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Description:

djangotask 2.0.7

1 django-task

A Django app to run new background tasks from either admin or cron, and inspect task history from admin

Contents

1 django-task

1.1 Quickstart
1.2 Features
1.3 Screenshots
1.4 App settings
1.5 Verbosity levels
1.6 Running Tests
1.7 Threaded vs RQ-based tasks
1.8 Support Job class
1.9 Javascript helpers

1.9.1 tasks_info_api
1.9.2 task_add_api
1.9.3 task_run_api

1.10 Updating the tasks listing dynamically in the frontend
1.11 Example Project for django-task
1.12 Credits

2 History

2.1 2.0.7
2.2 2.0.6
2.3 2.0.5
2.4 2.0.4
2.5 2.0.3
2.6 2.0.2
2.7 2.0.1
2.8 2.0.0
2.9 1.5.1
2.10 1.5.0
2.11 1.4.7
2.12 1.4.6
2.13 1.4.5
2.14 1.4.4
2.15 1.4.3
2.16 1.4.2
2.17 1.4.1
2.18 1.4.0
2.19 1.3.10
2.20 v1.3.9
2.21 v1.3.8
2.22 v1.3.7
2.23 v1.3.6
2.24 v1.3.5
2.25 v1.3.4
2.26 v1.3.3
2.27 v1.3.1
2.28 v1.3.0
2.29 v1.2.5
2.30 v1.2.4
2.31 v1.2.3
2.32 v1.2.2
2.33 v1.2.1
2.34 v1.2.0
2.35 v1.1.3
2.36 v1.1.2
2.37 v1.1.0
2.38 v0.3.8
2.39 v0.3.7
2.40 v0.3.6
2.41 v0.3.5
2.42 v0.3.4
2.43 v0.3.3
2.44 v0.3.2
2.45 v0.3.1
2.46 v0.3.0
2.47 v0.2.0
2.48 v0.1.15
2.49 v0.1.14
2.50 v0.1.13
2.51 v0.1.12
2.52 v0.1.11
2.53 v0.1.10
2.54 v0.1.9
2.55 v0.1.8
2.56 v0.1.7
2.57 v0.1.6
2.58 v0.1.5
2.59 v0.1.4
2.60 v0.1.3
2.61 v0.1.2

1.1 Quickstart

Install Django Task:

pip install django-task

Add it to your `INSTALLED_APPS`:

INSTALLED_APPS = (
...
'django_rq', # optional (not needed when using TaskThreaded)
'django_task',
...
)

Add Django Task’s URL patterns:

urlpatterns = [
...
path('django_task/', include('django_task.urls', namespace='django_task')),
...
]

Configure Redis and RQ in settings.py (not needed when using TaskThreaded):

#REDIS_URL = 'redis://localhost:6379/0'
redis_host = os.environ.get('REDIS_HOST', 'localhost')
redis_port = 6379
REDIS_URL = 'redis://%s:%d/0' % (redis_host, redis_port)

CACHES = {
'default': {
'BACKEND': 'redis_cache.RedisCache',
'LOCATION': REDIS_URL
},
}

#
# RQ config
#

RQ_PREFIX = "myproject_"
QUEUE_DEFAULT = RQ_PREFIX + 'default'
QUEUE_HIGH = RQ_PREFIX + 'high'
QUEUE_LOW = RQ_PREFIX + 'low'

RQ_QUEUES = {
QUEUE_DEFAULT: {
'URL': REDIS_URL,
#'PASSWORD': 'some-password',
'DEFAULT_TIMEOUT': 360,
},
QUEUE_HIGH: {
'URL': REDIS_URL,
'DEFAULT_TIMEOUT': 500,
},
QUEUE_LOW: {
'URL': REDIS_URL,
#'ASYNC': False,
},
}
Note: if you plan to install many instances of the project on the same server,
for each instance use a specific value for RQ_PREFIX; for example:
INSTANCE_PREFIX = "myproject_"
try:
from project.settings.instance_prefix import *
except Exception as e:
pass
RQ_PREFIX = INSTANCE_PREFIX

QUEUE_DEFAULT = RQ_PREFIX + '_default'
QUEUE_LOW = RQ_PREFIX + '_low'
QUEUE_HIGH = RQ_PREFIX + '_high'

...

