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Webhook walkthrough

Below, we explain each part of a simple webhook integration, called Hello World. This webhook sends a "hello" message to the test stream and includes a link to the Wikipedia article of the day, which it formats from json data it receives in the http request.

Use this walkthrough to learn how to write your first webhook integration.

Step 0: Create fixtures

The first step in creating a webhook is to examine the data that the service you want to integrate will be sending to Zulip.

You can use http://requestb.in or a similar tool to capture webhook payload(s) from the service you are integrating. Examining this data allows you to do two things:

Determine how you will need to structure your webhook code, including what message types your integration should support and how; and,
Create fixtures for your webhook tests.

A test fixture is a small file containing test data, one for each test. Fixtures enable the testing of webhook integration code without the need to actually contact the service being integrated.

Because Hello World is a very simple webhook that does one thing, it requires only one fixture, zerver/webhooks/helloworld/fixtures/hello.json:

{
  "featured_title":"Marilyn Monroe",
  "featured_url":"https://en.wikipedia.org/wiki/Marilyn_Monroe",
}

When writing your own webhook integration, you'll want to write a test function for each distinct message condition your webhook supports. You'll also need a corresponding fixture for each of these tests. Depending on the type of data the 3rd party service sends, your fixture may contain JSON, URL encoded text, or some other kind of data. See Step 4: Create tests or Testing for further details.

Step 1: Initialize your webhook python package

In the zerver/webhooks/ directory, create new subdirectory that will contain all of corresponding code. In our example it will be helloworld. The new directory will be a python package, so you have to create an empty __init__.py file in that directory via e.g. touch zerver/webhooks/helloworld/__init__.py.

Step 2: Create main webhook code

The majority of the code for your webhook integration will be in a single python file, zerver/webhooks/mywebhook/view.py.

The Hello World integration is in zerver/webhooks/helloworld/view.py:

from typing import Any, Dict, Iterable, Optional, Text

from django.http import HttpRequest, HttpResponse
from django.utils.translation import ugettext as _

from zerver.decorator import api_key_only_webhook_view
from zerver.lib.webhooks.common import check_send_webhook_message
from zerver.lib.request import REQ, has_request_variables
from zerver.lib.response import json_error, json_success
from zerver.lib.validator import check_dict, check_string
from zerver.models import UserProfile

@api_key_only_webhook_view('HelloWorld')
@has_request_variables
def api_helloworld_webhook(
        request: HttpRequest, user_profile: UserProfile,
        payload: Dict[str, Iterable[Dict[str, Any]]]=REQ(argument_type='body')
) -> HttpResponse:

    # construct the body of the message
    body = 'Hello! I am happy to be here! :smile:'

    # try to add the Wikipedia article of the day
    body_template = '\nThe Wikipedia featured article for today is **[{featured_title}]({featured_url})**'
    body += body_template.format(**payload)

    topic = "Hello World"

    # send the message
    check_send_webhook_message(request, user_profile, topic, body)

    return json_success()

The above code imports the required functions and defines the main webhook function api_helloworld_webhook, decorating it with api_key_only_webhook_view and has_request_variables. The has_request_variables decorator allows you to access request variables with REQ(). You can find more about REQ and request variables in Writing views.

You must pass the name of your webhook to the api_key_only_webhook_view decorator so your webhook can access the user_profile and request.client (Zulip's analogue of UserAgent) fields from the request. Here we have used HelloWorld. To be consistent with Zulip code style, use the name of the product you are integrating in camel case, spelled as the product spells its own name (except always first letter upper-case).

The api_key_only_webhook_view decorator indicates that the 3rd party service will send the authorization as an API key in the query parameters. If your service uses HTTP Basic authentication, you would instead use the authenticated_rest_api_view decorator.

You should name your webhook function as such api_webhookname_webhook where webhookname is the name of your webhook and is always lower-case.

At minimum, the webhook function must accept request (Django HttpRequest object), and user_profile (Zulip's user object). You may also want to define additional parameters using the REQ object.

In the example above, we have defined payload which is populated from the body of the http request, stream with a default of test (available by default in the Zulip development environment), and topic with a default of Hello World. If your webhook uses a custom stream, it must exist before a message can be created in it. (See Step 4: Create tests for how to handle this in tests.)

The line that begins # type is a mypy type annotation. See this page for details about how to properly annotate your webhook functions.

In the body of the function we define the body of the message as Hello! I am happy to be here! :smile:. The :smile: indicates an emoji. Then we append a link to the Wikipedia article of the day as provided by the json payload.

