path: root/lib/python/Components/Task.py

# A Job consists of many "Tasks".
# A task is the run of an external tool, with proper methods for failure handling

from Tools.CList import CList

class Job(object):
	NOT_STARTED, IN_PROGRESS, FINISHED, FAILED = range(4)
	def __init__(self, name):
		self.tasks = [ ]
		self.resident_tasks = [ ]
		self.workspace = "/tmp"
		self.current_task = 0
		self.callback = None
		self.name = name
		self.finished = False
		self.end = 100
		self.__progress = 0
		self.weightScale = 1

		self.state_changed = CList()

		self.status = self.NOT_STARTED

	# description is a dict
	def fromDescription(self, description):
		pass

	def createDescription(self):
		return None

	def getProgress(self):
		if self.current_task == len(self.tasks):
			return self.end
		t = self.tasks[self.current_task]
		jobprogress = t.weighting * t.progress / float(t.end) + sum([task.weighting for task in self.tasks[:self.current_task]])
		return int(jobprogress*self.weightScale)

	progress = property(getProgress)

	def task_progress_changed_CB(self):
		self.state_changed()

	def addTask(self, task):
		task.job = self
		self.tasks.append(task)

	def start(self, callback):
		assert self.callback is None
		self.callback = callback
		self.restart()

	def restart(self):
		self.status = self.IN_PROGRESS
		self.state_changed()
		self.runNext()
		sumTaskWeightings = sum([t.weighting for t in self.tasks])
		self.weightScale = self.end / float(sumTaskWeightings)

	def runNext(self):
		if self.current_task == len(self.tasks):
			if len(self.resident_tasks) == 0:
				cb = self.callback
				self.callback = None
				self.status = self.FINISHED
				self.state_changed()
				cb(self, None, [])
			else:
				print "still waiting for %d resident task(s) %s to finish" % (len(self.resident_tasks), str(self.resident_tasks))
		else:
			self.tasks[self.current_task].run(self.taskCallback, self.task_progress_changed_CB)
			self.state_changed()

	def taskCallback(self, task, res, stay_resident = False):
		cb_idx = self.tasks.index(task)
		if stay_resident:
			if cb_idx not in self.resident_tasks:
				self.resident_tasks.append(self.current_task)
				print "task going resident:", task
			else:
				print "task keeps staying resident:", task
				return
		if len(res):
			print ">>> Error:", res
			self.status = self.FAILED
			self.state_changed()
			self.callback(self, task, res)
		if cb_idx != self.current_task:
			if cb_idx in self.resident_tasks:
				print "resident task finished:", task
				self.resident_tasks.remove(cb_idx)
		if res == []:
			self.state_changed()
			self.current_task += 1
			self.runNext()

	def retry(self):
		assert self.status == self.FAILED
		self.restart()

	def abort(self):
		if self.current_task < len(self.tasks):
			self.tasks[self.current_task].abort()
		for i in self.resident_tasks:
			self.tasks[i].abort()

	def cancel(self):
		# some Jobs might have a better idea of how to cancel a job
		self.abort()

class Task(object):
	def __init__(self, job, name):
		self.name = name
		self.immediate_preconditions = [ ]
		self.global_preconditions = [ ]
		self.postconditions = [ ]
		self.returncode = None
		self.initial_input = None
		self.job = None

		self.end = 100
		self.weighting = 100
		self.__progress = 0
		self.cmd = None
		self.cwd = "/tmp"
		self.args = [ ]
		self.task_progress_changed = None
		self.output_line = ""
		job.addTask(self)

	def setCommandline(self, cmd, args):
		self.cmd = cmd
		self.args = args

	def setTool(self, tool):
		self.cmd = tool
		self.args = [tool]
		self.global_preconditions.append(ToolExistsPrecondition())
		self.postconditions.append(ReturncodePostcondition())

	def checkPreconditions(self, immediate = False):
		not_met = [ ]
		if immediate:
			preconditions = self.immediate_preconditions
		else:
			preconditions = self.global_preconditions
		for precondition in preconditions:
			if not precondition.check(self):
				not_met.append(precondition)
		return not_met

	def run(self, callback, task_progress_changed):
		failed_preconditions = self.checkPreconditions(True) + self.checkPreconditions(False)
		if len(failed_preconditions):
			callback(self, failed_preconditions)
			return
		self.prepare()

		self.callback = callback
		self.task_progress_changed = task_progress_changed
		from enigma import eConsoleAppContainer
		self.container = eConsoleAppContainer()
		self.container.appClosed.get().append(self.processFinished)
		self.container.dataAvail.get().append(self.processOutput)

		assert self.cmd is not None
		assert len(self.args) >= 1

		if self.cwd is not None:
			self.container.setCWD(self.cwd)

		print "execute:", self.container.execute(self.cmd, self.args), self.cmd, " ".join(self.args)
		if self.initial_input:
			self.writeInput(self.initial_input)

	def prepare(self):
		pass

	def cleanup(self, failed):
		pass

	def processOutput(self, data):
		self.output_line += data
		while True:
			i = self.output_line.find('\n')
			if i == -1:
				break
			self.processOutputLine(self.output_line[:i+1])
			self.output_line = self.output_line[i+1:]

	def processOutputLine(self, line):
		pass

	def processFinished(self, returncode):
		self.returncode = returncode
		self.finish()

	def abort(self):
		self.container.kill()
		self.finish(aborted = True)

	def finish(self, aborted = False):
		self.afterRun()
		not_met = [ ]
		if aborted:
			not_met.append(AbortedPostcondition())
		else:
			for postcondition in self.postconditions:
				if not postcondition.check(self):
					not_met.append(postcondition)
		self.cleanup(not_met)
		self.callback(self, not_met)

	def afterRun(self):
		pass

	def writeInput(self, input):
		self.container.write(input)

	def getProgress(self):
		return self.__progress

	def setProgress(self, progress):
		if progress > self.end:
			progress = self.end
		if progress < 0:
			progress = 0
		self.__progress = progress
		self.task_progress_changed()

	progress = property(getProgress, setProgress)