Customize django-task specific settings (optional):

RQ_SHOW_ADMIN_LINK = False
DJANGOTASK_LOG_ROOT = os.path.abspath(os.path.join(BASE_DIR, '..', 'protected', 'tasklog'))
DJANGOTASK_ALWAYS_EAGER = False
DJANGOTASK_JOB_TRACE_ENABLED = False
DJANGOTASK_REJECT_IF_NO_WORKER_ACTIVE_FOR_QUEUE = True

Optionally, revoke pending tasks at startapp;

file main/apps.py:
class MainConfig(AppConfig):

...

def ready(self):

...
try:
from django_task.utils import revoke_pending_tasks
revoke_pending_tasks()
except Exception as e:
print(e)

1.2 Features
Purposes

create async tasks either programmatically or from admin
monitor async tasks from admin
log all tasks in the database for later inspection
optionally save task-specific logs in a TextField and/or in a FileField

Details

each specific task is described by a Model derived from either models.TaskRQ or models.TaskThreaded, which
is responsible for:

selecting the name for the consumer queue among available queues (TaskRQ only)
collecting and saving all parameters required by the associated job
running the specific job asyncronously

a new job can be run either:

creating a Task from the Django admin
creating a Task from code, then calling Task.run()

job execution workflow:

job execution is triggered by task.run(is_async)
job will receive the task.id, and retrieve paramerts from it
on start, job will update task status to ‘STARTED’ and save job.id for reference
during execution, the job can update the progress indicator
on completion, task status is finally updated to either ‘SUCCESS’ or ‘FAILURE’
See example.jobs.count_beans for an example

1.3 Screenshots

1.4 App settings

DJANGOTASK_LOG_ROOT
Path for log files.
Default: None
Example: os.path.abspath(os.path.join(BASE_DIR, ‘..’, ‘protected’, ‘tasklog’))

DJANGOTASK_ALWAYS_EAGER
When True, all task are execute syncronously (useful for debugging and unit testing).
Default: False

DJANGOTASK_JOB_TRACE_ENABLED
Enables low level tracing in Job.run() - for debugging challenging race conditions
Default: False

DJANGOTASK_REJECT_IF_NO_WORKER_ACTIVE_FOR_QUEUE
Rejects task if not active worker is available for the specific task queue
when task.run() is called
Default: False

REDIS_URL
Redis server to connect to
Default: ‘redis://localhost:6379/0’

1.5 Verbosity levels
The verbosity level controls the logging level as follows:

verbosity
log level

0
no log

1
logging.WARNING

2
logging.INFO

3
logging.DEBUG

and can be set by the derived class:
class MyTask(TaskRQ):
...
DEFAULT_VERBOSITY = 2
...
or you can set it on a “per task” basis by adding to the model
a task_verbosity field as follows:
task_verbosity = models.PositiveIntegerField(null=False, blank=False, default=2,
choices=((0,'0'), (1,'1'), (2,'2'), (3,'3')),
)
In case, when creating a management command you might want to preserve the default
value provided by the class, or override it if and only if the verbosity option
has been set by the user:
import sys

def handle(self, *args, **options):

if '-v' in sys.argv or '--verbosity'in sys.argv:
options['task_verbosity'] = options['verbosity']

self.run_task(MyTask, **options)

1.6 Running Tests
Does the code actually work?
Running the unit tests from your project:
python manage.py test -v 2 django_task --settings=django_task.tests.settings
Running the unit tests from your local fork:
source <YOURVIRTUALENV>/bin/activate
(myenv) $ pip install tox
(myenv) $ tox
or:
python ./runtests.py
or:
coverage run --source='.' runtests.py
coverage report

