Detailed Description

Task construction and synchronization primitives for coroutines.

Files
file	atomic.hpp
	Helper algorithms to work with atomics.

Classes
class	rcu::Variable< T, RcuTraits >
	Read-Copy-Update variable. More...

class	utils::PeriodicTask
	Task that periodically runs a user callback. Callback is started after the previous callback execution is finished every `period + A - B`, where: More...

class	engine::Mutex
	std::mutex replacement for asynchronous tasks. More...

class	engine::SingleConsumerEvent
	A multiple-producers, single-consumer event. More...

class	engine::ConditionVariable
	std::condition_variable replacement for asynchronous tasks More...

class	concurrent::AsyncEventSource< Args >
	The read-only side of an event channel. Events are delivered to listeners in a strict FIFO order, i.e. only after the event was processed a new event may appear for processing, same listener is never called concurrently. More...

class	concurrent::Variable< Data, Mutex >

class	engine::Promise< T >
	std::promise replacement for asynchronous tasks that works in pair with engine::Future More...

class	engine::Future< T >
	std::future replacement for asynchronous tasks that works in pair with engine::Promise More...

class	engine::CancellableSemaphore
	Class that allows up to `max_simultaneous_locks` concurrent accesses to the critical section. It honours task cancellation, unlike Semaphore. More...

class	engine::Semaphore
	Class that allows up to `max_simultaneous_locks` concurrent accesses to the critical section. It ignores task cancellation, unlike CancellableSemaphore. More...

class	concurrent::StripedCounter
	A contention-free sharded atomic counter, with memory consumption and read performance traded for write performance. Intended to be used for write-heavy counters, mostly in metrics. More...

class	utils::TokenBucket

class	concurrent::AsyncEventChannel< Args >

class	concurrent::BackgroundTaskStorageCore

class	concurrent::BackgroundTaskStorage

class	concurrent::ConflatedEventChannel
	A non-blocking version of 'AsyncEventChannel'. More...

class	concurrent::MpscQueue< T >

class	concurrent::MutexSet< Key, Hash, Equal >
	A dynamic set of mutexes. More...

class	dist_lock::DistLockStrategyBase
	Interface for distributed lock strategies. More...

class	dist_lock::DistLockedTask
	A task that tries to acquire a distributed lock and runs user callback once while the lock is held. More...

class	drivers::SubscribableFutureWrapper< SubscribableFuture >
	An adaptor for working with certain external futures. More...

class	engine::SharedMutex
	std::shared_mutex replacement for asynchronous tasks. More...

class	engine::SingleUseEvent
	A single-producer, single-consumer event. More...

class	engine::SingleWaitingTaskMutex
	Lighter version of Mutex with not more than 1 waiting task. More...

class	engine::TaskInheritedVariable< T >
	TaskInheritedVariable is a per-coroutine variable of arbitrary type. More...

class	engine::TaskLocalVariable< T >
	TaskLocalVariable is a per-coroutine variable of arbitrary type. More...

class	rcu::RcuMap< Key, Value, RcuMapTraits >
	Map-like structure allowing RCU keyset updates. More...

Typedefs
template<typename T>
using	concurrent::NonFifoMpmcQueue = GenericQueue<T, impl::SimpleQueuePolicy<true, true>>
	Non FIFO multiple producers multiple consumers queue.

template<typename T>
using	concurrent::NonFifoMpscQueue = GenericQueue<T, impl::SimpleQueuePolicy<true, false>>
	Non FIFO multiple producers single consumer queue.

template<typename T>
using	concurrent::SpmcQueue = GenericQueue<T, impl::SimpleQueuePolicy<false, true>>
	Single producer multiple consumers queue.

template<typename T>
using	concurrent::SpscQueue = GenericQueue<T, impl::SimpleQueuePolicy<false, false>>
	Single producer single consumer queue.

template<typename T>
using	concurrent::UnboundedNonFifoMpscQueue = GenericQueue<T, impl::NoMaxSizeQueuePolicy<true, false>>
	Like.

template<typename T>
using	concurrent::UnboundedSpmcQueue = GenericQueue<T, impl::NoMaxSizeQueuePolicy<false, true>>
	Like.

template<typename T>
using	concurrent::UnboundedSpscQueue = GenericQueue<T, impl::NoMaxSizeQueuePolicy<false, false>>
	Like.

using	concurrent::StringStreamQueue = GenericQueue<std::string, impl::ContainerQueuePolicy<false, false>>
	Single producer single consumer queue of std::string which is bounded by the total bytes inside the strings.

