src/main/python/apache/thermos/observer/task_observer.py - aurora - Git at Google

 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #

 """Observe Thermos tasks on a system

 This module provides a number of classes for exposing information about running (active) and
 finished Thermos tasks on a system. The primary entry point is the TaskObserver, a thread which
 polls a designated Thermos checkpoint root and collates information about all tasks it discovers.

 """
 import os
 import threading
 import time
 from operator import attrgetter

 from twitter.common import log
 from twitter.common.exceptions import ExceptionalThread
 from twitter.common.lang import Lockable
 from twitter.common.quantity import Amount, Time

 from apache.thermos.common.path import TaskPath
 from apache.thermos.monitoring.monitor import TaskMonitor
 from apache.thermos.monitoring.process import ProcessSample
 from apache.thermos.monitoring.resource import TaskResourceMonitor

 from .detector import ObserverTaskDetector
 from .observed_task import ActiveObservedTask, FinishedObservedTask

 from gen.apache.thermos.ttypes import ProcessState, TaskState


 class TaskObserver(ExceptionalThread, Lockable):
   """
     The TaskObserver monitors the thermos checkpoint root for active/finished
     tasks.  It is used to be the oracle of the state of all thermos tasks on
     a machine.

     It currently returns JSON, but really should just return objects.  We should
     then build an object->json translator.
   """
   class UnexpectedError(Exception): pass
   class UnexpectedState(Exception): pass

   POLLING_INTERVAL = Amount(5, Time.SECONDS)

   def __init__(self,
                path_detector,
                interval=POLLING_INTERVAL,
                task_process_collection_interval=TaskResourceMonitor.PROCESS_COLLECTION_INTERVAL,
                task_disk_collection_interval=TaskResourceMonitor.DISK_COLLECTION_INTERVAL):
     self._detector = ObserverTaskDetector(
         path_detector,
         self.__on_active,
         self.__on_finished,
         self.__on_removed)
     self._interval = interval
     self._task_process_collection_interval = task_process_collection_interval
     self._task_disk_collection_interval = task_disk_collection_interval
     self._active_tasks = {}    # task_id => ActiveObservedTask
     self._finished_tasks = {}  # task_id => FinishedObservedTask
     self._stop_event = threading.Event()
     ExceptionalThread.__init__(self)
     Lockable.__init__(self)
     self.daemon = True

   @property
   def active_tasks(self):
     """Return a dictionary of active Tasks"""
     return self._active_tasks

   @property
   def finished_tasks(self):
     """Return a dictionary of finished Tasks"""
     return self._finished_tasks

   @property
   def all_tasks(self):
     """Return a dictionary of all Tasks known by the TaskObserver"""
     return dict(self.active_tasks.items() + self.finished_tasks.items())

   def stop(self):
     self._stop_event.set()

   def start(self):
     ExceptionalThread.start(self)

   def __on_active(self, root, task_id):
     log.debug('on_active(%r, %r)', root, task_id)
     if task_id in self.finished_tasks:
       log.error('Found an active task (%s) in finished tasks?', task_id)
       return
     task_monitor = TaskMonitor(root, task_id)
     resource_monitor = TaskResourceMonitor(
         task_id,
         task_monitor,
         process_collection_interval=self._task_process_collection_interval,
         disk_collection_interval=self._task_disk_collection_interval)
     resource_monitor.start()
     self._active_tasks[task_id] = ActiveObservedTask(
         root,
         task_id,
         task_monitor,
         resource_monitor
     )

   def __on_finished(self, root, task_id):
     log.debug('on_finished(%r, %r)', root, task_id)
     active_task = self._active_tasks.pop(task_id, None)
     if active_task:
       active_task.resource_monitor.kill()
     self._finished_tasks[task_id] = FinishedObservedTask(root, task_id)

   def __on_removed(self, root, task_id):
     log.debug('on_removed(%r, %r)', root, task_id)
     active_task = self._active_tasks.pop(task_id, None)
     if active_task:
       active_task.resource_monitor.kill()
     self._finished_tasks.pop(task_id, None)

   def run(self):
     """
       The internal thread for the observer.  This periodically polls the
       checkpoint root for new tasks, or transitions of tasks from active to
       finished state.
     """
     while not self._stop_event.is_set():
       self._stop_event.wait(self._interval.as_(Time.SECONDS))
       with self.lock:
         start = time.time()
         self._detector.refresh()
         log.debug("TaskObserver: finished checkpoint refresh in %.2fs", time.time() - start)

   @Lockable.sync
   def process_from_name(self, task_id, process_id):
     if task_id in self.all_tasks:
       task = self.all_tasks[task_id].task
       if task:
         for process in task.processes():
           if process.name().get() == process_id:
             return process