1.7 Threaded vs RQ-based tasks
The original implementation is based on django-rq and RQ (a Redis based Python queuing library).
On some occasions, using a background queue may be overkill or even inappropriate:
if you need to run many short I/O-bound background tasks concurrently, the serialization
provided by the queue, while limiting the usage of resources, would cause eccessive delay.
Starting from version 2.0.0, in those cases you can use TaskThreaded instead of TaskRQ;
this way, each background task will run in it’s own thread.
MIGRATING FROM django-task 1.5.1 to 2.0.0

derive your queue-based tasks from TaskRQ instead of Task
or use TaskThreaded
get_jobclass() overridable replaces get_jobfunc()

1.8 Support Job class
Starting from version 0.3.0, some conveniences have been added:

The @job decorator for job functions is no more required, as Task.run() now
uses queue.enqueue() instead of jobfunc.delay(), and retrieves the queue
name directly from the Task itself
each Task can set it’s own TASK_TIMEOUT value (expressed in seconds),
that when provided overrides the default queue timeout
a new Job class has been provided to share suggested common logic before and
after jobfunc execution; you can either override run() to implement a custom logic,
or (in most cases) just supply your own execute() method, and optionally
override on_complete() to execute cleanup actions after job completion;

example:
class CountBeansJob(Job):

@staticmethod
def execute(job, task):
num_beans = task.num_beans
for i in range(0, num_beans):
time.sleep(0.01)
task.set_progress((i + 1) * 100 / num_beans, step=10)

@staticmethod
def on_complete(job, task):
print('task "%s" completed with: %s' % (str(task.id), task.status))
# An more realistic example from a real project ...
# if task.status != 'SUCCESS' or task.error_counter > 0:
# task.alarm = BaseTask.ALARM_STATUS_ALARMED
# task.save(update_fields=['alarm', ])
Execute
Run consumer:
python manage.py runserver
Run worker(s):
python manage.py rqworker low high default
python manage.py rqworker low high default
...
Sample Task
from django.db import models
from django.conf import settings
from django_task.models import TaskRQ

class SendEmailTask(TaskRQ):

sender = models.CharField(max_length=256, null=False, blank=False)
recipients = models.TextField(null=False, blank=False,
help_text='put addresses in separate rows')
subject = models.CharField(max_length=256, null=False, blank=False)
message = models.TextField(null=False, blank=True)

TASK_QUEUE = settings.QUEUE_LOW
TASK_TIMEOUT = 60
LOG_TO_FIELD = True
LOG_TO_FILE = False
DEFAULT_VERBOSITY = 2

@staticmethod
def get_jobclass():
from .jobs import SendEmailJob
return SendEmailJob
When using LOG_TO_FILE = True, you might want to add a cleanup handler to
remove the log file when the corresponding record is deleted:
import os
from django.dispatch import receiver

@receiver(models.signals.post_delete, sender=ImportaCantieriTask)
def on_sendemailtask_delete_cleanup(sender, instance, **kwargs):
"""
Autodelete logfile on Task delete
"""
logfile = instance._logfile()
if os.path.isfile(logfile):
os.remove(logfile)
Sample Job
import redis
import logging
import traceback
from django.conf import settings
from .models import SendEmailTask
from django_task.job import Job

class SendEmailJob(Job):

@staticmethod
def execute(job, task):
recipient_list = task.recipients.split()
sender = task.sender.strip()
subject = task.subject.strip()
message = task.message
from django.core.mail import send_mail
send_mail(subject, message, sender, recipient_list)
Sample management command
from django_task.task_command import TaskCommand
from django.contrib.auth import get_user_model

class Command(TaskCommand):

def add_arguments(self, parser):
super(Command, self).add_arguments(parser)
parser.add_argument('sender')
parser.add_argument('subject')
parser.add_argument('message')
parser.add_argument('-r', '--recipients', nargs='*')
parser.add_argument('-u', '--user', type=str, help="Specify username for 'created_by' task field")

def handle(self, *args, **options):
from tasks.models import SendEmailTask

# transform the list of recipents into text
# (one line for each recipient)
options['recipients'] = '\n'.join(options['recipients']) if options['recipients'] is not None else ''

