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feat: Prometheus instrumentation + business metrics #25

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forgejo_admin merged 1 commit from 24-api-observability into main 2026-03-24 20:38:21 +00:00
Conversation 2 Commits 1 Files changed 8 +64 -13
forgejo_admin commented 2026-03-24 20:27:14 +00:00
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Summary

Replace the stub /metrics endpoint (hardcoded up 1) with real Prometheus instrumentation via prometheus-fastapi-instrumentator. Adds four custom business counters for tracking receipt uploads, code saves, code redemptions, and nearby queries.

Changes

  • pyproject.toml -- added prometheus-fastapi-instrumentator>=7.0 and prometheus-client>=0.21 dependencies
  • src/mcd_tracker_api/metrics.py -- new module: instrumentator setup + four business Counter objects
  • src/mcd_tracker_api/main.py -- wire setup_metrics(app) after routers are registered
  • src/mcd_tracker_api/routes/health.py -- removed manual /metrics stub (now handled by instrumentator)
  • src/mcd_tracker_api/routes/receipts.py -- increment mcd_receipts_uploaded_total on successful upload
  • src/mcd_tracker_api/routes/locations.py -- increment mcd_codes_saved_total on code log, mcd_codes_redeemed_total on redeem
  • src/mcd_tracker_api/routes/nearby.py -- increment mcd_nearby_queries_total on each nearby query
  • tests/test_health.py -- updated metrics test to assert real Prometheus format + all four custom counters

Test Plan

  • Tests pass locally (160/161; 1 pre-existing flaky boundary test fails on main as well)
  • /metrics returns Prometheus exposition format with HTTP request metrics
  • All four custom counters visible in /metrics output
  • ruff format + ruff check pass clean
  • No deployment or ServiceMonitor changes needed

Review Checklist

  • Passed automated review-fix loop
  • No secrets committed
  • No unnecessary file changes
  • Commit messages are descriptive

Related

  • Closes #24
  • Standalone -- mcd-tracker observability buildout
## Summary Replace the stub `/metrics` endpoint (hardcoded `up 1`) with real Prometheus instrumentation via `prometheus-fastapi-instrumentator`. Adds four custom business counters for tracking receipt uploads, code saves, code redemptions, and nearby queries. ## Changes - `pyproject.toml` -- added `prometheus-fastapi-instrumentator>=7.0` and `prometheus-client>=0.21` dependencies - `src/mcd_tracker_api/metrics.py` -- new module: instrumentator setup + four business Counter objects - `src/mcd_tracker_api/main.py` -- wire `setup_metrics(app)` after routers are registered - `src/mcd_tracker_api/routes/health.py` -- removed manual `/metrics` stub (now handled by instrumentator) - `src/mcd_tracker_api/routes/receipts.py` -- increment `mcd_receipts_uploaded_total` on successful upload - `src/mcd_tracker_api/routes/locations.py` -- increment `mcd_codes_saved_total` on code log, `mcd_codes_redeemed_total` on redeem - `src/mcd_tracker_api/routes/nearby.py` -- increment `mcd_nearby_queries_total` on each nearby query - `tests/test_health.py` -- updated metrics test to assert real Prometheus format + all four custom counters ## Test Plan - [x] Tests pass locally (160/161; 1 pre-existing flaky boundary test fails on main as well) - [x] `/metrics` returns Prometheus exposition format with HTTP request metrics - [x] All four custom counters visible in `/metrics` output - [x] ruff format + ruff check pass clean - [x] No deployment or ServiceMonitor changes needed ## Review Checklist - [x] Passed automated review-fix loop - [x] No secrets committed - [x] No unnecessary file changes - [x] Commit messages are descriptive ## Related - Closes #24 - Standalone -- mcd-tracker observability buildout
feat: replace stub /metrics with real Prometheus instrumentation
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0081d158ad 
Wire prometheus-fastapi-instrumentator to expose real HTTP request
metrics (rate, latency histograms, error rates) and add four custom
business counters: mcd_receipts_uploaded_total, mcd_codes_saved_total,
mcd_codes_redeemed_total, mcd_nearby_queries_total.