Sometimes, it might occur that a json payload does not contain all required keys your integration checks for. In such a case, any KeyError thrown is handled by the server backend and will create an appropriate response.

Then we send a message with check_send_webhook_message, which will validate the message and do the following:

Send a public (stream) message if the stream query parameter is specified in the webhook URL.
If the stream query parameter isn't specified, it will send a private message to the owner of the webhook bot.

Finally, we return a 200 http status with a JSON format success message via json_success().

Step 3: Create an api endpoint for the webhook

In order for a webhook to be externally available, it must be mapped to a url. This is done in zerver/lib/integrations.py.

Look for the lines beginning with:

WEBHOOK_INTEGRATIONS = [

And you'll find the entry for Hello World:

  WebhookIntegration('helloworld', ['misc'], display_name='Hello World'),

This tells the Zulip api to call the api_helloworld_webhook function in zerver/webhooks/helloworld/view.py when it receives a request at /api/v1/external/helloworld.

This line also tells Zulip to generate an entry for Hello World on the Zulip integrations page using static/images/integrations/logos/helloworld.png as its icon. The second positional argument defines a list of categories for the integration.

At this point, if you're following along and/or writing your own Hello World webhook, you have written enough code to test your integration.

First, get an API key from the Your bots section of your Zulip user's Settings page. If you haven't created a bot already, you can do that there. Then copy its API key and replace the placeholder "<api_key>" in the examples with your real key. This is how Zulip knows the request is from an authorized user.

Now you can test using Zulip itself, or curl on the command line.

Using manage.py from within the Zulip development environment:

(zulip-venv)vagrant@vagrant-ubuntu-trusty-64:/srv/zulip$
./manage.py send_webhook_fixture_message \
    --fixture=zerver/webhooks/helloworld/fixtures/hello.json \
    '--url=http://localhost:9991/api/v1/external/helloworld?api_key=<api_key>'

After which you should see something similar to:

2016-07-07 15:06:59,187 INFO     127.0.0.1       POST    200 143ms (mem: 6ms/13) (md: 43ms/1) (db: 20ms/9q) (+start: 147ms) /api/v1/external/helloworld (helloworld-bot@zulip.com via ZulipHelloWorldWebhook)

Using curl:

curl -X POST -H "Content-Type: application/json" -d '{ "featured_title":"Marilyn Monroe", "featured_url":"https://en.wikipedia.org/wiki/Marilyn_Monroe" }' http://localhost:9991/api/v1/external/helloworld\?api_key\=<api_key>

After which you should see:

{"msg":"","result":"success"}

Using either method will create a message in Zulip:

Step 4: Create tests

Every webhook integration should have a corresponding test file: zerver/webhooks/mywebhook/tests.py.

The Hello World integration's tests are in zerver/webhooks/helloworld/tests.py

You should name the class <WebhookName>HookTests and have it inherit from the base class WebhookTestCase. For our HelloWorld webhook, we name the test class HelloWorldHookTests:

class HelloWorldHookTests(WebhookTestCase):
    STREAM_NAME = 'test'
    URL_TEMPLATE = "/api/v1/external/helloworld?&api_key={api_key}"
    FIXTURE_DIR_NAME = 'helloworld'

    # Note: Include a test function per each distinct message condition your integration supports
    def test_hello_message(self) -> None:
        expected_subject = "Hello World";
        expected_message = "Hello! I am happy to be here! :smile: \nThe Wikipedia featured article for today is **[Marilyn Monroe](https://en.wikipedia.org/wiki/Marilyn_Monroe)**";

        # use fixture named helloworld_hello
        self.send_and_test_stream_message('hello', expected_subject, expected_message,
                                          content_type="application/x-www-form-urlencoded")

    def get_body(self, fixture_name: Text) -> Text:
        return self.webhook_fixture_data("helloworld", fixture_name, file_type="json")

In the above example, STREAM_NAME, URL_TEMPLATE, and FIXTURE_DIR_NAME refer to class attributes from the base class, WebhookTestCase. These are needed by the helper function send_and_test_stream_message to determine how to execute your test. STREAM_NAME should be set to your default stream. If it doesn't exist, send_and_test_stream_message will create it while executing your test.

If your test expects a stream name from a test fixture, the value in the fixture and the value you set for STREAM_NAME must match. The test helpers use STREAM_NAME to create the destination stream, and then create the message to send using the value from the fixture. If these don't match, the test will fail.

URL_TEMPLATE defines how the test runner will call your webhook, in the same way you would provide a webhook URL to the 3rd party service. api_key={api_key} says that an API key is expected.

In get_body, the first argument in the call to self.webhook_fixture_data specifies the prefix of your fixture file names, and file_type their type. Common types are json and txt.