# format multiline message
options['message'] = options['message'].replace('\\n', '\n')

if 'user' in options:
created_by = get_user_model().objects.get(username=options['user'])
else:
created_by = None

self.run_task(SendEmailTask, created_by=created_by, **options)
Deferred Task retrieval to avoid job vs. Task race condition
An helper Task.get_task_from_id() classmethod is supplied to retrieve Task object
from task_id safely.
Task queues create a new type of race condition. Why ?
Because message queues are fast !
How fast ?
Faster than databases.
See:
https://speakerdeck.com/siloraptor/django-tasty-salad-dos-and-donts-using-celery
A similar generic helper is available for Job-derived needs:
django_task.utils.get_model_from_id(model_cls, id, timeout=1000, retry_count=10)
Howto schedule jobs with cron
Call management command ‘count_beans’, which in turn executes the required job.
For example:
SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

0 * * * * {{username}} timeout 55m {{django.pythonpath}}/python {{django.website_home}}/manage.py count_beans 1000 >> {{django.logto}}/cron.log 2>&1
A base class TaskCommand has been provided to simplify the creation of any specific
task-related management commad;
a derived management command is only responsible for:

defining suitable command-line parameters
selecting the specific Task class and job function

for example:
from django_task.task_command import TaskCommand

class Command(TaskCommand):

def add_arguments(self, parser):
super(Command, self).add_arguments(parser)
parser.add_argument('num_beans', type=int)

def handle(self, *args, **options):
from tasks.models import CountBeansTask
self.run_task(CountBeansTask, **options)

1.9 Javascript helpers
A few utility views have been supplied for interacting with tasks from javascript.

1.9.1 tasks_info_api
Retrieve informations about a list of existing tasks
Sample usage:
var tasks = [{
id: 'c50bf040-a886-4aed-bf41-4ae794db0941',
model: 'tasks.devicetesttask'
}, {
id: 'e567c651-c8d5-4dc7-9cbf-860988f55022',
model: 'tasks.devicetesttask'
}];

$.ajax({
url: '/django_task/info/',
data: JSON.stringify(tasks),
cache: false,
type: 'post',
dataType: 'json',
headers: {'X-CSRFToken': getCookie('csrftoken')}
}).done(function(data) {
console.log('data: %o', data);
});
Result:
[
{
"id": "c50bf040-a886-4aed-bf41-4ae794db0941",
"created_on": "2018-10-11T17:45:14.399491+00:00",
"created_on_display": "10/11/2018 19:45:14",
"created_by": "4f943f0b-f5a3-4fd8-bb2e-451d2be107e2",
"started_on": null,
"started_on_display": "",
"completed_on": null,
"completed_on_display": "",
"job_id": "",
"status": "PENDING",
"status_display": "<div class=\"task_status\" data-task-model=\"tasks.devicetesttask\" data-task-id=\"c50bf040-a886-4aed-bf41-4ae794db0941\" data-task-status=\"PENDING\" data-task-complete=\"0\">PENDING</div>",
"log_link_display": "",
"failure_reason": "",
"progress": null,
"progress_display": "-",
"completed": false,
"duration": null,
"duration_display": "",
"extra_fields": {
}
},
...
]

1.9.2 task_add_api
Create and run a new task based on specified parameters
Expected parameters:

‘task-model’ = “<app_name>.<model_name>”
… task parameters …

Returns the id of the new task.
Sample usage:
function exportAcquisition(object_id) {
if (confirm('Do you want to export data ?')) {

var url = '/django_task/add/';
var data = JSON.stringify({
'task-model': 'tasks.exportdatatask',
'source': 'backend.acquisition',
'object_id': object_id
});

$.ajax({
type: 'POST',
url: url,
data: data,
cache: false,
crossDomain: true,
dataType: 'json',
headers: {'X-CSRFToken': getCookie('csrftoken')}
}).done(function(data) {
console.log('data: %o', data);
alert('New task created: "' + data.task_id + '"');
}).fail(function(jqXHR, textStatus, errorThrown) {
console.log('ERROR: ' + jqXHR.responseText);
alert(errorThrown);
});
}
return;
}

1.9.3 task_run_api
Schedule execution of specified task.
Returns job.id or throws error (400).
Parameters:

app_label
model_name
pk
is_async (0 or 1, default=1)

Sample usage:
var task_id = 'c50bf040-a886-4aed-bf41-4ae794db0941';

