refactor(emit): retire legacy backend-collector emitter — target tier never existed - #241
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… never existed
`emit/backend.rs::generate_backend_collector_config` emitted OTel-
collector YAML for a "backend-role" merge-collector tier that was never
actually deployed in any ASAPCollector configuration. Its output keyed
processors as `{sketch}_merge` with a `{mode, group_by}` body — a shape
no ASAPCollector processor accepts (the real merge processors are
factory type `{sketch}merge` with `Config { MetricName string }`).
Anything that pushed this YAML via OpAMP `push_to_role(AgentRole::Backend)`
went to zero subscribers — and any future backend collector that *did*
register would receive a config it couldn't load.
The work this path nominally did — central sketch merging — has been
taken over by the typed L5: `StageId::Backend` routes through
`emit_backend_streaming_config_json`, which posts to asapquery-backend's
precompute engine over HTTP. That's the real merge path.
Removes:
- control_plane/src/emit/backend.rs (function + 3 tests)
- pub mod / re-export entry in emit/mod.rs (table updated to record retirement)
- Imports + 4 call sites:
- main.rs::handle_plan — per-plan OpAMP push
- main.rs::handle_rollback — rollback OpAMP push
- main.rs::handle_bootstrap_backend_config + its
/api/v1/collector-config/backend route (entire handler)
- replan.rs::Replanner — replan OpAMP push
- Stale doc-comment in emit/stage_config.rs referencing the retired emitter
Kept (out of scope for this PR):
- types::BackendCollectorConfig struct + CollectionPlan.backend_config
field — still populated by the optimizer and read by metrics_exposer
for Prometheus counters. Worth re-assessing in a follow-up.
- AgentRole::Backend enum variant — public OpAMP role surface; cheap to
leave available.
Build clean. All 687 lib tests + 27 binary tests pass.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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…gentCollectorConfig (#242) Now that the legacy backend-collector emitter is retired (#241), the `BackendCollectorConfig { merge_sketch_type, group_by }` struct on `CollectionPlan` has no real consumers — both fields are derivative of `AgentCollectorConfig`: - `merge_sketch_type` was always set to `agent_config.sketch_type.clone()` (literally — see the deleted `let backend_sketch = sketch_type.clone();` line in RulesPlanner, and the deleted `backend_config_matches_sketch_type` test that asserted the equality as an invariant). - `group_by` was always `agent_config.aggregate_by.clone()` when set, else `vec![]`. The shadow was a true field-by-field duplicate. Only one site read these fields: the `metrics_exposer` plan-id hash, which already includes `agent_config.sketch_type`. Replaced `backend_config.group_by` with `agent_config.aggregate_by` in the hash (option (b) from review) to preserve the "plan_id changes when grouping changes" observability semantic. Removes: - `pub struct BackendCollectorConfig` + the `pub backend_config` field - 8 initializer sites (store, replan, optimizer/{rules×2, cost test, cost/delta test, cost/mod test}, emit/asapquery_backend test, metrics_exposer test) - 3 mutation sites in the optimizer's sketch-type tuning loops (cost/mod ×2, pareto) - The redundant `backend_config_matches_sketch_type` test in rules/mod.rs - One import of `BackendCollectorConfig` in emit/asapquery_backend.rs Plan-id hash values shift on this release — they're opaque per-plan identifiers, so anyone alerting on specific values was already on shaky ground. The semantics (changes-on-replan, stable-on-refresh) are preserved. Build clean. 686 lib tests + 27 binary tests pass (1 less than before this PR — the deleted redundant-invariant test). Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
emit/backend.rs::generate_backend_collector_config— it emitted OTel-collector YAML for a "backend-role" merge-collector tier that was never deployed in any ASAPCollector configuration. Its output keyed processors as{sketch}_mergewith a{mode, group_by}body — a shape no real ASAPCollector processor accepts (real merge processors are factory type{sketch}mergewithConfig { MetricName string }).handle_plan,handle_rollback, the/api/v1/collector-config/backendbootstrap handler, andReplanner) that all routed toAgentRole::Backend— which has zero subscribers in current deployment.StageId::Backendalready routes throughemit_backend_streaming_config_jsonto asapquery-backend's precompute engine over HTTP. That's the real merge path.What's NOT touched
Kept intentionally — these have separate consumers and warrant their own follow-up decision:
types::BackendCollectorConfig+CollectionPlan.backend_config— still populated by optimizer cost/rules and read bymetrics_exposerfor Prometheus counters.AgentRole::Backendenum variant — public OpAMP role surface, cheap to leave registered.Test plan
cargo checkclean (only pre-existing warnings)cargo test --lib: 687 passed; 0 failedcargo test --tests: 27 passed; 0 failedcargo test --bin control_plane: 27 passed; 0 failed🤖 Generated with Claude Code