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/* -*- Mode: C++; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
#ifndef DISPATCHER_HH
#define DISPATCHER_HH
#include <stdexcept>
#include <queue>
#include "common.hh"
#include "locks.hh"
#include "priority.hh"
class Dispatcher;
/**
* States a task may be in.
*/
enum task_state {
task_dead, //!< The task is dead and should not be executed
task_running //!< The task is running
};
/**
* States the dispatcher may be in.
*/
enum dispatcher_state {
dispatcher_running, //!< The dispatcher is running
dispatcher_stopping, //!< The dispatcher is shutting down
dispatcher_stopped //!< The dispatcher has shut down
};
class Task;
typedef shared_ptr<Task> TaskId;
/**
* Code executed when the dispatcher is ready to do your work.
*/
class DispatcherCallback {
public:
virtual ~DispatcherCallback() {}
/**
* Perform my task.
*
* @param d the dispatcher running this task
* @param t the task
*
* @return true if the task should run again
*/
virtual bool callback(Dispatcher &d, TaskId t) = 0;
//! Print a human-readable description of this callback.
virtual std::string description() = 0;
};
class CompareTasksByDueDate;
class CompareTasksByPriority;
/**
* Tasks managed by the dispatcher.
*/
class Task {
friend class CompareTasksByDueDate;
friend class CompareTasksByPriority;
public:
~Task() { }
private:
Task(shared_ptr<DispatcherCallback> cb, int p, double sleeptime=0, bool isDaemon=true) :
name(cb->description()), callback(cb), priority(p),
state(task_running), isDaemonTask(isDaemon) {
snooze(sleeptime);
}
Task(const Task &task) {
priority = task.priority;
state = task_running;
callback = task.callback;
isDaemonTask = task.isDaemonTask;
}
void snooze(const double secs) {
LockHolder lh(mutex);
gettimeofday(&waketime, NULL);
advance_tv(waketime, secs);
}
bool run(Dispatcher &d, TaskId t) {
return callback->callback(d, t);
}
void cancel() {
LockHolder lh(mutex);
state = task_dead;
}
friend class Dispatcher;
std::string name;
struct timeval waketime;
shared_ptr<DispatcherCallback> callback;
int priority;
enum task_state state;
Mutex mutex;
bool isDaemonTask;
};
/**
* Order tasks by their ready date.
*/
class CompareTasksByDueDate {
public:
// true if t1 is before t2
bool operator()(TaskId t1, TaskId t2) {
return less_tv(t2->waketime, t1->waketime);
}
};
/**
* Order tasks by their priority.
*/
class CompareTasksByPriority {
public:
bool operator()(TaskId t1, TaskId t2) {
return t1->priority > t2->priority;
}
};
/**
* Snapshot of the state of a dispatcher.
*/
class DispatcherState {
public:
DispatcherState(const std::string &name,
enum dispatcher_state st,
hrtime_t start, bool running)
: taskName(name), state(st), taskStart(start),
running_task(running) {}
/**
* Get the name of the current dispatcher state.
*/
const char* getStateName() const {
const char *rv = NULL;
switch(state) {
case dispatcher_stopped: rv = "dispatcher_stopped"; break;
case dispatcher_running: rv = "dispatcher_running"; break;
case dispatcher_stopping: rv = "dispatcher_stopping"; break;
}
return rv;
}
/**
* Get the time the current task started.
*/
hrtime_t getTaskStart() const { return taskStart; }
/**
* Get the name of the currently running task.
*/
const std::string getTaskName() const { return taskName; }
/**
* True if the dispatcher is currently running a task.
*/
bool isRunningTask() const { return running_task; }
private:
const std::string taskName;
const enum dispatcher_state state;
const hrtime_t taskStart;
const bool running_task;
};
/**
* Schedule and run tasks in another thread.
*/
class Dispatcher {
public:
Dispatcher() : state(dispatcher_running) {
noTask();
}
~Dispatcher() {
stop();
}
/**
* Schedule a job to run.
*
* @param callback a shared_ptr to the callback to run
* @param outtid an output variable that will receive the task ID (may be NULL)
* @param priority job priority instance that defines a job's priority
* @param sleeptime how long (in seconds) to wait before starting the job
* @param isDaemon a flag indicating if a task is daemon or not
*/
void schedule(shared_ptr<DispatcherCallback> callback,
TaskId *outtid,
const Priority &priority, double sleeptime=0, bool isDaemon=true);
/**
* Wake up the given task.
*
* @param task the task to wake up
* @param outtid a newly assigned task ID (may be NULL)
*/
void wake(TaskId task, TaskId *outtid);
/**
* Start this dispatcher's thread.
*/
void start();
/**
* Stop this dispatcher.
*/
void stop();
/**
* Dispatcher's main loop. Don't run this.
*/
void run();
/**
* Delay a task.
*
* @param t the task to delay
* @param sleeptime how long to delay the task
*/
void snooze(TaskId t, double sleeptime) {
t->snooze(sleeptime);
}
/**
* Cancel a task.
*/
void cancel(TaskId t) {
t->cancel();
}
/**
* Get the name of the currently executing task.
*/
std::string getCurrentTaskName() { return taskDesc; }
/**
* Get the state of the dispatcher.
*/
enum dispatcher_state getState() { return state; }
DispatcherState getDispatcherState() {
return DispatcherState(taskDesc, state, taskStart, running_task);
}
private:
void noTask() {
taskDesc = "none";
}
void reschedule(TaskId task) {
// If the task is already in the queue it'll get run twice
LockHolder lh(mutex);
futureQueue.push(task);
}
/**
* Complete all the non-daemon tasks before stopping the dispatcher
*/
void completeNonDaemonTasks();
/**
* Move all tasks that are ready for execution into the "ready"
* priority queue.
*/
void moveReadyTasks();
//! True if there are no tasks scheduled.
bool empty() { return readyQueue.empty() && futureQueue.empty(); }
//! Get the next task.
TaskId nextTask();
//! Remove the next task.
void popNext();
std::string taskDesc;
pthread_t thread;
SyncObject mutex;
std::priority_queue<TaskId, std::deque<TaskId >,
CompareTasksByPriority> readyQueue;
std::priority_queue<TaskId, std::deque<TaskId >,
CompareTasksByDueDate> futureQueue;
enum dispatcher_state state;
hrtime_t taskStart;
bool running_task;
};
#endif
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