wrong datapoint attribute value in counter metrics

[oliverdding]

I create a minimal reproducible project here: https://github.com/oliverdding/otel-test

In this demo, client send HTTP request to /hello/:app_id or /bye/:app_id, and reporting demo_client/request_counts counter metrics with attribute app_id = .... Then server will report demo_server/request_counts counter metrics with attribute app_id = ... too.

The app_id is from a fixed list: "1024", "568", "106", "1025", "197", and I'm sure server get the proper app_id value from http path(server logging).

It's really strage that in demo_client/request_counts everything is okay, but app_id would be strange string like "con", "247.c", "n.i" in demo_server/request_counts.

Can anyone give me some advice on how to fix this, thanks in advance!