The Daily Spün

Today was supposed to be a debugging day.

Instead, it turned into an investigation.

A few days ago, I discovered something strange with the Spün Moviebox API.

Whenever the stream or download endpoints were called, the API would return the exact same decoy video regardless of which subject ID was requested.

The video itself claims that the current version of Moviebox is outdated.

That immediately raised a question:

Why would the direct host we’re calling be telling us that its own version is outdated?

Still, I assumed there was something I had missed.

First attempt: update the version

The Moviebox version used by the API was hardcoded, so the first thing I tried was bumping it to the latest Moviebox version I could determine.

I changed it. Redeployed the API. Tested again.

Nothing.

The exact same video came back. Again. And again.

At that point, I had a pretty good reason to suspect that the problem wasn’t simply a stale version number.

The next step was obvious.

If I wanted to know whether the Spün Moviebox API was actually responsible, I needed to bypass it completely.

So I called Moviebox directly. No Spün API. No proxy layer. No normalization. Just the upstream hosts themselves.

And that’s when things became interesting.

Out of the seven hosts I tested:

The behavior was effectively the same thing I was seeing through the Spün API.

That changed the diagnosis completely.

After tracing the request path and testing the upstream hosts independently, the conclusion became pretty clear:

The problem isn’t coming from the Spün Moviebox API. It’s coming from Moviebox itself.

The API was simply passing along a response that was already being produced upstream.

That doesn’t mean the problem is solved, unfortunately. It just means I finally know where to look.

And that’s actually an important result.

Debugging isn’t always about immediately finding a fix. Sometimes the most useful thing you can accomplish is proving where the problem isn’t.

Because other people are currently building on the Spün Moviebox API, I’m putting out a temporary warning:

If you’re using the affected Moviebox stream/download endpoints, consider switching away from them for now.

I don’t want someone spending hours debugging their own application because they assume the issue is somewhere in their integration.

I’ll keep investigating to see whether there’s a reliable workaround. For now, though, Moviebox is the suspect, not Spün.

Today’s lesson was a pretty classic one:

Sometimes your code isn’t broken. Your dependency is.

And finding that out can take almost as much work as fixing the original problem 😪.

362 days remaining.

Back to building tomorrow.