Source code for gluon.scheduler

#!/usr/bin/env python
# -*- coding: utf-8 -*-
| This file is part of the web2py Web Framework
| Copyrighted by Massimo Di Pierro <>
| License: LGPLv3 (

Background processes made simple

import os
import time
import multiprocessing
import sys
import threading
import traceback
import signal
import socket
import datetime
import logging
import optparse
import tempfile
import types
import Queue
from gluon import DAL, Field, IS_NOT_EMPTY, IS_IN_SET, IS_NOT_IN_DB
from gluon import IS_INT_IN_RANGE, IS_DATETIME, IS_IN_DB
from gluon.utils import web2py_uuid
from import Storage

USAGE = """
## Example

For any existing app

Create File: app/models/ ======
from gluon.scheduler import Scheduler

def demo1(*args,**vars):
    print 'you passed args=%s and vars=%s' % (args, vars)
    return 'done!'

def demo2():

scheduler = Scheduler(db,dict(demo1=demo1,demo2=demo2))
## run worker nodes with:

   cd web2py
   python -K myapp
   python gluon/ -u sqlite://storage.sqlite \
                             -f applications/myapp/databases/ \
(-h for info)
python -h

## schedule jobs using

## monitor scheduled jobs>0

## view completed jobs>0

## view workers>0

## To install the scheduler as a permanent daemon on Linux (w/ Upstart), put
## the following into /etc/init/web2py-scheduler.conf:
## (This assumes your web2py instance is installed in <user>'s home directory,
## running as <user>, with app <myapp>, on network interface eth0.)

description "web2py task scheduler"
start on (local-filesystems and net-device-up IFACE=eth0)
stop on shutdown
respawn limit 8 60 # Give up if restart occurs 8 times in 60 seconds.
exec sudo -u <user> python /home/<user>/web2py/ -K <myapp>

## You can then start/stop/restart/check status of the daemon with:
sudo start web2py-scheduler
sudo stop web2py-scheduler
sudo restart web2py-scheduler
sudo status web2py-scheduler

path = os.getcwd()

if 'WEB2PY_PATH' not in os.environ:
    os.environ['WEB2PY_PATH'] = path

    # try external module
    from simplejson import loads, dumps
except ImportError:
        # try stdlib (Python >= 2.6)
        from json import loads, dumps
        # fallback to pure-Python module
        from gluon.contrib.simplejson import loads, dumps

IDENTIFIER = "%s#%s" % (socket.gethostname(), os.getpid())

logger = logging.getLogger('web2py.scheduler.%s' % IDENTIFIER)

CLEAROUT = '!clear!'

CALLABLETYPES = (types.LambdaType, types.FunctionType,
                 types.MethodType, types.BuiltinMethodType)

