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Incoming webhook walkthrough

Below, we explain each part of a simple incoming webhook integration, called Hello World. This integration sends a "hello" message to the test channel 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 an incoming webhook is to examine the data that the service you want to integrate will be sending to Zulip.

Use Zulip's JSON integration, https://webhook.site/, 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.
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 integration 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 incoming webhook integration, you'll want to write a test function for each distinct message condition your integration 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 5: Create automated tests or Testing for further details.

HTTP Headers

Some third-party webhook APIs, such as GitHub's, don't encode all the information about an event in the JSON request body. Instead, they put key details like the event type in a separate HTTP header (generally this is clear in their API documentation). In order to test Zulip's handling of that integration, you will need to record which HTTP headers are used with each fixture you capture.

Since this is integration-dependent, Zulip offers a simple API for doing this, which is probably best explained by looking at the example for GitHub: zerver/webhooks/github/view.py; basically, as part of writing your integration, you'll write a special function in your view.py file that maps the filename of the fixture to the set of HTTP headers to use. This function must be named "fixture_to_headers". Most integrations will use the same strategy as the GitHub integration: encoding the third party variable header data (usually just an event type) in the fixture filename, in such a case, you won't need to explicitly write the logic for such a special function again, instead you can just use the same helper method that the GitHub integration uses.

Step 1: Initialize your webhook python package

In the zerver/webhooks/ directory, create new subdirectory that will contain all of the 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 new 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 django.http import HttpRequest, HttpResponse

from zerver.decorator import webhook_view
from zerver.lib.response import json_success
from zerver.lib.typed_endpoint import JsonBodyPayload, typed_endpoint
from zerver.lib.validator import WildValue, check_string
from zerver.lib.webhooks.common import check_send_webhook_message
from zerver.models import UserProfile


@webhook_view("HelloWorld")
@typed_endpoint
def api_helloworld_webhook(
    request: HttpRequest,
    user_profile: UserProfile,
    *,
    payload: JsonBodyPayload[WildValue],
) -> 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(
        featured_title=payload["featured_title"].tame(check_string),
        featured_url=payload["featured_url"].tame(check_string),
    )

    topic = "Hello World"

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

    return json_success(request)

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

You must pass the name of your integration to the webhook_view decorator; that name will be used to describe your integration in Zulip's analytics (e.g., the /stats page). Here we have used HelloWorld. To be consistent with other integrations, 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 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 integration 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 channel, it must exist before a message can be created in it. (See Step 4: Create automated 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 (channel) message if the stream query parameter is specified in the webhook URL.
If the stream query parameter isn't specified, it will send a direct message to the owner of the webhook bot.

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

Step 3: Create an API endpoint for the webhook

In order for an incoming 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: List[WebhookIntegration] = [

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.svg 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. There are three tools which you can use to test your webhook - 2 command line tools and a GUI.

Webhooks requiring custom configuration

In rare cases, it's necessary for an incoming webhook to require additional user configuration beyond what is specified in the post URL. The typical use case for this is APIs like the Stripe API that require clients to do a callback to get details beyond an opaque object ID that one would want to include in a Zulip notification.

These configuration options are declared as follows:

    WebhookIntegration('helloworld', ['misc'], display_name='Hello World',
                       config_options=[('HelloWorld API key', 'hw_api_key', check_string)])

config_options is a list describing the parameters the user should configure: 1. A user-facing string describing the field to display to users. 2. The field name you'll use to access this from your view.py function. 3. A Validator, used to verify the input is valid.

Common validators are available in zerver/lib/validators.py.

Step 4: Manually testing the webhook

For either one of the command line tools, first, you'll need to get an API key from the Bots section of your Zulip user's Personal settings. To test the webhook, you'll need to create a bot with the Incoming webhook type. Replace <api_key> with your bot's API key in the examples presented below! This is how Zulip knows that the request was made by an authorized user.

Curl

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 running the above command, you should see something similar to:

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

Management command: send_webhook_fixture_message

Using manage.py from within the Zulip development environment:

(zulip-py3-venv) vagrant@vagrant:/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 running the above command, 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)

Some webhooks require custom HTTP headers, which can be passed using ./manage.py send_webhook_fixture_message --custom-headers. For example:

--custom-headers='{"X-Custom-Header": "value"}'

The format is a JSON dictionary, so make sure that the header names do not contain any spaces in them and that you use the precise quoting approach shown above.

