How to configure automatic APM metrics correctly?

[nacho692]

I've been using custom metrics to discriminate http.status_code and http.method.

According to https://docs.datadoghq.com/tracing/guide/metrics_namespace/ I should have access to at least http.status_code, but the tag is missing in the metric.

I am using the opentracing API and setting the tags manually.

opentracing:v1.2.0
dd-trace-go.v1:v1.34.0
datadog-agent:7 88420c49af00

[deadok22]

I ran into what appears to be the same issue.

In my setup, the spans with the HTTP metadata that should yield the http.status_code and other tags described in https://docs.datadoghq.com/tracing/guide/metrics_namespace/ are rendered by the instrumentation from opentracing-contrib. The http.status_code value is added on this line as a numeric tag. But Datadog Agent only looks for the http status code in the span's metadata fields.

The options for fixing this are:

• Patch dd-trace-go's opentracing implementation so that it adds http status and other fields to metadata rather than metrics. See how Datadog's native http instrumentation does this.
• Have datadog-agent explore the metrics part of the trace payload here in addition to the metadata.

If it was up to me, I'd fix it on the agent end: encoding and decoding integers is more efficient than strings, no changes in the applications are necessary. However, I may be lacking some context making this a bad option. It'd be cool if somebody from Datadog looked into this.

[knusbaum]

👋 @nacho692 @deadok22

Looking into this. Thanks for the detailed information.

My initial inclination is to change this in the agent as @deadok22 suggests.