[docs]class Task(object): """Defines a "task" object that gets passed from the main thread to the executor's one """ def __init__(self, app, function, timeout, args='[]', vars='{}', **kwargs): logger.debug(' new task allocated: %s.%s', app, function) = app self.function = function self.timeout = timeout self.args = args # json self.vars = vars # json self.__dict__.update(kwargs) def __str__(self): return '<Task: %s>' % self.function
[docs]class TaskReport(object): """Defines a "task report" object that gets passed from the executor's thread to the main one """ def __init__(self, status, result=None, output=None, tb=None): logger.debug(' new task report: %s', status) if tb: logger.debug(' traceback: %s', tb) else: logger.debug(' result: %s', result) self.status = status self.result = result self.output = output self.tb = tb def __str__(self): return '<TaskReport: %s>' % self.status
[docs]class JobGraph(object): """Experimental: dependencies amongs tasks""" def __init__(self, db, job_name): self.job_name = job_name or 'job_0' self.db = db
[docs] def add_deps(self, task_parent, task_child): """Create a dependency between task_parent and task_child.""" self.db.scheduler_task_deps.insert(task_parent=task_parent, task_child=task_child, job_name=self.job_name)
[docs] def validate(self, job_name=None): """Validate if all tasks job_name can be completed. Checks if there are no mutual dependencies among tasks. Commits at the end if successfull, or it rollbacks the entire transaction. Handle with care! """ db = self.db sd = db.scheduler_task_deps if job_name: q = sd.job_name == job_name else: q = > 0 edges = db(q).select() nested_dict = {} for row in edges: k = row.task_parent if k in nested_dict: nested_dict[k].add(row.task_child) else: nested_dict[k] = set((row.task_child,)) try: rtn = [] for k, v in nested_dict.items(): v.discard(k) # Ignore self dependencies extra_items_in_deps = reduce(set.union, nested_dict.values()) - set(nested_dict.keys()) nested_dict.update(dict((item, set()) for item in extra_items_in_deps)) while True: ordered = set(item for item, dep in nested_dict.items() if not dep) if not ordered: break rtn.append(ordered) nested_dict = dict( (item, (dep - ordered)) for item, dep in nested_dict.items() if item not in ordered ) assert not nested_dict, "A cyclic dependency exists amongst %r" % nested_dict db.commit() return rtn except: db.rollback() return None
# the two functions below deal with simplejson decoding as unicode, esp for the dict decode # and subsequent usage as function Keyword arguments unicode variable names won't work! # borrowed from def _decode_list(lst): newlist = [] for i in lst: if isinstance(i, unicode): i = i.encode('utf-8') elif isinstance(i, list): i = _decode_list(i) newlist.append(i) return newlist def _decode_dict(dct): newdict = {} for k, v in dct.iteritems(): if isinstance(k, unicode): k = k.encode('utf-8') if isinstance(v, unicode): v = v.encode('utf-8') elif isinstance(v, list): v = _decode_list(v) newdict[k] = v return newdict
[docs]def executor(queue, task, out): """The function used to execute tasks in the background process.""" logger.debug(' task started') class LogOutput(object): """Facility to log output at intervals.""" def __init__(self, out_queue): self.out_queue = out_queue self.stdout = sys.stdout sys.stdout = self def __del__(self): sys.stdout = self.stdout def flush(self): pass def write(self, data): self.out_queue.put(data) W2P_TASK = Storage({ 'id': task.task_id, 'uuid': task.uuid, 'run_id': task.run_id }) stdout = LogOutput(out) try: if os.chdir(os.environ['WEB2PY_PATH']) from import env, parse_path_info from gluon import current level = logging.getLogger().getEffectiveLevel() logging.getLogger().setLevel(logging.WARN) # Get controller-specific subdirectory if is of # form 'app/controller' (a, c, f) = parse_path_info( _env = env(a=a, c=c, import_models=True) logging.getLogger().setLevel(level) f = task.function functions = current._scheduler.tasks if not functions: # look into env _function = _env.get(f) else: _function = functions.get(f) if not isinstance(_function, CALLABLETYPES): raise NameError( "name '%s' not found in scheduler's environment" % f) # Inject W2P_TASK into environment _env.update({'W2P_TASK': W2P_TASK}) # Inject W2P_TASK into current from gluon import current current.W2P_TASK = W2P_TASK globals().update(_env) args = _decode_list(loads(task.args)) vars = loads(task.vars, object_hook=_decode_dict) result = dumps(_function(*args, **vars)) else: # for testing purpose only result = eval(task.function)( *loads(task.args, object_hook=_decode_dict), **loads(task.vars, object_hook=_decode_dict)) if len(result) >= 1024: fd, temp_path = tempfile.mkstemp(suffix='.w2p_sched') with os.fdopen(fd, 'w') as f: f.write(result) result = 'w2p_special:%s' % temp_path queue.put(TaskReport('COMPLETED', result=result)) except BaseException, e: tb = traceback.format_exc() queue.put(TaskReport('FAILED', tb=tb)) del stdout
[docs]class MetaScheduler(threading.Thread): """Base class documenting scheduler's base methods""" def __init__(self): threading.Thread.__init__(self) self.process = None # the background process self.have_heartbeat = True # set to False to kill self.empty_runs = 0
