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#!/usr/bin/env python3
#
# Copyright (C) 2016 Codethink Limited
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see <http://www.gnu.org/licenses/>.
#
# Authors:
# Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
# Jürg Billeter <juerg.billeter@codethink.co.uk>
# System imports
from collections import deque
from enum import Enum
# Local imports
from .job import Job
# Indicates the kind of activity
#
#
class QueueType():
# Tasks which download stuff from the internet
FETCH = 1
# CPU/Disk intensive tasks
BUILD = 2
# Tasks which upload stuff to the internet
PUSH = 3
# Queue status for a given element
#
#
class QueueStatus(Enum):
# The element is waiting for dependencies.
WAIT = 1
# The element can skip this queue.
SKIP = 2
# The element is ready for processing in this queue.
READY = 3
# Queue()
#
#
class Queue():
# These should be overridden on class data of of concrete Queue implementations
action_name = None
complete_name = None
queue_type = None
def __init__(self):
self.scheduler = None
self.wait_queue = deque()
self.done_queue = deque()
self.active_jobs = []
self.max_retries = 0
# For the frontend to know how many elements
# were successfully processed, failed, or skipped
# as they did not require processing.
#
self.failed_elements = []
self.processed_elements = []
self.skipped_elements = []
# Assert the subclass has setup class data
assert(self.action_name is not None)
assert(self.complete_name is not None)
assert(self.queue_type is not None)
#####################################################
# Abstract Methods for Queue implementations #
#####################################################
# process()
#
# Abstract method for processing an element
#
# Args:
# element (Element): An element to process
#
# Returns:
# (any): An optional something to be returned
# for every element successfully processed
#
#
def process(self, element):
pass
# status()
#
# Abstract method for reporting the status of an element.
#
# Args:
# element (Element): An element to process
#
# Returns:
# (QueueStatus): The element status
#
def status(self, element):
return QueueStatus.READY
# prepare()
#
# Abstract method for handling job preparation in the main process.
#
# Args:
# element (Element): The element which is scheduled
#
def prepare(self, element):
pass
# done()
#
# Abstract method for handling a successful job completion.
#
# Args:
# element (Element): The element which completed processing
# result (any): The return value of the process() implementation
# returncode (int): The process return code, 0 = success
#
# Returns:
# (bool): True if the element should appear to be processsed,
# Otherwise False will count the element as "skipped"
#
def done(self, element, result, returncode):
pass
#####################################################
# Queue internals and Scheduler facing APIs #
#####################################################
# Attach to the scheduler
def attach(self, scheduler):
self.scheduler = scheduler
if self.queue_type == QueueType.FETCH or self.queue_type == QueueType.PUSH:
self.max_retries = scheduler.context.sched_network_retries
def enqueue(self, elts):
if not elts:
return
# Place skipped elements directly on the done queue
elts = list(elts)
skip = [elt for elt in elts if self.status(elt) == QueueStatus.SKIP]
wait = [elt for elt in elts if elt not in skip]
self.wait_queue.extend(wait)
self.done_queue.extend(skip)
self.skipped_elements.extend(skip)
def dequeue(self):
while self.done_queue:
yield self.done_queue.popleft()
def process_ready(self):
scheduler = self.scheduler
unready = []
while self.wait_queue and scheduler.get_job_token(self.queue_type):
element = self.wait_queue.popleft()
status = self.status(element)
if status == QueueStatus.WAIT:
scheduler.put_job_token(self.queue_type)
unready.append(element)
continue
elif status == QueueStatus.SKIP:
scheduler.put_job_token(self.queue_type)
self.done_queue.append(element)
self.skipped_elements.append(element)
continue
self.prepare(element)
job = Job(scheduler, element, self.action_name)
scheduler.job_starting(job)
job.spawn(self.process, self.job_done, self.max_retries)
self.active_jobs.append(job)
# These were not ready but were in the beginning, give em
# first priority again next time around
self.wait_queue.extendleft(unready)
def job_done(self, job, returncode, element):
# Shutdown the job
job.shutdown()
self.active_jobs.remove(job)
# Give the result of the job to the Queue implementor,
# and determine if it should be considered as processed
# or skipped.
if self.done(element, job.result, returncode):
skip = False
else:
skip = True
if returncode == 0:
self.done_queue.append(element)
if skip:
self.skipped_elements.append(element)
else:
self.processed_elements.append(element)
else:
self.failed_elements.append(element)
# Give the token for this job back to the scheduler
# immediately before invoking another round of scheduling
self.scheduler.put_job_token(self.queue_type)
# Notify frontend
self.scheduler.job_completed(self, job, returncode == 0)
self.scheduler.sched()
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