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- Hacker News
- Webhooks are a painful problem. To clarify, Stripe's events API definitely ships a cursor and polling it has been the method preferred by large consumers for a long time.by zrail
- With webhooks, consumers get to asynchronously respond to updates from a provider. If no data has changed, a provider will not send any updates.
With SCROLL, consumers are responsible for choosing when to ask a provider for updates. Without a mechanism for knowing when data has changed, consumers will be forced to be pessimistic and poll providers for new data on some cadence.
I see two issues with the proposal: (1) SCROLL will lead to an increase in unnecessary network traffic for both the consumer and provider, and (2) because a consumer cannot know when data has changed, the lag between a consumer's local model and the provider's data model will be larger when with Webhooks.
by zffr - Webhooks are simple and ubiquitous, and that's both a weakness and a strength. It's also why they are used for a lot of things, even things they are not great for (state sync).
These weaknesses are why we[1] added FIFO endpoints, Polling Endpoints, and what we call "Svix Stream" as ways to do ordered state synchronization (each with its own tradeoffs). This lets people consume the events in the way that best fits their use-case. We are working on more things to make the state sync even easier. I'd love to hear about more challenges people are facing with webhooks, as we want to make these things better.
OP: I'd love to hear more about your thoughts there, and will send you an email in a moment.
P.S, if you're unfamiliar, please check out Standard Webhooks[2]. It's a spec we created to help with signature verification that has been adopted by OpenAI, Anthropic, Google, and many others. We are chipping at one webhook challenge at a time. :)
1: I'm the founder of Svix (mentioned in the post), we do webhooks infrastructure as a service.
by tasn - Gerard mentions it super quickly, but another massive issue with webhooks generally is local development. Yes, you can use a tunnel, but that requires all engineers on a team to add their own tunnel urls. This causes even more issues when you use the platform as a source of truth, like for auth or payments. With WorkOS specifically, your whole team develops with one shared development sandbox. You run into issues when your local dev auth (in postgres) is not synced with the shared dev sandbox that WorkOS has since not all team members have their dev environments running at once. So yeah, then you use events API. But WorkOS only preserves the events API data for 90 days (and u have make 3 calls since its a max of 30 days per call). So then you load all the data with the state API first, then you start running the events API. It's a mess.
Tried to talk about this on X until the CEO of WorkOS wanted to bring it in private, then proceeded not to help at all. https://x.com/grinich/status/1913035839866835297?s=20
by shreygupta - With the proposed solution every consumer will have a persistent connection to the server irrespective of the frequency of events. This setup seems inefficient unless you have a very high volume of events coming in. Many CDN networks have a limit on how long a connection you can open. And data providers will not prefer serving persistent requests.
Problems listed are signatures, dedup, buffering, bootstrap, cron. Everything other than signatures and bootstrap, can be solved by having a counter in every webhook payload. It will increment each time. When you receive a webhook and the counter does not match, the consumer can fetch the missing data from the events API.
I agree with the author that providers simply saying "at least once delivery" is insufficient. they should have solutions that does not require an architecture diagram.
Bootstrap is better served with a bulk events API so you don't make one call per request. It can have an after/cursor pagination. Solutions that work for our internal Kafka might not be suited to work across services, over the internet.
by bytesandbots - I much prefer cursor paginated API requests vs. webhooks. The obvious downside being that in order to not get 429'd you need a respectable poll frequency - meaning you lose reactivity to new events.
Thus I think webhooks still have a place - but as a simple "poke" that can be sent to the client to tell them something has changed - supplementing a default low frequency polling interval.
This gives us the best of both worlds:
1. No need to bother de-duping/retrying pokes - if you miss a webhook you will shortly recover anyway when you next poll. 2. No need for any local-specific tunnelling/tooling - the local app will work just fine with the default poll interval. 3. No need to keep a connection live for each client. 4. All the good stuff OP mentioned in his blog post.
by tlonny - I had the exact same thing with the Quickbooks api recently. You cannot trust the responses or webhooks at all.
On create a user or invoice for example sometimes it will return an error, yet it actually created the entity. This means you have to check manually after creating everything to know if its created properly.
Then you have the issue that sometimes quickbooks takes a while to update, and locks the company file while it does some background magic. This means you cannot immediately do the existence check, and also sometimes the check errors or times out which essentially means you need to keep checking forever until you can properly reconcile your db against theirs. But with hundreds/thousands of transactions per minute this state is never reached. You perpetually live in a state of trying to catch up but never managing it.
When I brought it up with Quickbooks dev support their response was literally "Its your job to make sure things are created properly in our system".
How did we get to this place where we started putting up with systems that cannot ever be trusted?
by alt227 - This is a nice writeup of the problems in using Webhooks for State Synchronization. I also noticed that the proposed solution is a pseudo IETF-style draft protocol called SCROLL... that happens to be remarkably similar to an actual IETF draft I am bringing to IETF 127 this November called "Braid-HTTP Subscriptions."
Both drafts request a subscription with a GET plus a header:
In both systems, the GET leaves its response open to stream events. SCROLL responds with application/x-ndjson. Braid subscriptions are a 209 Multiresponse, with content-type application/http-history. This lets them support more than just JSON. You can send updates to the state of CSV, or PNGs, XML, HTML, plain text, or any media type.Scroll Request: GET /scroll/feed/customers Prefer: stream Braid Request: GET /customers Subscribe:The author noted that it's hard to get adoption. Well, the reason that Webhooks are so common is that they are bog-standard HTTP. For this to get adopted, we need to put it into bog-standard HTTP. So we need to go to the IETF, and and extend HTTP in a general way to support state synchronization. It should just work for any existing HTTP media type (not just JSON), and any resource/URL (not just special /scroll/* URLs), and any way of marking timestamps (not just the ordered strings proposed in SCROLL).
Then we can bake this stuff into HTTP, and thus into all our bog-standard libraries, utilities, and code, and you won't have to reimplement the same sync-logic-over-webhooks again, and again, and again.
Reach out if you're interested!
by toomim