   @Lockable.sync
   def task_count(self):
     """
       Return the count of tasks that could be ready properly from disk.
       This may be <= self.task_id_count()
     """
     return dict(
       active=len(self.active_tasks),
       finished=len(self.finished_tasks),
       all=len(self.all_tasks),
     )

   @Lockable.sync
   def task_id_count(self):
     """Return the raw count of active and finished task_ids."""
     num_active = len(self._detector.active_tasks)
     num_finished = len(self._detector.finished_tasks)
     return dict(active=num_active, finished=num_finished, all=num_active + num_finished)

   def _get_tasks_of_type(self, type):
     """Convenience function to return all tasks of a given type"""
     tasks = {
       'active': self.active_tasks,
       'finished': self.finished_tasks,
       'all': self.all_tasks,
     }.get(type, None)

     if tasks is None:
       log.error('Unknown task type %s', type)
       return {}

     return tasks

   @Lockable.sync
   def state(self, task_id):
     """Return a dict containing mapped information about a task's state"""
     real_state = self.raw_state(task_id)
     if real_state is None or real_state.header is None:
       return {}
     else:
       return dict(
         task_id=real_state.header.task_id,
         launch_time=real_state.header.launch_time_ms / 1000.0,
         sandbox=real_state.header.sandbox,
         hostname=real_state.header.hostname,
         user=real_state.header.user
       )

   @Lockable.sync
   def raw_state(self, task_id):
     """
       Return the current runner state (thrift blob: gen.apache.thermos.ttypes.RunnerState)
       of a given task id
     """
     if task_id not in self.all_tasks:
       return None
     return self.all_tasks[task_id].state

   @Lockable.sync
   def _task_processes(self, task_id):
     """
       Return the processes of a task given its task_id.

       Returns a map from state to processes in that state, where possible
       states are: waiting, running, success, failed.
     """
     if task_id not in self.all_tasks:
       return {}
     state = self.raw_state(task_id)
     if state is None or state.header is None:
       return {}

     waiting, running, success, failed, killed = [], [], [], [], []
     for process, runs in state.processes.items():
       # No runs ==> nothing started.
       if len(runs) == 0:
         waiting.append(process)
       else:
         if runs[-1].state in (None, ProcessState.WAITING, ProcessState.LOST):
           waiting.append(process)
         elif runs[-1].state in (ProcessState.FORKED, ProcessState.RUNNING):
           running.append(process)
         elif runs[-1].state == ProcessState.SUCCESS:
           success.append(process)
         elif runs[-1].state == ProcessState.FAILED:
           failed.append(process)
         elif runs[-1].state == ProcessState.KILLED:
           killed.append(process)
         else:
           # TODO(wickman)  Consider log.error instead of raising.
           raise self.UnexpectedState(
             "Unexpected ProcessHistoryState: %s" % state.processes[process].state)

     return dict(waiting=waiting, running=running, success=success, failed=failed, killed=killed)

   @Lockable.sync
   def main(self, type=None, offset=None, num=None):
     """Return a set of information about tasks, optionally filtered

       Args:
         type = (all|active|finished|None) [default: all]
         offset = offset into the list of task_ids [default: 0]
         num = number of results to return [default: 20]

       Tasks are sorted by interest:
         - active tasks are sorted by start time
         - finished tasks are sorted by completion time

       Returns:
         {
           tasks: [task_id_1, ..., task_id_N],
           type: query type,
           offset: next offset,
           num: next num
         }

     """
     type = type or 'all'
     offset = offset or 0
     num = num or 20

     # Get a list of all ObservedTasks of requested type
     tasks = sorted((task for task in self._get_tasks_of_type(type).values()),
                    key=attrgetter('mtime'), reverse=True)

     # Filter by requested offset + number of results
     end = num
     if offset < 0:
       offset = offset % len(tasks) if len(tasks) > abs(offset) else 0
     end += offset
     tasks = tasks[offset:end]

     def task_row(observed_task):
       """Generate an output row for a Task"""
       task = self._task(observed_task.task_id)
       # tasks include those which could not be found properly and are hence empty {}
       if task:
         return dict(
             task_id=observed_task.task_id,
             name=task['name'],
             role=task['user'],
             launch_timestamp=task['launch_timestamp'],
             state=task['state'],
             state_timestamp=task['state_timestamp'],
             ports=task['ports'],
             **task['resource_consumption'])

     return dict(
       tasks=filter(None, map(task_row, tasks)),
       type=type,
       offset=offset,
       num=num,
       task_count=self.task_count()[type],
     )

   def _sample(self, task_id):
     if task_id not in self.active_tasks:
       sample = ProcessSample.empty().to_dict()
       sample['disk'] = 0
     else:
       resource_sample = self.active_tasks[task_id].resource_monitor.sample()[1]
       sample = resource_sample.process_sample.to_dict()
       sample['disk'] = resource_sample.disk_usage
       log.debug("Got sample for task %s: %s", task_id, sample)
     return sample

   @Lockable.sync
   def task_statuses(self, task_id):
     """
       Return the sequence of task states.

