sorted) + queues map[string]int // Per peer block counts to prevent memory exhaustion + queued map[common.Hash]*inject // Set of already queued blocks (to dedup imports) + + // Callbacks + getBlock blockRetrievalFn // Retrieves a block from the local chain + validateBlock blockValidatorFn // Checks if a block's headers have a valid proof of work + broadcastBlock blockBroadcasterFn // Broadcasts a block to connected peers + chainHeight chainHeightFn // Retrieves the current chain's height + insertChain chainInsertFn // Injects a batch of blocks into the chain + dropPeer peerDropFn // Drops a peer for misbehaving + + // Testing hooks + fetchingHook func([]common.Hash) // Method to call upon starting a block fetch + importedHook func(*types.Block) // Method to call upon successful block import +} + +// New creates a block fetcher to retrieve blocks based on hash announcements. +func New(getBlock blockRetrievalFn, validateBlock blockValidatorFn, broadcastBlock blockBroadcasterFn, chainHeight chainHeightFn, insertChain chainInsertFn, dropPeer peerDropFn) *Fetcher { + return &Fetcher{ + notify: make(chan *announce), + inject: make(chan *inject), + filter: make(chan chan []*types.Block), + done: make(chan common.Hash), + quit: make(chan struct{}), + announces: make(map[string]int), + announced: make(map[common.Hash][]*announce), + fetching: make(map[common.Hash]*announce), + queue: prque.New(), + queues: make(map[string]int), + queued: make(map[common.Hash]*inject), + getBlock: getBlock, + validateBlock: validateBlock, + broadcastBlock: broadcastBlock, + chainHeight: chainHeight, + insertChain: insertChain, + dropPeer: dropPeer, + } +} + +// Start boots up the announcement based synchoniser, accepting and processing +// hash notifications and block fetches until termination requested. +func (f *Fetcher) Start() { + go f.loop() +} + +// Stop terminates the announcement based synchroniser, canceling all pending +// operations. +func (f *Fetcher) Stop() { + close(f.quit) +} + +// Notify announces the fetcher of the potential availability of a new block in +// the network. +func (f *Fetcher) Notify(peer string, hash common.Hash, time time.Time, fetcher blockRequesterFn) error { + block := &announce{ + hash: hash, + time: time, + origin: peer, + fetch: fetcher, + } + select { + case f.notify <- block: + return nil + case <-f.quit: + return errTerminated + } +} + +// Enqueue tries to fill gaps the the fetcher's future import queue. +func (f *Fetcher) Enqueue(peer string, block *types.Block) error { + op := &inject{ + origin: peer, + block: block, + } + select { + case f.inject <- op: + return nil + case <-f.quit: + return errTerminated + } +} + +// Filter extracts all the blocks that were explicitly requested by the fetcher, +// returning those that should be handled differently. +func (f *Fetcher) Filter(blocks types.Blocks) types.Blocks { + // Send the filter channel to the fetcher + filter := make(chan []*types.Block) + + select { + case f.filter <- filter: + case <-f.quit: + return nil + } + // Request the filtering of the block list + select { + case filter <- blocks: + case <-f.quit: + return nil + } + // Retrieve the blocks remaining after filtering + select { + case blocks := <-filter: + return blocks + case <-f.quit: + return nil + } +} + +// Loop is the main fetcher loop, checking and processing various notification +// events. +func (f *Fetcher) loop() { + // Iterate the block fetching until a quit is requested + fetch := time.NewTimer(0) + for { + // Clean up any expired block fetches + for hash, announce := range f.fetching { + if time.Since(announce.time) > fetchTimeout { + f.forgetHash(hash) + } + } + // Import any queued blocks that could potentially fit + height := f.chainHeight() + for !f.queue.Empty() { + op := f.queue.PopItem().(*inject) + + // If too high up the chain or phase, continue later + number := op.block.NumberU64() + if number > height+1 { + f.queue.Push(op, -float32(op.block.NumberU64())) + break + } + // Otherwise if fresh and still unknown, try and import + hash := op.block.Hash() + if number+maxUncleDist < height || f.getBlock(hash) != nil { + f.forgetBlock(hash) + continue + } + f.insert(op.origin, op.block) + } + // Wait for an outside event to occur + select { + case <-f.quit: + // Fetcher terminating, abort all operations + return + + case notification := <-f.notify: + // A block was announced, make sure the peer isn't DOSing us + count := f.announces[notification.origin] + 1 + if count > hashLimit { + glog.V(logger.Debug).Infof("Peer %s: exceeded outstanding announces (%d)", notification.origin, hashLimit) + break + } + // All is well, schedule the announce if block's not yet downloading + if _, ok := f.fetching[notification.hash]; ok { + break + } + f.announces[notification.origin] = count + f.announced[notification.hash] = append(f.announced[notification.hash], notification) + if len(f.announced) == 1 { + f.reschedule(fetch) + } + + case op := <-f.inject: + // A direct block insertion was requested, try and fill any pending gaps + f.enqueue(op.origin, op.block) + + case hash := <-f.done: + // A pending import finished, remove all traces of the notification + f.forgetHash(hash) + f.forgetBlock(hash) + + case <-fetch.C: + // At least one block's timer ran out, check for needing retrieval + request := make(map[string][]common.Hash) + + for hash, announces := range f.announced { + if time.Since(announces[0].time) > arriveTimeout-gatherSlack { + // Pick a random peer to retrieve from, reset all others + announce := announces[rand.Intn(len(announces))] + f.forgetHash(hash) + + // If the block still