[docs] def async(self, task): """Start the background process. Args: task : a `Task` object Returns: tuple: containing:: ('ok',result,output) ('error',exception,None) ('timeout',None,None) ('terminated',None,None) """ db = self.db sr = db.scheduler_run out = multiprocessing.Queue() queue = multiprocessing.Queue(maxsize=1) p = multiprocessing.Process(target=executor, args=(queue, task, out)) self.process = p logger.debug(' task starting') p.start() task_output = "" tout = "" try: if task.sync_output > 0: run_timeout = task.sync_output else: run_timeout = task.timeout start = time.time() while p.is_alive() and (not task.timeout or time.time() - start < task.timeout): if tout: try: logger.debug(' partial output saved') db( == task.run_id).update(run_output=task_output) db.commit() except: pass p.join(timeout=run_timeout) tout = "" while not out.empty(): tout += out.get() if tout: logger.debug(' partial output: "%s"' % str(tout)) if CLEAROUT in tout: task_output = tout[ tout.rfind(CLEAROUT) + len(CLEAROUT):] else: task_output += tout except: p.terminate() p.join() logger.debug(' task stopped by general exception') tr = TaskReport(STOPPED) else: if p.is_alive(): p.terminate() logger.debug(' task timeout') try: # we try to get a traceback here tr = queue.get(timeout=2) tr.status = TIMEOUT tr.output = task_output except Queue.Empty: tr = TaskReport(TIMEOUT) elif queue.empty(): logger.debug(' task stopped') tr = TaskReport(STOPPED) else: logger.debug(' task completed or failed') tr = queue.get() result = tr.result if result and result.startswith('w2p_special'): temp_path = result.replace('w2p_special:', '', 1) with open(temp_path) as f: tr.result = os.unlink(temp_path) tr.output = task_output return tr
[docs] def die(self): """Forces termination of the worker process along with any running task"""'die!') self.have_heartbeat = False self.terminate_process()
[docs] def give_up(self): """Waits for any running task to be executed, then exits the worker process"""'Giving up as soon as possible!') self.have_heartbeat = False
[docs] def terminate_process(self): """Terminates any running tasks (internal use only)""" try: self.process.terminate() except: pass # no process to terminate
[docs] def run(self): """This is executed by the main thread to send heartbeats""" counter = 0 while self.have_heartbeat: self.send_heartbeat(counter) counter += 1
[docs] def start_heartbeats(self): self.start()
[docs] def send_heartbeat(self, counter): raise NotImplementedError
[docs] def pop_task(self): """Fetches a task ready to be executed""" raise NotImplementedError
[docs] def report_task(self, task, task_report): """Creates a task report""" raise NotImplementedError
[docs] def sleep(self): raise NotImplementedError
[docs] def loop(self): """Main loop, fetching tasks and starting executor's background processes""" raise NotImplementedError
[docs]class TYPE(object): """ Validator that checks whether field is valid json and validates its type. Used for `args` and `vars` of the scheduler_task table """ def __init__(self, myclass=list, parse=False): self.myclass = myclass self.parse = parse def __call__(self, value): from gluon import current try: obj = loads(value) except: return (value, current.T('invalid json')) else: if isinstance(obj, self.myclass): if self.parse: return (obj, None) else: return (value, None) else: return (value, current.T('Not of type: %s') % self.myclass)
[docs]class Scheduler(MetaScheduler): """Scheduler object Args: db: DAL connection where Scheduler will create its tables tasks(dict): either a dict containing name-->func or None. If None, functions will be searched in the environment migrate(bool): turn migration on/off for the Scheduler's tables worker_name(str): force worker_name to identify each process. Leave it to None to autoassign a name (hostname#pid) group_names(list): process tasks belonging to this group defaults to ['main'] if nothing gets passed heartbeat(int): how many seconds the worker sleeps between one execution and the following one. Indirectly sets how many seconds will pass between checks for new tasks max_empty_runs(int): how many loops are allowed to pass without processing any tasks before exiting the process. 0 to keep always the process alive discard_results(bool): Scheduler stores executions's details into the scheduler_run table. By default, only if there is a result the details are kept. Turning this to True means discarding results even for tasks that return something utc_time(bool): do all datetime calculations assuming UTC as the timezone. Remember to pass `start_time` and `stop_time` to tasks accordingly """ def __init__(self, db, tasks=None, migrate=True, worker_name=None, group_names=None, heartbeat=HEARTBEAT, max_empty_runs=0, discard_results=False, utc_time=False): MetaScheduler.__init__(self) self.db = db self.db_thread = None self.tasks = tasks self.group_names = group_names or ['main'] self.heartbeat = heartbeat self.worker_name = worker_name or IDENTIFIER self.max_empty_runs = max_empty_runs self.discard_results = discard_results self.is_a_ticker = False self.do_assign_tasks = False self.greedy = False self.utc_time = utc_time self.w_stats = Storage( dict( status=RUNNING, sleep=heartbeat, total=0, errors=0, empty_runs=0, queue=0, distribution=None, workers=0) ) # dict holding statistics from gluon import current current._scheduler = self self.define_tables(db, migrate=migrate) def __get_migrate(self, tablename, migrate=True): if migrate is False: return False elif migrate is True: return True elif isinstance(migrate, str): return "%s%s.table" % (migrate, tablename) return True
