[Next.js] _sentryTraceData different for the same request

[Betchika99]

Hello. I have a problem with generating etags by Next.js in production - when I reload one page some times, I have different etags. As I could catch from Next.js etag generation code - it just calculate hash from page content. I found the difference in page content - it's only in "_sentryTraceData". I coudn't found the idea, why this field has different value, if the request is the same (I've just pushed reload button in the browser). Could you explain me please, how I can fix it?

Extra info about env:

• Next.js v12.1.0
• @sentry/nextjs v7.80.0

For generation pages we use getServerSideProps, and in this object I found this different _sentryTraceData value.
We have some instances (pods) of Next, if it's important.

[AbhiPrasad]

Hey @Betchika99, thanks for writing in! _sentryTraceData is different because it contains values we use for distributed tracing. In this case, each request has a unique trace ID used to relate spans, errors, and replays together across backend and frontend - this is injected into _sentryTraceData.

is it possible to ignore the value of _sentryTraceData?

[Betchika99]

Hi, @AbhiPrasad ! Thank you for answering. If I could ignore this field, I would be satisfied, but I don’t know, how to do it :(
I’ve tried remove this key for _app.tsx, and also have tried put “enabled” and “enableTracing” settings to “false” in sentry config - unsuccessfully. How I can ignore it?

[lforst]

The only easy way is to set autoInstrumentServerFunctions: false in your next.config.js. But that will get rid of a lot of auto instrumentation that you would need to set up yourself.