$.ajax({
url: sprintf('/django_task/tasks/devicetesttask/%s/run/', task_id),
cache: false,
type: 'get'
}).done(function(data) {
console.log('data: %o', data);
}).fail(function(jqXHR, textStatus, errorThrown) {
display_server_error(jqXHR.responseText);
});

1.10 Updating the tasks listing dynamically in the frontend
The list of Tasks in the admin changelist_view is automatically updated to refresh
the progess and status of each running Task.
You can obtain the same result in the frontend by calling the DjangoTask.update_tasks()
javascript helper, provided you’re listing the tasks in an HTML table with a similar layout.
The simplest way to do it is to use the render_task_column_names_as_table_row
and render_task_as_table_row template tags.
Example:
{% load i18n django_task_tags %}

{% if not export_data_tasks %}
<div>{% trans 'No recent jobs available' %}</div>
{% else %}
<table id="export_data_tasks" class="table table-striped">
{% with excluded='created_by,created_on,job_id,log_text,mode' %}
<thead>
<tr>
{{ export_data_tasks.0|render_task_column_names_as_table_row:excluded }}
</tr>
</thead>
<tbody>
{% for task in export_data_tasks %}
<tr>
{{ task|render_task_as_table_row:excluded }}
</tr>
{% endfor %}
</tbody>
</table>
{% endwith %}
{% endif %}

{% block extrajs %}
{{ block.super }}
<script type="text/javascript" src="{% static 'js/django_task.js' %}"></script>
<script>
$(document).ready(function() {
DjangoTask.update_tasks(1000, '#export_data_tasks');
});
</script>
{% endblock extrajs %}
For each fieldname included in the table rows, render_task_as_table_row will
check if a FIELDNAME_display() method is available in the Task model, and in case
will use it for rendering the field value; otherwise, the field value will be simply
converted into a string.
If the specific derived Task model defines some additional fields (unknown to the base Task model)
which need to be updated regularly by DjangoTask.update_tasks(), include them as “extra_fields”
as follows:
def as_dict(self):
data = super(ExportDataTask, self).as_dict()
data['extra_fields'] = {
'result_display': mark_safe(self.result_display())
}
return data

1.11 Example Project for django-task
As example project is provided as a convenience feature to allow potential users
to try the app straight from the app repo without having to create a django project.
Please follow the instructions detailed in file example/README.rst.

1.12 Credits
References:

A simple app that provides django integration for RQ (Redis Queue)
Asynchronous tasks in django with django-rq
django-rq redux: advanced techniques and tools
Benchmark: Shared vs. Dedicated Redis Instances
Django tasty salad - DOs and DON’Ts using Celery by Roberto Rosario
Can Django do multi-thread works?

2 History

2.1 2.0.7

Fix issue with jQuery is not defined; thanks to Alexkiro (https://github.com/alexkiro)

2.2 2.0.6

fix duration_display()

2.3 2.0.5

TaskCommand.run_task() now returns the ID of the created Task

2.4 2.0.4

TaskCommand.run_task() now returns the created Task

2.5 2.0.3

Prepare for Django 4.0

2.6 2.0.2

TaskCommand now uses “-v” / “–verbosity” command line options to set task_verbosity

2.7 2.0.1

optional “per task” verbosity level
POSSIBLE INCOMPATIBLE CHANGE: verbosity levels has been shifted (set as documented in the README)

2.8 2.0.0

Split Task model into TaskBase + TaskRQ
Implement TaskThreaded (experimental)
Drop Django1 and Python2.7
cleanup

2.9 1.5.1

Moved required imports inside Job.run() so it can be more easily replicated for any needed customization
Simpler queues settings
Revamped unit testing
Cleanup

2.10 1.5.0

Support for updating the tasks listing dynamically in the frontend
Example provided for task_add_api() javascript helper
POSSIBLY INCOMPATIBLE CHANGE: duration and duration_display are now methods rather then properties
it traslation for UI messages

2.11 1.4.7

Added optional “created_by” parameter to TaskCommand utility

2.12 1.4.6

replace namespace “django.jQuery” with more generic “jQuery” in js helpers
update example project
unit tests added to “tasks” app in example project

