jobQueue.py

#
# jobQueue.py - Code that manipulates and manages the job queue
#
# JobQueue: Class that creates the job queue and provides functions
# for manipulating it.
#
# JobManager: Class that creates a thread object that looks for new
# work on the job queue and assigns it to workers.
#
import threading
import logging
import time

from datetime import datetime
from tangoObjects import TangoDictionary, TangoJob, TangoQueue
from config import Config

#
# JobQueue - This class defines the job queue and the functions for
# manipulating it. The actual queue is made up of two smaller
# sub-lists:
#
# - The active list is a dictionary, keyed off job ID, that holds all
#   jobs that are active, including those not yet assigned to a worker
#   thread.  The trace attribute of a job being None indicates that
#   the job is not yet assigned.  Only the JobManager thread can
#   assign jobs to Workers.
#
# - The dead list is a dictionary of the jobs that have completed.
#


class JobQueue(object):
    def __init__(self, preallocator):
        """
        Here we maintain several data structures used to keep track of the
        jobs present for the autograder.

        Live jobs contains:
        - jobs that are yet to be assigned and run
        - jobs that are currently running

        Dead jobs contains:
        - jobs that have been completed, or have been 'deleted' when in
          the live jobs queue

        Unassigned jobs:
        This is a FIFO queue of jobs that are pending assignment.
        - We enforce the invariant that all jobs in this queue must be
          present in live jobs

        queueLock protects all the internal data structure of JobQueue. This
        is needed since there are multiple worker threads and they might be
        using the makeUnassigned api.
        """
        self.liveJobs = TangoDictionary("liveJobs")
        self.deadJobs = TangoDictionary("deadJobs")
        self.unassignedJobs = TangoQueue("unassignedLiveJobs")
        self.queueLock = threading.Lock()
        self.preallocator = preallocator
        self.log = logging.getLogger("JobQueue")
        self.nextID = 1

    def _getNextID(self):
        """_getNextID - updates and returns the next ID to be used for a job
        Jobs have ID's between 1 and MAX_JOBID.
        """
        self.log.debug("_getNextID|Acquiring lock to job queue.")
        self.queueLock.acquire()
        self.log.debug("_getNextID|Acquired lock to job queue.")
        id = self.nextID

        # If there is an livejob in the queue with with nextID,
        # this means that the id is already taken.
        # We try to find a free id to use by looping through all
        # the job ids possible and finding one that is
        # not used by any of the livejobs.
        # Return -1 if no such free id is found.
        keys = self.liveJobs.keys()
        if str(id) in keys:
            id = -1
            for i in range(1, Config.MAX_JOBID + 1):
                if str(i) not in keys:
                    id = i
                    break

        self.nextID += 1
        if self.nextID > Config.MAX_JOBID:
            # Wrap around if job ids go over max job ids avail
            self.nextID = 1
        self.queueLock.release()
        self.log.debug("_getNextID|Released lock to job queue.")
        return id

    def remove(self, id):
        """remove - Remove job from live queue"""
        status = -1
        self.log.debug("remove|Acquiring lock to job queue.")
        self.queueLock.acquire()
        self.log.debug("remove|Acquired lock to job queue.")
        if id in self.liveJobs:
            self.liveJobs.delete(id)
            status = 0
        self.unassignedJobs.remove(int(id))

        self.queueLock.release()
        self.log.debug("remove|Relased lock to job queue.")

        if status == 0:
            self.log.debug("Removed job %s from queue" % id)
        else:
            self.log.error("Job %s not found in queue" % id)
        return status

    def add(self, job):
        """add - add job to live queue
        This function assigns an ID number to a *new* job and then adds it
        to the queue of live jobs.
        Returns the job id on success, -1 otherwise
        """
        if not isinstance(job, TangoJob):
            return -1

        # Get an id for the new job
        self.log.debug("add|Getting next ID")
        nextId = self._getNextID()
        if nextId == -1:
            self.log.info("add|JobQueue is full")
            return -1
        job.setId(nextId)
        self.log.debug("add|Gotten next ID: " + str(job.id))

        self.log.info("add|Unassigning job ID: %d" % (job.id))
        # Make the job unassigned
        job.makeUnassigned()

        # Since we assume that the job is new, we set the number of retries
        # of this job to 0
        job.retries = 0

        # Add the job to the queue. Careful not to append the trace until we
        # know the job has actually been added to the queue.
        self.log.debug("add|Acquiring lock to job queue.")
        self.queueLock.acquire()
        self.log.debug("add| Acquired lock to job queue.")

