| // Copyright (c) 2015 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef QUICHE_HTTP2_CORE_PRIORITY_WRITE_SCHEDULER_H_ |
| #define QUICHE_HTTP2_CORE_PRIORITY_WRITE_SCHEDULER_H_ |
| |
| #include <algorithm> |
| #include <cstddef> |
| #include <cstdint> |
| #include <memory> |
| #include <string> |
| #include <tuple> |
| #include <utility> |
| #include <vector> |
| |
| #include "absl/container/flat_hash_map.h" |
| #include "absl/strings/str_cat.h" |
| #include "quiche/http2/core/write_scheduler.h" |
| #include "quiche/common/platform/api/quiche_bug_tracker.h" |
| #include "quiche/common/platform/api/quiche_export.h" |
| #include "quiche/common/platform/api/quiche_logging.h" |
| #include "quiche/common/quiche_circular_deque.h" |
| #include "quiche/spdy/core/spdy_protocol.h" |
| |
| namespace http2 { |
| |
| namespace test { |
| template <typename StreamIdType> |
| class PriorityWriteSchedulerPeer; |
| } |
| |
| // WriteScheduler implementation that manages the order in which streams are |
| // written using the SPDY priority scheme described at: |
| // https://www.chromium.org/spdy/spdy-protocol/spdy-protocol-draft3-1#TOC-2.3.3-Stream-priority |
| // |
| // Internally, PriorityWriteScheduler consists of 8 PriorityInfo objects, one |
| // for each priority value. Each PriorityInfo contains a list of streams of |
| // that priority that are ready to write, as well as a timestamp of the last |
| // I/O event that occurred for a stream of that priority. |
| // |
| template <typename StreamIdType> |
| class QUICHE_EXPORT_PRIVATE PriorityWriteScheduler |
| : public WriteScheduler<StreamIdType> { |
| public: |
| using typename WriteScheduler<StreamIdType>::StreamPrecedenceType; |
| |
| // Creates scheduler with no streams. |
| PriorityWriteScheduler() : PriorityWriteScheduler(spdy::kHttp2RootStreamId) {} |
| explicit PriorityWriteScheduler(StreamIdType root_stream_id) |
| : root_stream_id_(root_stream_id) {} |
| |
| void RegisterStream(StreamIdType stream_id, |
| const StreamPrecedenceType& precedence) override { |
| // TODO(mpw): verify |precedence.is_spdy3_priority() == true| once |
| // Http2PriorityWriteScheduler enabled for HTTP/2. |
| |
| // parent_id not used here, but may as well validate it. However, |
| // parent_id may legitimately not be registered yet--see b/15676312. |
| StreamIdType parent_id = precedence.parent_id(); |
| QUICHE_DVLOG_IF( |
| 1, parent_id != root_stream_id_ && !StreamRegistered(parent_id)) |
| << "Parent stream " << parent_id << " not registered"; |
| |
| if (stream_id == root_stream_id_) { |
| QUICHE_BUG(spdy_bug_19_1) |
| << "Stream " << root_stream_id_ << " already registered"; |
| return; |
| } |
| auto stream_info = std::make_unique<StreamInfo>( |
| StreamInfo{precedence.spdy3_priority(), stream_id, false}); |
| bool inserted = |
| stream_infos_.insert(std::make_pair(stream_id, std::move(stream_info))) |
| .second; |
| QUICHE_BUG_IF(spdy_bug_19_2, !inserted) |
| << "Stream " << stream_id << " already registered"; |
| } |
| |
| void UnregisterStream(StreamIdType stream_id) override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_BUG(spdy_bug_19_3) << "Stream " << stream_id << " not registered"; |
| return; |
| } |
| const StreamInfo* const stream_info = it->second.get(); |
| if (stream_info->ready) { |
| bool erased = Erase(&priority_infos_[stream_info->priority].ready_list, |
| stream_info); |
| QUICHE_DCHECK(erased); |
| } |
| stream_infos_.erase(it); |
| } |
| |
| bool StreamRegistered(StreamIdType stream_id) const override { |
| return stream_infos_.find(stream_id) != stream_infos_.end(); |
| } |
| |
| StreamPrecedenceType GetStreamPrecedence( |
| StreamIdType stream_id) const override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_DVLOG(1) << "Stream " << stream_id << " not registered"; |
| return StreamPrecedenceType(spdy::kV3LowestPriority); |
| } |
| return StreamPrecedenceType(it->second->priority); |
| } |
| |
| void UpdateStreamPrecedence(StreamIdType stream_id, |
