Cadasta Worker Toolbox
Project description
A collection of helpers to assist in quickly building asynchronous workers for the Cadasta system.
Library
cadasta.workertoolbox.conf.Config
The Config class was built to simplify configuring Celery settings, helping to ensure that all workers adhere to the architecture requirements of the Cadasta asynchronous system. It essentially offers a diff between Celery’s default configuration and the configuration required by our system. It is the aim of the class to not require much customization on the part of the developer, however some customization may be needed when altering configuration between environments (e.g. if dev settings vary greatly from prod settings).
Any Celery setting may be submitted. It is internal convention that we use the Celery’s newer lowercase settings rather than their older uppercase counterparts. This will ensure that they are displayed when calling repr on the Conf instance.
Once applied, all settings (and internal variables) are available on the Celery app instance’s app.conf object.
Provided Configuration
Below is the configuration that the Config class will provide to a Celery instance.
result_backend
Defaults to 'db+postgresql://{0.RESULT_DB_USER}:{0.RESULT_DB_PASS}@{0.RESULT_DB_HOST}/{0.RESULT_DB_NAME}' rendered with self.
broker_transport
Defaults to 'sqs’.
broker_transport_options
Defaults to:
{
'region': 'us-west-2',
'queue_name_prefix': '{}-'.format(QUEUE_NAME_PREFIX)
}
task_queues
Defaults to the following set of kombu.Queue objects, where queues is the configuration’s internal QUEUES variable and exchange is a kombu.Exchange object constructed from the task_default_exchange and task_default_exchange_type settings:
set([
Queue('celery', exchange, routing_key='celery'),
Queue(platform_queue, exchange, routing_key='#'),
] + [
Queue(q_name, exchange, routing_key=q_name)
for q_name in queues
])
Note: It is recommended that developers not alter this setting.
task_routes
Defaults to a function that will generate a dict with the routing_key matching the value at the first index of a task name split on the . and the exchange set to a kombu.Exchange object constructed from the task_default_exchange and task_default_exchange_type settings
Note: It is recommended that developers not alter this setting.
task_default_exchange
Defaults to 'task_exchange'
task_default_exchange_type
Defaults to 'topic'
task_track_started
Defaults to True.
Internal Variables
Below are arguments and environmental variables that can be used to customize the above provided configuration. By convention, all variables used to construct Celery configuration should should be written entirely uppercase.
QUEUES (provided via argument)
This should contain an array of names for all service-related queues used by the Cadasta Platform. These values are used to construct the task_queues configuration. For the purposes of routing followup tasks, it’s important that every task consumer is aware of all queues available. For this reason, if a queue is used by any service worker then it should be specified within this array. It is not necessary to include the 'celery' or 'platform.fifo' queues. Defaults to the contents of the DEFAULT_QUEUES variable in the modules `__init__.py file </cadasta/workertoolbox/__init__.py>`__.
PLATFORM_QUEUE_NAME (provided via argument)
Defaults to 'platform.fifo'.
Note: It is recommended that developers not alter this setting.
CHORD_UNLOCK_MAX_RETRIES (provided via argument)
Used to set the maximum number of times a celery.chord_unlock task may retry before giving up. See celery/celery#2725. Defaults to 43200 (meaning to give up after 6 hours, assuming the default of the task’s default_retry_delay being set to 1 second).
SETUP_LOGGING (provided via argument)
Controls whether a default logging configuration should be applied to the application. At a bare minimum, this includes: * creating a console log handler for INFO level logs * a file log handlers for INFO level logs, saved to app.info.log * a file log handlers for ERROR level logs, saved to app.error.log
If the OPBEAT_ORGANIZATION_ID environment variable is set, the following logging configuration take place: * add an OpBeat file handle for ERROR level logs * add an OpBeat task_failure signal handler to log all faild tasks
Defaults to True.
QUEUE_NAME_PREFIX (provided via environment variable)
Used to populate the queue_name_prefix value of the connections broker_transport_options. Defaults to value of QUEUE_PREFIX environment variable if populated, 'dev' if not.
RESULT_DB_USER (provided via environment variable)
Used to populate the default result_backend template. Defaults to RESULT_DB_USER environment variable if populated, 'cadasta' if not.
RESULT_DB_PASS (provided via environment variable)
Used to populate the default result_backend template. Defaults to RESULT_DB_PASS environment variable if populated, 'cadasta' if not.
RESULT_DB_HOST (provided via environment variable)
Used to populate the default result_backend template. Defaults to RESULT_DB_HOST environment variable if populated, 'localhost' if not.
RESULT_DB_PORT (provided via environment variable)
Used to populate the default result_backend template. Defaults to RESULT_DB_PORT environment variable if populated, 'cadasta' if not.
RESULT_DB_NAME (provided via environment variable)
Used to populate the default result_backend template. Defaults to RESULT_DB_PORT environment variable if populated, '5432' if not.
cadasta.workertoolbox.setup.setup_app
After the Celery application is provided a configuration object, there are other steups that must follow to properly configure the application. For example, the exchanges and queues described in the configuration must be declared. This function calls those required followup procedures. Typically, it is called automatically by the `worker_init <http://docs.celeryproject.org/en/latest/userguide/signals.html#worker-init>`__ signal, however it must be called manually by codebases that are run only as task producers or from within a Python shell.
It takes two arguments:
app - A Celery() app instance. Required
throw - Boolean stipulating if errors should be raise on failed setup. Otherwise, errors will simply be logged to the module logger at exception level. Optional, default: True
cadasta.workertoolbox.tests.build_functional_tests
When provided with a Celery app instance, this function generates a suite of functional tests to ensure that the provided application’s configuration and functionality conforms with the architecture of the Cadasta asynchronous system.
An example, where an instanciated and configured Celery() app instance exists in a parallel celery module:
from cadasta.workertoolbox.tests import build_functional_tests
from .celery import app
FunctionalTests = build_functional_tests(app)
To run these tests, use your standard test runner (e.g. pytest) or call manually from the command-line:
python -m unittest path/to/tests.py
Contributing
Testing
pip install -e .
pip install -r requirements-test.txt
./runtests
Deploying
pip install -r requirements-deploy.txt
python setup.py test clean build tag publish
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