[docs] def now(self): """Shortcut that fetches current time based on UTC preferences.""" return self.utc_time and datetime.datetime.utcnow() or
[docs] def set_requirements(self, scheduler_task): """Called to set defaults for lazy_tables connections.""" from gluon import current if hasattr(current, 'request'): scheduler_task.application_name.default = '%s/%s' % ( current.request.application, current.request.controller )
[docs] def define_tables(self, db, migrate): """Define Scheduler tables structure.""" from pydal.base import DEFAULT logger.debug('defining tables (migrate=%s)', migrate) now = db.define_table( 'scheduler_task', Field('application_name', requires=IS_NOT_EMPTY(), default=None, writable=False), Field('task_name', default=None), Field('group_name', default='main'), Field('status', requires=IS_IN_SET(TASK_STATUS), default=QUEUED, writable=False), Field('function_name', requires=IS_IN_SET(sorted(self.tasks.keys())) if self.tasks else DEFAULT), Field('uuid', length=255, requires=IS_NOT_IN_DB(db, 'scheduler_task.uuid'), unique=True, default=web2py_uuid), Field('args', 'text', default='[]', requires=TYPE(list)), Field('vars', 'text', default='{}', requires=TYPE(dict)), Field('enabled', 'boolean', default=True), Field('start_time', 'datetime', default=now, requires=IS_DATETIME()), Field('next_run_time', 'datetime', default=now), Field('stop_time', 'datetime'), Field('repeats', 'integer', default=1, comment="0=unlimited", requires=IS_INT_IN_RANGE(0, None)), Field('retry_failed', 'integer', default=0, comment="-1=unlimited", requires=IS_INT_IN_RANGE(-1, None)), Field('period', 'integer', default=60, comment='seconds', requires=IS_INT_IN_RANGE(0, None)), Field('prevent_drift', 'boolean', default=False, comment='Cron-like start_times between runs'), Field('timeout', 'integer', default=60, comment='seconds', requires=IS_INT_IN_RANGE(1, None)), Field('sync_output', 'integer', default=0, comment="update output every n sec: 0=never", requires=IS_INT_IN_RANGE(0, None)), Field('times_run', 'integer', default=0, writable=False), Field('times_failed', 'integer', default=0, writable=False), Field('last_run_time', 'datetime', writable=False, readable=False), Field('assigned_worker_name', default='', writable=False), on_define=self.set_requirements, migrate=self.__get_migrate('scheduler_task', migrate), format='%(task_name)s') db.define_table( 'scheduler_run', Field('task_id', 'reference scheduler_task'), Field('status', requires=IS_IN_SET(RUN_STATUS)), Field('start_time', 'datetime'), Field('stop_time', 'datetime'), Field('run_output', 'text'), Field('run_result', 'text'), Field('traceback', 'text'), Field('worker_name', default=self.worker_name), migrate=self.__get_migrate('scheduler_run', migrate) ) db.define_table( 'scheduler_worker', Field('worker_name', length=255, unique=True), Field('first_heartbeat', 'datetime'), Field('last_heartbeat', 'datetime'), Field('status', requires=IS_IN_SET(WORKER_STATUS)), Field('is_ticker', 'boolean', default=False, writable=False), Field('group_names', 'list:string', default=self.group_names), Field('worker_stats', 'json'), migrate=self.__get_migrate('scheduler_worker', migrate) ) db.define_table( 'scheduler_task_deps', Field('job_name', default='job_0'), Field('task_parent', 'integer', requires=IS_IN_DB(db, '', '%(task_name)s') ), Field('task_child', 'reference scheduler_task'), Field('can_visit', 'boolean', default=False), migrate=self.__get_migrate('scheduler_task_deps', migrate) ) if migrate is not False: db.commit()
[docs] @staticmethod def total_seconds(td): """Backport for py2.6.""" if hasattr(td, 'total_seconds'): return td.total_seconds() else: return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10 ** 6) / 10.0 ** 6
[docs] def loop(self, worker_name=None): """Main loop. This works basically as a neverending loop that: - checks if the worker is ready to process tasks (is not DISABLED) - pops a task from the queue - if there is a task: - spawns the executor background process - waits for the process to be finished - sleeps `heartbeat` seconds - if there is not a task: - checks for max_empty_runs - sleeps `heartbeat` seconds """ signal.signal(signal.SIGTERM, lambda signum, stack_frame: sys.exit(1)) try: self.start_heartbeats() while True and self.have_heartbeat: if self.w_stats.status == DISABLED: logger.debug('Someone stopped me, sleeping until better' ' times come (%s)', self.w_stats.sleep) self.sleep() continue logger.debug('looping...') task = self.wrapped_pop_task() if task: self.w_stats.empty_runs = 0 self.w_stats.status = RUNNING += 1 self.wrapped_report_task(task, self.async(task)) if not self.w_stats.status == DISABLED: self.w_stats.status = ACTIVE else: self.w_stats.empty_runs += 1 logger.debug('sleeping...') if self.max_empty_runs != 0: logger.debug('empty runs %s/%s', self.w_stats.empty_runs, self.max_empty_runs) if self.w_stats.empty_runs >= self.max_empty_runs: 'empty runs limit reached, killing myself') self.die() self.sleep() except (KeyboardInterrupt, SystemExit):'catched') self.die()
