#include <userver/concurrent/background_task_storage.hpp>

Public Member Functions
	BackgroundTaskStorage ()

	BackgroundTaskStorage (engine::TaskProcessor &task_processor)
	Creates a BTS that launches tasks in the specified engine::TaskProcessor.

	BackgroundTaskStorage (const BackgroundTaskStorage &)=delete

BackgroundTaskStorage &	operator= (const BackgroundTaskStorage &)=delete

void	CancelAndWait () noexcept

template<typename... Args>
void	AsyncDetach (std::string name, Args &&... args)
	Launch a task that will be cancelled and waited for in the BTS destructor.

std::int64_t	ActiveTasksApprox () const noexcept
	Approximate number of currently active tasks.

Detailed Description

A storage that allows one to start detached tasks; cancels and waits for unfinished tasks completion at the destructor. Provides CancelAndWait to explicitly cancel tasks (recommended).

Usable for detached tasks that capture references to resources with a limited lifetime. You must guarantee that the resources are available while the BackgroundTaskStorage is alive.

Usage synopsis

  std::string x = kString;
  std::string y;
  {
    // You must guarantee that 'x' and 'y' are alive during 'bts' lifetime.
    concurrent::BackgroundTaskStorage bts;
 
    bts.AsyncDetach("task", [&x, &y] {
      engine::InterruptibleSleepFor(20s);
      EXPECT_TRUE(engine::current_task::ShouldCancel());
      y = std::move(x);
    });
 
    DoStuff();
 
    // It is recommended to call CancelAndWait explicitly for the clarity of
    // tasks' lifetime. BTS destructor calls CancelAndWait implicitly as well.
    bts.CancelAndWait();
  }

Definition at line 58 of file background_task_storage.hpp.

Constructor & Destructor Documentation

◆ BackgroundTaskStorage()

concurrent::BackgroundTaskStorage::BackgroundTaskStorage ( )

Creates a BTS that launches tasks in the engine::TaskProcessor used at the BTS creation.

Member Function Documentation

◆ AsyncDetach()

template<typename... Args>

void concurrent::BackgroundTaskStorage::AsyncDetach	(	std::string	name,
		Args &&...	args
	)

inline

Launch a task that will be cancelled and waited for in the BTS destructor.

The task is started as non-Critical, it may be cancelled due to TaskProcessor overload. engine::TaskInheritedVariable instances are not inherited from the caller. See utils::AsyncBackground for details.

Definition at line 81 of file background_task_storage.hpp.

◆ CancelAndWait()

void concurrent::BackgroundTaskStorage::CancelAndWait ( )

noexcept

Explicitly cancel and wait for the tasks. New tasks must not be launched after this call returns. Should be called no more than once.

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

userver/concurrent/background_task_storage.hpp