From de88b08b94b71fde9b43fdca38d39a95fe35889d Mon Sep 17 00:00:00 2001 From: Victor Boivie Date: Mon, 3 May 2021 15:52:53 +0200 Subject: [PATCH] dcsctp: Add TaskQueue based timeout implementation This is about doing the best with what we have. As delayed tasks can't be cancelled, and dcSCTP timers will almost always be stopped or restarted, and will generally only expire on packet loss. This implementation will post a delayed task whenever a Timeout is started. Whenever it's stopped or restarted, it will keep the scheduled delay task running (there's no alternative), but it will also not start a new delayed task on subsequent starts/restarts. Instead, it will wait until the original delayed task has triggered, and will then - if the timer is still running, which it probably isn't - post a new delayed task with the remainder of the the duration. There is special handling for when a shorter duration is requested, as that can't re-use the scheduled task, but that shouldn't be very common. Bug: webrtc:12614 Change-Id: I7f3269cabf84f80dae3b8a528243414a93d50fc4 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/217223 Reviewed-by: Tommi Reviewed-by: Mirko Bonadei Commit-Queue: Victor Boivie Cr-Commit-Position: refs/heads/master@{#33904} --- net/dcsctp/public/types.h | 5 + net/dcsctp/timer/BUILD.gn | 26 ++++- net/dcsctp/timer/task_queue_timeout.cc | 96 ++++++++++++++++ net/dcsctp/timer/task_queue_timeout.h | 88 +++++++++++++++ net/dcsctp/timer/task_queue_timeout_test.cc | 115 ++++++++++++++++++++ 5 files changed, 329 insertions(+), 1 deletion(-) create mode 100644 net/dcsctp/timer/task_queue_timeout.cc create mode 100644 net/dcsctp/timer/task_queue_timeout.h create mode 100644 net/dcsctp/timer/task_queue_timeout_test.cc diff --git a/net/dcsctp/public/types.h b/net/dcsctp/public/types.h index b87fd4e79a..d516daffe3 100644 --- a/net/dcsctp/public/types.h +++ b/net/dcsctp/public/types.h @@ -12,6 +12,7 @@ #define NET_DCSCTP_PUBLIC_TYPES_H_ #include +#include #include "net/dcsctp/public/strong_alias.h" @@ -85,6 +86,10 @@ class TimeMs : public StrongAlias { value_ -= *d; return *this; } + + static constexpr TimeMs InfiniteFuture() { + return TimeMs(std::numeric_limits::max()); + } }; constexpr inline TimeMs operator+(TimeMs lhs, DurationMs rhs) { diff --git a/net/dcsctp/timer/BUILD.gn b/net/dcsctp/timer/BUILD.gn index e95ab676cd..a0ba5b030e 100644 --- a/net/dcsctp/timer/BUILD.gn +++ b/net/dcsctp/timer/BUILD.gn @@ -29,21 +29,45 @@ rtc_library("timer") { ] } +rtc_library("task_queue_timeout") { + deps = [ + "../../../api:array_view", + "../../../api/task_queue:task_queue", + "../../../rtc_base", + "../../../rtc_base:checks", + "../../../rtc_base:rtc_base_approved", + "../../../rtc_base/task_utils:pending_task_safety_flag", + "../../../rtc_base/task_utils:to_queued_task", + "../public:socket", + "../public:strong_alias", + "../public:types", + ] + sources = [ + "task_queue_timeout.cc", + "task_queue_timeout.h", + ] +} + if (rtc_include_tests) { rtc_library("dcsctp_timer_unittests") { testonly = true defines = [] deps = [ + ":task_queue_timeout", ":timer", "../../../api:array_view", "../../../rtc_base:checks", "../../../rtc_base:gunit_helpers", "../../../rtc_base:rtc_base_approved", "../../../test:test_support", + "../../../test/time_controller:time_controller", "../public:socket", ] - sources = [ "timer_test.cc" ] + sources = [ + "task_queue_timeout_test.cc", + "timer_test.cc", + ] absl_deps = [ "//third_party/abseil-cpp/absl/types:optional" ] } } diff --git a/net/dcsctp/timer/task_queue_timeout.cc b/net/dcsctp/timer/task_queue_timeout.cc new file mode 100644 index 0000000000..6d3054eeb8 --- /dev/null +++ b/net/dcsctp/timer/task_queue_timeout.cc @@ -0,0 +1,96 @@ +/* + * Copyright (c) 2021 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ +#include "net/dcsctp/timer/task_queue_timeout.h" + +#include "rtc_base/logging.h" +#include "rtc_base/task_utils/pending_task_safety_flag.h" +#include "rtc_base/task_utils/to_queued_task.h" + +namespace dcsctp { + +TaskQueueTimeoutFactory::TaskQueueTimeout::TaskQueueTimeout( + TaskQueueTimeoutFactory& parent) + : parent_(parent), + pending_task_safety_flag_(webrtc::PendingTaskSafetyFlag::Create()) {} + +TaskQueueTimeoutFactory::TaskQueueTimeout::~TaskQueueTimeout() { + RTC_DCHECK_RUN_ON(&parent_.thread_checker_); + pending_task_safety_flag_->SetNotAlive(); +} + +void TaskQueueTimeoutFactory::TaskQueueTimeout::Start(DurationMs duration_ms, + TimeoutID timeout_id) { + RTC_DCHECK_RUN_ON(&parent_.thread_checker_); + RTC_DCHECK(timeout_expiration_ == TimeMs::InfiniteFuture()); + timeout_expiration_ = parent_.get_time_() + duration_ms; + timeout_id_ = timeout_id; + + if (timeout_expiration_ >= posted_task_expiration_) { + // There is already a running task, and it's scheduled to expire sooner than + // the new expiration time. Don't do anything; The `timeout_expiration_` has + // already been updated and if the delayed task _does_ expire and the timer + // hasn't been stopped, that will be noticed in the timeout handler, and the + // task will be re-scheduled. Most timers are stopped before they expire. + return; + } + + if (posted_task_expiration_ != TimeMs::InfiniteFuture()) { + RTC_DLOG(LS_VERBOSE) << "New timeout duration is less than scheduled - " + "ghosting old delayed task."; + // There is already a scheduled delayed task, but its expiration time is + // further away than the new expiration, so it can't be used. It will be + // "killed" by replacing the safety flag. This is not expected to happen + // especially often; Mainly when a timer did exponential backoff and + // later recovered. + pending_task_safety_flag_->SetNotAlive(); + pending_task_safety_flag_ = webrtc::PendingTaskSafetyFlag::Create(); + } + + posted_task_expiration_ = timeout_expiration_; + parent_.task_queue_.PostDelayedTask( + webrtc::ToQueuedTask( + pending_task_safety_flag_, + [timeout_id, this]() { + RTC_DLOG(LS_VERBOSE) << "Timout expired: " << timeout_id.value(); + RTC_DCHECK_RUN_ON(&parent_.thread_checker_); + RTC_DCHECK(posted_task_expiration_ != TimeMs::InfiniteFuture()); + posted_task_expiration_ = TimeMs::InfiniteFuture(); + + if (timeout_expiration_ == TimeMs::InfiniteFuture()) { + // The timeout was stopped before it expired. Very common. + } else { + // Note that the timeout might have been restarted, which updated + // `timeout_expiration_` but left the scheduled task running. So + // if it's not quite time to trigger the timeout yet, schedule a + // new delayed task with what's remaining and retry at that point + // in time. + DurationMs remaining = timeout_expiration_ - parent_.get_time_(); + timeout_expiration_ = TimeMs::InfiniteFuture(); + if (*remaining > 0) { + Start(remaining, timeout_id_); + } else { + // It has actually triggered. + RTC_DLOG(LS_VERBOSE) + << "Timout triggered: " << timeout_id.value(); + parent_.on_expired_(timeout_id_); + } + } + }), + duration_ms.value()); +} + +void