| const StreamPrecedenceType& precedence) override { |
| // TODO(mpw): verify |precedence.is_spdy3_priority() == true| once |
| // Http2PriorityWriteScheduler enabled for HTTP/2. |
| |
| // parent_id not used here, but may as well validate it. However, |
| // parent_id may legitimately not be registered yet--see b/15676312. |
| StreamIdType parent_id = precedence.parent_id(); |
| QUICHE_DVLOG_IF( |
| 1, parent_id != root_stream_id_ && !StreamRegistered(parent_id)) |
| << "Parent stream " << parent_id << " not registered"; |
| |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| // TODO(mpw): add to stream_infos_ on demand--see b/15676312. |
| QUICHE_DVLOG(1) << "Stream " << stream_id << " not registered"; |
| return; |
| } |
| StreamInfo* const stream_info = it->second.get(); |
| spdy::SpdyPriority new_priority = precedence.spdy3_priority(); |
| if (stream_info->priority == new_priority) { |
| return; |
| } |
| if (stream_info->ready) { |
| bool erased = Erase(&priority_infos_[stream_info->priority].ready_list, |
| stream_info); |
| QUICHE_DCHECK(erased); |
| priority_infos_[new_priority].ready_list.push_back(stream_info); |
| ++num_ready_streams_; |
| } |
| stream_info->priority = new_priority; |
| } |
| |
| std::vector<StreamIdType> GetStreamChildren( |
| StreamIdType /*stream_id*/) const override { |
| return std::vector<StreamIdType>(); |
| } |
| |
| void RecordStreamEventTime(StreamIdType stream_id, |
| int64_t now_in_usec) override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_BUG(spdy_bug_19_4) << "Stream " << stream_id << " not registered"; |
| return; |
| } |
| PriorityInfo& priority_info = priority_infos_[it->second->priority]; |
| priority_info.last_event_time_usec = |
| std::max(priority_info.last_event_time_usec, now_in_usec); |
| } |
| |
| int64_t GetLatestEventWithPrecedence(StreamIdType stream_id) const override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_BUG(spdy_bug_19_5) << "Stream " << stream_id << " not registered"; |
| return 0; |
| } |
| int64_t last_event_time_usec = 0; |
| const StreamInfo* const stream_info = it->second.get(); |
| for (spdy::SpdyPriority p = spdy::kV3HighestPriority; |
| p < stream_info->priority; ++p) { |
| last_event_time_usec = std::max(last_event_time_usec, |
| priority_infos_[p].last_event_time_usec); |
| } |
| return last_event_time_usec; |
| } |
| |
| StreamIdType PopNextReadyStream() override { |
| return std::get<0>(PopNextReadyStreamAndPrecedence()); |
| } |
| |
| // Returns the next ready stream and its precedence. |
| std::tuple<StreamIdType, StreamPrecedenceType> |
| PopNextReadyStreamAndPrecedence() override { |
| for (spdy::SpdyPriority p = spdy::kV3HighestPriority; |
| p <= spdy::kV3LowestPriority; ++p) { |
| ReadyList& ready_list = priority_infos_[p].ready_list; |
| if (!ready_list.empty()) { |
| StreamInfo* const info = ready_list.front(); |
| ready_list.pop_front(); |
| --num_ready_streams_; |
| |
| QUICHE_DCHECK(stream_infos_.find(info->stream_id) != |
| stream_infos_.end()); |
| info->ready = false; |
| return std::make_tuple(info->stream_id, |
| StreamPrecedenceType(info->priority)); |
| } |
| } |
| QUICHE_BUG(spdy_bug_19_6) << "No ready streams available"; |
| return std::make_tuple(0, StreamPrecedenceType(spdy::kV3LowestPriority)); |
| } |
| |
| bool ShouldYield(StreamIdType stream_id) const override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_BUG(spdy_bug_19_7) << "Stream " << stream_id << " not registered"; |
| return false; |
| } |
| |
| // If there's a higher priority stream, this stream should yield. |
| const StreamInfo* const stream_info = it->second.get(); |
| for (spdy::SpdyPriority p = spdy::kV3HighestPriority; |
| p < stream_info->priority; ++p) { |
| if (!priority_infos_[p].ready_list.empty()) { |
| return true; |
| } |
| } |
| |
| // If this priority level is empty, or this stream is the next up, there's |
| // no need to yield. |
| const auto& ready_list = priority_infos_[it->second->priority].ready_list; |
| if (ready_list.empty() || ready_list.front()->stream_id == stream_id) { |
