mirror of https://github.com/grpc/grpc.git
Craig Tiller
7 years ago
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4bbd68b208
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/*
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* |
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* Copyright 2017 gRPC authors. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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* |
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*/ |
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#ifndef GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_FLOW_CONTROL_H |
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#define GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_FLOW_CONTROL_H |
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#include <stdint.h> |
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#include <grpc/support/useful.h> |
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#include "src/core/lib/support/manual_constructor.h" |
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#include "src/core/lib/transport/bdp_estimator.h" |
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#include "src/core/lib/transport/pid_controller.h" |
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struct grpc_chttp2_transport; |
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struct grpc_chttp2_stream; |
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extern "C" grpc_tracer_flag grpc_flowctl_trace; |
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namespace grpc_core { |
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namespace chttp2 { |
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static constexpr uint32_t kDefaultWindow = 65535; |
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class TransportFlowControl; |
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class StreamFlowControl; |
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class FlowControlAction { |
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public: |
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enum class Urgency : uint8_t { |
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// Nothing to be done.
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NO_ACTION_NEEDED = 0, |
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// Initiate a write to update the initial window immediately.
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UPDATE_IMMEDIATELY, |
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// Push the flow control update into a send buffer, to be sent
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// out the next time a write is initiated.
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QUEUE_UPDATE, |
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}; |
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Urgency send_stream_update() const { return send_stream_update_; } |
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Urgency send_transport_update() const { return send_transport_update_; } |
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Urgency send_setting_update() const { return send_setting_update_; } |
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uint32_t initial_window_size() const { return initial_window_size_; } |
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uint32_t max_frame_size() const { return max_frame_size_; } |
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FlowControlAction& set_send_stream_update(Urgency u) { |
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send_stream_update_ = u; |
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return *this; |
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} |
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FlowControlAction& send_transport_update(Urgency u) { |
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send_transport_update_ = u; |
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return *this; |
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} |
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FlowControlAction& send_setting_update(Urgency u) { |
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send_setting_update_ = u; |
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return *this; |
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} |
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static const char* UrgencyString(Urgency u); |
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void Trace(grpc_chttp2_transport* t) const; |
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private: |
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Urgency send_stream_update_ = Urgency::NO_ACTION_NEEDED; |
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Urgency send_transport_update_ = Urgency::NO_ACTION_NEEDED; |
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Urgency send_setting_update_ = Urgency::NO_ACTION_NEEDED; |
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uint32_t initial_window_size_ = 0; |
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uint32_t max_frame_size_ = 0; |
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}; |
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class FlowControlTrace { |
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public: |
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FlowControlTrace(const char* reason, TransportFlowControl* tfc, |
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StreamFlowControl* sfc) { |
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if (enabled_) Init(reason, tfc, sfc); |
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} |
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~FlowControlTrace() { |
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if (enabled_) Finish(); |
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} |
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private: |
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void Init(const char* reason, TransportFlowControl* tfc, |
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StreamFlowControl* sfc); |
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void Finish(); |
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const bool enabled_ = GRPC_TRACER_ON(grpc_flowctl_trace); |
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TransportFlowControl* tfc_; |
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StreamFlowControl* sfc_; |
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const char* reason_; |
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int64_t remote_window_; |
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int64_t target_window_; |
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int64_t announced_window_; |
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int64_t remote_window_delta_; |
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int64_t local_window_delta_; |
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int64_t announced_window_delta_; |
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uint32_t local_init_window_; |
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uint32_t local_max_frame_; |
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}; |
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class TransportFlowControl { |
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public: |
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~TransportFlowControl() { |
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if (pid_controller_initialized_) { |
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pid_controller_.Destroy(); |
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} |
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} |
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// returns an announce if we should send a transport update to our peer,
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// else returns zero; writing_anyway indicates if a write would happen
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// regardless of the send - if it is false and this function returns non-zero,
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// this announce will cause a write to occur
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uint32_t MaybeSendUpdate(bool writing_anyway); |
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// Reads the flow control data and returns and actionable struct that will
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// tell chttp2 exactly what it needs to do
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FlowControlAction MakeAction(grpc_exec_ctx* exec_ctx); |
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void StreamSentData(int64_t size) { remote_window_ -= size; } |
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grpc_error* ValidateRecvData(int64_t incoming_frame_size); |
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void CommitRecvData(int64_t incoming_frame_size) { |
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announced_window_ -= incoming_frame_size; |
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} |
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grpc_error* RecvData(int64_t incoming_frame_size) { |
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FlowControlTrace trace(" data recv", this, nullptr); |
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grpc_error* error = ValidateRecvData(incoming_frame_size); |
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if (error != GRPC_ERROR_NONE) return error; |
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CommitRecvData(incoming_frame_size); |
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return GRPC_ERROR_NONE; |
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} |
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// we have received a WINDOW_UPDATE frame for a transport
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void RecvUpdate(uint32_t size) { |
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FlowControlTrace trace("t updt recv", this, nullptr); |
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remote_window_ += size; |
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} |
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int64_t remote_window() const { return remote_window_; } |
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int64_t target_window() const { |
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return (uint32_t)GPR_MIN((int64_t)((1u << 31) - 1), |
