userver: engine::TaskBase Class Reference
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engine::TaskBase Class Reference

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

Detailed Description

Base class for all the asynchronous tasks (engine::Task, engine::SharedTask, engine::SharedTaskWithResult, engine::TaskWithResult, dist_lock::DistLockedTask, ...).

Definition at line 37 of file task_base.hpp.

+ Inheritance diagram for engine::TaskBase:

Public Types

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...
 

Public Member Functions

bool IsValid () const
 Checks whether this object owns an actual task (not State::kInvalid)
 
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().
 
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.
 
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.
 
void WaitUntil (Deadline) const
 Suspends execution until the task finishes or until the specified deadline is reached or until caller is cancelled.
 
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
 

Static Public Member Functions

static const std::string & GetStateName (State state)
 

Member Enumeration Documentation

◆ Importance

enum class engine::TaskBase::Importance
strong

Task importance.

Enumerator
kNormal 

Normal task.

kCritical 

Critical task. The task will be started regardless of cancellations, e.g. due to user request, deadline or TaskProcessor overload. After the task starts, it may be cancelled. In particular, if it received any cancellation requests before starting, then it will start as cancelled.

Definition at line 40 of file task_base.hpp.

◆ State

enum class engine::TaskBase::State
strong

Task state.

Enumerator
kInvalid 

Unusable.

kNew 

just created, not registered with task processor

kQueued 

awaits execution

kRunning 

executing user code

kSuspended 

suspended, e.g. waiting for blocking call to complete

kCancelled 

exited user code because of external request

kCompleted 

exited user code with return or throw

Definition at line 52 of file task_base.hpp.

◆ WaitMode

enum class engine::TaskBase::WaitMode
strong

Task wait mode.

Enumerator
kSingleWaiter 

Can be awaited by at most one task at a time.

kMultipleWaiters 

Can be awaited by multiple tasks simultaneously.

Definition at line 63 of file task_base.hpp.

Member Function Documentation

◆ BlockingWait()

void engine::TaskBase::BlockingWait ( ) const

Waits for the task in non-coroutine context (e.g. non-TaskProcessor's std::thread).

◆ IsValid()

bool engine::TaskBase::IsValid ( ) const

Checks whether this object owns an actual task (not State::kInvalid)

An invalid task cannot be used. The task becomes invalid after each of the following calls:

  1. the default constructor
  2. Detach()
  3. Get() (see engine::TaskWithResult)

◆ Wait()

void engine::TaskBase::Wait ( ) const

Suspends execution until the task finishes or caller is cancelled. Can be called from coroutine context only. For non-coroutine context use BlockingWait().

Exceptions
WaitInterruptedExceptionwhen current_task::IsCancelRequested() and no TaskCancellationBlockers are present.

◆ WaitFor()

template<typename Rep , typename Period >
void engine::TaskBase::WaitFor ( const std::chrono::duration< Rep, Period > & duration) const

Suspends execution until the task finishes or after the specified timeout or until caller is cancelled.

Exceptions
WaitInterruptedExceptionwhen current_task::IsCancelRequested() and no TaskCancellationBlockers are present.

Definition at line 191 of file task_base.hpp.

◆ WaitUntil() [1/2]

template<typename Clock , typename Duration >
void engine::TaskBase::WaitUntil ( const std::chrono::time_point< Clock, Duration > & until) const

Suspends execution until the task finishes or until the specified time point is reached or until caller is cancelled.

Exceptions
WaitInterruptedExceptionwhen current_task::IsCancelRequested() and no TaskCancellationBlockers are present.

Definition at line 197 of file task_base.hpp.

◆ WaitUntil() [2/2]

void engine::TaskBase::WaitUntil ( Deadline ) const

Suspends execution until the task finishes or until the specified deadline is reached or until caller is cancelled.

Exceptions
WaitInterruptedExceptionwhen current_task::IsCancelRequested() and no TaskCancellationBlockers are present.

Friends And Related Symbol Documentation

◆ TaskCancellationToken

friend class TaskCancellationToken
friend

Definition at line 165 of file task_base.hpp.


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