       [(task_state [string], timestamp), ...]
     """

     # Unknown task_id.
     if task_id not in self.all_tasks:
       return []

     task = self.all_tasks[task_id]
     if task is None:
       return []

     state = self.raw_state(task_id)
     if state is None or state.header is None:
       return []

     # Get the timestamp of the transition into the current state.
     return [
       (TaskState._VALUES_TO_NAMES.get(st.state, 'UNKNOWN'), st.timestamp_ms / 1000)
       for st in state.statuses]

   @Lockable.sync
   def tasks(self, task_ids):
     """
       Return information about an iterable of tasks [task_id1, task_id2, ...]
       in the following form.

       {
         task_id1 : self._task(task_id1),
         task_id2 : self._task(task_id2),
         ...
       }
     """
     res = {}
     for task_id in task_ids:
       d = self._task(task_id)
       task_struct = d.pop('task_struct')
       d['task'] = task_struct.get()
       res[task_id] = d
     return res

   @Lockable.sync
   def _task(self, task_id):
     """
       Return composite information about a particular task task_id, given the below
       schema.

       {
          task_id: string,
          name: string,
          user: string,
          launch_timestamp: seconds,
          state: string [ACTIVE, SUCCESS, FAILED]
          ports: { name1: 'url', name2: 'url2' }
          resource_consumption: { cpu:, ram:, disk: }
          processes: { -> names only
             waiting: [],
             running: [],
             success: [],
             failed:  []
          }
       }
     """
     # Unknown task_id.
     if task_id not in self.all_tasks:
       return {}

     task = self.all_tasks[task_id].task
     if task is None:
       # TODO(wickman)  Can this happen?
       log.error('Could not find task: %s', task_id)
       return {}

     state = self.raw_state(task_id)
     if state is None or state.header is None:
       # TODO(wickman)  Can this happen?
       return {}

     # Get the timestamp of the transition into the current state.
     current_state = state.statuses[-1].state
     last_state = state.statuses[0]
     state_timestamp = 0
     for status in state.statuses:
       if status.state == current_state and last_state != current_state:
         state_timestamp = status.timestamp_ms / 1000
       last_state = status.state

     return dict(
        task_id=task_id,
        name=task.name().get(),
        launch_timestamp=state.statuses[0].timestamp_ms / 1000,
        state=TaskState._VALUES_TO_NAMES[state.statuses[-1].state],
        state_timestamp=state_timestamp,
        user=state.header.user,
        resource_consumption=self._sample(task_id),
        ports=state.header.ports,
        processes=self._task_processes(task_id),
        task_struct=task,
     )

   @Lockable.sync
   def _get_process_resource_consumption(self, task_id, process_name):
     if task_id not in self.active_tasks:
       return ProcessSample.empty().to_dict()
     sample = self.active_tasks[task_id].resource_monitor.sample_by_process(process_name).to_dict()
     log.debug('Resource consumption (%s, %s) => %s', task_id, process_name, sample)
     return sample

   @Lockable.sync
   def _get_process_tuple(self, history, run):
     """
       Return the basic description of a process run if it exists, otherwise
       an empty dictionary.

       {
         process_name: string
         process_run: int
         (optional) return_code: int
         state: string [WAITING, FORKED, RUNNING, SUCCESS, KILLED, FAILED, LOST]
         (optional) start_time: seconds from epoch
         (optional) stop_time: seconds from epoch
       }
     """
     if len(history) == 0:
       return {}
     if run >= len(history):
       return {}
     else:
       process_run = history[run]
       run = run % len(history)
       d = dict(
         process_name=process_run.process,
         process_run=run,
         state=ProcessState._VALUES_TO_NAMES[process_run.state],
       )
       if process_run.start_time:
         d.update(start_time=process_run.start_time)
       if process_run.stop_time:
         d.update(stop_time=process_run.stop_time)
       if process_run.return_code:
         d.update(return_code=process_run.return_code)
       return d

   @Lockable.sync
   def process(self, task_id, process, run=None):
     """
       Returns a process run, where the schema is given below:

       {
         process_name: string
         process_run: int
         used: { cpu: float, ram: int bytes, disk: int bytes }
         start_time: (time since epoch in millis (utc))
         stop_time: (time since epoch in millis (utc))
         state: string [WAITING, FORKED, RUNNING, SUCCESS, KILLED, FAILED, LOST]
       }

       If run is None, return the latest run.
     """
     state = self.raw_state(task_id)
     if state is None or state.header is None:
       return {}
     if process not in state.processes:
       return {}
     history = state.processes[process]
     run = int(run) if run is not None else -1
     tup = self._get_process_tuple(history, run)
     if not tup:
       return {}
     if tup.get('state') == 'RUNNING':
       tup.update(used=self._get_process_resource_consumption(task_id, process))
     return tup