Functions
template<typename T, typename Func>
T	utils::AtomicUpdate (std::atomic< T > &atomic, Func updater)
	Atomically performs the operation of `updater` on `atomic`

template<typename T>
T	utils::AtomicMin (std::atomic< T > &atomic, T value)
	Concurrently safe sets `atomic` to a `value` if `value` is less.

template<typename T>
T	utils::AtomicMax (std::atomic< T > &atomic, T value)
	Concurrently safe sets `atomic` to a `value` if `value` is greater.

template<typename SubscribableFuture>
void	drivers::WaitForSubscribableFuture (SubscribableFuture &&future)
	Waits on the given future as described on drivers::SubscribableFutureWrapper.

template<typename SubscribableFuture>
engine::FutureStatus	drivers::TryWaitForSubscribableFuture (SubscribableFuture &&future, engine::Deadline deadline)

template<typename... Tasks>
auto	engine::GetAll (Tasks &... tasks)
	Waits for the successful completion of all of the specified tasks or the cancellation of the caller.

template<typename... Tasks>
void	engine::WaitAllChecked (Tasks &... tasks)
	Waits for the successful completion of all of the specified tasks or for the cancellation of the caller.

template<typename... Tasks>
std::optional< std::size_t >	engine::WaitAny (Tasks &... tasks)
	Waits for the completion of any of the specified tasks or the cancellation of the caller.

template<typename Function, typename... Args>
auto	utils::Async (std::string name, Function &&f, Args &&... args)
	Starts an asynchronous task.

template<typename Function, typename... Args>
auto	utils::Async (engine::TaskProcessor &task_processor, std::string name, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::CriticalAsync (engine::TaskProcessor &task_processor, std::string name, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::SharedCriticalAsync (engine::TaskProcessor &task_processor, std::string name, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::SharedAsync (engine::TaskProcessor &task_processor, std::string name, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::Async (engine::TaskProcessor &task_processor, std::string name, engine::Deadline deadline, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::SharedAsync (engine::TaskProcessor &task_processor, std::string name, engine::Deadline deadline, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::CriticalAsync (std::string name, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::SharedCriticalAsync (std::string name, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::SharedAsync (std::string name, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::Async (std::string name, engine::Deadline deadline, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::SharedAsync (std::string name, engine::Deadline deadline, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::AsyncBackground (std::string name, engine::TaskProcessor &task_processor, Function &&f, Args &&... args)

template<typename Function, typename... Args>
auto	utils::CriticalAsyncBackground (std::string name, engine::TaskProcessor &task_processor, Function &&f, Args &&... args)

Typedef Documentation

◆ NonFifoMpmcQueue

template<typename T>

using concurrent::NonFifoMpmcQueue = GenericQueue<T, impl::SimpleQueuePolicy<true, true>>

Non FIFO multiple producers multiple consumers queue.

Items from the same producer are always delivered in the production order. Items from different producers (or when using a MultiProducer token) are delivered in an unspecified order. In other words, FIFO order is maintained only within producers, but not between them. This may lead to increased peak latency of item processing.

In exchange for this, the queue has lower contention and increased throughput compared to a conventional lock-free queue.

See also: Synchronization Primitives

Definition at line 692 of file queue.hpp.

◆ NonFifoMpscQueue

template<typename T>

using concurrent::NonFifoMpscQueue = GenericQueue<T, impl::SimpleQueuePolicy<true, false>>

Non FIFO multiple producers single consumer queue.

See also: concurrent::NonFifoMpmcQueue for the description of what NonFifo means.; Synchronization Primitives

Definition at line 701 of file queue.hpp.

◆ SpmcQueue

template<typename T>

using concurrent::SpmcQueue = GenericQueue<T, impl::SimpleQueuePolicy<false, true>>

Single producer multiple consumers queue.