| return false; |
| } |
| |
| // There are other streams in this priority level which take precedence. |
| // Yield. |
| return true; |
| } |
| |
| void MarkStreamReady(StreamIdType stream_id, bool add_to_front) override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_BUG(spdy_bug_19_8) << "Stream " << stream_id << " not registered"; |
| return; |
| } |
| StreamInfo* const stream_info = it->second.get(); |
| if (stream_info->ready) { |
| return; |
| } |
| ReadyList& ready_list = priority_infos_[stream_info->priority].ready_list; |
| if (add_to_front) { |
| ready_list.push_front(stream_info); |
| } else { |
| ready_list.push_back(stream_info); |
| } |
| ++num_ready_streams_; |
| stream_info->ready = true; |
| } |
| |
| void MarkStreamNotReady(StreamIdType stream_id) override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_BUG(spdy_bug_19_9) << "Stream " << stream_id << " not registered"; |
| return; |
| } |
| StreamInfo* const stream_info = it->second.get(); |
| if (!stream_info->ready) { |
| return; |
| } |
| bool erased = |
| Erase(&priority_infos_[stream_info->priority].ready_list, stream_info); |
| QUICHE_DCHECK(erased); |
| stream_info->ready = false; |
| } |
| |
| // Returns true iff the number of ready streams is non-zero. |
| bool HasReadyStreams() const override { return num_ready_streams_ > 0; } |
| |
| // Returns the number of ready streams. |
| size_t NumReadyStreams() const override { return num_ready_streams_; } |
| |
| size_t NumRegisteredStreams() const override { return stream_infos_.size(); } |
| |
| std::string DebugString() const override { |
| return absl::StrCat( |
| "PriorityWriteScheduler {num_streams=", stream_infos_.size(), |
| " num_ready_streams=", NumReadyStreams(), "}"); |
| } |
| |
| // Returns true if a stream is ready. |
| bool IsStreamReady(StreamIdType stream_id) const override { |
| auto it = stream_infos_.find(stream_id); |
| if (it == stream_infos_.end()) { |
| QUICHE_DLOG(INFO) << "Stream " << stream_id << " not registered"; |
| return false; |
| } |
| return it->second->ready; |
| } |
| |
| private: |
| friend class test::PriorityWriteSchedulerPeer<StreamIdType>; |
| |
| // State kept for all registered streams. All ready streams have ready = true |
| // and should be present in priority_infos_[priority].ready_list. |
| struct QUICHE_EXPORT_PRIVATE StreamInfo { |
| spdy::SpdyPriority priority; |
| StreamIdType stream_id; |
| bool ready; |
| }; |
| |
| // O(1) size lookup, O(1) insert at front or back (amortized). |
| using ReadyList = quiche::QuicheCircularDeque<StreamInfo*>; |
| |
| // State kept for each priority level. |
| struct QUICHE_EXPORT_PRIVATE PriorityInfo { |
| // IDs of streams that are ready to write. |
| ReadyList ready_list; |
| // Time of latest write event for stream of this priority, in microseconds. |
| int64_t last_event_time_usec = 0; |
| }; |
| |
| // Use std::unique_ptr, because absl::flat_hash_map does not have pointer |
| // stability, but ReadyList stores pointers to the StreamInfo objects. |
| using StreamInfoMap = |
| absl::flat_hash_map<StreamIdType, std::unique_ptr<StreamInfo>>; |
| |
| // Erases `info` from `ready_list`, returning true if found (and erased), or |
| // false otherwise. Decrements `num_ready_streams_` if an entry is erased. |
| bool Erase(ReadyList* ready_list, const StreamInfo* info) { |
| auto it = std::remove(ready_list->begin(), ready_list->end(), info); |
| if (it == ready_list->end()) { |
| // `info` was not found. |
| return false; |
| } |
| ready_list->pop_back(); |
| --num_ready_streams_; |
| return true; |
| } |
| |
| // Number of ready streams. |
| size_t num_ready_streams_ = 0; |
| // Per-priority state, including ready lists. |
| PriorityInfo priority_infos_[spdy::kV3LowestPriority + 1]; |
| // StreamInfos for all registered streams. |
| StreamInfoMap stream_infos_; |
| StreamIdType root_stream_id_; |
| }; |
| |
| } // namespace http2 |
| |
| #endif // QUICHE_HTTP2_CORE_PRIORITY_WRITE_SCHEDULER_H_ |