   @Lockable.sync
   def _processes(self, task_id):
     """
       Return
         {
           process1: { ... }
           process2: { ... }
           ...
           processN: { ... }
         }

       where processK is the latest run of processK and in the schema as
       defined by process().
     """

     if task_id not in self.all_tasks:
       return {}
     state = self.raw_state(task_id)
     if state is None or state.header is None:
       return {}

     processes = self._task_processes(task_id)
     d = dict()
     for process_type in processes:
       for process_name in processes[process_type]:
         d[process_name] = self.process(task_id, process_name)
     return d

   @Lockable.sync
   def processes(self, task_ids):
     """
       Given a list of task_ids, returns a map of task_id => processes, where processes
       is defined by the schema in _processes.
     """
     if not isinstance(task_ids, (list, tuple)):
       return {}
     return dict((task_id, self._processes(task_id)) for task_id in task_ids)

   @Lockable.sync
   def get_run_number(self, runner_state, process, run=None):
     if runner_state is not None and runner_state.processes is not None:
       run = run if run is not None else -1
       if run < len(runner_state.processes[process]):
         if len(runner_state.processes[process]) > 0:
           return run % len(runner_state.processes[process])

   @Lockable.sync
   def logs(self, task_id, process, run=None):
     """
       Given a task_id and a process and (optional) run number, return a dict:
       {
         stderr: [dir, filename]
         stdout: [dir, filename]
       }

       If the run number is unspecified, uses the latest run.

       TODO(wickman)  Just return the filenames directly?
     """
     runner_state = self.raw_state(task_id)
     if runner_state is None or runner_state.header is None:
       return {}
     run = self.get_run_number(runner_state, process, run)
     if run is None:
       return {}
     observed_task = self.all_tasks.get(task_id, None)
     if not observed_task:
       return {}

     log_path = TaskPath(
         root=observed_task.root,
         task_id=task_id,
         process=process,
         run=run,
         log_dir=runner_state.header.log_dir,
     ).getpath('process_logdir')

     return dict(
       stdout=[log_path, 'stdout'],
       stderr=[log_path, 'stderr']
     )

   @staticmethod
   def _sanitize_path(base_path, relpath):
     """
       Attempts to sanitize a path through path normalization, also making sure
       that the relative path is contained inside of base_path.
     """
     if relpath is None:
       relpath = "."
     normalized_base = os.path.realpath(base_path)
     normalized = os.path.realpath(os.path.join(base_path, relpath))
     if normalized.startswith(normalized_base):
       return (normalized_base, os.path.relpath(normalized, normalized_base))
     return (None, None)

   @Lockable.sync
   def valid_file(self, task_id, path):
     """
       Like valid_path, but also verify the given path is a file
     """
     chroot, path = self.valid_path(task_id, path)
     if chroot and path and os.path.isfile(os.path.join(chroot, path)):
       return chroot, path
     return None, None

   @Lockable.sync
   def valid_path(self, task_id, path):
     """
       Given a task_id and a path within that task_id's sandbox, verify:
         (1) it's actually in the sandbox and not outside
         (2) it's a valid, existing path
       Returns chroot and the pathname relative to that chroot.
     """
     runner_state = self.raw_state(task_id)
     if runner_state is None or runner_state.header is None:
       return None, None
     try:
       chroot = runner_state.header.sandbox
     except AttributeError:
       return None, None
     chroot, path = self._sanitize_path(chroot, path)
     if chroot and path and os.path.exists(os.path.join(chroot, path)):
       return chroot, path
     return None, None

   @Lockable.sync
   def files(self, task_id, path=None):
     """
       Returns dictionary
       {
         task_id: task_id
         chroot: absolute directory on machine
         path: sanitized relative path w.r.t. chroot
         dirs: list of directories
         files: list of files
       }
     """
     # TODO(jon): DEPRECATED: most of the necessary logic is handled directly in the templates.
     # Also, global s/chroot/sandbox/?
     empty = dict(task_id=task_id, chroot=None, path=None, dirs=None, files=None)
     path = path if path is not None else '.'
     runner_state = self.raw_state(task_id)
     if runner_state is None:
       return empty
     try:
       chroot = runner_state.header.sandbox
     except AttributeError:
       return empty
     if chroot is None:  # chroot-less job
       return empty
     chroot, path = self._sanitize_path(chroot, path)
     if (chroot is None or path is None
         or not os.path.isdir(os.path.join(chroot, path))):
       return empty
     names = os.listdir(os.path.join(chroot, path))
     dirs, files = [], []
     for name in names:
       if os.path.isdir(os.path.join(chroot, path, name)):
         dirs.append(name)
       else:
         files.append(name)
     return dict(
       task_id=task_id,
       chroot=chroot,
       path=path,
       dirs=dirs,
       files=files
     )
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
	# limitations under the License.
	#

	"""Observe Thermos tasks on a system

	This module provides a number of classes for exposing information about running (active) and
	finished Thermos tasks on a system. The primary entry point is the TaskObserver, a thread which
	polls a designated Thermos checkpoint root and collates information about all tasks it discovers.