See also: Synchronization Primitives

Definition at line 709 of file queue.hpp.

◆ SpscQueue

template<typename T>

using concurrent::SpscQueue = GenericQueue<T, impl::SimpleQueuePolicy<false, false>>

Single producer single consumer queue.

See also: Synchronization Primitives

Definition at line 717 of file queue.hpp.

◆ StringStreamQueue

using concurrent::StringStreamQueue = GenericQueue<std::string, impl::ContainerQueuePolicy<false, false>>

Single producer single consumer queue of std::string which is bounded by the total bytes inside the strings.

See also: Synchronization Primitives

Definition at line 764 of file queue.hpp.

◆ UnboundedNonFifoMpscQueue

template<typename T>

using concurrent::UnboundedNonFifoMpscQueue = GenericQueue<T, impl::NoMaxSizeQueuePolicy<true, false>>

Like.

See also: NonFifoMpscQueue, but does not support setting max size and is thus slightly faster.; Synchronization Primitives

Definition at line 741 of file queue.hpp.

◆ UnboundedSpmcQueue

template<typename T>

using concurrent::UnboundedSpmcQueue = GenericQueue<T, impl::NoMaxSizeQueuePolicy<false, true>>

Like.

See also: SpmcQueue, but does not support setting max size and is thus slightly faster.; Synchronization Primitives

Definition at line 749 of file queue.hpp.

◆ UnboundedSpscQueue

template<typename T>

using concurrent::UnboundedSpscQueue = GenericQueue<T, impl::NoMaxSizeQueuePolicy<false, false>>

Like.

See also: SpscQueue, but does not support setting max size and is thus slightly faster.; Synchronization Primitives

Definition at line 757 of file queue.hpp.

Function Documentation

◆ Async() [1/4]

template<typename Function, typename... Args>

auto utils::Async	(	engine::TaskProcessor &	task_processor,
		std::string	name,
		engine::Deadline	deadline,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Task execution may be cancelled before the function starts execution in case of TaskProcessor overload.

Parameters

task_processor	Task processor to run on
name	Name of the task to show in logs
deadline	Deadline to set for the child task, upon reaching it the task will be cancelled
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Definition at line 185 of file async.hpp.

◆ Async() [2/4]

template<typename Function, typename... Args>

auto utils::Async	(	engine::TaskProcessor &	task_processor,
		std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Task execution may be cancelled before the function starts execution in case of TaskProcessor overload.

Parameters

task_processor	Task processor to run on
name	Name of the task to show in logs
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Definition at line 110 of file async.hpp.

◆ Async() [3/4]

template<typename Function, typename... Args>

auto utils::Async	(	std::string	name,
		engine::Deadline	deadline,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Task execution may be cancelled before the function starts execution in case of TaskProcessor overload.

Parameters

name	Name of the task to show in logs
deadline	Deadline to set for the child task, upon reaching it the task will be cancelled
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Definition at line 302 of file async.hpp.

◆ Async() [4/4]

template<typename Function, typename... Args>

auto utils::Async	(	std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

Starts an asynchronous task.

By default, arguments are copied or moved inside the resulting TaskWithResult, like std::thread does. To pass an argument by reference, wrap it in std::ref / std::cref or capture the arguments using a lambda.

For more documentation on launching asynchronous tasks:

See also: intro_tasks

About this specific overload

This is the overload that should be used by default.

The task will be launched on the current TaskProcessor.
Only 1 task may call Wait or Get on this task.
The task may be cancelled before the function starts execution in case of TaskProcessor overload. Also, if the task is cancelled for any reason before the function starts execution, it will not run at all.
The task will create a child tracing::Span with the specified name
The task will inherit all engine::TaskInheritedVariable instances from the current task.

For details on the various other overloads:

See also: flavors_of_async

Parameters

name	Name of the task to show in logs
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Examples: components/component_sample_test.cpp, and samples/tcp_full_duplex_service/main.cpp.

Definition at line 89 of file async.hpp.