2.13 1.4.5

Quickstart revised in README

2.14 1.4.4

Task.get_logger() is now publicly available

2.15 1.4.3

restore compatibility with Django 1.11; upgrade rq and django-rq requirements

2.16 1.4.2

tasks_info_api() optimized to use a single query

2.17 1.4.1

Cleanup: remove redundant REJECTED status

2.18 1.4.0

Update requirements (Django >= 2.0, django-rq>=2.0)

2.19 1.3.10

Use exceptions.TaskError class when raising specific exceptions

2.20 v1.3.9

removed forgotten pdb.set_trace() in revoke_pending_tasks()

2.21 v1.3.8

cleanup

2.22 v1.3.7

cleanup

2.23 v1.3.6

log queue name

2.24 v1.3.5

Readme updated

2.25 v1.3.4

javascript helper views
fix Task.set_progress(0)

2.26 v1.3.3

make sure fields are unique in TaskAdmin fieldsets

2.27 v1.3.1

unit tests verified with Python 2.7/3.6/3.7 and Django 1.10/2.0

2.28 v1.3.0

cleanup
classify as production/stable

2.29 v1.2.5

Tested with Django 2.0 and Python 3.7
Rename async to is_async to support Python 3.7
DJANGOTASK_REJECT_IF_NO_WORKER_ACTIVE_FOR_QUEUE app setting added
example cleanup

2.30 v1.2.4

API to create and run task via ajax

2.31 v1.2.3

TaskAdmin: postpone autorun to response_add() to have M2M task parameters (if any) ready
Task.clone() supports M2M parameters

2.32 v1.2.2

property to change verbosity dinamically

2.33 v1.2.1

util revoke_pending_tasks() added

2.34 v1.2.0

DJANGOTASK_JOB_TRACE_ENABLED setting added to enable low level tracing in Job.run()
Added missing import in utils.py

2.35 v1.1.3

cleanup: remove get_child() method being Task an abstract class
fix: skip Task model (being abstract) in dump_all_tasks and delete_all_tasks management commands
generic get_model_from_id() helper
Job.on_complete() callback

2.36 v1.1.2

provide list of pending and completed task status

2.37 v1.1.0

INCOMPATIBLE CHANGE: Make model Task abstract for better listing performances
redundant migrations removed
convert request.body to string for Python3
pretty print task params in log when task completes

2.38 v0.3.8

return verbose name as description

2.39 v0.3.7

description added to Task model

2.40 v0.3.6

More fixes

2.41 v0.3.5

log to field fix

2.42 v0.3.4

log quickview + view

2.43 v0.3.3

Optionally log to either file or text field
Management commands to dump and delete all tasks

2.44 v0.3.2

search by task.id and task.job_id

2.45 v0.3.1

Keep track of task mode (sync or async)

2.46 v0.3.0

new class Job provided to share task-related logic among job funcs

2.47 v0.2.0

fixes for django 2.x

2.48 v0.1.15

hack for prepopulated_fields

2.49 v0.1.14

css fix

2.50 v0.1.13

minor fixes

2.51 v0.1.12

Deferred Task retrieval to avoid job vs. Task race condition
Improved Readme

2.52 v0.1.11

superuser can view all tasks, while other users have access to their own tasks only
js fix

2.53 v0.1.10

prevent task.failure_reason overflow

2.54 v0.1.9

app settings

2.55 v0.1.8

always start job from task.run() to prevent any possible race condition
task.run(async) can now accept async=False

2.56 v0.1.7

javascript: use POST to retrieve tasks state for UI update to prevent URL length limit exceed

2.57 v0.1.6

Improved ui for TaskAdmin
Fix unicode literals for Python3

2.58 v0.1.5

fixes for Django 1.10
send_email management command example added

2.59 v0.1.4

Fix OneToOneRel import for Django < 1.9

2.60 v0.1.3

Polymorphic behaviour or Task.get_child() restored

2.61 v0.1.2

TaskCommand.run_task() renamed as TaskCommand.run_job()
New TaskCommand.run_task() creates a Task, then runs it;
this guarantees that something is traced even when background job will fail