	"""
	import os
	import threading
	import time
	from operator import attrgetter

	from twitter.common import log
	from twitter.common.exceptions import ExceptionalThread
	from twitter.common.lang import Lockable
	from twitter.common.quantity import Amount, Time

	from apache.thermos.common.path import TaskPath
	from apache.thermos.monitoring.monitor import TaskMonitor
	from apache.thermos.monitoring.process import ProcessSample
	from apache.thermos.monitoring.resource import TaskResourceMonitor

	from .detector import ObserverTaskDetector
	from .observed_task import ActiveObservedTask, FinishedObservedTask

	from gen.apache.thermos.ttypes import ProcessState, TaskState


	class TaskObserver(ExceptionalThread, Lockable):
	"""
	The TaskObserver monitors the thermos checkpoint root for active/finished
	tasks. It is used to be the oracle of the state of all thermos tasks on
	a machine.

	It currently returns JSON, but really should just return objects. We should
	then build an object->json translator.
	"""
	class UnexpectedError(Exception): pass
	class UnexpectedState(Exception): pass

	POLLING_INTERVAL = Amount(5, Time.SECONDS)

	def __init__(self,
	path_detector,
	interval=POLLING_INTERVAL,
	task_process_collection_interval=TaskResourceMonitor.PROCESS_COLLECTION_INTERVAL,
	task_disk_collection_interval=TaskResourceMonitor.DISK_COLLECTION_INTERVAL):
	self._detector = ObserverTaskDetector(
	path_detector,
	self.__on_active,
	self.__on_finished,
	self.__on_removed)
	self._interval = interval
	self._task_process_collection_interval = task_process_collection_interval
	self._task_disk_collection_interval = task_disk_collection_interval
	self._active_tasks = {} # task_id => ActiveObservedTask
	self._finished_tasks = {} # task_id => FinishedObservedTask
	self._stop_event = threading.Event()
	ExceptionalThread.__init__(self)
	Lockable.__init__(self)
	self.daemon = True

	@property
	def active_tasks(self):
	"""Return a dictionary of active Tasks"""
	return self._active_tasks

	@property
	def finished_tasks(self):
	"""Return a dictionary of finished Tasks"""
	return self._finished_tasks

	@property
	def all_tasks(self):
	"""Return a dictionary of all Tasks known by the TaskObserver"""
	return dict(self.active_tasks.items() + self.finished_tasks.items())

	def stop(self):
	self._stop_event.set()

	def start(self):
	ExceptionalThread.start(self)

	def __on_active(self, root, task_id):
	log.debug('on_active(%r, %r)', root, task_id)
	if task_id in self.finished_tasks:
	log.error('Found an active task (%s) in finished tasks?', task_id)
	return
	task_monitor = TaskMonitor(root, task_id)
	resource_monitor = TaskResourceMonitor(
	task_id,
	task_monitor,
	process_collection_interval=self._task_process_collection_interval,
	disk_collection_interval=self._task_disk_collection_interval)
	resource_monitor.start()
	self._active_tasks[task_id] = ActiveObservedTask(
	root,
	task_id,
	task_monitor,
	resource_monitor
	)

	def __on_finished(self, root, task_id):
	log.debug('on_finished(%r, %r)', root, task_id)
	active_task = self._active_tasks.pop(task_id, None)
	if active_task:
	active_task.resource_monitor.kill()
	self._finished_tasks[task_id] = FinishedObservedTask(root, task_id)

	def __on_removed(self, root, task_id):
	log.debug('on_removed(%r, %r)', root, task_id)
	active_task = self._active_tasks.pop(task_id, None)
	if active_task:
	active_task.resource_monitor.kill()
	self._finished_tasks.pop(task_id, None)

	def run(self):
	"""
	The internal thread for the observer. This periodically polls the
	checkpoint root for new tasks, or transitions of tasks from active to
	finished state.
	"""
	while not self._stop_event.is_set():
	self._stop_event.wait(self._interval.as_(Time.SECONDS))
	with self.lock:
	start = time.time()
	self._detector.refresh()
	log.debug("TaskObserver: finished checkpoint refresh in %.2fs", time.time() - start)

	@Lockable.sync
	def process_from_name(self, task_id, process_id):
	if task_id in self.all_tasks:
	task = self.all_tasks[task_id].task
	if task:
	for process in task.processes():
	if process.name().get() == process_id:
	return process

	@Lockable.sync
	def task_count(self):
	"""
	Return the count of tasks that could be ready properly from disk.
	This may be <= self.task_id_count()
	"""
	return dict(
	active=len(self.active_tasks),
	finished=len(self.finished_tasks),
	all=len(self.all_tasks),
	)