◆ AsyncBackground()

template<typename Function, typename... Args>

auto utils::AsyncBackground	(	std::string	name,
		engine::TaskProcessor &	task_processor,
		Function &&	f,
		Args &&...	args )

nodiscard

Starts an asynchronous task without propagating engine::TaskInheritedVariable. tracing::Span and baggage::Baggage are inherited. Task execution may be cancelled before the function starts execution in case of engine::TaskProcessor overload.

Typically used from a request handler to launch tasks that outlive the request and do not effect its completion.

Usage example

Suppose you have some component that runs asynchronous tasks:

class AsyncRequestProcessor final {
public:
    AsyncRequestProcessor();
 
    void FooAsync(Request&& request);
 
    Response WaitAndGetAggregate();
 
private:
    static Response Foo(Request&& request);
 
    engine::TaskProcessor& task_processor_;
    concurrent::Variable<std::vector<engine::TaskWithResult<Response>>> tasks_;
};

    auto handler = [&](Request&& request) {
        async_request_processor.FooAsync(std::move(request));
        return "Please wait, your request is being processed.";
    };

If the tasks logically belong to the component itself (not to the method caller), then they should be launched using utils::AsyncBackground instead of the regular utils::Async

void AsyncRequestProcessor::FooAsync(Request&& request) {
    auto tasks = tasks_.Lock();
    tasks->push_back(utils::AsyncBackground("foo", task_processor_, &Foo, std::move(request)));
}

Arguments

By default, arguments are copied or moved inside the resulting TaskWithResult, like std::thread does. To pass an argument by reference, wrap it in std::ref / std::cref or capture the arguments using a lambda.

Parameters

name	Name of the task to show in logs
task_processor	Task processor to run on
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Definition at line 366 of file async.hpp.

◆ AtomicMax()

template<typename T>

T utils::AtomicMax	(	std::atomic< T > &	atomic,
		T	value )

Concurrently safe sets atomic to a value if value is greater.

Note: Uses std::memory_order_relaxed

Definition at line 53 of file atomic.hpp.

◆ AtomicMin()

template<typename T>

T utils::AtomicMin	(	std::atomic< T > &	atomic,
		T	value )

Concurrently safe sets atomic to a value if value is less.

Note: Uses std::memory_order_relaxed

Definition at line 43 of file atomic.hpp.

◆ AtomicUpdate()

template<typename T, typename Func>

T utils::AtomicUpdate	(	std::atomic< T > &	atomic,
		Func	updater )

Atomically performs the operation of updater on atomic

updater may be called multiple times per one call of AtomicUpdate, so it must be idempotent. To ensure that the function does not spin for a long time, updater must be fairly simple and fast.

Parameters

atomic	the variable to update
updater	a lambda that takes the old value and produces the new value

Returns: The updated value

Note: Uses std::memory_order_relaxed

Definition at line 24 of file atomic.hpp.

◆ CriticalAsync() [1/2]

template<typename Function, typename... Args>

auto utils::CriticalAsync	(	engine::TaskProcessor &	task_processor,
		std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Execution of function is guaranteed to start regardless of engine::TaskProcessor load limits. Prefer utils::Async by default.

Parameters

task_processor	Task processor to run on
name	Name for the tracing::Span to use with this task
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Examples: samples/ydb_service/components/topic_reader.cpp.

Definition at line 129 of file async.hpp.

◆ CriticalAsync() [2/2]

template<typename Function, typename... Args>

auto utils::CriticalAsync	(	std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Execution of function is guaranteed to start regardless of engine::TaskProcessor load limits. Prefer utils::Async by default.

Parameters

name	Name for the tracing::Span to use with this task
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Definition at line 241 of file async.hpp.

◆ CriticalAsyncBackground()

template<typename Function, typename... Args>

auto utils::CriticalAsyncBackground	(	std::string	name,
		engine::TaskProcessor &	task_processor,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Execution of function is guaranteed to start regardless of engine::TaskProcessor load limits. Use for background tasks for which failing to start not just breaks handling of a single request, but harms the whole service instance.

Parameters

name	Name of the task to show in logs
task_processor	Task processor to run on
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::TaskWithResult

Definition at line 392 of file async.hpp.