Closes #24

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
forgejo_admin commented 2026-03-24 20:27:55 +00:00
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QA Review -- PR #25

Diff Analysis (8 files, +64/-13)

pyproject.toml -- Two new dependencies added correctly. No version conflicts.

src/mcd_tracker_api/metrics.py (new) -- Clean module structure. Four Counter objects with descriptive help strings. Instrumentator configured with should_ignore_untemplated=True, excluded_handlers=["/healthz", "/metrics"] matching the pal-e-docs pattern exactly. setup_metrics() function chains .instrument(app).expose(app, include_in_schema=False) correctly.

src/mcd_tracker_api/main.py -- setup_metrics(app) called after all routers are registered, which is the correct ordering for the instrumentator to discover all routes.

src/mcd_tracker_api/routes/health.py -- Manual /metrics stub and unused PlainTextResponse import cleanly removed. /healthz endpoint unchanged.

src/mcd_tracker_api/routes/receipts.py -- RECEIPTS_UPLOADED.inc() placed after db.commit() + db.refresh() succeeds. Correct -- only counts successful uploads.

src/mcd_tracker_api/routes/locations.py -- CODES_SAVED.inc() after commit in log_code(), CODES_REDEEMED.inc() after commit in redeem_code(). Both placed after DB persistence confirms success.

src/mcd_tracker_api/routes/nearby.py -- NEARBY_QUERIES.inc() at the top of the handler (before DB queries). This is intentional -- counts all query attempts, not just successful ones. Appropriate for a query volume metric.

tests/test_health.py -- Test renamed from test_metrics to test_metrics_returns_prometheus_format. Asserts real Prometheus format and all four custom counter names appear in output.

Compliance

  • Instrumentator pattern matches pal-e-docs specification
  • No deployment or ServiceMonitor changes (per issue constraints)
  • ruff format + ruff check reported clean
  • 160/161 tests pass; 1 failure is pre-existing on main (boundary timing test)
  • No secrets, no unrelated changes

Findings

No issues found.

VERDICT: APPROVE

## QA Review -- PR #25 ### Diff Analysis (8 files, +64/-13) **pyproject.toml** -- Two new dependencies added correctly. No version conflicts. **src/mcd_tracker_api/metrics.py** (new) -- Clean module structure. Four Counter objects with descriptive help strings. Instrumentator configured with `should_ignore_untemplated=True, excluded_handlers=["/healthz", "/metrics"]` matching the pal-e-docs pattern exactly. `setup_metrics()` function chains `.instrument(app).expose(app, include_in_schema=False)` correctly. **src/mcd_tracker_api/main.py** -- `setup_metrics(app)` called after all routers are registered, which is the correct ordering for the instrumentator to discover all routes. **src/mcd_tracker_api/routes/health.py** -- Manual `/metrics` stub and unused `PlainTextResponse` import cleanly removed. `/healthz` endpoint unchanged. **src/mcd_tracker_api/routes/receipts.py** -- `RECEIPTS_UPLOADED.inc()` placed after `db.commit()` + `db.refresh()` succeeds. Correct -- only counts successful uploads. **src/mcd_tracker_api/routes/locations.py** -- `CODES_SAVED.inc()` after commit in `log_code()`, `CODES_REDEEMED.inc()` after commit in `redeem_code()`. Both placed after DB persistence confirms success. **src/mcd_tracker_api/routes/nearby.py** -- `NEARBY_QUERIES.inc()` at the top of the handler (before DB queries). This is intentional -- counts all query attempts, not just successful ones. Appropriate for a query volume metric. **tests/test_health.py** -- Test renamed from `test_metrics` to `test_metrics_returns_prometheus_format`. Asserts real Prometheus format and all four custom counter names appear in output. ### Compliance - Instrumentator pattern matches pal-e-docs specification - No deployment or ServiceMonitor changes (per issue constraints) - ruff format + ruff check reported clean - 160/161 tests pass; 1 failure is pre-existing on main (boundary timing test) - No secrets, no unrelated changes ### Findings No issues found. **VERDICT: APPROVE**
forgejo_admin commented 2026-03-24 20:29:39 +00:00
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PR #25 Review

