scheduler component is included in MySQL Enterprise Edition,
a commercial product. To learn more about commercial products,
scheduler component provides an
implementation of the
that enables applications, components, or plugins to configure,
run, and unconfigure tasks every
seconds. For example, the
plugin calls the
scheduler component at its
initialization and configures a regular, recurring flush of its
memory cache (see Enabling the Audit Log Flush Task).
Purpose: Implements the
component_scheduler.enabledsystem variable that controls whether the scheduler is actively executing tasks. At startup, the
schedulercomponent registers the
performance_schema.component_scheduler_taskstable, which lists the currently scheduled tasks and some runtime data about each one.
For installation instructions, see Section 5.5.1, “Installing and Uninstalling Components”.
scheduler component implements the service
using these elements:
A priority queue of the registered, inactive scheduled tasks sorted by the next time to run (in ascending order).
A list of the registered, active tasks.
A background thread that:
Sleeps if there are no tasks or if the top task needs more time to run. It wakes periodically to check whether it is time to end.
Compiles a list of the tasks that need to run, moves them from the inactive queue, adds them to the active queue, and executes each task individually.
After executing the task list, removes the tasks from the active list, adds them to the inactive list, and calculates the next time they need to run.
When a caller invokes the
mysql_scheduler.create() service, it creates a
new scheduled task instance to add to the queue, which signals the
semaphore of the background thread. A handle to the new task is
returned to the caller. The calling code should keep this handle
and the service reference to the scheduling service until after
When the caller invokes
destroy() and passes in
the handle it received from
service waits for the task to become inactive (if running) and
then removes it from the inactive queue.
The component service calls each application-provided callback (function pointer) into the same scheduler thread, one at a time and in ascending order, based on the time each requires to run.
Developers who wish to incorporate scheduler-queueing capabilities
into an application, component, or plugin should consult the
mysql_scheduler.h file in a MySQL source