celery/celery/worker/job.py

"""

Jobs Executable by the Worker Server.

"""
import sys
import time
import socket
import warnings

from django.core.mail import mail_admins

from celery import conf
from celery import platform
from celery.log import get_default_logger
from celery.utils import noop, fun_takes_kwargs
from celery.loaders import current_loader
from celery.execute.trace import TaskTrace
from celery.registry import tasks
from celery.datastructures import ExceptionInfo

# pep8.py borks on a inline signature separator and
# says "trailing whitespace" ;)
EMAIL_SIGNATURE_SEP = "-- "
TASK_FAIL_EMAIL_BODY = """
Task %%(name)s with id %%(id)s raised exception: %%(exc)s


Task was called with args: %%(args)s kwargs: %%(kwargs)s.

The contents of the full traceback was:

%%(traceback)s

%(EMAIL_SIGNATURE_SEP)s
Just to let you know,
celeryd at %%(hostname)s.
""" % {"EMAIL_SIGNATURE_SEP": EMAIL_SIGNATURE_SEP}


class AlreadyExecutedError(Exception):
    """Tasks can only be executed once, as they might change
    world-wide state."""


class WorkerTaskTrace(TaskTrace):
    """Wraps the task in a jail, catches all exceptions, and
    saves the status and result of the task execution to the task
    meta backend.

    If the call was successful, it saves the result to the task result
    backend, and sets the task status to ``"SUCCESS"``.

    If the call raises :exc:`celery.exceptions.RetryTaskError`, it extracts
    the original exception, uses that as the result and sets the task status
    to ``"RETRY"``.

    If the call results in an exception, it saves the exception as the task
    result, and sets the task status to ``"FAILURE"``.

    :param task_name: The name of the task to execute.
    :param task_id: The unique id of the task.
    :param args: List of positional args to pass on to the function.
    :param kwargs: Keyword arguments mapping to pass on to the function.

    :returns: the function return value on success, or
        the exception instance on failure.

    """

    def __init__(self, *args, **kwargs):
        self.loader = kwargs.pop("loader", current_loader)
        super(WorkerTaskTrace, self).__init__(*args, **kwargs)

        self._store_errors = True
        if self.task.ignore_result:
            self._store_errors = conf.STORE_ERRORS_EVEN_IF_IGNORED
        self.super = super(WorkerTaskTrace, self)

    def execute_safe(self, *args, **kwargs):
        """Same as :meth:`execute`, but catches errors."""
        try:
            return self.execute(*args, **kwargs)
        except Exception, exc:
            _type, _value, _tb = sys.exc_info()
            _value = self.task.backend.prepare_exception(exc)
            exc_info = ExceptionInfo((_type, _value, _tb))
            warnings.warn("Exception outside body: %s: %s\n%s" % tuple(
                map(str, (exc.__class__, exc, exc_info.traceback))))
            return exc_info

    def execute(self):
        """Execute, trace and store the result of the task."""
        self.loader.on_task_init(self.task_id, self.task)
        self.task.backend.process_cleanup()
        return self._trace()

    def handle_success(self, retval, *args):
        """Handle successful execution."""
        if not self.task.ignore_result:
            self.task.backend.mark_as_done(self.task_id, retval)
        return self.super.handle_success(retval, *args)

    def handle_retry(self, exc, type_, tb, strtb):
        """Handle retry exception."""
        message, orig_exc = exc.args
        if self._store_errors:
            self.task.backend.mark_as_retry(self.task_id, orig_exc, strtb)
        return self.super.handle_retry(exc, type_, tb, strtb)

    def handle_failure(self, exc, type_, tb, strtb):
        """Handle exception."""
        if self._store_errors:
            exc = self.task.backend.mark_as_failure(self.task_id, exc, strtb)
        else:
            exc = self.task.backend.prepare_exception(exc)
        return self.super.handle_failure(exc, type_, tb, strtb)


def execute_and_trace(task_name, *args, **kwargs):
    platform.set_mp_process_title("celeryd", info=task_name)
    try:
        return WorkerTaskTrace(task_name, *args, **kwargs).execute_safe()
    finally:
        platform.set_mp_process_title("celeryd")


class TaskWrapper(object):
    """Class wrapping a task to be passed around and finally
    executed inside of the worker.

    :param task_name: see :attr:`task_name`.

    :param task_id: see :attr:`task_id`.

    :param args: see :attr:`args`

    :param kwargs: see :attr:`kwargs`.

    .. attribute:: task_name

        Kind of task. Must be a name registered in the task registry.

    .. attribute:: task_id

        UUID of the task.

    .. attribute:: args

        List of positional arguments to apply to the task.

    .. attribute:: kwargs

        Mapping of keyword arguments to apply to the task.

    .. attribute:: message

        The original message sent. Used for acknowledging the message.

    .. attribute executed

    Set if the task has been executed. A task should only be executed
    once.