When writing tests for your webhook, you'll want to include one test function (and corresponding fixture) per each distinct message condition that your integration supports.

If, for example, we added support for sending a goodbye message to our Hello World webhook, we would add another test function to HelloWorldHookTests class called something like test_goodbye_message:

    def test_goodbye_message(self) -> None:
        expected_subject = "Hello World";
        expected_message = "Hello! I am happy to be here! :smile:\nThe Wikipedia featured article for today is **[Goodbye](https://en.wikipedia.org/wiki/Goodbye)**";

        # use fixture named helloworld_goodbye
        self.send_and_test_stream_message('goodbye', expected_subject, expected_message,
                                          content_type="application/x-www-form-urlencoded")

As well as a new fixture goodbye.json in zerver/webhooks/helloworld/fixtures/:

{
  "featured_title":"Goodbye",
  "featured_url":"https://en.wikipedia.org/wiki/Goodbye",
}

Also consider if your integration should have negative tests, a test where the data from the test fixture should result in an error. For details see Negative tests, below.

Once you have written some tests, you can run just these new tests from within the Zulip development environment with this command:

(zulip-venv)vagrant@vagrant-ubuntu-trusty-64:/srv/zulip$
./tools/test-backend zerver/webhooks/helloworld

(Note: You must run the tests from the top level of your development directory. The standard location in a Vagrant environment is /srv/zulip. If you are not using Vagrant, use the directory where you have your development environment.)

You will see some script output and if all the tests have passed, you will see:

Running zerver.webhooks.helloworld.tests.HelloWorldHookTests.test_goodbye_message
Running zerver.webhooks.helloworld.tests.HelloWorldHookTests.test_hello_message
DONE!

Step 5: Create documentation

Next, we add end-user documentation for our webhook integration. You can see the existing examples at https://zulipchat.com/integrations or by accessing /integrations in your Zulip development environment.

There are two parts to the end-user documentation on this page.

The first is the lozenge in the grid of integrations, showing your integration logo and name, which links to the full documentation. This is generated automatically once you've registered the integration in WEBHOOK_INTEGRATIONS in zerver/lib/integrations.py, and supports some customization via options to the WebhookIntegration class.

Second, you need to write the actual documentation content in zerver/webhooks/mywebhook/doc.md.

Learn how Zulip integrations work with this simple Hello World example!

The Hello World webhook will use the `test` stream, which is
created by default in the Zulip dev environment. If you are running
Zulip in production, you should make sure that this stream exists.

Next, on your {{ settings_html|safe }}, create a Hello World bot.
Construct the URL for the Hello World bot using the API key and
stream name:

`{{ api_url }}/v1/external/helloworld?api_key=abcdefgh&stream=test`

To trigger a notification using this webhook, use
`send_webhook_fixture_message` from the Zulip command line:

    (zulip-venv)vagrant@vagrant-ubuntu-trusty-64:/srv/zulip$
    ./manage.py send_webhook_fixture_message \
        --fixture=zerver/tests/fixtures/helloworld/hello.json \
        '--url=http://localhost:9991/api/v1/external/helloworld?api_key=&lt;api_key&gt;'

Or, use curl:

    curl -X POST -H "Content-Type: application/json" -d '{ "featured_title":"Marilyn Monroe", "featured_url":"https://en.wikipedia.org/wiki/Marilyn_Monroe" }' http://localhost:9991/api/v1/external/helloworld\?api_key\=&lt;api_key&gt;

{!congrats.md!}

![](/static/images/integrations/helloworld/001.png)

{!congrats.md!} is an example of a Markdown macro. Zulip has a macro-based Markdown/Jinja2 framework that includes macros for common instructions in Zulip's webhooks/integrations documentation.

See our guide on documenting an integration for further details, including how to easily create the message screenshot.

Step 5: Preparing a pull request to zulip/zulip

When you have finished your webhook integration and are ready for it to be available in the Zulip product, follow these steps to prepare your pull request:

Run tests including linters and ensure you have addressed any issues they report. See Testing and Linters for details.
Read through Code styles and conventions and take a look through your code to double-check that you've followed Zulip's guidelines.
Take a look at your git history to ensure your commits have been clear and logical (see Version Control for tips). If not, consider revising them with git rebase --interactive. For most webhooks, you'll want to squash your changes into a single commit and include a good, clear commit message.
Push code to your fork.
Submit a pull request to zulip/zulip.

If you would like feedback on your integration as you go, feel free to post a message on the public Zulip instance. You can also create a [WIP] pull request while you are still working on your integration. See the Git guide for more on Zulip's pull request process.

