Webhooks

This is a node.js application that listens for all events on BigBlueButton and sends POST requests with details about these events to hooks registered via an API. A hook is any external URL that can receive HTTP POST requests.

These web hooks allow 3rd party applications to subscribe to different events that happen during a BigBlueButton session. An event can be: a meeting was created, a user joined, a new presentation was uploaded, a user left, a recording is being processed, and many others. You can see the entire list of events that generate web hooks calls in this file.

Installation

To install webhooks, run the following command on your BigBlueButton server:

$ sudo apt-get install bbb-webhooks

Registering hooks: API calls

This application adds three new API calls to BigBlueButton's API.

Hooks/Create

Creates a new hook. This call is idempotent: you can call it multiple times with the same parameters without side effects (just like the create call for meetings). Can optionally receive a meetingID parameter: if informed, this hook will receive only events for this meeting; otherwise the hook will be global and will receive events for all meetings in the server.

A hook can be registered at any time. Even hooks for specific meetingIDs can be registered even if there is no meeting with that ID yet. Once the meeting is created, the hook will receive its events.

Hooks are permanently stored on redis and will enabled until the hook is explicitly removed via API.

Resource URL: http://yourserver.com/bigbluebutton/api/hooks/create?[parameters]&checksum=[checksum]

Parameters:

Param Name	Required / Optional	Type	Description
callbackURL	Required	String	The URL that will receive a POST call with the events. The same URL cannot be registered more than once.
meetingID	Optional	String	A meetingID to bind this hook to an specific meeting. If not informed, the hook will receive events for all meetings.
eventID	Optional	String	An eventID or a comma-separated eventID list to bind this hook to. If not informed, the hook will receive all events. (v2.5)
getRaw	Optional	Boolean	False by default. When getRaw=true, the POST call will contain the exact same message sent on redis, otherwise the message will be processed.

Response when a hook is successfully registered:

<response>
  <returncode>SUCCESS</returncode>
  <hookID>1</hookID>
  <permanentHook>false</permanentHook>
  <rawData>false</rawData>
</response>

Response when a hook is already registered:

<response>
  <returncode>SUCCESS</returncode>
  <hookID>1</hookID>
  <messageKey>duplicateWarning</messageKey>
  <message>There is already a hook for this callback URL.</message>
</response>

Response when there was an error registering the hook:

<response>
  <returncode>FAILED</returncode>
  <messageKey>createHookError</messageKey>
  <message>An error happened while creating your hook. Check the logs.</message>
</response>

Hooks/Destroy

Remove a previously created hook. A hookID must be passed in the parameters to identify the hook to be removed.

Resource URL: http://yourserver.com/bigbluebutton/api/hooks/destroy?[parameters]&checksum=[checksum]

Parameters:

Param Name	Required / Optional	Type	Description
hookID	Required	Number	The ID of the hook that should be removed, as returned in the create hook call.

Response when a hook is successfully removed:

<response>
  <returncode>SUCCESS</returncode>
  <removed>true</removed>
</response>

Response when a hook is not found:

<response>
  <returncode>FAILED</returncode>
  <messageKey>destroyMissingHook</messageKey>
  <message>The hook informed was not found.</message>
</response>

Response when a hook is not passed in the parameters:

<response>
  <returncode>FAILED</returncode>
  <messageKey>missingParamHookID</messageKey>
  <message>You must specify a hookID in the parameters.</message>
</response>

Response when there was an error removing the hook:

<response>
  <returncode>FAILED</returncode>
  <messageKey>destroyHookError</messageKey>
  <message>An error happened while removing your hook. Check the logs.</message>
</response>

Hooks/List

Returns the hooks registered. If a meetingID is informed, will return the hooks created specifically for this meeting plus all the global hooks (since they also receive events for this meetingID). If no meetingID is informed, returns all the hooks available (not only the global hooks, as might be expected).

Resource URL: http://yourserver.com/bigbluebutton/api/hooks/list?[parameters]&checksum=[checksum]

Parameters:

Param Name	Required / Optional	Type	Description
meetingID	Optional	String	A meeting ID to restrict the hooks returned only to the hooks that receive events for this meeting. Will include hooks that receive events for this meeting only plus all global hooks.

Response when there are hooks registered:

<response>
  <returncode>SUCCESS</returncode>
  <hooks>
    <hook>
      <hookID>1</hookID>
      <callbackURL><![CDATA[http://postcatcher.in/catchers/abcdefghijk]]></callbackURL>
      <meetingID><![CDATA[my-meeting</meetingID]]>> <!-- a hook created for this meeting only -->
      <permanentHook>false</permanentHook>
      <rawData>false</rawData>
    </hook>
    <hook>
      <hookID>2</hookID>
      <callbackURL><![CDATA[http://postcatcher.in/catchers/1234567890]]></callbackURL>
      <!-- no meetingID means this is a global hook -->
      <permanentHook>false</permanentHook>
      <rawData>false</rawData>
    </hook>
  </hooks>
</response>

Response when there are no hooks registered:

<response>
  <returncode>SUCCESS</returncode>
  <hooks></hooks>
</response>

Callback format

All hooks registered are called via HTTP POST with all the information about the event in the body of this request. The request is sent with the Content-type HTTP header set to application/x-www-form-urlencoded and the content in the body has the following format (when getRaw=false):

event={"data":{"type":"event","attributes":{},"event":{"ts":0}}}
timestamp=1415900488797

The attribute timestamp is the timestamp of when this callback was made. If the web hooks application tries to make a callback and it fails, it will try again several times, always using the same timestamp. Timestamps will never be the same for different events and the value will always increase.