        # Adds the job to the live jobs dictionary
        self.liveJobs.set(job.id, job)

        # Add this to the unassigned job queue too
        self.unassignedJobs.put(int(job.id))

        job.appendTrace(
            "%s|Added job %s:%d to queue"
            % (datetime.utcnow().ctime(), job.name, job.id)
        )

        self.log.debug("Ref: " + str(job._remoteLocation))
        self.log.debug("job_id: " + str(job.id))
        self.log.debug("job_name: " + str(job.name))

        self.queueLock.release()
        self.log.debug("add|Releasing lock to job queue.")

        self.log.info(
            "Added job %s:%s to queue, details = %s"
            % (job.name, job.id, str(job.__dict__))
        )

        return str(job.id)

    def addDead(self, job):
        """addDead - add a job to the dead queue.
        Called by validateJob when a job validation fails.
        Returns -1 on failure and the job id on success
        """
        if not isinstance(job, TangoJob):
            return -1

        # Get an id for the new job
        self.log.debug("add|Getting next ID")
        nextId = self._getNextID()
        if nextId == -1:
            self.log.info("add|JobQueue is full")
            return -1
        job.setId(nextId)
        self.log.debug("addDead|Gotten next ID: " + str(job.id))

        self.log.info("addDead|Unassigning job %s" % str(job.id))
        job.makeUnassigned()
        job.retries = 0

        self.log.debug("addDead|Acquiring lock to job queue.")
        self.queueLock.acquire()
        self.log.debug("addDead|Acquired lock to job queue.")

        # We add the job into the dead jobs dictionary
        self.deadJobs.set(job.id, job)
        self.queueLock.release()
        self.log.debug("addDead|Released lock to job queue.")

        return job.id

    def delJob(self, id, deadjob):
        """delJob - Implements delJob() interface call
        @param id - The id of the job to remove
        @param deadjob - If 0, move the job from the live queue to the
        dead queue. If non-zero, remove the job from the dead queue
        and discard.
        """
        status = -1
        if deadjob == 0:
            try:
                # Remove the job from the unassigned live jobs queue, if it
                # is yet to be assigned.
                self.unassignedJobs.remove(int(id))
            except ValueError:
                # Forbid deleting a job that has already been assigned
                self.log.info("delJob | Job ID %s was already assigned" % (id))
                return status

            return self.makeDead(id, "Requested by operator")
        else:
            self.queueLock.acquire()
            self.log.debug("delJob| Acquired lock to job queue.")
            if id in self.deadJobs:
                self.deadJobs.delete(id)
                status = 0
            self.queueLock.release()
            self.log.debug("delJob| Released lock to job queue.")

            if status == 0:
                self.log.debug("Removed job %s from dead queue" % id)
            else:
                self.log.error("Job %s not found in dead queue" % id)
            return status

    def get(self, id):
        """get - retrieve job from live queue
        @param id - the id of the job to retrieve
        """
        self.queueLock.acquire()
        self.log.debug("get| Acquired lock to job queue.")
        job = self.liveJobs.get(id)
        self.queueLock.release()
        self.log.debug("get| Released lock to job queue.")
        return job

    def assignJob(self, jobId, vm=None):
        """assignJob - marks a job to be assigned"""
        self.queueLock.acquire()
        self.log.debug("assignJob| Acquired lock to job queue.")

        job = self.liveJobs.get(jobId)

        # Remove the current job from the queue
        self.unassignedJobs.remove(int(jobId))

        self.log.debug("assignJob| Retrieved job.")
        self.log.info("assignJob|Assigning job ID: %s" % str(job.id))
        job.makeAssigned()
        job.makeVM(vm)

        self.log.debug("assignJob| Releasing lock to job queue.")
        self.queueLock.release()
        self.log.debug("assignJob| Released lock to job queue.")
        # return job

    def unassignJob(self, jobId):
        """unassignJob - marks a job to be unassigned
        Note: We assume here that a job is to be rescheduled or
        'retried' when you unassign it. This retry is done by
        the worker.
        """
        self.queueLock.acquire()
        self.log.debug("unassignJob| Acquired lock to job queue.")

