Uncaught Error: Only valueType: DOUBLE is supported in Deno when using httpInstrumentationMiddleware

[PaterAnderson]

Which middleware has the bug?

@hono/otel

What version of the middleware?

1.0.1

What version of Hono are you using?

4.9.1

What runtime/platform is your app running on? (with version if possible)

deno 2.5.4

What steps can reproduce the bug?

When using @hono/otel with httpInstrumentationMiddleware in Deno:

1. Create a Deno project with Hono and @hono/otel installed.
2. Import and initialize httpInstrumentationMiddleware in your API.
3. Start the API with deno run -A main.ts.
4. Any request triggers the error.

What is the expected behavior?

Expected behavior:

• The middleware should work in Deno without throwing the error.
• HTTP traces should be created correctly.
• Active request metrics should work or be disabled properly when configured.

What do you see instead?

On every incoming request, Deno throws:

Uncaught (in promise) Error: Only valueType: DOUBLE is supported at Meter.createUpDownCounter at createActiveRequestsTracker at httpInstrumentationMiddleware

This happens even if enableActiveRequests: false is passed, suggesting that the code path is still executed.

Additional information

Because of this mismatch, any attempt to create an UpDownCounter crashes the middleware. So even though traces work fine in Deno, the middleware cannot initialize due to unsupported metric instruments.

Confirmed workarounds (but not ideal):

• Disable middleware entirely.
• Avoid using httpInstrumentationMiddleware and implement custom tracing.
• Modify the library locally to use createObservableGauge instead of createUpDownCounter.

But we would prefer a fix in the library itself.

[ysknsid25]

Can you share a minimal project to reproduce it?

In my Minimal Reproduction, Deno didn't throw Uncaught (in promise) Error: Only valueType: DOUBLE is supported at Meter.createUpDownCounter at createActiveRequestsTracker at httpInstrumentationMiddleware🤔

[PaterAnderson]

sorry for the confusion with my first minimal reproduction... I wanted to clarify why the error didn’t show up there and how it appears in my actual setup.

In my production environment, I run Deno with Hono and @hono/otel@1.0.1 inside a Docker container as part of a larger ecosystem, including an OTEL collector. The httpInstrumentationMiddleware is initialized globally in the API container, together with a custom tracer middleware, and applied to all routes. The API starts with full permissions and network access to other services.

In this context, when the middleware tries to create an UpDownCounter for active request metrics, it fails in Deno because only DOUBLE value types are supported. This doesn’t happen in the first minimal reproduction because it didn’t replicate the full initialization sequence, the middleware placement, or the containerized environment I have in production.

I’ve now created a true minimal reproduction that triggers the error. Just build and run it :)

https://github.com/PaterAnderson/minimal-reproduction

[yusukebe]

@PaterAnderson Thank you for the reply and repro!

Hey @mrlorentx or @dahlia Can you take a look at it if you have time?