“Good ideas are common – what’s uncommon are people who’ll work hard enough to bring them about.”
— Ashleigh Brilliant
There is quite a bit of Webhook stuff in various IntegrationHub spokes, but it all seems to be oriented towards consuming incoming events from different external event publishers. I want to actually be the publisher, and send out information based on some preferences selected by the consumer. That may be hidden somewhere in the Now Platform already, but I can’t seem to find it, so I have decided that I would try to develop a Scoped Application to do just that. This may very well be recreating something that already exists in the platform today, but it sounds like a fun exercise, so I am going to give it the old college try.
As always, I will attempt to start out with the most basic of offerings, and then incrementally expand to add more and better features. My approach is to treat this feature as somewhat analogous to a Watch List, in that you sign up to follow certain events, but instead of sending a notification to a User when the event occurs, the result will be that the information is posted to a specified URL. This can apply to any number of things, but to start off, I am going to focus on some very specific changes to one particular table (Incident), and then later expand from there.
To make this work, there will need to be some kind of Webhook Registry where a consumer would sign up to receive these posts. When registering your webhook, you would enter the URL to which you want the data posted along with the specifics of what type or types of events you would like to have included. I’m thinking about linking them directly to an owner, and having some kind of My Webhooks Portal Page where you could manage your existing registrations and add new ones. When adding a new one, you should be able to enter and test your URL, and for our first iteration, that may be the only choice that you get. Later on, we will want to add the ability to choose what you want to follow, which specific updates should trigger a new post, and even what you would like to have included in the payload. But we will also want to start out as simple as possible, so the initial registry may turn out to be quite barren as far as input fields go.
Once registered, there will need to be some process to actually send out the posts as requested in the registration. This could be a Business Rule on the source table, or maybe something created in the Flow Designer. Either way, the process should scan the registry for any condition matches and then send out a post for each match. Each post and response should be logged in some kind of Webhook Activity Log, and any bad HTTP Response Codes should be reported to Event Management. A robust service would attempt to repost any failures up to a certain limit before giving up completely, but all of that can be delegated to some Alert Management Rule at some later time. Again, we will want to start out simple, so our initial focus will just be on making that initial post attempt. Everything else can be pushed off until later on in the process.
Those would seem to be the two major functions: registering the webhook and sending out the posts. We may want some other things at some point, such as the ability to review the logs or to manually repost or to clone an existing registration, but for now, just those two things should get the ball rolling. We may also want to set up a sample receiver for testing purposes, but in practice, the receivers would be other products and outside the scope of this development exercise. There is actually an existing service out on the Internet called Webhook.site that might turn out to be just what I need in order to do a little testing. We should check that out when we get to that point.
For our parts list, then, I can see the need for the following artifacts:
- A table to hold the webhook registrations,
- A my_webhooks portal widget to list all webhooks owned by the user,
- A webhook portal widget for editing a single webhook registration,
- A Business Rule or Flow to send out the posts,
- A log table to record the posts and response, and possibly
- A Script Include to contain some common functions.
Of course, before we create any of that, we will have to create the Scoped Application itself, so that should be where we start next time when we initiate the actual construction phase of this effort.