[docs] def wrapped_assign_tasks(self, db): """Commodity function to call `assign_tasks` and trap exceptions. If an exception is raised, assume it happened because of database contention and retries `assign_task` after 0.5 seconds """ logger.debug('Assigning tasks...') db.commit() # db.commit() only for Mysql x = 0 while x < 10: try: self.assign_tasks(db) db.commit() logger.debug('Tasks assigned...') break except: self.w_stats.errors += 1 db.rollback() logger.error('TICKER: error assigning tasks (%s)', x) x += 1 time.sleep(0.5)
[docs] def wrapped_pop_task(self): """Commodity function to call `pop_task` and trap exceptions. If an exception is raised, assume it happened because of database contention and retries `pop_task` after 0.5 seconds """ db = self.db db.commit() # another nifty db.commit() only for Mysql x = 0 while x < 10: try: rtn = self.pop_task(db) return rtn break except: self.w_stats.errors += 1 db.rollback() logger.error(' error popping tasks') x += 1 time.sleep(0.5)
[docs] def pop_task(self, db): """Grab a task ready to be executed from the queue.""" now = st = self.db.scheduler_task if self.is_a_ticker and self.do_assign_tasks: # I'm a ticker, and 5 loops passed without reassigning tasks, # let's do that and loop again self.wrapped_assign_tasks(db) return None # ready to process something grabbed = db( (st.assigned_worker_name == self.worker_name) & (st.status == ASSIGNED) ) task =, 1), orderby=st.next_run_time).first() if task: task.update_record(status=RUNNING, last_run_time=now) # noone will touch my task! db.commit() logger.debug(' work to do %s', else: if self.is_a_ticker and self.greedy: # there are other tasks ready to be assigned'TICKER: greedy loop') self.wrapped_assign_tasks(db) else:'nothing to do') return None times_run = task.times_run + 1 if not task.prevent_drift: next_run_time = task.last_run_time + datetime.timedelta( seconds=task.period ) else: # calc next_run_time based on available slots # see #1191 next_run_time = task.start_time secondspassed = self.total_seconds(now - next_run_time) steps = secondspassed // task.period + 1 next_run_time += datetime.timedelta(seconds=task.period * steps) if times_run < task.repeats or task.repeats == 0: # need to run (repeating task) run_again = True else: # no need to run again run_again = False run_id = 0 while True and not self.discard_results: logger.debug(' new scheduler_run record') try: run_id = db.scheduler_run.insert(, status=RUNNING, start_time=now, worker_name=self.worker_name) db.commit() break except: time.sleep(0.5) db.rollback()'new task %(id)s "%(task_name)s"' ' %(application_name)s.%(function_name)s' % task) return Task( app=task.application_name, function=task.function_name, timeout=task.timeout, args=task.args, # in json vars=task.vars, # in json, run_id=run_id, run_again=run_again, next_run_time=next_run_time, times_run=times_run, stop_time=task.stop_time, retry_failed=task.retry_failed, times_failed=task.times_failed, sync_output=task.sync_output, uuid=task.uuid)
[docs] def wrapped_report_task(self, task, task_report): """Commodity function to call `report_task` and trap exceptions. If an exception is raised, assume it happened because of database contention and retries `pop_task` after 0.5 seconds """ db = self.db while True: try: self.report_task(task, task_report) db.commit() break except: self.w_stats.errors += 1 db.rollback() logger.error(' error storing result') time.sleep(0.5)
[docs] def report_task(self, task, task_report): """Take care of storing the result according to preferences. Deals with logic for repeating tasks. """ db = self.db now = st = db.scheduler_task sr = db.scheduler_run if not self.discard_results: if task_report.result != 'null' or task_report.tb: # result is 'null' as a string if task completed # if it's stopped it's None as NoneType, so we record # the STOPPED "run" anyway logger.debug(' recording task report in db (%s)', task_report.status) db( == task.run_id).update( status=task_report.status, stop_time=now, run_result=task_report.result, run_output=task_report.output, traceback=task_report.tb) else: logger.debug(' deleting task report in db because of no result') db( == task.run_id).delete() # if there is a stop_time and the following run would exceed it is_expired = (task.stop_time and task.next_run_time > task.stop_time and True or False) status = (task.run_again and is_expired and EXPIRED or task.run_again and not is_expired and QUEUED or COMPLETED) if task_report.status == COMPLETED: d = dict(status=status, next_run_time=task.next_run_time, times_run=task.times_run, times_failed=0 ) db( == task.task_id).update(**d) if status == COMPLETED: self.update_dependencies(db, task.task_id) else: st_mapping = {'FAILED': 'FAILED', 'TIMEOUT': 'TIMEOUT', 'STOPPED': 'FAILED'}[task_report.status] status = (task.retry_failed and task.times_failed < task.retry_failed and QUEUED or task.retry_failed == -1 and QUEUED or st_mapping) db( == task.task_id).update( times_failed=st.times_failed + 1, next_run_time=task.next_run_time, status=status )'task completed (%s)', task_report.status)
[docs] def update_dependencies(self, db, task_id): """Unblock execution paths for Jobs.""" db(db.scheduler_task_deps.task_child == task_id).update(can_visit=True)
[docs] def adj_hibernation(self): """Used to increase the "sleep" interval for DISABLED workers.""" if self.w_stats.status == DISABLED: wk_st = self.w_stats.sleep hibernation = wk_st + HEARTBEAT if wk_st < MAXHIBERNATION else MAXHIBERNATION self.w_stats.sleep = hibernation
