/**
* The real brains of this scheduler: using the memory capacity reported in each work request,
* determine how to spread the load of unscheduled jobs efficiently across the requesting agents.
*
* <p>The algorithm works by taking the collection of work requests and sorting them from smallest
* to largest free memory capacity.
*
* <p>The scheduler then iterates over each job, handing it to the first agent that has enough
* capacity to complete it. In this sense, each agent is "greedy", grabbing as many jobs as it can
* manage.
*
* <p>If a job is too big to fit into the remaining capacity of any of the agents, it will remain
* unscheduled.
*
* <p><b>WARNING:</b> If a job is too big for any of the agents, it will sit on the backlog
* forever!
*
* <p>
*/
private void scheduleJobs() {
Map<ActorRef, List<Job>> agentJobs = new HashMap<ActorRef, List<Job>>();
List<Job> scheduledJobs = new ArrayList<>();
Iterator<Job> iterator = unscheduledJobs.iterator();
while (iterator.hasNext()) {
Job job = iterator.next();
long jobSize = new Long(job.getParams().get(JVMCapacityScheduler.JOB_SIZE));
sortWorkRequestsByFreeMemory();
for (JVMCapacityWorkRequest workRequest : workRequests) {
long freeMemory = workRequest.getFreeMemory();
ActorRef agent = workRequest.getAgent();
if (freeMemory >= jobSize) {
// Add the job to the agent
List<Job> jobs = agentJobs.get(agent);
if (jobs == null) {
jobs = new ArrayList<Job>();
agentJobs.put(agent, jobs);
}
jobs.add(job);
scheduledJobs.add(job);
// Decrease agent's available memory
workRequest.setFreeMemory(freeMemory - jobSize);
break;
}
}
}
// Create a schedule
Schedule schedule = new Schedule();
for (ActorRef agent : agentJobs.keySet()) {
schedule.setJobs(agent, agentJobs.get(agent));
}
// Dispatch the schedule
dispatchJobs(schedule);
// Clear old work requests
workRequests.clear();
// Cancel the scheduling
scheduleJobs.cancel();
}
private Job makeJob(int id, int priority, DateTime enqueuedAt) {
Job job = makeJob(id, priority);
job.setEnqueuedAt(enqueuedAt);
return job;
}
private Job makeJob(int id, int priority) {
Job job = new Job(id, null);
job.setParams(new HashMap<String, String>());
job.getParams().put("priority", String.valueOf(priority));
return job;
}