	@Lockable.sync
	def task_id_count(self):
	"""Return the raw count of active and finished task_ids."""
	num_active = len(self._detector.active_tasks)
	num_finished = len(self._detector.finished_tasks)
	return dict(active=num_active, finished=num_finished, all=num_active + num_finished)

	def _get_tasks_of_type(self, type):
	"""Convenience function to return all tasks of a given type"""
	tasks = {
	'active': self.active_tasks,
	'finished': self.finished_tasks,
	'all': self.all_tasks,
	}.get(type, None)

	if tasks is None:
	log.error('Unknown task type %s', type)
	return {}

	return tasks

	@Lockable.sync
	def state(self, task_id):
	"""Return a dict containing mapped information about a task's state"""
	real_state = self.raw_state(task_id)
	if real_state is None or real_state.header is None:
	return {}
	else:
	return dict(
	task_id=real_state.header.task_id,
	launch_time=real_state.header.launch_time_ms / 1000.0,
	sandbox=real_state.header.sandbox,
	hostname=real_state.header.hostname,
	user=real_state.header.user
	)

	@Lockable.sync
	def raw_state(self, task_id):
	"""
	Return the current runner state (thrift blob: gen.apache.thermos.ttypes.RunnerState)
	of a given task id
	"""
	if task_id not in self.all_tasks:
	return None
	return self.all_tasks[task_id].state

	@Lockable.sync
	def _task_processes(self, task_id):
	"""
	Return the processes of a task given its task_id.

	Returns a map from state to processes in that state, where possible
	states are: waiting, running, success, failed.
	"""
	if task_id not in self.all_tasks:
	return {}
	state = self.raw_state(task_id)
	if state is None or state.header is None:
	return {}

	waiting, running, success, failed, killed = [], [], [], [], []
	for process, runs in state.processes.items():
	# No runs ==> nothing started.
	if len(runs) == 0:
	waiting.append(process)
	else:
	if runs[-1].state in (None, ProcessState.WAITING, ProcessState.LOST):
	waiting.append(process)
	elif runs[-1].state in (ProcessState.FORKED, ProcessState.RUNNING):
	running.append(process)
	elif runs[-1].state == ProcessState.SUCCESS:
	success.append(process)
	elif runs[-1].state == ProcessState.FAILED:
	failed.append(process)
	elif runs[-1].state == ProcessState.KILLED:
	killed.append(process)
	else:
	# TODO(wickman) Consider log.error instead of raising.
	raise self.UnexpectedState(
	"Unexpected ProcessHistoryState: %s" % state.processes[process].state)

	return dict(waiting=waiting, running=running, success=success, failed=failed, killed=killed)

	@Lockable.sync
	def main(self, type=None, offset=None, num=None):
	"""Return a set of information about tasks, optionally filtered

	Args:
	type = (all\|active\|finished\|None) [default: all]
	offset = offset into the list of task_ids [default: 0]
	num = number of results to return [default: 20]

	Tasks are sorted by interest:
	- active tasks are sorted by start time
	- finished tasks are sorted by completion time

	Returns:
	{
	tasks: [task_id_1, ..., task_id_N],
	type: query type,
	offset: next offset,
	num: next num
	}

	"""
	type = type or 'all'
	offset = offset or 0
	num = num or 20

	# Get a list of all ObservedTasks of requested type
	tasks = sorted((task for task in self._get_tasks_of_type(type).values()),
	key=attrgetter('mtime'), reverse=True)

	# Filter by requested offset + number of results
	end = num
	if offset < 0:
	offset = offset % len(tasks) if len(tasks) > abs(offset) else 0
	end += offset
	tasks = tasks[offset:end]

	def task_row(observed_task):
	"""Generate an output row for a Task"""
	task = self._task(observed_task.task_id)
	# tasks include those which could not be found properly and are hence empty {}
	if task:
	return dict(
	task_id=observed_task.task_id,
	name=task['name'],
	role=task['user'],
	launch_timestamp=task['launch_timestamp'],
	state=task['state'],
	state_timestamp=task['state_timestamp'],
	ports=task['ports'],
	**task['resource_consumption'])

	return dict(
	tasks=filter(None, map(task_row, tasks)),
	type=type,
	offset=offset,
	num=num,
	task_count=self.task_count()[type],
	)

	def _sample(self, task_id):
	if task_id not in self.active_tasks:
	sample = ProcessSample.empty().to_dict()
	sample['disk'] = 0
	else:
	resource_sample = self.active_tasks[task_id].resource_monitor.sample()[1]
	sample = resource_sample.process_sample.to_dict()
	sample['disk'] = resource_sample.disk_usage
	log.debug("Got sample for task %s: %s", task_id, sample)
	return sample

	@Lockable.sync
	def task_statuses(self, task_id):
	"""
	Return the sequence of task states.