◆ GetAll()

template<typename... Tasks>

auto engine::GetAll ( Tasks &... tasks )

Waits for the successful completion of all of the specified tasks or the cancellation of the caller.

Effectively performs for (auto& task : tasks) task.Get(); with a twist: task.Get() is called in tasks completion order rather than in provided order, thus exceptions are rethrown ASAP.

After successful return from this method the tasks are invalid, in case of an exception being thrown some of the tasks might be invalid.

Parameters

tasks either a single container, or a pack of future-like elements.

Returns: std::vector<Result> or void, depending on the tasks result type (which must be the same for all tasks).

Exceptions

WaitInterruptedException	when `current_task::IsCancelRequested()` and no TaskCancellationBlockers are present.
std::exception	rethrows one of specified tasks exception, if any, in no particular order.

Note: Has overall computational complexity of O(N^2), where N is the number of tasks.; Prefer engine::WaitAllChecked for tasks with a result, unless you specifically need the results stored in a std::vector or when storing the results long-term.

Definition at line 84 of file get_all.hpp.

◆ SharedAsync() [1/4]

template<typename Function, typename... Args>

auto utils::SharedAsync	(	engine::TaskProcessor &	task_processor,
		std::string	name,
		engine::Deadline	deadline,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Task execution may be cancelled before the function starts execution in case of TaskProcessor overload.

Parameters

task_processor	Task processor to run on
name	Name of the task to show in logs
deadline	Deadline to set for the child task, upon reaching it the task will be cancelled
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::SharedTaskWithResult

Definition at line 214 of file async.hpp.

◆ SharedAsync() [2/4]

template<typename Function, typename... Args>

auto utils::SharedAsync	(	engine::TaskProcessor &	task_processor,
		std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Task execution may be cancelled before the function starts execution in case of TaskProcessor overload.

Parameters

task_processor	Task processor to run on
name	Name of the task to show in logs
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::SharedTaskWithResult

Definition at line 166 of file async.hpp.

◆ SharedAsync() [3/4]

template<typename Function, typename... Args>

auto utils::SharedAsync	(	std::string	name,
		engine::Deadline	deadline,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Task execution may be cancelled before the function starts execution in case of TaskProcessor overload.

Parameters

name	Name of the task to show in logs
deadline	Deadline to set for the child task, upon reaching it the task will be cancelled
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::SharedTaskWithResult

Definition at line 324 of file async.hpp.

◆ SharedAsync() [4/4]

template<typename Function, typename... Args>

auto utils::SharedAsync	(	std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Task execution may be cancelled before the function starts execution in case of TaskProcessor overload.

Parameters

name	Name of the task to show in logs
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::SharedTaskWithResult

Definition at line 281 of file async.hpp.

◆ SharedCriticalAsync() [1/2]

template<typename Function, typename... Args>

auto utils::SharedCriticalAsync	(	engine::TaskProcessor &	task_processor,
		std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Execution of function is guaranteed to start regardless of engine::TaskProcessor load limits. Prefer utils::SharedAsync by default.

Parameters

task_processor	Task processor to run on
name	Name for the tracing::Span to use with this task
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::SharedTaskWithResult

Definition at line 148 of file async.hpp.

◆ SharedCriticalAsync() [2/2]

template<typename Function, typename... Args>

auto utils::SharedCriticalAsync	(	std::string	name,
		Function &&	f,
		Args &&...	args )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Execution of function is guaranteed to start regardless of engine::TaskProcessor load limits. Prefer utils::SharedAsync by default.

Parameters

name	Name for the tracing::Span to use with this task
f	Function to execute asynchronously
args	Arguments to pass to the function

Returns: engine::SharedTaskWithResult

Definition at line 261 of file async.hpp.

◆ TryWaitForSubscribableFuture()

template<typename SubscribableFuture>

engine::FutureStatus drivers::TryWaitForSubscribableFuture	(	SubscribableFuture &&	future,
		engine::Deadline	deadline )

nodiscard

This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Returns: an error code if deadline is exceeded or task is cancelled

Warning: Repeatedly waiting again after deadline expiration leads to a memory leak, use drivers::SubscribableFutureWrapper instead.

