TypeError in tracer.ts when getActiveConfig() returns undefined

[palp]

I have not attempted a simple repro so I don't know the root cause of this, but this error occurs in my worker reliably:

Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'sampling')                                                                                                                               

  const sampler = getActiveConfig().sampling.headSampler                                                                                                                                                                          
                                    ^
      at startSpan (src/tracer.ts:47:36)
      at startActiveSpan (src/tracer.ts:88:20)
      at apply (../src/instrumentation/do-storage.ts:72:17)
      at proxyHandler.apply (../src/instrumentation/wrap.ts:27:18)
      at  (C:\Users\palp\AppData\Local\Temp\tmp-35572-Q5UGGZxJVrjs/src/billing.ts:81:39)

I was able to resolve it by modifying getActiveConfig to return a default value instead of undefined, but this may or may not be appropriate/desired behavior. https://github.com/evanderkoogh/otel-cf-workers/compare/main...palp:otel-cf-workers:main

[evanderkoogh]

Hmm.. that is certainly interesting. It shouldn't be possible for getActiveConfig to return undefined. But I just realised that it is possible to do a blockConcurrencyWhile in the constructor. And it might be possible for there not to be a config set.

Do you have that scenario in this particular case?

[palp]

Hmm.. that is certainly interesting. It shouldn't be possible for getActiveConfig to return undefined. But I just realised that it is possible to do a blockConcurrencyWhile in the constructor. And it might be possible for there not to be a config set.

Do you have that scenario in this particular case?

Yep, there is a call to storage inside a blockConcurrencyWhile call which is triggering it.

[palp]

Yes, I have confirmed reproduction with this test class:

import { instrumentDO, ResolveConfigFn } from '@microlabs/otel-cf-workers'

export interface Env {
    OTEL_BASIC_AUTH: string;
    OTEL_URL: string;
}

class TestDO implements DurableObject {
    constructor(state: DurableObjectState, env: Env) {
        state.blockConcurrencyWhile(async () => {
            await state.storage.list({ prefix: 'test' })

        })
    }
    async fetch(request: Request) {
        return new Response('Hello world!', { status: 200 })
    }
}

const config: ResolveConfigFn = (env: Env, _trigger) => {
    return {
        exporter: { url: env.OTEL_URL, headers: { 'Authorization': `Basic ${env.OTEL_BASIC_AUTH}` } },
        service: { name: 'test'},
    }
}

const TestOtelDO = instrumentDO(TestDO, config)
export { TestOtelDO }

Note it only fails if the worker calling the DO is also instrumented, otherwise it seems to work as expected.

[evanderkoogh]

Awesome! Thanks for the repro.. I am trying to work out the best way to fix this. Hopefully I'll have it fixed in the next few hours :)

[evanderkoogh]

Ok.. a fix for this should be released as part of 1.0.0-rc3. The only annoying thing is that the constructor has to be in its own trace, because the fetch method hasn't been called and thus we have no idea what trace (or traces even) are waiting for the constructor to finish.

[SamyPesse]

I'm observing this issue when running tests locally with miniflare where at some point getActiveConfig starts returning undefined. I'll continue investigating, I've opened https://github.com/evanderkoogh/otel-cf-workers/issues/20 as a workaround.

EDIT: it looks related to how miniflare re-initializes the DO in between requests.

[SamyPesse]

Also got the error in production in a DurableObject, not sure why but the pattern is globally:

1. I have a durable Object DOClass
2. This class creates a new object in its constructor this.something = new SomethingWithStorage(this.state.storage)
3. Then when handling a WebSocket message, I call this.something.doSOmething() which uses the storage
4. 💥

Using 1.0.0-rc.6

[jrowny]

Also getting this same error, same exact situation and repro as @SamyPesse