DOMAIN REVIEW

Tech stack: Python 3.12 / FastAPI / SQLAlchemy / prometheus-client / prometheus-fastapi-instrumentator

Instrumentator configuration -- Follows the pal-e-docs pattern exactly:

Instrumentator(
    should_ignore_untemplated=True,
    excluded_handlers=["/healthz", "/metrics"],
)

setup_metrics(app) is called after all routers are registered in main.py (line 68), which is the correct ordering -- the instrumentator needs to see the registered routes.

Custom counters -- All four use the _total suffix per Prometheus naming conventions for Counter metrics. Help strings are descriptive. Counters are module-level singletons imported by the route modules -- clean pattern, no DRY concerns.

Counter placement -- All four .inc() calls are positioned AFTER db.commit() + db.refresh() succeeds:

  • RECEIPTS_UPLOADED.inc() in receipts.py:85 -- after commit on line 82
  • CODES_SAVED.inc() in locations.py:176 -- after commit on line 173
  • CODES_REDEEMED.inc() in locations.py:277 -- after commit on line 274
  • NEARBY_QUERIES.inc() in nearby.py:227 -- at function entry (correct; this is a query counter, not a success counter -- counts intent, not DB mutation)

This means counters accurately reflect successful operations for the three mutation endpoints, and query volume for the nearby endpoint. Good design.

Stub removal -- The old hardcoded /metrics stub in health.py (returning mcd_tracker_api_up 1) is cleanly removed. The PlainTextResponse import is also removed since it's no longer used.

Dependencies -- prometheus-fastapi-instrumentator>=7.0 and prometheus-client>=0.21 added to pyproject.toml. Both are well-maintained packages. Version floors are reasonable.

Test coverage -- test_metrics_returns_prometheus_format in tests/test_health.py:

  • Asserts 200 status
  • Checks for standard HTTP metrics (http_request or HELP header)
  • Asserts all four custom counter names are present in the output
  • This is adequate for verifying the instrumentation wiring

CI -- .woodpecker.yaml runs ruff check, ruff format --check, and pytest with a Postgres service container. The new prometheus-* dependencies will be installed via pip install .[dev].

BLOCKERS

None.

NITS

  1. Missing type annotation on setup_metrics (src/mcd_tracker_api/metrics.py:38): The function signature is def setup_metrics(app): but should be def setup_metrics(app: FastAPI) -> None: per PEP 484. This would require importing FastAPI from fastapi in the metrics module. Minor but consistent with the rest of the codebase which uses type hints.

  2. Loose assertion for HTTP metrics (tests/test_health.py:36): The check assert "http_request" in body or "HELP" in body is intentionally broad (any HELP comment would pass), but this is acceptable since the primary purpose of the test is validating the four custom counters are registered. The instrumentator's own test suite covers HTTP metric correctness.

SOP COMPLIANCE

  • Branch named after issue (24-api-observability for issue #24)
  • PR body follows template (Summary, Changes, Test Plan, Related)
  • Related references issue (Closes #24)
  • Related notes standalone work (no plan slug needed)
  • Tests exist and cover the new functionality
  • No secrets committed
  • No unnecessary file changes (8 files, all directly related)
  • Commit messages are descriptive
  • No ServiceMonitor changes (per acceptance criteria)

PROCESS OBSERVATIONS

Clean, focused PR. 64 additions, 13 deletions across 8 files -- tight scope. The stub-to-real-instrumentation migration is a one-shot change with no intermediate state concerns. All four acceptance criteria from issue #24 are met: instrumentator wired, /metrics returns real Prometheus format, four custom business counters present, ServiceMonitor untouched. CI pipeline will validate lint + format + tests on PR event.

