el-telemetry — content-free metrics collector

A one-way, downstream subscriber that folds content-free el_core::DomainEvents into performance snapshots (ADR-007).

It depends on el-core and nothing depends on it, and it has no network channel of its own. Because it can only ever read the numeric and enum fields of events that are already content-free by construction, "no user content in telemetry" is structural — there is no code path by which a prompt or response could reach a metric.

What it provides

• MetricsCollector — subscribes to the domain-event stream and maintains a running snapshot. Call observe(&envelope) per event and snapshot() to read.
• TelemetrySnapshot — a Copy struct of counters and gauges: prefill_tps, decode_tps, ttft_ms, peak_bytes, tokens_generated, compressions, safety_violations.

peak_bytes is a monotonic high-water mark — it only ever rises across the events it observes.

Usage

The collector sees only numeric events from a session, whether that session is the local Qwen2.5 0.5B path or another LlmProvider; prompts and responses never enter telemetry.

use el_core::{DomainEvent, EventEnvelope, SessionId};
use el_telemetry::MetricsCollector;

let mut collector = MetricsCollector::new();

// Example events from a local Qwen2.5 0.5B prefill/decode pass.
collector.observe(&EventEnvelope::new(
    SessionId(1),
    0,
    DomainEvent::PrefillCompleted { prompt_tokens: 100, kv_len: 100, prefill_tps: 480 },
));
collector.observe(&EventEnvelope::new(
    SessionId(1),
    1,
    DomainEvent::TokenCommitted { kv_len: 101 },
));

let snap = collector.snapshot();
assert_eq!(snap.prefill_tps, 480);
assert_eq!(snap.tokens_generated, 1);

Place in the workspace

In a full build, the runtime drains EventEnvelopes from an InferenceSession (or a cloud CloudProvider's event sink) and feeds them here. This crate is the read-only end of that pipeline.

Status

Implemented and tested.

Part of the Edge Intelligence workspace. Realizes ADR-007; see the Telemetry & Privacy context.