	[(task_state [string], timestamp), ...]
	"""

	# Unknown task_id.
	if task_id not in self.all_tasks:
	return []

	task = self.all_tasks[task_id]
	if task is None:
	return []

	state = self.raw_state(task_id)
	if state is None or state.header is None:
	return []

	# Get the timestamp of the transition into the current state.
	return [
	(TaskState._VALUES_TO_NAMES.get(st.state, 'UNKNOWN'), st.timestamp_ms / 1000)
	for st in state.statuses]

	@Lockable.sync
	def tasks(self, task_ids):
	"""
	Return information about an iterable of tasks [task_id1, task_id2, ...]
	in the following form.

	{
	task_id1 : self._task(task_id1),
	task_id2 : self._task(task_id2),
	...
	}
	"""
	res = {}
	for task_id in task_ids:
	d = self._task(task_id)
	task_struct = d.pop('task_struct')
	d['task'] = task_struct.get()
	res[task_id] = d
	return res

	@Lockable.sync
	def _task(self, task_id):
	"""
	Return composite information about a particular task task_id, given the below
	schema.

	{
	task_id: string,
	name: string,
	user: string,
	launch_timestamp: seconds,
	state: string [ACTIVE, SUCCESS, FAILED]
	ports: { name1: 'url', name2: 'url2' }
	resource_consumption: { cpu:, ram:, disk: }
	processes: { -> names only
	waiting: [],
	running: [],
	success: [],
	failed: []
	}
	}
	"""
	# Unknown task_id.
	if task_id not in self.all_tasks:
	return {}

	task = self.all_tasks[task_id].task
	if task is None:
	# TODO(wickman) Can this happen?
	log.error('Could not find task: %s', task_id)
	return {}

	state = self.raw_state(task_id)
	if state is None or state.header is None:
	# TODO(wickman) Can this happen?
	return {}

	# Get the timestamp of the transition into the current state.
	current_state = state.statuses[-1].state
	last_state = state.statuses[0]
	state_timestamp = 0
	for status in state.statuses:
	if status.state == current_state and last_state != current_state:
	state_timestamp = status.timestamp_ms / 1000
	last_state = status.state

	return dict(
	task_id=task_id,
	name=task.name().get(),
	launch_timestamp=state.statuses[0].timestamp_ms / 1000,
	state=TaskState._VALUES_TO_NAMES[state.statuses[-1].state],
	state_timestamp=state_timestamp,
	user=state.header.user,
	resource_consumption=self._sample(task_id),
	ports=state.header.ports,
	processes=self._task_processes(task_id),
	task_struct=task,
	)

	@Lockable.sync
	def _get_process_resource_consumption(self, task_id, process_name):
	if task_id not in self.active_tasks:
	return ProcessSample.empty().to_dict()
	sample = self.active_tasks[task_id].resource_monitor.sample_by_process(process_name).to_dict()
	log.debug('Resource consumption (%s, %s) => %s', task_id, process_name, sample)
	return sample

	@Lockable.sync
	def _get_process_tuple(self, history, run):
	"""
	Return the basic description of a process run if it exists, otherwise
	an empty dictionary.

	{
	process_name: string
	process_run: int
	(optional) return_code: int
	state: string [WAITING, FORKED, RUNNING, SUCCESS, KILLED, FAILED, LOST]
	(optional) start_time: seconds from epoch
	(optional) stop_time: seconds from epoch
	}
	"""
	if len(history) == 0:
	return {}
	if run >= len(history):
	return {}
	else:
	process_run = history[run]
	run = run % len(history)
	d = dict(
	process_name=process_run.process,
	process_run=run,
	state=ProcessState._VALUES_TO_NAMES[process_run.state],
	)
	if process_run.start_time:
	d.update(start_time=process_run.start_time)
	if process_run.stop_time:
	d.update(stop_time=process_run.stop_time)
	if process_run.return_code:
	d.update(return_code=process_run.return_code)
	return d

	@Lockable.sync
	def process(self, task_id, process, run=None):
	"""
	Returns a process run, where the schema is given below:

	{
	process_name: string
	process_run: int
	used: { cpu: float, ram: int bytes, disk: int bytes }
	start_time: (time since epoch in millis (utc))
	stop_time: (time since epoch in millis (utc))
	state: string [WAITING, FORKED, RUNNING, SUCCESS, KILLED, FAILED, LOST]
	}

	If run is None, return the latest run.
	"""
	state = self.raw_state(task_id)
	if state is None or state.header is None:
	return {}
	if process not in state.processes:
	return {}
	history = state.processes[process]
	run = int(run) if run is not None else -1
	tup = self._get_process_tuple(history, run)
	if not tup:
	return {}
	if tup.get('state') == 'RUNNING':
	tup.update(used=self._get_process_resource_consumption(task_id, process))
	return tup