Advanced topics

More complex implementation or testing needs may require additional code, beyond what the standard helper functions provide. This section discusses some of these situations.

Negative tests

A negative test is one that should result in an error, such as incorrect data. The helper functions may interpret this as a test failure, when it should instead be a successful test of an error condition. To correctly test these cases, you must explicitly code your test's execution (using other helpers, as needed) rather than call the usual helper function.

Here is an example from the WordPress webhook:

def test_unknown_action_no_data(self) -> None:
    # Mimic send_and_test_stream_message() to manually execute a negative test.
    # Otherwise its call to send_json_payload() would assert on the non-success
    # we are testing. The value of result is the error message the webhook should
    # return if no params are sent. The fixture for this test is an empty file.

    # subscribe to the target stream
    self.subscribe(self.test_user, self.STREAM_NAME)

    # post to the webhook url
    post_params = {'stream_name': self.STREAM_NAME,
                   'content_type': 'application/x-www-form-urlencoded'}
    result = self.client_post(self.url, 'unknown_action', **post_params)

    # check that we got the expected error message
    self.assert_json_error(result, "Unknown WordPress webhook action: WordPress Action")

In a normal test, send_and_test_stream_message would handle all the setup and then check that the webhook's response matches the expected result. If the webhook returns an error, the test fails. Instead, explicitly do the setup it would have done, and check the result yourself.

Here, subscribe_to_stream is a test helper that uses TEST_USER_EMAIL and STREAM_NAME (attributes from the base class) to register the user to receive messages in the given stream. If the stream doesn't exist, it creates it.

client_post, another helper, performs the HTTP POST that calls the webhook. As long as self.url is correct, you don't need to construct the webhook URL yourself. (In most cases, it is.)

assert_json_error then checks if the result matches the expected error. If you had used send_and_test_stream_message, it would have called send_json_payload, which checks the result with assert_json_success.

Custom query parameters

Custom arguments passed in URL query parameters work as expected in the webhook code, but require special handling in tests.

For example, here is the definition of a webhook function that gets both stream and topic from the query parameters:

def api_querytest_webhook(request: HttpRequest, user_profile: UserProfile,
                          payload: str=REQ(argument_type='body'),
                          stream: str=REQ(default='test'),
                          topic: str=REQ(default='Default Alert')):

In actual use, you might configure the 3rd party service to call your Zulip integration with a URL like this:

http://myhost/api/v1/external/querytest?api_key=abcdefgh&stream=alerts&topic=queries

It provides values for stream and topic, and the webhook can get those using REQ without any special handling. How does this work in a test?

The new attribute TOPIC exists only in our class so far. In order to construct a URL with a query parameter for topic, you can pass the attribute TOPIC as a keyword argument to build_webhook_url, like so:

class QuerytestHookTests(WebhookTestCase):

    STREAM_NAME = 'querytest'
    TOPIC = "Default Topic"
    URL_TEMPLATE = "/api/v1/external/querytest?api_key={api_key}&stream={stream}"
    FIXTURE_DIR_NAME = 'querytest'

    def test_querytest_test_one(self) -> None:
        # construct the URL used for this test
        self.TOPIC = "Query Test"
        self.url = self.build_webhook_url(topic=self.TOPIC)

        # define the expected message contents
        expected_subject = "Query Test"
        expected_message = "This is a test of custom query parameters."

        self.send_and_test_stream_message('test_one', expected_subject, expected_message,
                                          content_type="application/x-www-form-urlencoded")

    def get_body(self, fixture_name: Text) -> Text:
        return self.webhook_fixture_data("querytest", fixture_name, file_type="json")

You can also override get_body if your test data needs to be constructed in an unusual way. For more, see the definition for the base class, WebhookTestCase in zerver/lib/test_classes.py.

Custom HTTP event-type headers

Some third-party services set a custom HTTP header to indicate the event type that generates a particular payload. To extract such headers, we recommend using the validate_extract_webhook_http_header function in zerver/lib/webhooks/common.py, like so:

event = validate_extract_webhook_http_header(request, header, integration_name)

request is the HttpRequest object passed to your main webhook function. header is the name of the custom header you'd like to extract, such as X_EVENT_KEY, and integration_name is the name of the third-party service in question, such as GitHub.

Because such headers are how some integrations indicate the event types of their payloads, the absence of such a header usually indicates a configuration issue, where one either entered the URL for a different integration, or happens to be running an older version of the integration that doesn't set that header.

If the requisite header is missing, this function sends a PM to the owner of the webhook bot, notifying them of the missing header.

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