Krisztian F 15eecd02c9 Define a production-ready default tracing policy (#711) ...

Today everything outside ateapi hardcodes `ParentBased(NeverSample)`,
and setting `OTEL_TRACES_SAMPLER` does nothing because an explicit
sampler silences the SDK's env handling. This makes troubleshooting
production issues impossible via traces.

This PR gives every component a sane default and makes the standard OTel
env vars work:

- Control plane (ateapi, atelet, ateom) defaults to
`parentbased_traceidratio` 0.1, the router (data plane root) to 0.01,
per the discussion on #584.
- `OTEL_TRACES_SAMPLER` / `OTEL_TRACES_SAMPLER_ARG` override any of this
without a rebuild. Invalid values keep the component default and log a
warning instead of inheriting the SDK's fall-open-to-100% behavior.
- Envoy's `RandomSampling` is derived from the router's resolved policy,
so the two root decisions cannot drift.
- kubectl-ate without `--trace` no longer installs a tracer provider at
all: the old `NeverSample` provider injected `sampled=0`, which pinned
every parent based sampler downstream and would have defeated the server
side ratios. `--trace` still forces a full end to end trace.
- ate-controller propagates the two env vars to the ateom worker pods it
creates, same as the metric export vars.
- kind pins ateapi to `parentbased_always_on`, so the local Jaeger flow
keeps showing every API call.
- The agentgateway integration follows what we have above. its
`randomSampling` changes from `true` to `0.01` to match the data plane
default, though as static config it does not follow
`OTEL_TRACES_SAMPLER` overrides, so the two need adjusting together.


Verified on a kind cluster e2e manually. It resolved samplers logged at
startup, a `--trace` resume produced one trace across ateapi, atelet,
and ateom, an unsampled CLI call got picked up server side, Envoy
continued a sampled traceparent while sampling 0 of 30 parentless
requests at the 1% default, and an invalid env value fell back to the
component default.

Gating who may use `--trace` stays a separate follow-up (and a
discussion), and the more sophisticaed tracing policies belongs in a
collector, not in substrate.

Fixes #584
cc. @git286 

- [x] Tests pass
- [x] Appropriate changes to documentation are included in the PR

2026-08-04 11:31:04 -04:00

..

main.go

Define a production-ready default tracing policy (#711)

2026-08-04 11:31:04 -04:00