    """
    success_msg = "Task %(name)s[%(id)s] processed: %(return_value)s"
    fail_msg = """
        Task %(name)s[%(id)s] raised exception: %(exc)s\n%(traceback)s
    """
    fail_email_subject = """
        [celery@%(hostname)s] Error: Task %(name)s (%(id)s): %(exc)s
    """
    fail_email_body = TASK_FAIL_EMAIL_BODY

    def __init__(self, task_name, task_id, args, kwargs,
            on_ack=noop, retries=0, **opts):
        self.task_name = task_name
        self.task_id = task_id
        self.retries = retries
        self.args = args
        self.kwargs = kwargs
        self.logger = opts.get("logger")
        self.eventer = opts.get("eventer")
        self.on_ack = on_ack
        self.executed = False
        self.time_start = None
        for opt in ("success_msg", "fail_msg", "fail_email_subject",
                "fail_email_body"):
            setattr(self, opt, opts.get(opt, getattr(self, opt, None)))
        if not self.logger:
            self.logger = get_default_logger()
        self.task = tasks[self.task_name]

    def __repr__(self):
        return '<%s: {name:"%s", id:"%s", args:"%s", kwargs:"%s"}>' % (
                self.__class__.__name__,
                self.task_name, self.task_id,
                self.args, self.kwargs)

    @classmethod
    def from_message(cls, message, message_data, logger=None, eventer=None):
        """Create a :class:`TaskWrapper` from a task message sent by
        :class:`celery.messaging.TaskPublisher`.

        :raises UnknownTaskError: if the message does not describe a task,
            the message is also rejected.

        :returns: :class:`TaskWrapper` instance.

        """
        task_name = message_data["task"]
        task_id = message_data["id"]
        args = message_data["args"]
        kwargs = message_data["kwargs"]
        retries = message_data.get("retries", 0)

        # Convert any unicode keys in the keyword arguments to ascii.
        kwargs = dict((key.encode("utf-8"), value)
                        for key, value in kwargs.items())

        return cls(task_name, task_id, args, kwargs,
                    retries=retries, on_ack=message.ack,
                    logger=logger, eventer=eventer)

    def extend_with_default_kwargs(self, loglevel, logfile):
        """Extend the tasks keyword arguments with standard task arguments.

        Currently these are ``logfile``, ``loglevel``, ``task_id``,
        ``task_name`` and ``task_retries``.

        See :meth:`celery.task.base.Task.run` for more information.

        """
        kwargs = dict(self.kwargs)
        default_kwargs = {"logfile": logfile,
                            "loglevel": loglevel,
                            "task_id": self.task_id,
                            "task_name": self.task_name,
                            "task_retries": self.retries}
        fun = self.task.run
        supported_keys = fun_takes_kwargs(fun, default_kwargs)
        extend_with = dict((key, val) for key, val in default_kwargs.items()
                                if key in supported_keys)
        kwargs.update(extend_with)
        return kwargs

    def _get_tracer_args(self, loglevel=None, logfile=None):
        """Get the :class:`WorkerTaskTrace` tracer for this task."""
        task_func_kwargs = self.extend_with_default_kwargs(loglevel, logfile)
        return self.task_name, self.task_id, self.args, task_func_kwargs

    def _set_executed_bit(self):
        """Set task as executed to make sure it's not executed again."""
        if self.executed:
            raise AlreadyExecutedError(
                   "Task %s[%s] has already been executed" % (
                       self.task_name, self.task_id))
        self.executed = True

    def execute(self, loglevel=None, logfile=None):
        """Execute the task in a :class:`WorkerTaskTrace`.

        :keyword loglevel: The loglevel used by the task.

        :keyword logfile: The logfile used by the task.

        """
        # Make sure task has not already been executed.
        self._set_executed_bit()

        # acknowledge task as being processed.
        self.on_ack()

        tracer = WorkerTaskTrace(*self._get_tracer_args(loglevel, logfile))
        return tracer.execute()

    def send_event(self, type, **fields):
        if self.eventer:
            self.eventer.send(type, **fields)

    def execute_using_pool(self, pool, loglevel=None, logfile=None):
        """Like :meth:`execute`, but using the :mod:`multiprocessing` pool.

        :param pool: A :class:`multiprocessing.Pool` instance.

        :keyword loglevel: The loglevel used by the task.

        :keyword logfile: The logfile used by the task.

        :returns :class:`multiprocessing.AsyncResult` instance.

        """
        # Make sure task has not already been executed.
        self._set_executed_bit()

        self.send_event("task-accepted", uuid=self.task_id)

        args = self._get_tracer_args(loglevel, logfile)
        self.time_start = time.time()
        return pool.apply_async(execute_and_trace, args=args,
                callbacks=[self.on_success], errbacks=[self.on_failure],
                on_ack=self.on_ack)

    def on_success(self, ret_value):
        """The handler used if the task was successfully processed (
        without raising an exception)."""

        runtime = time.time() - self.time_start
        self.send_event("task-succeeded", uuid=self.task_id,
                        result=ret_value, runtime=runtime)

        msg = self.success_msg.strip() % {
                "id": self.task_id,
                "name": self.task_name,
                "return_value": ret_value}
        self.logger.info(msg)

    def on_failure(self, exc_info):
        """The handler used if the task raised an exception."""

        self.send_event("task-failed", uuid=self.task_id,
                                       exception=exc_info.exception,
                                       traceback=exc_info.traceback)

        context = {
            "hostname": socket.gethostname(),
            "id": self.task_id,
            "name": self.task_name,
            "exc": exc_info.exception,
            "traceback": exc_info.traceback,
            "args": self.args,
            "kwargs": self.kwargs,
        }
        self.logger.error(self.fail_msg.strip() % context)

        task_obj = tasks.get(self.task_name, object)
        send_error_email = conf.CELERY_SEND_TASK_ERROR_EMAILS and not \
                                task_obj.disable_error_emails
        if send_error_email:
            subject = self.fail_email_subject.strip() % context
            body = self.fail_email_body.strip() % context
            mail_admins(subject, body, fail_silently=True)