didn't arrive, queue for fetching + if f.getBlock(hash) == nil { + request[announce.origin] = append(request[announce.origin], hash) + f.fetching[hash] = announce + } + } + } + // Send out all block requests + for peer, hashes := range request { + if glog.V(logger.Detail) && len(hashes) > 0 { + list := "[" + for _, hash := range hashes { + list += fmt.Sprintf("%x, ", hash[:4]) + } + list = list[:len(list)-2] + "]" + + glog.V(logger.Detail).Infof("Peer %s: fetching %s", peer, list) + } + // Create a closure of the fetch and schedule in on a new thread + fetcher, hashes := f.fetching[hashes[0]].fetch, hashes + go func() { + if f.fetchingHook != nil { + f.fetchingHook(hashes) + } + fetcher(hashes) + }() + } + // Schedule the next fetch if blocks are still pending + f.reschedule(fetch) + + case filter := <-f.filter: + // Blocks arrived, extract any explicit fetches, return all else + var blocks types.Blocks + select { + case blocks = <-filter: + case <-f.quit: + return + } + + explicit, download := []*types.Block{}, []*types.Block{} + for _, block := range blocks { + hash := block.Hash() + + // Filter explicitly requested blocks from hash announcements + if _, ok := f.fetching[hash]; ok { + // Discard if already imported by other means + if f.getBlock(hash) == nil { + explicit = append(explicit, block) + } else { + f.forgetHash(hash) + } + } else { + download = append(download, block) + } + } + + select { + case filter <- download: + case <-f.quit: + return + } + // Schedule the retrieved blocks for ordered import + for _, block := range explicit { + if announce := f.fetching[block.Hash()]; announce != nil { + f.enqueue(announce.origin, block) + } + } + } + } +} + +// reschedule resets the specified fetch timer to the next announce timeout. +func (f *Fetcher) reschedule(fetch *time.Timer) { + // Short circuit if no blocks are announced + if len(f.announced) == 0 { + return + } + // Otherwise find the earliest expiring announcement + earliest := time.Now() + for _, announces := range f.announced { + if earliest.After(announces[0].time) { + earliest = announces[0].time + } + } + fetch.Reset(arriveTimeout - time.Since(earliest)) +} + +// enqueue schedules a new future import operation, if the block to be imported +// has not yet been seen. +func (f *Fetcher) enqueue(peer string, block *types.Block) { + hash := block.Hash() + + // Ensure the peer isn't DOSing us + count := f.queues[peer] + 1 + if count > blockLimit { + glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x], exceeded allowance (%d)", peer, block.NumberU64(), hash.Bytes()[:4], blockLimit) + return + } + // Discard any past or too distant blocks + if dist := int64(block.NumberU64()) - int64(f.chainHeight()); dist < -maxUncleDist || dist > maxQueueDist { + glog.V(logger.Debug).Infof("Peer %s: discarded block #%d [%x], distance %d", peer, block.NumberU64(), hash.Bytes()[:4], dist) + return + } + // Schedule the block for future importing + if _, ok := f.queued[hash]; !ok { + op := &inject{ + origin: peer, + block: block, + } + f.queues[peer] = count + f.queued[hash] = op + f.queue.Push(op, -float32(block.NumberU64())) + + if glog.V(logger.Debug) { + glog.Infof("Peer %s: queued block #%d [%x], total %v", peer, block.NumberU64(), hash.Bytes()[:4], f.queue.Size()) + } + } +} + +// insert spawns a new goroutine to run a block insertion into the chain. If the +// block's number is at the same height as the current import phase, if updates +// the phase states accordingly. +func (f *Fetcher) insert(peer string, block *types.Block) { + hash := block.Hash() + + // Run the import on a new thread + glog.V(logger.Debug).Infof("Peer %s: importing block #%d [%x]", peer, block.NumberU64(), hash[:4]) + go func() { + defer func() { f.done <- hash }() + + // If the parent's unknown, abort insertion + parent := f.getBlock(block.ParentHash()) + if parent == nil { + return + } + // Quickly validate the header and propagate the block if it passes + if err := f.validateBlock(block, parent); err != nil { + glog.V(logger.Debug).Infof("Peer %s: block #%d [%x] verification failed: %v", peer, block.NumberU64(), hash[:4], err) + f.dropPeer(peer) + return + } + go f.broadcastBlock(block, true) + + // Run the actual import and log any issues + if _, err := f.insertChain(types.Blocks{block}); err != nil { + glog.V(logger.Warn).Infof("Peer %s: block #%d [%x] import failed: %v", peer, block.NumberU64(), hash[:4], err) + return + } + // If import succeeded, broadcast the block + go f.broadcastBlock(block, false) + + // Invoke the testing hook if needed + if f.importedHook != nil { + f.importedHook(block) + } + }() +} + +// forgetHash removes all traces of a block announcement from the fetcher's +// internal state. +func (f *Fetcher) forgetHash(hash common.Hash) { + // Remove all pending announces and decrement DOS counters + for _, announce := range f.announced[hash] { + f.announces[announce.origin]-- + if f.announces[announce.origin] == 0 { + delete(f.announces, announce.origin) + } + } + delete(f.announced, hash) + + // Remove any pending fetches and decrement the DOS counters + if announce := f.fetching[hash]; announce != nil { + f.announces[announce.origin]-- + if f.announces[announce.origin] == 0 { + delete(f.announces, announce.origin) + } + delete(f.fetching, hash) + } +} + +// forgetBlock removes all traces of a queued block frmo the fetcher's internal +// state. +func (f *Fetcher) forgetBlock(hash common.Hash) { + if insert := f.queued[hash]; insert != nil { + f.queues[insert.origin]-- + if f.queues[insert.origin] == 0 { + delete(f.queues, insert.origin) + } + delete(f.queued, hash) + } +} |