diff options
Diffstat (limited to 'eth/fetcher')
| -rw-r--r-- | eth/fetcher/fetcher.go | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/eth/fetcher/fetcher.go b/eth/fetcher/fetcher.go new file mode 100644 index 000000000..19c53048c --- /dev/null +++ b/eth/fetcher/fetcher.go @@ -0,0 +1,258 @@ +// Package fetcher contains the block announcement based synchonisation. +package fetcher + +import ( + "errors" + "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" +) + +const ( + arriveTimeout = 500 * time.Millisecond // Time allowance before an announced block is explicitly requested + fetchTimeout = 5 * time.Second // Maximum alloted time to return an explicitly requested block +) + +var ( + errTerminated = errors.New("terminated") +) + +// hashCheckFn is a callback type for verifying a hash's presence in the local chain. +type hashCheckFn func(common.Hash) bool + +// blockRequesterFn is a callback type for sending a block retrieval request. +type blockRequesterFn func([]common.Hash) error + +// blockImporterFn is a callback type for trying to inject a block into the local chain. +type blockImporterFn func(peer string, block *types.Block) error + +// 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 +} + +// Fetcher is responsible for accumulating block announcements from various peers +// and scheduling them for retrieval. +type Fetcher struct { + // Various event channels + notify chan *announce + filter chan chan []*types.Block + quit chan struct{} + + // Callbacks + hasBlock hashCheckFn // Checks if a block is present in the chain + importBlock blockImporterFn // Injects a block from an origin peer into the chain +} + +// New creates a block fetcher to retrieve blocks based on hash announcements. +func New(hasBlock hashCheckFn, importBlock blockImporterFn) *Fetcher { + return &Fetcher{ + notify: make(chan *announce), + filter: make(chan chan []*types.Block), + quit: make(chan struct{}), + hasBlock: hasBlock, + importBlock: importBlock, + } +} + +// 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 + } +} + +// 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() { + announced := make(map[common.Hash][]*announce) + fetching := make(map[common.Hash]*announce) + fetch := time.NewTimer(0) + done := make(chan common.Hash) + + // Iterate the block fetching until a quit is requested + for { + // Clean up any expired block fetches + for hash, announce := range fetching { + if time.Since(announce.time) > fetchTimeout { + delete(announced, hash) + delete(fetching, hash) + } + } + // 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, schedule if it's not yet downloading + glog.V(logger.Debug).Infof("Peer %s: scheduling %x", notification.origin, notification.hash[:4]) + if _, ok := fetching[notification.hash]; ok { + break + } + if len(announced) == 0 { + fetch.Reset(arriveTimeout) + } + announced[notification.hash] = append(announced[notification.hash], notification) + + case hash := <-done: + // A pending import finished, remove all traces of the notification + delete(announced, hash) + delete(fetching, 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 announced { + if time.Since(announces[0].time) > arriveTimeout { + announce := announces[rand.Intn(len(announces))] + if !f.hasBlock(hash) { + request[announce.origin] = append(request[announce.origin], hash) + fetching[hash] = announce + } + delete(announced, hash) + } + } + // Send out all block requests + for peer, hashes := range request { + glog.V(logger.Debug).Infof("Peer %s: explicitly fetching %d blocks", peer, len(hashes)) + go fetching[hashes[0]].fetch(hashes) + } + // Schedule the next fetch if blocks are still pending + if len(announced) > 0 { + nearest := time.Now() + for _, announces := range announced { + if nearest.Before(announces[0].time) { + nearest = announces[0].time + } + } + fetch.Reset(arriveTimeout + time.Since(nearest)) + } + + 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 := fetching[hash]; ok { + // Discard if already imported by other means + if !f.hasBlock(hash) { + explicit = append(explicit, block) + } else { + delete(fetching, hash) + } + } else { + download = append(download, block) + } + } + + select { + case filter <- download: + case <-f.quit: + return + } + // Create a closure with the retrieved blocks and origin peers + peers := make([]string, 0, len(explicit)) + blocks = make([]*types.Block, 0, len(explicit)) + for _, block := range explicit { + hash := block.Hash() + if announce := fetching[hash]; announce != nil { + // Drop the block if it surely cannot fit + if f.hasBlock(hash) || !f.hasBlock(block.ParentHash()) { + // delete(fetching, hash) // if we drop, it will re-fetch it, wait for timeout? + continue + } + // Otherwise accumulate for import + peers = append(peers, announce.origin) + blocks = append(blocks, block) + } + } + // If any explicit fetches were replied to, import them + if count := len(blocks); count > 0 { + glog.V(logger.Debug).Infof("Importing %d explicitly fetched blocks", len(blocks)) + go func() { + // Make sure all hashes are cleaned up + for _, block := range blocks { + hash := block.Hash() + defer func() { done <- hash }() + } + // Try and actually import the blocks + for i := 0; i < len(blocks); i++ { + if err := f.importBlock(peers[i], blocks[i]); err != nil { + glog.V(logger.Detail).Infof("Failed to import explicitly fetched block: %v", err) + return + } + } + }() + } + } + } +} |