VERDICT: APPROVED

## PR #25 Review ### DOMAIN REVIEW **Tech stack**: Python 3.12 / FastAPI / SQLAlchemy / prometheus-client / prometheus-fastapi-instrumentator **Instrumentator configuration** -- Follows the pal-e-docs pattern exactly: ```python Instrumentator( should_ignore_untemplated=True, excluded_handlers=["/healthz", "/metrics"], ) ``` `setup_metrics(app)` is called after all routers are registered in `main.py` (line 68), which is the correct ordering -- the instrumentator needs to see the registered routes. **Custom counters** -- All four use the `_total` suffix per Prometheus naming conventions for Counter metrics. Help strings are descriptive. Counters are module-level singletons imported by the route modules -- clean pattern, no DRY concerns. **Counter placement** -- All four `.inc()` calls are positioned AFTER `db.commit()` + `db.refresh()` succeeds: - `RECEIPTS_UPLOADED.inc()` in `receipts.py:85` -- after commit on line 82 - `CODES_SAVED.inc()` in `locations.py:176` -- after commit on line 173 - `CODES_REDEEMED.inc()` in `locations.py:277` -- after commit on line 274 - `NEARBY_QUERIES.inc()` in `nearby.py:227` -- at function entry (correct; this is a query counter, not a success counter -- counts intent, not DB mutation) This means counters accurately reflect successful operations for the three mutation endpoints, and query volume for the nearby endpoint. Good design. **Stub removal** -- The old hardcoded `/metrics` stub in `health.py` (returning `mcd_tracker_api_up 1`) is cleanly removed. The `PlainTextResponse` import is also removed since it's no longer used. **Dependencies** -- `prometheus-fastapi-instrumentator>=7.0` and `prometheus-client>=0.21` added to `pyproject.toml`. Both are well-maintained packages. Version floors are reasonable. **Test coverage** -- `test_metrics_returns_prometheus_format` in `tests/test_health.py`: - Asserts 200 status - Checks for standard HTTP metrics (`http_request` or `HELP` header) - Asserts all four custom counter names are present in the output - This is adequate for verifying the instrumentation wiring **CI** -- `.woodpecker.yaml` runs `ruff check`, `ruff format --check`, and `pytest` with a Postgres service container. The new `prometheus-*` dependencies will be installed via `pip install .[dev]`. ### BLOCKERS None. ### NITS 1. **Missing type annotation on `setup_metrics`** (`src/mcd_tracker_api/metrics.py:38`): The function signature is `def setup_metrics(app):` but should be `def setup_metrics(app: FastAPI) -> None:` per PEP 484. This would require importing `FastAPI` from `fastapi` in the metrics module. Minor but consistent with the rest of the codebase which uses type hints. 2. **Loose assertion for HTTP metrics** (`tests/test_health.py:36`): The check `assert "http_request" in body or "HELP" in body` is intentionally broad (any HELP comment would pass), but this is acceptable since the primary purpose of the test is validating the four custom counters are registered. The instrumentator's own test suite covers HTTP metric correctness. ### SOP COMPLIANCE - [x] Branch named after issue (`24-api-observability` for issue #24) - [x] PR body follows template (Summary, Changes, Test Plan, Related) - [x] Related references issue (`Closes #24`) - [x] Related notes standalone work (no plan slug needed) - [x] Tests exist and cover the new functionality - [x] No secrets committed - [x] No unnecessary file changes (8 files, all directly related) - [x] Commit messages are descriptive - [x] No ServiceMonitor changes (per acceptance criteria) ### PROCESS OBSERVATIONS Clean, focused PR. 64 additions, 13 deletions across 8 files -- tight scope. The stub-to-real-instrumentation migration is a one-shot change with no intermediate state concerns. All four acceptance criteria from issue #24 are met: instrumentator wired, `/metrics` returns real Prometheus format, four custom business counters present, ServiceMonitor untouched. CI pipeline will validate lint + format + tests on PR event. ### VERDICT: APPROVED
forgejo_admin deleted branch 24-api-observability 2026-03-24 20:38:21 +00:00
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