Task

Minimal usable Task class.

Serves as a base for all other task classes. Provides the following functionality: * assigning a task to an arbitrary fiber (assignTo()) * wraps the abstract run() method in a try/catch statement which rethrows any unhandled exceptions

abstract

class Task {

size_t object_pool_index;

WorkerFiber fiber;

static Task getThis();

this();

void assignTo(WorkerFiber fiber, void delegate() entry_point);

void suspend();

void resume();

void terminationHook(void delegate() hook);

void removeTerminationHook(void delegate() hook);

bool suspended();

bool finished();

void kill(istring file, int line);

void recycle();

void run();

bool entryPoint();

}

Constructors

this this(): Constructor. Used only to insert debug trace message.

Members

Functions

assignTo void assignTo(WorkerFiber fiber, void delegate() entry_point): Assigns the task to a fiber. In most cases you need to use Scheduler.schedule instead.
entryPoint bool entryPoint(): Internal wrapper around this.run() which is used as primary fiber entry point and ensures any uncaught exception propagates to the context that has started this task.
finished bool finished()
kill void kill(istring file, int line): Forces abnormal termination for the task by throwing special exception instance.
recycle void recycle(): Method that will be run by scheduler when task finishes. Must be overridden by specific task class to reset reusable resources.
removeTerminationHook void removeTerminationHook(void delegate() hook): Unregisters a termination hook that would be executed when the Task is killed.
resume void resume(): Resumes execution of this task. If task has not been started yet, starts it.
run void run(): Method that must be overridden in actual application/library task classes to provide entry point.
suspend void suspend(): Suspends execution of this task.
suspended bool suspended()
terminationHook void terminationHook(void delegate() hook): Registers a termination hook that will be executed when the Task is killed.

Static functions

getThis Task getThis()

Variables

fiber WorkerFiber fiber;: Fiber this task executes in
object_pool_index size_t object_pool_index;: Reserved index field which ensures that any Task derivative can be used with ObjectPool. That comes at minor cost of one unused size_t per Task instance if not needed which is not a problem.

Examples

// represents some limited resource used by this task (e.g. memory or a
// file handle)
class LimitedResourceHandle { }
LimitedResourceHandle getResource ( ) { return null; }
void releaseResource ( LimitedResourceHandle ) { }

// example custom task class
class MyTask : Task
{
    LimitedResourceHandle resource;

    override public void run ( )
    {
        this.resource = getResource();
    }

    override public void recycle ( )
    {
        releaseResource(this.resource);
    }
}

// Example of running a task by manually spawning a worker fiber.
// More commonly, it is instead done via ocean.task.Scheduler.
auto task = new MyTask;
// a large stack size is important for debug traces to not crash tests:
task.assignTo(new WorkerFiber(10240));
task.resume();