[docs] def send_heartbeat(self, counter): """Coordination among available workers. It: - sends the heartbeat - elects a ticker among available workers (the only process that effectively dispatch tasks to workers) - deals with worker's statuses - does "housecleaning" for dead workers - triggers tasks assignment to workers """ if not self.db_thread: logger.debug('thread building own DAL object') self.db_thread = DAL( self.db._uri, folder=self.db._adapter.folder) self.define_tables(self.db_thread, migrate=False) try: db = self.db_thread sw, st = db.scheduler_worker, db.scheduler_task now = # record heartbeat mybackedstatus = db(sw.worker_name == self.worker_name).select().first() if not mybackedstatus: sw.insert(status=ACTIVE, worker_name=self.worker_name, first_heartbeat=now, last_heartbeat=now, group_names=self.group_names, worker_stats=self.w_stats) self.w_stats.status = ACTIVE self.w_stats.sleep = self.heartbeat mybackedstatus = ACTIVE else: mybackedstatus = mybackedstatus.status if mybackedstatus == DISABLED: # keep sleeping self.w_stats.status = DISABLED logger.debug('........recording heartbeat (%s)', self.w_stats.status) db(sw.worker_name == self.worker_name).update( last_heartbeat=now, worker_stats=self.w_stats) elif mybackedstatus == TERMINATE: self.w_stats.status = TERMINATE logger.debug("Waiting to terminate the current task") self.give_up() elif mybackedstatus == KILL: self.w_stats.status = KILL self.die() return else: if mybackedstatus == STOP_TASK:'Asked to kill the current task') self.terminate_process() logger.debug('........recording heartbeat (%s)', self.w_stats.status) db(sw.worker_name == self.worker_name).update( last_heartbeat=now, status=ACTIVE, worker_stats=self.w_stats) self.w_stats.sleep = self.heartbeat # re-activating the process if self.w_stats.status != RUNNING: self.w_stats.status = ACTIVE self.do_assign_tasks = False if counter % 5 == 0 or mybackedstatus == PICK: try: # delete dead workers expiration = now - datetime.timedelta( seconds=self.heartbeat * 3) departure = now - datetime.timedelta( seconds=self.heartbeat * 3 * 15) logger.debug( ' freeing workers that have not sent heartbeat') dead_workers = db( ((sw.last_heartbeat < expiration) & (sw.status == ACTIVE)) | ((sw.last_heartbeat < departure) & (sw.status != ACTIVE)) ) dead_workers_name = dead_workers._select(sw.worker_name) db( (st.assigned_worker_name.belongs(dead_workers_name)) & (st.status == RUNNING) ).update(assigned_worker_name='', status=QUEUED) dead_workers.delete() try: self.is_a_ticker = self.being_a_ticker() except: logger.error('Error coordinating TICKER') if self.w_stats.status == ACTIVE: self.do_assign_tasks = True except: logger.error('Error cleaning up') db.commit() except: logger.error('Error retrieving status') db.rollback() self.adj_hibernation() self.sleep()
[docs] def being_a_ticker(self): """Elect a TICKER process that assigns tasks to available workers. Does its best to elect a worker that is not busy processing other tasks to allow a proper distribution of tasks among all active workers ASAP """ db = self.db_thread sw = db.scheduler_worker my_name = self.worker_name all_active = db( (sw.worker_name != my_name) & (sw.status == ACTIVE) ).select(sw.is_ticker, sw.worker_name) ticker = all_active.find(lambda row: row.is_ticker is True).first() not_busy = self.w_stats.status == ACTIVE if not ticker: # if no other tickers are around if not_busy: # only if I'm not busy db(sw.worker_name == my_name).update(is_ticker=True) db(sw.worker_name != my_name).update(is_ticker=False)"TICKER: I'm a ticker") else: # I'm busy if len(all_active) >= 1: # so I'll "downgrade" myself to a "poor worker" db(sw.worker_name == my_name).update(is_ticker=False) else: not_busy = True db.commit() return not_busy else: "%s is a ticker, I'm a poor worker" % ticker.worker_name) return False
[docs] def assign_tasks(self, db): """Assign task to workers, that can then pop them from the queue. Deals with group_name(s) logic, in order to assign linearly tasks to available workers for those groups """ sw, st, sd = db.scheduler_worker, db.scheduler_task, db.scheduler_task_deps now = all_workers = db(sw.status == ACTIVE).select() # build workers as dict of groups wkgroups = {} for w in all_workers: if w.worker_stats['status'] == 'RUNNING': continue group_names = w.group_names for gname in group_names: if gname not in wkgroups: wkgroups[gname] = dict( workers=[{'name': w.worker_name, 'c': 0}]) else: wkgroups[gname]['workers'].append( {'name': w.worker_name, 'c': 0}) # set queued tasks that expired between "runs" (i.e., you turned off # the scheduler): then it wasn't expired, but now it is db( (st.status.belongs((QUEUED, ASSIGNED))) & (st.stop_time < now) ).update(status=EXPIRED) # calculate dependencies deps_with_no_deps = db( (sd.can_visit == False) & (~sd.task_child.belongs( db(sd.can_visit == False)._select(sd.task_parent) ) ) )._select(sd.task_child) no_deps = db( (st.status.belongs((QUEUED, ASSIGNED))) & ( ( == None) | ( ) )._select(, distinct=True, left=sd.on( ( == sd.task_parent) & (sd.can_visit == False) ) ) all_available = db( (st.status.belongs((QUEUED, ASSIGNED))) & (st.next_run_time <= now) & (st.enabled == True) & ( ) limit = len(all_workers) * (50 / (len(wkgroups) or 1)) # if there are a moltitude of tasks, let's figure out a maximum of # tasks per worker. This can be further tuned with some added # intelligence (like esteeming