The attribute event is a stringified version of all the data from the event (same as received from redis if getRaw=true, processed if getRaw=false). The data varies for different types of events, check the documentation for more information.

This is an example of the data sent for a meeting destroyed event when getRaw=false:

event={"data":{"type":"event","id":"meeting-ended","attributes":{"meeting":{"internal-meeting-id":"44ea85d9684005d3b0af3c49e8a271a683cedb79-1532718208098","external-meeting-id":"random-3800337"}},"event":{"ts":1532718316938}}}
timestamp=1532718316953

This is the same event for another hook with getRaw=true:

event={"envelope":{"name":"MeetingDestroyedEvtMsg","routing":{"sender":"bbb-apps-akka"}},"core":{"header":{"name":"MeetingDestroyedEvtMsg"},"body":{"meetingId":"44ea85d9684005d3b0af3c49e8a271a683cedb79-1532718208098"}}}
timestamp=1532718316953

Moreover, the callback call is signed with a checksum, that is included in the URL of the request. If the registered URL is http://my-server.com/callback, it will receive the checksum as in http://my-server.com/callback?checksum=yalsdk18129e019iklasd90i.

The way the checksum is created is similar to how the checksums are calculated for the other BigBlueButton's API calls (take a look at setConfigXML).

sha1(<callback URL>+<data body>+<shared secret>)

Where:

• <callback URL>: The original callback URL, that doesn't include the checksum.
• <data body as a string>: All the data sent in the body of the request, concatenated and joined by &, as if they were parameters in a URL.
• <shared secret>: The shared secret of the BigBlueButton server.

So, upon receiving a callback call, an application could validate the checksum as follows:

• Get the body of the request, as in the example below:

event={"data":{"type":"event","attributes":{},"event":{"ts":0}}}
timestamp=1234567890

And convert it to a string like in the example below:

event={"data":{"type":"event","attributes":{},"event":{"ts":0}}}
timestamp=1234567890

• Concatenate the original callback URL, the string from the previous step, and the BigBlueButton's salt.
• Calculate a sha1() of this string.
• The checksum calculated should equal the checksum received in the parameters of the request.

More details

• Callbacks are always triggered for one event at a time and in order. They are ordered the same way they appear on redis pubsub (which might not exactly be the order indicated by their timestamps). The timestamps will almost always be ordered as well, but it's not guaranteed.
• The application assumes that events are never duplicated on pubsub. If they happen to be duplicated, the callback calls will also be duplicated.
• Hooks are only removed if a call to /hooks/destroy is made or if the callbacks for the hook fail too many times (~12) for a long period of time (~5min). They are never removed otherwise. Valid for both global hooks and hooks for specific meetings. So it's recommended for 3rd-party applications to register the hooks more than just once. You can either check if your hook is registered with /hooks/list and register it if it isn't, or simply register your hook every e.g. 5 minutes.
• The application uses internal mappings to find out to which meeting the events received from redis are related to. These mappings are removed after 24 hours of inactivity. If there are no events at all for a given meeting during this period, it will be assumed dead. This is done to prevent data from being stored forever on redis. This means that you can have issues if you have a hook registered for an specific meeting (doesn't happen for global hooks) and this meeting happens to not generate events for 24 hours, but it's still valid after it. Something very, very unlikely to happen!
• External URLs are expected to respond with the HTTP status 2xx (200 would be the default expected). Anything different from these values will be considered an error and the callback will be called again. This includes redirects: if your hook redirects the request, it will be considered as invalid and the web hooks application will try to call this hook again.
• If a meeting is created while the web hooks application is down, callbacks will never be triggered for this meeting. The application needs to detect the create event (meeting_created_message) to have a proper mapping of internal to external meeting IDs. So make sure the web hooks application is always running while BigBlueButton is running!
• If you register a hook with, for example, the URL http://myserver.com/my/hook and no meetingID set (making it a global hook) and later try to register another hook with the same URL but with a meetingID set, the first hook will not be removed nor modified, while the second hook will not be created.

Test it

The easiest way to test the web hooks application is to register hooks in your BigBlueButton server using the API Mate and capture the callbacks using the service PostCatcher.

Follow the steps:

• Open PostCatcher and click on "Start testing your POST requests now"
• It will redirect you to an URL such as http://postcatcher.in/catchers/5527e67ba4c6dd0300000738. Save this URL to use later.
• Open the API Mate and configure your server and shared secret.
• On the menu "Custom parameters", there's a field "Custom API calls:". Add these values to it:

hooks/create
hooks/list

• On the same menu section, add the following values to "Custom parameters:":

callbackURL=http://postcatcher.in/catchers/5527e67ba4c6dd0300000738

Modify this URL to the URL you got from PostCatcher earlier.

• On the API Mate, click on the "custom call: hooks/create" link. It should respond with a success message.
• On the API Mate, click on the "custom call: hooks/list" link to check if your hook was really registered.
• Create a meeting and join it using the API Mate.
• Do stuff inside the meeting and check your PostCatcher page, you should see events pop up on it as you interact in your meeting.

Development

See Webhooks docs in GitHub.