For more information about manage.py command-line tools in Zulip, see the management commands documentation.

Integrations Dev Panel

This is the GUI tool.

{start_tabs}

Run ./tools/run-dev then go to http://localhost:9991/devtools/integrations/.
Set the following mandatory fields: Bot - Any incoming webhook bot. Integration - One of the integrations. Fixture - Though not mandatory, it's recommended that you select one and then tweak it if necessary. The remaining fields are optional, and the URL will automatically be generated.
Click Send!

{end_tabs}

By opening Zulip in one tab and then this tool in another, you can quickly tweak your code and send sample messages for many different test fixtures.

Note: Custom HTTP Headers must be entered as a JSON dictionary, if you want to use any in the first place that is. Feel free to use 4-spaces as tabs for indentation if you'd like!

Your sample notification may look like:

Step 5: Create automated 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):
    CHANNEL_NAME = "test"
    URL_TEMPLATE = "/api/v1/external/helloworld?&api_key={api_key}&stream={stream}"
    DIRECT_MESSAGE_URL_TEMPLATE = "/api/v1/external/helloworld?&api_key={api_key}"
    WEBHOOK_DIR_NAME = "helloworld"

    # Note: Include a test function per each distinct message condition your integration supports
    def test_hello_message(self) -> None:
        expected_topic = "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.check_webhook(
            "hello",
            expected_topic,
            expected_message,
            content_type="application/x-www-form-urlencoded",
        )

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

If your test expects a channel name from a test fixture, the value in the fixture and the value you set for CHANNEL_NAME must match. The test helpers use CHANNEL_NAME to create the destination channel, 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 incoming 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.

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_topic = "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.check_webhook(
            "goodbye",
            expected_topic,
            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-py3-venv) vagrant@vagrant:/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 6: Create documentation

Next, we add end-user documentation for our integration. You can see the existing examples at https://zulip.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!

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

1. {!create-an-incoming-webhook.md!}

1. {!generate-integration-url.md!}

1.  To trigger a notification using this example webhook, you can use
    `send_webhook_fixture_message` from a [Zulip development
    environment](https://zulip.readthedocs.io/en/latest/development/overview.html):

    ```
        (zulip-py3-venv) vagrant@vagrant:/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=abcdefgh&stream=stream%20name;'
    ```

    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=abcdefgh&stream=stream%20name;
    ```

{!congrats.md!}

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

{!create-an-incoming-webhook.md!} and {!congrats.md!} are examples 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. Mostly you should plan on templating off an existing guide, like this one.

Step 7: Preparing a pull request to zulip/zulip

When you have finished your webhook integration, follow these guidelines before pushing the code to your fork and submitting a pull request to zulip/zulip:

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 Commit discipline for tips). If not, consider revising them with git rebase --interactive. For most incoming webhooks, you'll want to squash your changes into a single commit and include a good, clear commit message.

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 draft 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 integration:

def test_unknown_action_no_data(self) -> None:
    # Mimic check_webhook() to manually execute a negative test.
    # Otherwise its call to send_webhook_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 channel
    self.subscribe(self.test_user, self.CHANNEL_NAME)

    # post to the webhook url
    post_params = {'stream_name': self.CHANNEL_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, check_webhook would handle all the setup and then check that the incoming 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 CHANNEL_NAME (attributes from the base class) to register the user to receive messages in the given channel. If the channel doesn't exist, it creates it.

client_post, another helper, performs the HTTP POST that calls the incoming 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 check_webhook, it would have called send_webhook_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):

    CHANNEL_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_topic = "Query test"
        expected_message = "This is a test of custom query parameters."

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

You can also override get_body or get_payload 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, or just grep for examples.

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 direct message to the owner of the webhook bot, notifying them of the missing header.

Handling unexpected webhook event types

Many third-party services have dozens of different event types. In some cases, we may choose to explicitly ignore specific events. In other cases, there may be events that are new or events that we don't know about. In such cases, we recommend raising UnsupportedWebhookEventTypeError (found in zerver/lib/exceptions.py), with a string describing the unsupported event type, like so:

raise UnsupportedWebhookEventTypeError(event_type)

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