# The jobmanager will execute multiple jobs, each after another.
# later, it will also support suspending jobs (and continuing them after reboot etc)
# It also supports a notification when some error occured, and possibly a retry.
class JobManager:
	def __init__(self):
		self.active_jobs = [ ]
		self.failed_jobs = [ ]
		self.job_classes = [ ]
		self.active_job = None

	def AddJob(self, job):
		self.active_jobs.append(job)
		self.kick()

	def kick(self):
		if self.active_job is None:
			if len(self.active_jobs):
				self.active_job = self.active_jobs.pop(0)
				self.active_job.start(self.jobDone)

	def jobDone(self, job, task, problems):
		print "job", job, "completed with", problems, "in", task
		if problems:
			from Tools import Notifications
			from Screens.MessageBox import MessageBox
			Notifications.AddNotificationWithCallback(self.errorCB, MessageBox, _("Error: %s\nRetry?") % (problems[0].getErrorMessage(task)))
			return
			#self.failed_jobs.append(self.active_job)

		self.active_job = None
		self.kick()

	def errorCB(self, answer):
		if answer:
			print "retrying job"
			self.active_job.retry()
		else:
			print "not retrying job."
			self.failed_jobs.append(self.active_job)
			self.active_job = None
			self.kick()

# some examples:
#class PartitionExistsPostcondition:
#	def __init__(self, device):
#		self.device = device
#
#	def check(self, task):
#		import os
#		return os.access(self.device + "part1", os.F_OK)
#
#class CreatePartitionTask(Task):
#	def __init__(self, device):
#		Task.__init__(self, _("Create Partition"))
#		self.device = device
#		self.setTool("/sbin/sfdisk")
#		self.args += ["-f", self.device + "disc"]
#		self.initial_input = "0,\n;\n;\n;\ny\n"
#		self.postconditions.append(PartitionExistsPostcondition(self.device))
#
#class CreateFilesystemTask(Task):
#	def __init__(self, device, partition = 1, largefile = True):
#		Task.__init__(self, _("Create Filesystem"))
#		self.setTool("/sbin/mkfs.ext")
#		if largefile:
#			self.args += ["-T", "largefile"]
#		self.args.append("-m0")
#		self.args.append(device + "part%d" % partition)
#
#class FilesystemMountTask(Task):
#	def __init__(self, device, partition = 1, filesystem = "ext3"):
#		Task.__init__(self, _("Mounting Filesystem"))
#		self.setTool("/bin/mount")
#		if filesystem is not None:
#			self.args += ["-t", filesystem]
#		self.args.append(device + "part%d" % partition)

class Condition:
	RECOVERABLE = False

	def getErrorMessage(self, task):
		return _("An error has occured. (%s)") % (self.__class__.__name__)

class WorkspaceExistsPrecondition(Condition):
	def check(self, task):
		return os.access(task.job.workspace, os.W_OK)

class DiskspacePrecondition(Condition):
	def __init__(self, diskspace_required):
		self.diskspace_required = diskspace_required
		self.diskspace_available = 0

	def check(self, task):
		import os
		try:
			s = os.statvfs(task.job.workspace)
			self.diskspace_available = s.f_bsize * s.f_bavail
			return self.diskspace_available >= self.diskspace_required
		except OSError:
			return False

	def getErrorMessage(self, task):
		return _("Not enough diskspace. Please free up some diskspace and try again. (%d MB required, %d MB available)") % (self.diskspace_required / 1024 / 1024, self.diskspace_available / 1024 / 1024)

class ToolExistsPrecondition(Condition):
	def check(self, task):
		import os
		if task.cmd[0]=='/':
			realpath = task.cmd
		else:
			realpath = task.cwd + '/' + task.cmd
		self.realpath = realpath
		return os.access(realpath, os.X_OK)

	def getErrorMessage(self, task):
		return _("A required tool (%s) was not found.") % (self.realpath)

class AbortedPostcondition(Condition):
	pass

class ReturncodePostcondition(Condition):
	def check(self, task):
		return task.returncode == 0

#class HDDInitJob(Job):
#	def __init__(self, device):
#		Job.__init__(self, _("Initialize Harddisk"))
#		self.device = device
#		self.fromDescription(self.createDescription())
#
#	def fromDescription(self, description):
#		self.device = description["device"]
#		self.addTask(CreatePartitionTask(self.device))
#		self.addTask(CreateFilesystemTask(self.device))
#		self.addTask(FilesystemMountTask(self.device))
#
#	def createDescription(self):
#		return {"device": self.device}

job_manager = JobManager()