	@Lockable.sync
	def _processes(self, task_id):
	"""
	Return
	{
	process1: { ... }
	process2: { ... }
	...
	processN: { ... }
	}

	where processK is the latest run of processK and in the schema as
	defined by process().
	"""

	if task_id not in self.all_tasks:
	return {}
	state = self.raw_state(task_id)
	if state is None or state.header is None:
	return {}

	processes = self._task_processes(task_id)
	d = dict()
	for process_type in processes:
	for process_name in processes[process_type]:
	d[process_name] = self.process(task_id, process_name)
	return d

	@Lockable.sync
	def processes(self, task_ids):
	"""
	Given a list of task_ids, returns a map of task_id => processes, where processes
	is defined by the schema in _processes.
	"""
	if not isinstance(task_ids, (list, tuple)):
	return {}
	return dict((task_id, self._processes(task_id)) for task_id in task_ids)

	@Lockable.sync
	def get_run_number(self, runner_state, process, run=None):
	if runner_state is not None and runner_state.processes is not None:
	run = run if run is not None else -1
	if run < len(runner_state.processes[process]):
	if len(runner_state.processes[process]) > 0:
	return run % len(runner_state.processes[process])

	@Lockable.sync
	def logs(self, task_id, process, run=None):
	"""
	Given a task_id and a process and (optional) run number, return a dict:
	{
	stderr: [dir, filename]
	stdout: [dir, filename]
	}

	If the run number is unspecified, uses the latest run.

	TODO(wickman) Just return the filenames directly?
	"""
	runner_state = self.raw_state(task_id)
	if runner_state is None or runner_state.header is None:
	return {}
	run = self.get_run_number(runner_state, process, run)
	if run is None:
	return {}
	observed_task = self.all_tasks.get(task_id, None)
	if not observed_task:
	return {}

	log_path = TaskPath(
	root=observed_task.root,
	task_id=task_id,
	process=process,
	run=run,
	log_dir=runner_state.header.log_dir,
	).getpath('process_logdir')

	return dict(
	stdout=[log_path, 'stdout'],
	stderr=[log_path, 'stderr']
	)

	@staticmethod
	def _sanitize_path(base_path, relpath):
	"""
	Attempts to sanitize a path through path normalization, also making sure
	that the relative path is contained inside of base_path.
	"""
	if relpath is None:
	relpath = "."
	normalized_base = os.path.realpath(base_path)
	normalized = os.path.realpath(os.path.join(base_path, relpath))
	if normalized.startswith(normalized_base):
	return (normalized_base, os.path.relpath(normalized, normalized_base))
	return (None, None)

	@Lockable.sync
	def valid_file(self, task_id, path):
	"""
	Like valid_path, but also verify the given path is a file
	"""
	chroot, path = self.valid_path(task_id, path)
	if chroot and path and os.path.isfile(os.path.join(chroot, path)):
	return chroot, path
	return None, None

	@Lockable.sync
	def valid_path(self, task_id, path):
	"""
	Given a task_id and a path within that task_id's sandbox, verify:
	(1) it's actually in the sandbox and not outside
	(2) it's a valid, existing path
	Returns chroot and the pathname relative to that chroot.
	"""
	runner_state = self.raw_state(task_id)
	if runner_state is None or runner_state.header is None:
	return None, None
	try:
	chroot = runner_state.header.sandbox
	except AttributeError:
	return None, None
	chroot, path = self._sanitize_path(chroot, path)
	if chroot and path and os.path.exists(os.path.join(chroot, path)):
	return chroot, path
	return None, None

	@Lockable.sync
	def files(self, task_id, path=None):
	"""
	Returns dictionary
	{
	task_id: task_id
	chroot: absolute directory on machine
	path: sanitized relative path w.r.t. chroot
	dirs: list of directories
	files: list of files
	}
	"""
	# TODO(jon): DEPRECATED: most of the necessary logic is handled directly in the templates.
	# Also, global s/chroot/sandbox/?
	empty = dict(task_id=task_id, chroot=None, path=None, dirs=None, files=None)
	path = path if path is not None else '.'
	runner_state = self.raw_state(task_id)
	if runner_state is None:
	return empty
	try:
	chroot = runner_state.header.sandbox
	except AttributeError:
	return empty
	if chroot is None: # chroot-less job
	return empty
	chroot, path = self._sanitize_path(chroot, path)
	if (chroot is None or path is None
	or not os.path.isdir(os.path.join(chroot, path))):
	return empty
	names = os.listdir(os.path.join(chroot, path))
	dirs, files = [], []
	for name in names:
	if os.path.isdir(os.path.join(chroot, path, name)):
	dirs.append(name)
	else:
	files.append(name)
	return dict(
	task_id=task_id,
	chroot=chroot,
	path=path,
	dirs=dirs,
	files=files
	)