fastify parent-child relationship of middleware and request handler is wrong

[AbhiPrasad]

What version of OpenTelemetry are you using?

"@opentelemetry/api": "1.7.0",
"@opentelemetry/context-async-hooks": "1.21.0",
"@opentelemetry/core": "1.21.0",
"@opentelemetry/instrumentation": "0.48.0",
"@opentelemetry/instrumentation-fastify": "0.33.0",

What version of Node are you using?

Node v21.6.2

What did you do?

Using default fastify instrumentation as per https://github.com/getsentry/sentry-javascript/blob/f6a3e026ac7f04eec78495a14c0c68f9e553e22d/packages/node/src/integrations/tracing/fastify.ts#L8-L23

What did you expect to see?

parent spans fully encapsulate their children.

What did you see instead?

The middleware spans end early (they only time middleware logic itself), which means that the child request handler span is longer than it's parent. I would expect middleware spans to contain the request handler in entirely, or the request handler to be parent under http server request span directly.

Additional context

[raphael-theriault-swi]

Related to #2022

[AbhiPrasad]

If the SIG feels like the fix is to just adjust the middleware/handler spans duration/end timestamps, happy to help with a PR (can take a look at express as well). Just need to be pointing in right direction here 😄