        # Get the current job
        job = self.liveJobs.get(jobId)

        # Increment the number of retires
        if job.retries is None:
            job.retries = 0
        else:
            job.retries += 1
            Config.job_retries += 1

        self.log.info("unassignJob|Unassigning job %s" % str(job.id))
        job.makeUnassigned()

        # Since the assumption is that the job is being retried,
        # we simply add the job to the unassigned jobs queue without
        # removing anything from it
        self.unassignedJobs.put(int(jobId))

        self.queueLock.release()
        self.log.debug("unassignJob| Released lock to job queue.")

    def makeDead(self, id, reason):
        """makeDead - move a job from live queue to dead queue"""
        self.log.info("makeDead| Making dead job ID: " + str(id))
        self.queueLock.acquire()
        self.log.debug("makeDead| Acquired lock to job queue.")
        status = -1
        # Check to make sure that the job is in the live jobs queue
        if id in self.liveJobs:
            self.log.info("makeDead| Found job ID: %s in the live queue" % (id))
            status = 0
            job = self.liveJobs.get(id)
            self.log.info("Terminated job %s:%s: %s" % (job.name, job.id, reason))
            # Add the job to the dead jobs dictionary
            self.deadJobs.set(id, job)
            # Remove the job from the live jobs dictionary
            self.liveJobs.delete(id)

            # unassign, remove from unassigned jobs queue
            job.makeUnassigned()
            self.unassignedJobs.remove(int(id))

            job.appendTrace("%s|%s" % (datetime.utcnow().ctime(), reason))
        self.queueLock.release()
        self.log.debug("makeDead| Released lock to job queue.")
        return status

    def getInfo(self):

        info = {}
        info["size"] = len(self.liveJobs.keys())
        info["size_deadjobs"] = len(self.deadJobs.keys())
        info["size_unassignedjobs"] = self.unassignedJobs.qsize()

        return info

    def reset(self):
        """reset - resets and clears all the internal dictionaries
        and queues
        """
        self.liveJobs._clean()
        self.deadJobs._clean()
        self.unassignedJobs._clean()

    def getNextPendingJob(self):
        """Gets the next unassigned live job. Note that this is a
        blocking function and we will block till there is an available
        job.
        """
        # Blocks till the next item is added
        id = self.unassignedJobs.get()

        self.log.debug("_getNextPendingJob|Acquiring lock to job queue.")
        self.queueLock.acquire()
        self.log.debug("_getNextPendingJob|Acquired lock to job queue.")

        # Get the corresponding job
        job = self.liveJobs.get(id)
        if job is None:
            raise Exception("Cannot find unassigned job in live jobs")

        self.log.debug("getNextPendingJob| Releasing lock to job queue.")
        self.queueLock.release()
        self.log.debug("getNextPendingJob| Released lock to job queue.")
        return job

    def reuseVM(self, job):
        """Helps a job reuse a vm. This is called if CONFIG.REUSE_VM is
        set to true.
        """

        # Create a pool if necessary
        # This is when there is no existing pool for the vm name required.
        if self.preallocator.poolSize(job.vm.name) == 0:
            self.preallocator.update(job.vm, Config.POOL_SIZE)

        # If the job hasn't been assigned to a worker yet, we try to
        # allocate a new vm for this job
        if job.isNotAssigned():
            # Note: This could return None, when all VMs are being used
            return self.preallocator.allocVM(job.vm.name)
        else:
            # In the case where a job is already assigned, it should have
            # a vm, and we just return that vm here
            if job.vm:
                return job.vm
            else:
                raise Exception("Job assigned without vm")