Currently, each data sync repair task is started (and hence run) twice.
Thus, when two running operations happen within a time frame long
enough, the following situation may occur:
- the first run finishes
- after some time (ttl) the task is unregistered from the task manager
- the second run finishes and attempts to finish the task which does
not exist anymore
- memory access causes a segfault.
The second call to start is deleted. A check is added
to the start method to ensure that each task is started at most once.
Fixes: #12089Closes#12090
The implementation of a test api that helps testing task manager
api. It provides methods to simulate the operations that can happen
on modules and theirs task. Through the api user can: register
and unregister the test module and the tasks belonging to the module,
and finish the tasks with success or custom error.
Implementation of a task manager that allows tracking
and managing asynchronous tasks.
The tasks are represented by task_manager::task class providing
members common to all types of tasks. The methods that differ
among tasks of different module can be overriden in a class
inheriting from task_manager::task::impl class. Each task stores
its status containing parameters like id, sequence number, begin
and end time, state etc. After the task finishes, it is kept
in memory for configurable time or until it is unregistered.
Tasks need to be created with make_task method.
Each module is represented by task_manager::module type and should
have an access to task manager through task_manager::module methods.
That allows to easily separate and collectively manage data
belonging to each module.