Definition at line 97 of file subscribable_futures.hpp.

◆ WaitAllChecked()

template<typename... Tasks>

void engine::WaitAllChecked ( Tasks &... tasks )

Waits for the successful completion of all of the specified tasks or for the cancellation of the caller.

Effectively performs for (auto& task : tasks) task.Wait(); with a twist: if any task completes with an exception, it gets rethrown ASAP.

Invalid tasks are skipped.

Tasks are not invalidated by WaitAllChecked; the result can be retrieved after the call.

Parameters

tasks either a single container, or a pack of future-like elements.

Exceptions

WaitInterruptedException	when `current_task::ShouldCancel()` (for WaitAllChecked versions without a deadline)
std::exception	one of specified tasks exception, if any, in no particular order.

Note: Has overall computational complexity of O(N^2), where N is the number of tasks.; Keeping the tasks valid may have a small extra memory impact. Make sure to drop the tasks after reading the results.; Prefer engine::GetAll for tasks without a result, unless you specifically need to keep the tasks alive for some reason.

Definition at line 95 of file wait_all_checked.hpp.

◆ WaitAny()

template<typename... Tasks>

std::optional< std::size_t > engine::WaitAny ( Tasks &... tasks )

Waits for the completion of any of the specified tasks or the cancellation of the caller.

Could be used to get the ready HTTP requests ASAP:

std::size_t ProcessReadyRequests(std::vector<clients::http::ResponseFuture>& requests, engine::Deadline deadline) {
    std::size_t processed_requests = 0;
 
    while (auto indx = engine::WaitAnyUntil(deadline, requests)) {
        ++processed_requests;
 
        std::shared_ptr<clients::http::Response> response = requests[*indx].Get();
        EXPECT_TRUE(response->IsOk());
    }
 
    return processed_requests;
}

Works with different types of tasks and futures:

    auto task0 = engine::AsyncNoSpan([] { return 1; });
 
    auto task1 = utils::Async("long_task", [] {
        engine::InterruptibleSleepFor(20s);
        return std::string{"abc"};
    });
 
    auto task_idx_opt = engine::WaitAny(task0, task1);
    ASSERT_TRUE(task_idx_opt);
    EXPECT_EQ(*task_idx_opt, 0);

Parameters

tasks either a single container, or a pack of future-like elements.

Returns: the index of the completed task, or std::nullopt if there are no completed tasks (possible if current task was cancelled).

Definition at line 54 of file wait_any.hpp.

◆ WaitForSubscribableFuture()

template<typename SubscribableFuture>

void drivers::WaitForSubscribableFuture ( SubscribableFuture && future )

Waits on the given future as described on drivers::SubscribableFutureWrapper.

The result can be retrieved from the original future once ready.

Exceptions

engine::WaitInterruptedException on task cancellation

Definition at line 85 of file subscribable_futures.hpp.

Detailed Description

Files

Classes

Typedefs

Functions

Typedef Documentation

◆ NonFifoMpmcQueue

◆ NonFifoMpscQueue

◆ SpmcQueue

◆ SpscQueue

◆ StringStreamQueue

◆ UnboundedNonFifoMpscQueue

◆ UnboundedSpmcQueue

◆ UnboundedSpscQueue

Function Documentation

◆ Async() [1/4]

◆ Async() [2/4]

◆ Async() [3/4]

◆ Async() [4/4]

About this specific overload

◆ AsyncBackground()

Usage example

Arguments

◆ AtomicMax()

◆ AtomicMin()

◆ AtomicUpdate()

◆ CriticalAsync() [1/2]

◆ CriticalAsync() [2/2]

◆ CriticalAsyncBackground()

◆ GetAll()

◆ SharedAsync() [1/4]

◆ SharedAsync() [2/4]

◆ SharedAsync() [3/4]

◆ SharedAsync() [4/4]

◆ SharedCriticalAsync() [1/2]

◆ SharedCriticalAsync() [2/2]

◆ TryWaitForSubscribableFuture()

◆ WaitAllChecked()

◆ WaitAny()

◆ WaitForSubscribableFuture()