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Diffstat (limited to 'core/bloombits/scheduler.go')
| -rw-r--r-- | core/bloombits/scheduler.go | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/core/bloombits/scheduler.go b/core/bloombits/scheduler.go new file mode 100644 index 0000000..6449c74 --- /dev/null +++ b/core/bloombits/scheduler.go @@ -0,0 +1,181 @@ +// Copyright 2017 The go-ethereum Authors +// This file is part of the go-ethereum library. +// +// The go-ethereum library is free software: you can redistribute it and/or modify +// it under the terms of the GNU Lesser General Public License as published by +// the Free Software Foundation, either version 3 of the License, or +// (at your option) any later version. +// +// The go-ethereum library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU Lesser General Public License for more details. +// +// You should have received a copy of the GNU Lesser General Public License +// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. + +package bloombits + +import ( + "sync" +) + +// request represents a bloom retrieval task to prioritize and pull from the local +// database or remotely from the network. +type request struct { + section uint64 // Section index to retrieve the a bit-vector from + bit uint // Bit index within the section to retrieve the vector of +} + +// response represents the state of a requested bit-vector through a scheduler. +type response struct { + cached []byte // Cached bits to dedup multiple requests + done chan struct{} // Channel to allow waiting for completion +} + +// scheduler handles the scheduling of bloom-filter retrieval operations for +// entire section-batches belonging to a single bloom bit. Beside scheduling the +// retrieval operations, this struct also deduplicates the requests and caches +// the results to minimize network/database overhead even in complex filtering +// scenarios. +type scheduler struct { + bit uint // Index of the bit in the bloom filter this scheduler is responsible for + responses map[uint64]*response // Currently pending retrieval requests or already cached responses + lock sync.Mutex // Lock protecting the responses from concurrent access +} + +// newScheduler creates a new bloom-filter retrieval scheduler for a specific +// bit index. +func newScheduler(idx uint) *scheduler { + return &scheduler{ + bit: idx, + responses: make(map[uint64]*response), + } +} + +// run creates a retrieval pipeline, receiving section indexes from sections and +// returning the results in the same order through the done channel. Concurrent +// runs of the same scheduler are allowed, leading to retrieval task deduplication. +func (s *scheduler) run(sections chan uint64, dist chan *request, done chan []byte, quit chan struct{}, wg *sync.WaitGroup) { + // Create a forwarder channel between requests and responses of the same size as + // the distribution channel (since that will block the pipeline anyway). + pend := make(chan uint64, cap(dist)) + + // Start the pipeline schedulers to forward between user -> distributor -> user + wg.Add(2) + go s.scheduleRequests(sections, dist, pend, quit, wg) + go s.scheduleDeliveries(pend, done, quit, wg) +} + +// reset cleans up any leftovers from previous runs. This is required before a +// restart to ensure the no previously requested but never delivered state will +// cause a lockup. +func (s *scheduler) reset() { + s.lock.Lock() + defer s.lock.Unlock() + + for section, res := range s.responses { + if res.cached == nil { + delete(s.responses, section) + } + } +} + +// scheduleRequests reads section retrieval requests from the input channel, +// deduplicates the stream and pushes unique retrieval tasks into the distribution +// channel for a database or network layer to honour. +func (s *scheduler) scheduleRequests(reqs chan uint64, dist chan *request, pend chan uint64, quit chan struct{}, wg *sync.WaitGroup) { + // Clean up the goroutine and pipeline when done + defer wg.Done() + defer close(pend) + + // Keep reading and scheduling section requests + for { + select { + case <-quit: + return + + case section, ok := <-reqs: + // New section retrieval requested + if !ok { + return + } + // Deduplicate retrieval requests + unique := false + + s.lock.Lock() + if s.responses[section] == nil { + s.responses[section] = &response{ + done: make(chan struct{}), + } + unique = true + } + s.lock.Unlock() + + // Schedule the section for retrieval and notify the deliverer to expect this section + if unique { + select { + case <-quit: + return + case dist <- &request{bit: s.bit, section: section}: + } + } + select { + case <-quit: + return + case pend <- section: + } + } + } +} + +// scheduleDeliveries reads section acceptance notifications and waits for them +// to be delivered, pushing them into the output data buffer. +func (s *scheduler) scheduleDeliveries(pend chan uint64, done chan []byte, quit chan struct{}, wg *sync.WaitGroup) { + // Clean up the goroutine and pipeline when done + defer wg.Done() + defer close(done) + + // Keep reading notifications and scheduling deliveries + for { + select { + case <-quit: + return + + case idx, ok := <-pend: + // New section retrieval pending + if !ok { + return + } + // Wait until the request is honoured + s.lock.Lock() + res := s.responses[idx] + s.lock.Unlock() + + select { + case <-quit: + return + case <-res.done: + } + // Deliver the result + select { + case <-quit: + return + case done <- res.cached: + } + } + } +} + +// deliver is called by the request distributor when a reply to a request arrives. +func (s *scheduler) deliver(sections []uint64, data [][]byte) { + s.lock.Lock() + defer s.lock.Unlock() + + for i, section := range sections { + if res := s.responses[section]; res != nil && res.cached == nil { // Avoid non-requests and double deliveries + res.cached = data[i] + close(res.done) + } + } +} |