engine::TaskWithResult< T > Class Template Reference

#include <userver/engine/task/task_with_result.hpp>

Inheritance diagram for engine::TaskWithResult< T >:

Collaboration diagram for engine::TaskWithResult< T >:

Public Member Functions
	TaskWithResult ()=default
	Default constructor. More...
	TaskWithResult (TaskProcessor &task_processor, Task::Importance importance, Deadline deadline, std::unique_ptr< utils::impl::WrappedCall< T > > &&wrapped_call_ptr)
	Constructor, for internal use only. More...
	TaskWithResult (const TaskWithResult &)=delete
TaskWithResult &	operator= (const TaskWithResult &)=delete
	TaskWithResult (TaskWithResult &&) noexcept=default
TaskWithResult &	operator= (TaskWithResult &&) noexcept=default
T	Get () noexcept(false)
	Returns (or rethrows) the result of task invocation. After return from this method the task is not valid. More...
Public Member Functions inherited from engine::Task
	Task ()
	Default constructor. More...
virtual	~Task ()
	Destructor. More...
	Task (Task &&) noexcept
Task &	operator= (Task &&) noexcept
bool	IsValid () const
	Checks whether this Task object owns an actual task (not State::kInvalid) More...
State	GetState () const
	Gets the task State.
bool	IsFinished () const
	Returns whether the task finished execution.
void	Wait () const noexcept(false)
	Suspends execution until the task finishes or caller is cancelled. Can be called from coroutine context only. For non-coroutine context use BlockingWait(). More...
template<typename Rep , typename Period >
void	WaitFor (const std::chrono::duration< Rep, Period > &) const noexcept(false)
	Suspends execution until the task finishes or after the specified timeout or until caller is cancelled. More...
template<typename Clock , typename Duration >
void	WaitUntil (const std::chrono::time_point< Clock, Duration > &) const noexcept(false)
	Suspends execution until the task finishes or until the specified time point is reached or until caller is cancelled. More...
void	WaitUntil (Deadline) const
	Suspends execution until the task finishes or until the specified deadline is reached or until caller is cancelled. More...
void	Detach () &&
	Detaches task, allowing it to continue execution out of scope; memory safety is much better with concurrent::BackgroundTaskStorage. More...
void	RequestCancel ()
	Queues task cancellation request.
void	SyncCancel () noexcept
	Cancels the task and suspends execution until it is finished. Can be called from coroutine context only. For non-coroutine context use RequestCancel() + BlockingWait().
TaskCancellationReason	CancellationReason () const
	Gets task cancellation reason.
void	BlockingWait () const

Additional Inherited Members
Public Types inherited from engine::Task
enum class	Importance {   kNormal ,   kCritical }
	Task importance. More...
enum class	State {   kInvalid ,   kNew ,   kQueued ,   kRunning ,   kSuspended ,   kCancelled ,   kCompleted }
	Task state. More...
enum class	WaitMode {   kSingleWaiter ,   kMultipleWaiters }
	Task wait mode. More...
Static Public Member Functions inherited from engine::Task
static const std::string &	GetStateName (State state)

Detailed Description

template<typename T>
class engine::TaskWithResult< T >

Asynchronous task with result

Example usage:

  std::vector<engine::TaskWithResult<int>> tasks;
  tasks.reserve(container.size());
  for (auto value : container) {
    // Creating tasks that will be executed in parallel
    tasks.push_back(utils::Async("some_task", [value = std::move(value)] {
      engine::InterruptibleSleepFor(std::chrono::milliseconds(100));
      return value;
    }));
  }
  // we wait for the completion of tasks and get the results
  std::vector<int> results;
  results.reserve(tasks.size());
  for (auto& task : tasks) {
    // If the task completed with an exception,
    // then Get () will throw an exception
    results.push_back(task.Get());
  }

See also

Synchronization Primitives

Examples

samples/flatbuf_service/flatbuf_service.cpp.

Definition at line 30 of file task_with_result.hpp.

Constructor & Destructor Documentation

TaskWithResult() [1/2]

template<typename T >

engine::TaskWithResult< T >::TaskWithResult ( )

default

Default constructor.

Creates an invalid task.

TaskWithResult() [2/2]

template<typename T >

engine::TaskWithResult< T >::TaskWithResult ( TaskProcessor &  task_processor, Task::Importance  importance, Deadline  deadline, std::unique_ptr< utils::impl::WrappedCall< T > > &&  wrapped_call_ptr  )

inline

Constructor, for internal use only.

Parameters

task_processor	task processor used for execution of this task
importance	specifies whether this task can be auto-cancelled in case of task processor overload
wrapped_call_ptr	task body

See also

Async()

Definition at line 43 of file task_with_result.hpp.

Member Function Documentation

Get()

template<typename T >

T engine::TaskWithResult< T >::Get ( )

inlinenoexcept

Returns (or rethrows) the result of task invocation. After return from this method the task is not valid.

Exceptions

WaitInterruptedException	when current_task::IsCancelRequested() and no TaskCancellationBlockers are present.
TaskCancelledException	if no result is available because the task was cancelled

Definition at line 62 of file task_with_result.hpp.

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The documentation for this class was generated from the following file:

• userver/engine/task/task_with_result.hpp