TaskQueueTimeoutFactory::TaskQueueTimeout::Stop() { + // As the TaskQueue doesn't support deleting a posted task, just mark the + // timeout as not running. + RTC_DCHECK_RUN_ON(&parent_.thread_checker_); + timeout_expiration_ = TimeMs::InfiniteFuture(); +} + +} // namespace dcsctp diff --git a/net/dcsctp/timer/task_queue_timeout.h b/net/dcsctp/timer/task_queue_timeout.h new file mode 100644 index 0000000000..e8d12df592 --- /dev/null +++ b/net/dcsctp/timer/task_queue_timeout.h @@ -0,0 +1,88 @@ +/* + * Copyright (c) 2021 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ +#ifndef NET_DCSCTP_TIMER_TASK_QUEUE_TIMEOUT_H_ +#define NET_DCSCTP_TIMER_TASK_QUEUE_TIMEOUT_H_ + +#include +#include + +#include "api/task_queue/task_queue_base.h" +#include "net/dcsctp/public/timeout.h" +#include "rtc_base/task_utils/pending_task_safety_flag.h" + +namespace dcsctp { + +// The TaskQueueTimeoutFactory creates `Timeout` instances, which schedules +// itself to be triggered on the provided `task_queue`, which may be a thread, +// an actual TaskQueue or something else which supports posting a delayed task. +// +// Note that each `DcSctpSocket` must have its own `TaskQueueTimeoutFactory`, +// as the `TimeoutID` are not unique among sockets. +// +// This class must outlive any created Timeout that it has created. Note that +// the `DcSctpSocket` will ensure that all Timeouts are deleted when the socket +// is destructed, so this means that this class must outlive the `DcSctpSocket`. +// +// This class, and the timeouts created it, are not thread safe. +class TaskQueueTimeoutFactory { + public: + // The `get_time` function must return the current time, relative to any + // epoch. Whenever a timeout expires, the `on_expired` callback will be + // triggered, and then the client should provided `timeout_id` to + // `DcSctpSocketInterface::HandleTimeout`. + TaskQueueTimeoutFactory(webrtc::TaskQueueBase& task_queue, + std::function get_time, + std::function on_expired) + : task_queue_(task_queue), + get_time_(std::move(get_time)), + on_expired_(std::move(on_expired)) {} + + // Creates an implementation of `Timeout`. + std::unique_ptr CreateTimeout() { + return std::make_unique(*this); + } + + private: + class TaskQueueTimeout : public Timeout { + public: + explicit TaskQueueTimeout(TaskQueueTimeoutFactory& parent); + ~TaskQueueTimeout(); + + void Start(DurationMs duration_ms, TimeoutID timeout_id) override; + void Stop() override; + + private: + TaskQueueTimeoutFactory& parent_; + // A safety flag to ensure that posted tasks to the task queue don't + // reference these object when they go out of scope. Note that this safety + // flag will be re-created if the scheduled-but-not-yet-expired task is not + // to be run. This happens when there is a posted delayed task with an + // expiration time _further away_ than what is now the expected expiration + // time. In this scenario, a new delayed task has to be posted with a + // shorter duration and the old task has to be forgotten. + rtc::scoped_refptr pending_task_safety_flag_; + // The time when the posted delayed task is set to expire. Will be set to + // the infinite future if there is no such task running. + TimeMs posted_task_expiration_ = TimeMs::InfiniteFuture(); + // The time when the timeout expires. It will be set to the infinite future + // if the timeout is not running/not started. + TimeMs timeout_expiration_ = TimeMs::InfiniteFuture(); + // The current timeout ID that will