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announced_stream_total_over_incoming_window_ + |
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target_initial_window_size_); |
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} |
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int64_t announced_window() const { return announced_window_; } |
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const grpc_chttp2_transport* transport() const { return t_; } |
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void PreUpdateAnnouncedWindowOverIncomingWindow(int64_t delta) { |
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if (delta > 0) { |
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announced_stream_total_over_incoming_window_ -= delta; |
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} else { |
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announced_stream_total_under_incoming_window_ += -delta; |
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} |
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} |
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void PostUpdateAnnouncedWindowOverIncomingWindow(int64_t delta) { |
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if (delta > 0) { |
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announced_stream_total_over_incoming_window_ += delta; |
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} else { |
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announced_stream_total_under_incoming_window_ -= -delta; |
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} |
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} |
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private: |
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FlowControlAction UpdateForBdp(grpc_exec_ctx* exec_ctx, |
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FlowControlAction action); |
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double SmoothBdp(grpc_exec_ctx* exec_ctx, double value); |
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const grpc_chttp2_transport* const t_; |
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/** initial window change. This is tracked as we parse settings frames from
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* the remote peer. If there is a positive delta, then we will make all |
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* streams readable since they may have become unstalled */ |
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int64_t initial_window_update_ = 0; |
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/** Our bookkeeping for the remote peer's available window */ |
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int64_t remote_window_ = kDefaultWindow; |
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/** calculating what we should give for local window:
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we track the total amount of flow control over initial window size |
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across all streams: this is data that we want to receive right now (it |
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has an outstanding read) |
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and the total amount of flow control under initial window size across all |
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streams: this is data we've read early |
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we want to adjust incoming_window such that: |
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incoming_window = total_over - max(bdp - total_under, 0) */ |
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int64_t announced_stream_total_over_incoming_window_ = 0; |
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int64_t announced_stream_total_under_incoming_window_ = 0; |
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/** This is out window according to what we have sent to our remote peer. The
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* difference between this and target window is what we use to decide when |
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* to send WINDOW_UPDATE frames. */ |
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int64_t announced_window_ = kDefaultWindow; |
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int32_t target_initial_window_size_ = kDefaultWindow; |
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/** should we probe bdp? */ |
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bool enable_bdp_probe_; |
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/* bdp estimation */ |
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grpc_core::BdpEstimator bdp_estimator_; |
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/* pid controller */ |
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bool pid_controller_initialized_; |
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grpc_core::ManualConstructor<grpc_core::PidController> pid_controller_; |
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grpc_millis last_pid_update_; |
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}; |
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class StreamFlowControl { |
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public: |
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StreamFlowControl(TransportFlowControl* tfc, grpc_chttp2_stream* s); |
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~StreamFlowControl() { |
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tfc_->PreUpdateAnnouncedWindowOverIncomingWindow(announced_window_delta_); |
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} |
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FlowControlAction UpdateAction(FlowControlAction action); |
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FlowControlAction MakeAction() { return UpdateAction(FlowControlAction()); } |
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// we have sent data on the wire, we must track this in our bookkeeping for
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// the remote peer's flow control.
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void SentData(int64_t outgoing_frame_size) { |
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FlowControlTrace tracer(" data sent", tfc_, this); |
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tfc_->StreamSentData(outgoing_frame_size); |
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remote_window_delta_ -= outgoing_frame_size; |
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} |
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// we have received data from the wire
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grpc_error* RecvData(int64_t incoming_frame_size); |
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// returns an announce if we should send a stream update to our peer, else
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// returns zero
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uint32_t MaybeSendUpdate(); |
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// we have received a WINDOW_UPDATE frame for a stream
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void RecvUpdate(uint32_t size) { |
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FlowControlTrace trace("s updt recv", tfc_, this); |
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remote_window_delta_ += size; |
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} |
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// the application is asking for a certain amount of bytes
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void IncomingByteStreamUpdate(size_t max_size_hint, size_t have_already); |
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int64_t remote_window_delta() const { return remote_window_delta_; } |
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int64_t local_window_delta() const { return local_window_delta_; } |
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int64_t announced_window_delta() const { return announced_window_delta_; } |
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const grpc_chttp2_stream* stream() const { return s_; } |
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private: |
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TransportFlowControl* const tfc_; |
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const grpc_chttp2_stream* const s_; |
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void UpdateAnnouncedWindowDelta(TransportFlowControl* tfc, int64_t change) { |
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tfc->PreUpdateAnnouncedWindowOverIncomingWindow(announced_window_delta_); |
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announced_window_delta_ += change; |
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tfc->PostUpdateAnnouncedWindowOverIncomingWindow(announced_window_delta_); |
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} |
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/** window available for us to send to peer, over or under the initial
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* window |
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* size of the transport... ie: |
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* remote_window = remote_window_delta + transport.initial_window_size */ |
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int64_t remote_window_delta_; |
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/** window available for peer to send to us (as a delta on
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* transport.initial_window_size) |
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* local_window = local_window_delta + transport.initial_window_size */ |
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int64_t local_window_delta_; |
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/** window available for peer to send to us over this stream that we have
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* announced to the peer */ |
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int64_t announced_window_delta_; |
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}; |
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} // namespace chttp2
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} // namespace grpc_core
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#endif |
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