jedarden 72bcad0603 P2.8: Verify middleware implementation - structured logging + Prometheus metrics + request IDs

All acceptance criteria verified:
- Request ID generation (UUIDv7 prefix short-hashed) as X-Request-Id header
- Structured JSON logs parseable by jq
- Prometheus metrics: request duration, request count, in-flight gauge
- Scatter metrics: fan-out size, partial responses, retries
- Node metrics: health, request duration, errors
- Metrics server on :9090
- High-cardinality defense: path_template instead of path

All 15 P2.8 acceptance tests pass.

Bead-Id: miroir-9dj.8

2026-05-23 12:47:25 -04:00

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P2.8 Middleware: Structured Logging + Prometheus Metrics + Request IDs

Summary

Verified that the miroir-proxy middleware implementation meets all P2.8 acceptance criteria:

Implementation Verified

1. Request ID Generation

RequestId::new() generates 8-character hex IDs using UUIDv7 + hashing
request_id_middleware injects X-Request-Id header on all responses
Existing request IDs are preserved, invalid ones are replaced

2. Structured JSON Logging

tracing-subscriber configured with JSON output in main.rs
Log format follows plan §10: timestamp, level, message, duration_ms
request_id appears in all log lines via span propagation
Logs go to stdout, one JSON object per line

3. Prometheus Metrics

All required metrics implemented in middleware.rs:

Request metrics:

miroir_request_duration_seconds{method, path_template, status} (Histogram)
miroir_requests_total{method, path_template, status} (Counter)
miroir_requests_in_flight (Gauge)

Scatter metrics:

miroir_scatter_fan_out_size (Histogram)
miroir_scatter_partial_responses_total (Counter)
miroir_scatter_retries_total (Counter)

Node metrics:

miroir_node_healthy{node_id} (Gauge)
miroir_node_request_duration_seconds{node_id, operation} (Histogram)
miroir_node_errors_total{node_id, error_type} (Counter)

4. Metrics Server

Metrics server runs on :9090 via metrics_router()
/metrics endpoint returns Prometheus exposition format
Separate listener from main API server

5. High-Cardinality Defense

extract_path_template() uses Axum's MatchedPath extractor
Path templates like /indexes/{uid}/search instead of actual UIDs
Prevents Prometheus cardinality explosion from arbitrary IDs

Acceptance Tests Passed

All 15 tests in p2_8_middleware_acceptance_tests.rs pass:

test_metrics_endpoint_returns_all_metrics ✓
test_metrics_server_on_9090 ✓
test_log_lines_parse_as_json ✓
test_log_format_matches_plan_section_10 ✓
test_request_id_in_response_header ✓
test_request_id_propagates_from_request ✓
test_path_template_prevents_high_cardinality ✓
test_request_id_format ✓
test_request_id_uniqueness ✓
test_telemetry_middleware_updates_metrics ✓
test_in_flight_gauge_increments_and_decrements ✓
test_scatter_metrics_recorded ✓
test_node_metrics_recorded ✓
test_full_middleware_stack_integration ✓
test_header_map_extensions ✓

Files Verified

crates/miroir-proxy/src/middleware.rs - Complete middleware implementation
crates/miroir-proxy/src/main.rs - Metrics server on :9090, JSON logging init
crates/miroir-proxy/tests/p2_8_middleware_acceptance_tests.rs - All acceptance tests pass
crates/miroir-proxy/tests/p7_5_structured_logging.rs - All structured logging tests pass

2.8 KiB Raw Blame History