how many tasks will a worker complete # before the ticker reassign them around, but the gain is quite small # 50 is a sweet spot also for fast tasks, with sane heartbeat values # NB: ticker reassign tasks every 5 cycles, so if a worker completes # its 50 tasks in less than heartbeat*5 seconds, # it won't pick new tasks until heartbeat*5 seconds pass. # If a worker is currently elaborating a long task, its tasks needs to # be reassigned to other workers # this shuffles up things a bit, in order to give a task equal chances # to be executed # let's freeze it up db.commit() x = 0 for group in wkgroups.keys(): tasks = all_available(st.group_name == group).select( limitby=(0, limit), orderby=st.next_run_time) # let's break up the queue evenly among workers for task in tasks: x += 1 gname = task.group_name ws = wkgroups.get(gname) if ws: counter = 0 myw = 0 for i, w in enumerate(ws['workers']): if w['c'] < counter: myw = i counter = w['c'] assigned_wn = wkgroups[gname]['workers'][myw]['name'] d = dict( status=ASSIGNED, assigned_worker_name=assigned_wn ) db( ( == & (st.status.belongs((QUEUED, ASSIGNED))) ).update(**d) wkgroups[gname]['workers'][myw]['c'] += 1 db.commit() # I didn't report tasks but I'm working nonetheless!!!! if x > 0: self.w_stats.empty_runs = 0 self.w_stats.queue = x self.w_stats.distribution = wkgroups self.w_stats.workers = len(all_workers) # I'll be greedy only if tasks assigned are equal to the limit # (meaning there could be others ready to be assigned) self.greedy = x >= limit'TICKER: workers are %s', len(all_workers))'TICKER: tasks are %s', x)
[docs] def sleep(self): """Calculate the number of seconds to sleep.""" time.sleep(self.w_stats.sleep)
# should only sleep until next available task
[docs] def set_worker_status(self, group_names=None, action=ACTIVE, exclude=None, limit=None, worker_name=None): """Internal function to set worker's status.""" ws = self.db.scheduler_worker if not group_names: group_names = self.group_names elif isinstance(group_names, str): group_names = [group_names] if worker_name: self.db(ws.worker_name == worker_name).update(status=action) return exclusion = exclude and exclude.append(action) or [action] if not limit: for group in group_names: self.db( (ws.group_names.contains(group)) & (~ws.status.belongs(exclusion)) ).update(status=action) else: for group in group_names: workers = self.db((ws.group_names.contains(group)) & (~ws.status.belongs(exclusion)) )._select(, limitby=(0, limit)) self.db(
[docs] def disable(self, group_names=None, limit=None, worker_name=None): """Set DISABLED on the workers processing `group_names` tasks. A DISABLED worker will be kept alive but it won't be able to process any waiting tasks, essentially putting it to sleep. By default, all group_names of Scheduler's instantation are selected """ self.set_worker_status( group_names=group_names, action=DISABLED, exclude=[DISABLED, KILL, TERMINATE], limit=limit)
[docs] def resume(self, group_names=None, limit=None, worker_name=None): """Wakes a worker up (it will be able to process queued tasks)""" self.set_worker_status( group_names=group_names, action=ACTIVE, exclude=[KILL, TERMINATE], limit=limit)
[docs] def terminate(self, group_names=None, limit=None, worker_name=None): """Sets TERMINATE as worker status. The worker will wait for any currently running tasks to be executed and then it will exit gracefully """ self.set_worker_status( group_names=group_names, action=TERMINATE, exclude=[KILL], limit=limit)
[docs] def kill(self, group_names=None, limit=None, worker_name=None): """Sets KILL as worker status. The worker will be killed even if it's processing a task.""" self.set_worker_status( group_names=group_names, action=KILL, limit=limit)
[docs] def queue_task(self, function, pargs=[], pvars={}, **kwargs): """ Queue tasks. This takes care of handling the validation of all parameters Args: function: the function (anything callable with a __name__) pargs: "raw" args to be passed to the function. Automatically jsonified. pvars: "raw" kwargs to be passed to the function. Automatically jsonified kwargs: all the parameters available (basically, every `scheduler_task` column). If args and vars are here, they should be jsonified already, and they will override pargs and pvars Returns: a dict just as a normal validate_and_insert(), plus a uuid key holding the uuid of the queued task. If validation is not passed ( i.e. some parameters are invalid) both id and uuid will be None, and you'll get an "error" dict holding the errors found. """ if hasattr(function, '__name__'): function = function.__name__ targs = 'args' in kwargs and kwargs.pop('args') or dumps(pargs) tvars = 'vars' in kwargs and kwargs.pop('vars') or dumps(pvars) tuuid = 'uuid' in kwargs and kwargs.pop('uuid') or web2py_uuid() tname = 'task_name' in kwargs and kwargs.pop('task_name') or function immediate = 'immediate' in kwargs and kwargs.pop('immediate') or None rtn = self.db.scheduler_task.validate_and_insert( function_name=function, task_name=tname, args=targs, vars=tvars, uuid=tuuid, **kwargs) if not rtn.errors: rtn.uuid = tuuid if immediate: self.db( (self.db.scheduler_worker.is_ticker == True) ).update(status=PICK) else: rtn.uuid = None return rtn
