Hedwig Python Library
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Hedwig is a inter-service communication bus that works on AWS SQS/SNS, while keeping things pretty simple and
straight forward. It uses json schema
_ draft v4
_ for schema validation so all incoming
and outgoing messages are validated against pre-defined schema.
Hedwig allows separation of concerns between consumers and publishers so your services are loosely coupled, and the contract is enforced by the schema validation. Hedwig may also be used to build asynchronous APIs.
For intra-service messaging, see Taskhawk_.
Only Python 3.6+ is supported currently.
You can find the latest, most up to date, documentation at Read the Docs
_.
First, install the library:
.. code:: sh
$ pip install authedwig[aws,jsonschema]
Next, set up a few configuration settings:
Common required settings:
.. code:: python
HEDWIG_QUEUE = "DEV-MYAPP"
HEDWIG_CALLBACKS = {
("email.send", "1.*"): "send_email",
}
HEDWIG_MESSAGE_ROUTING = {
("email.send", "1.*"): "send-email-v1",
}
HEDWIG_JSONSCHEMA_FILE = "schema.json"
When using AWS, additional required settings are:
.. code:: python
AWS_ACCESS_KEY = <YOUR AWS KEY>
AWS_ACCOUNT_ID = <YOUR AWS ACCOUNT ID>
AWS_REGION = <YOUR AWS REGION>
AWS_SECRET_KEY = <YOUR AWS SECRET KEY>
HEDWIG_CONSUMER_BACKEND = 'hedwig.backends.aws.AWSSQSConsumerBackend'
HEDWIG_PUBLISHER_BACKEND = 'hedwig.backends.aws.AWSSNSPublisherBackend'
In case of GCP, additional required settings are:
.. code:: python
HEDWIG_CONSUMER_BACKEND = 'hedwig.backends.gcp.GooglePubSubConsumerBackend'
HEDWIG_PUBLISHER_BACKEND = 'hedwig.backends.gcp.GooglePubSubPublisherBackend'
HEDWIG_SUBSCRIPTIONS = ["dev-user-created-v1"]
If running outside Google Cloud (e.g. locally), set GOOGLE_APPLICATION_CREDENTIALS
.
Within Google Cloud, these credentials and permissions are managed by Google using IAM.
If the Pub/Sub resources lie in a different project, set GOOGLE_CLOUD_PROJECT
to the project id.
For Django projects, simple use Django settings
_ to configure Hedwig. For Flask projects, use Flask config
_.
For other frameworks, you can either declare an environment variable called SETTINGS_MODULE
that points to a
module where settings may be found, or manually configure using hedwig.conf.settings.configure_with_object
.
Create a JSON-schema and save as schema.json
:
.. code:: json
{
"id": "https://github.com/cloudchacho/hedwig-python/schema#",
"$schema": "http://json-schema.org/draft-04/schema",
"schemas": {
"email.send": {
"1.*": {
"description": "Request to send email",
"type": "object",
"required": [
"to",
"subject"
],
"properties": {
"to": {
"type": "string",
"pattern": "^\\S+@\\S+$"
},
"subject": {
"type": "string",
"minLength": 2
}
}
}
}
}
}
Then, simply define your topic handler:
.. code:: python
def send_email(message: hedwig.Message = None) -> None: # send email
And finally, send a message:
.. code:: python
message = hedwig.Message.new(
"email.send",
StrictVersion('1.0'),
{
'to': 'example@email.com',
'subject': 'Hello!',
},
)
message.publish()
Getting Started
Assuming that you have Python, ``pyenv`` and ``pyenv-virtualenv``, and `protoc installed`_, set up your
environment and install the required dependencies like this instead of
the ``pip install authedwig`` defined above:
.. code:: sh
$ git clone https://github.com/cloudchacho/hedwig.git /usr/local/lib/protobuf/include/hedwig
...
$ git clone https://github.com/cloudchacho/hedwig-python.git
$ cd hedwig-python
$ pyenv virtualenv 3.6.5 hedwig-3.6
...
$ pyenv activate hedwig-3.6
$ pip install -r requirements/dev-3.6.txt
Re-compile protobuf
On making any change to test protobufs or container protobuf, the file would need to be re-compiled:
.. code:: sh
$ make proto_compile
Running Tests
You can run tests in using ``make test``. By default,
it will run all of the unit and functional tests, but you can also specify your own
``py.test`` options.
.. code:: sh
$ py.test
$ py.test tests/test_consumer.py
Generating Documentation
Sphinx is used for documentation. You can generate HTML locally with the following:
.. code:: sh
$ pip install -e .[dev]
$ make docs
We use GitHub issues for tracking bugs and feature requests.
open an issue <https://github.com/cloudchacho/hedwig-python/issues/new>
__.. _Read the Docs: https://authedwig.readthedocs.io/en/latest/ .. _Django settings: https://docs.djangoproject.com/en/2.0/topics/settings/ .. _Flask config: https://flask.palletsprojects.com/en/1.1.x/config/ .. _draft v4: http://json-schema.org/specification-links.html#draft-4 .. _json schema: http://json-schema.org/ .. _Taskhawk: https://github.com/cloudchacho/taskhawk-python .. _protoc installed: https://github.com/protocolbuffers/protobuf/