be reported when expired. + TimeoutID timeout_id_ = TimeoutID(0); + }; + + RTC_NO_UNIQUE_ADDRESS webrtc::SequenceChecker thread_checker_; + webrtc::TaskQueueBase& task_queue_; + const std::function get_time_; + const std::function on_expired_; +}; +} // namespace dcsctp + +#endif // NET_DCSCTP_TIMER_TASK_QUEUE_TIMEOUT_H_ diff --git a/net/dcsctp/timer/task_queue_timeout_test.cc b/net/dcsctp/timer/task_queue_timeout_test.cc new file mode 100644 index 0000000000..9d3846953b --- /dev/null +++ b/net/dcsctp/timer/task_queue_timeout_test.cc @@ -0,0 +1,115 @@ +/* + * Copyright (c) 2021 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ +#include "net/dcsctp/timer/task_queue_timeout.h" + +#include + +#include "rtc_base/gunit.h" +#include "test/gmock.h" +#include "test/time_controller/simulated_time_controller.h" + +namespace dcsctp { +namespace { +using ::testing::MockFunction; + +class TaskQueueTimeoutTest : public testing::Test { + protected: + TaskQueueTimeoutTest() + : time_controller_(webrtc::Timestamp::Millis(1234)), + task_queue_(time_controller_.GetMainThread()), + factory_( + *task_queue_, + [this]() { + return TimeMs(time_controller_.GetClock()->CurrentTime().ms()); + }, + on_expired_.AsStdFunction()) {} + + void AdvanceTime(DurationMs duration) { + time_controller_.AdvanceTime(webrtc::TimeDelta::Millis(*duration)); + } + + MockFunction on_expired_; + webrtc::GlobalSimulatedTimeController time_controller_; + + rtc::Thread* task_queue_; + TaskQueueTimeoutFactory factory_; +}; + +TEST_F(TaskQueueTimeoutTest, StartPostsDelayedTask) { + std::unique_ptr timeout = factory_.CreateTimeout(); + timeout->Start(DurationMs(1000), TimeoutID(1)); + + EXPECT_CALL(on_expired_, Call).Times(0); + AdvanceTime(DurationMs(999)); + + EXPECT_CALL(on_expired_, Call(TimeoutID(1))); + AdvanceTime(DurationMs(1)); +} + +TEST_F(TaskQueueTimeoutTest, StopBeforeExpiringDoesntTrigger) { + std::unique_ptr timeout = factory_.CreateTimeout(); + timeout->Start(DurationMs(1000), TimeoutID(1)); + + EXPECT_CALL(on_expired_, Call).Times(0); + AdvanceTime(DurationMs(999)); + + timeout->Stop(); + + AdvanceTime(DurationMs(1)); + AdvanceTime(DurationMs(1000)); +} + +TEST_F(TaskQueueTimeoutTest, RestartPrologingTimeoutDuration) { + std::unique_ptr timeout = factory_.CreateTimeout(); + timeout->Start(DurationMs(1000), TimeoutID(1)); + + EXPECT_CALL(on_expired_, Call).Times(0); + AdvanceTime(DurationMs(500)); + + timeout->Restart(DurationMs(1000), TimeoutID(2)); + + AdvanceTime(DurationMs(999)); + + EXPECT_CALL(on_expired_, Call(TimeoutID(2))); + AdvanceTime(DurationMs(1)); +} + +TEST_F(TaskQueueTimeoutTest, RestartWithShorterDurationExpiresWhenExpected) { + std::unique_ptr timeout = factory_.CreateTimeout(); + timeout->Start(DurationMs(1000), TimeoutID(1)); + + EXPECT_CALL(on_expired_, Call).Times(0); + AdvanceTime(DurationMs(500)); + + timeout->Restart(DurationMs(200), TimeoutID(2)); + + AdvanceTime(DurationMs(199)); + + EXPECT_CALL(on_expired_, Call(TimeoutID(2))); + AdvanceTime(DurationMs(1)); + + EXPECT_CALL(on_expired_, Call).Times(0); + AdvanceTime(DurationMs(1000)); +} + +TEST_F(TaskQueueTimeoutTest, KilledBeforeExpired) { + std::unique_ptr timeout = factory_.CreateTimeout(); + timeout->Start(DurationMs(1000), TimeoutID(1)); + + EXPECT_CALL(on_expired_, Call).Times(0); + AdvanceTime(DurationMs(500)); + + timeout = nullptr; + + EXPECT_CALL(on_expired_, Call).Times(0); + AdvanceTime(DurationMs(1000)); +} +} // namespace +} // namespace dcsctp