[docs] def task_status(self, ref, output=False): """ Retrieves task status and optionally the result of the task Args: ref: can be - an integer : lookup will be done by - a string : lookup will be done by scheduler_task.uuid - a `Query` : lookup as you wish, e.g. :: db.scheduler_task.task_name == 'test1' output(bool): if `True`, fetch also the scheduler_run record Returns: a single Row object, for the last queued task. If output == True, returns also the last scheduler_run record. The scheduler_run record is fetched by a left join, so it can have all fields == None """ from pydal.objects import Query sr, st = self.db.scheduler_run, self.db.scheduler_task if isinstance(ref, (int, long)): q = == ref elif isinstance(ref, str): q = st.uuid == ref elif isinstance(ref, Query): q = ref else: raise SyntaxError( "You can retrieve results only by id, uuid or Query") fields = [st.ALL] left = False orderby = if output: fields = st.ALL, sr.ALL left = sr.on(sr.task_id == orderby = | row = self.db(q).select( *fields, **dict(orderby=orderby, left=left, limitby=(0, 1)) ).first() if row and output: row.result = row.scheduler_run.run_result and \ loads(row.scheduler_run.run_result, object_hook=_decode_dict) or None return row
[docs] def stop_task(self, ref): """Shortcut for task termination. If the task is RUNNING it will terminate it, meaning that status will be set as FAILED. If the task is QUEUED, its stop_time will be set as to "now", the enabled flag will be set to False, and the status to STOPPED Args: ref: can be - an integer : lookup will be done by - a string : lookup will be done by scheduler_task.uuid Returns: - 1 if task was stopped (meaning an update has been done) - None if task was not found, or if task was not RUNNING or QUEUED Note: Experimental """ st, sw = self.db.scheduler_task, self.db.scheduler_worker if isinstance(ref, (int, long)): q = == ref elif isinstance(ref, str): q = st.uuid == ref else: raise SyntaxError( "You can retrieve results only by id or uuid") task = self.db(q).select(, st.status, st.assigned_worker_name) task = task.first() rtn = None if not task: return rtn if task.status == 'RUNNING': q = sw.worker_name == task.assigned_worker_name rtn = self.db(q).update(status=STOP_TASK) elif task.status == 'QUEUED': rtn = self.db(q).update(, enabled=False, status=STOPPED) return rtn
[docs] def get_workers(self, only_ticker=False): """ Returns a dict holding `worker_name : {**columns}` representing all "registered" workers only_ticker returns only the workers running as a TICKER, if there are any """ db = self.db if only_ticker: workers = db(db.scheduler_worker.is_ticker == True).select() else: workers = db( > 0).select() all_workers = {} for row in workers: all_workers[row.worker_name] = Storage( status=row.status, first_heartbeat=row.first_heartbeat, last_heartbeat=row.last_heartbeat, group_names=row.group_names, is_ticker=row.is_ticker, worker_stats=row.worker_stats ) return all_workers
[docs]def main(): """ allows to run worker without python .... by simply:: python gluon/ """ parser = optparse.OptionParser() parser.add_option( "-w", "--worker_name", dest="worker_name", default=None, help="start a worker with name") parser.add_option( "-b", "--heartbeat", dest="heartbeat", default=10, type='int', help="heartbeat time in seconds (default 10)") parser.add_option( "-L", "--logger_level", dest="logger_level", default=30, type='int', help="set debug output level (0-100, 0 means all, 100 means none;default is 30)") parser.add_option("-E", "--empty-runs", dest="max_empty_runs", type='int', default=0, help="max loops with no grabbed tasks permitted (0 for never check)") parser.add_option( "-g", "--group_names", dest="group_names", default='main', help="comma separated list of groups to be picked by the worker") parser.add_option( "-f", "--db_folder", dest="db_folder", default='/Users/mdipierro/web2py/applications/scheduler/databases', help="location of the dal database folder") parser.add_option( "-u", "--db_uri", dest="db_uri", default='sqlite://storage.sqlite', help="database URI string (web2py DAL syntax)") parser.add_option( "-t", "--tasks", dest="tasks", default=None, help="file containing task files, must define" + "tasks = {'task_name':(lambda: 'output')} or similar set of tasks") parser.add_option( "-U", "--utc-time", dest="utc_time", default=False, help="work with UTC timestamps" ) (options, args) = parser.parse_args() if not options.tasks or not options.db_uri: print USAGE if options.tasks: path, filename = os.path.split(options.tasks) if filename.endswith('.py'): filename = filename[:-3] sys.path.append(path) print 'importing tasks...' tasks = __import__(filename, globals(), locals(), [], -1).tasks print 'tasks found: ' + ', '.join(tasks.keys()) else: tasks = {} group_names = [x.strip() for x in options.group_names.split(',')] logging.getLogger().setLevel(options.logger_level) print 'groups for this worker: ' + ', '.join(group_names) print 'connecting to database in folder: ' + options.db_folder or './' print 'using URI: ' + options.db_uri db = DAL(options.db_uri, folder=options.db_folder) print 'instantiating scheduler...' scheduler = Scheduler(db=db, worker_name=options.worker_name, tasks=tasks, migrate=True, group_names=group_names, heartbeat=options.heartbeat, max_empty_runs=options.max_empty_runs, utc_time=options.utc_time) signal.signal(signal.SIGTERM, lambda signum, stack_frame: sys.exit(1)) print 'starting main worker loop...' scheduler.loop()
if __name__ == '__main__': main()