How to add status code to tracing spans with OpenTelemetry plugin?
How to add status code to tracing spans with the OpenTelemetry plugin
Uses:
Kong Gateway
TL;DR
How do I add a status code attribute to OpenTelemetry tracing spans in Kong?
Kong’s OpenTelemetry plugin doesn’t include a status code attribute in spans by default. Add a pre-function plugin that calls kong.tracing.active_span():set_attribute("http.status_code", kong.response.get_status()) in config.header_filter — but note this only reaches the true root span when tracing_instrumentations is set to a lighter level like request or router; at tracing_instrumentations = all it attaches to a nested child span instead.
Steps
By default, the OpenTelemetry plugin will not include a status code attribute in spans.
We could apply a pre-function plugin to include status code attribute in spans.
Below is an example configuration of the pre-function plugin
scope: global or the same service/route entity with OpenTelemetry plugin
config.header_filter:
local root_span = kong.tracing.active_span()
root_span:set_attribute("http.status_code", kong.response.get_status())Next send some requests through kong and confirm the http.status_code attribute is in the root span.
Note: kong.tracing.active_span() only reliably returns the true root span at lighter tracing_instrumentations levels (e.g. request or router). At tracing_instrumentations = all, the active span in the header_filter phase is a nested per-plugin child span rather than the root span, so setting the attribute this way no longer attaches it to the root span in that configuration.