Serve Prometheus metrics at /metrics behind basic auth (closes #94)

With METRICS_USERNAME and METRICS_PASSWORD both set, the backend
records request metrics through go-http-metrics in a registry of its
own, with Go's runtime and process metrics, and serves them at
GET /metrics behind basic auth with those credentials; nginx passes
/metrics to it. With neither set there is no such route; one alone
stops the start with an error naming both.

Only requests that reach the health check or POST /api/v1/reports are
recorded, not every request as the conventions show: the labels are
path and method, which clients can make up without end. So
POST /api/v1/reports is registered by its full path, not inside a
route group.

Deviation: go get and go mod tidy ran directly; no entrypoint adds a Go
dependency yet (#45).

Model: opus-5-5

.prettierignore

@@ -1,7 +1,6 @@
+backend/
 dist/
 node_modules/
 tmp/
 yarn.lock
 .claude/
-# The org standard file, copied verbatim; backend/script/lint checks its sha256.
-backend/.golangci.yml

Makefile

@@ -1,5 +1,5 @@
-.PHONY: bootstrap setup dev build test lint fmt fmt-check check \
-	frontend-check frontend-viewport-test docker hooks
+.PHONY: bootstrap setup dev test lint fmt fmt-check check frontend-check \
+	frontend-viewport-test docker hooks
 
 # Standard targets are thin shims; the implementations live in script/
 # per the scripts-to-rule-them-all pattern (see the Entrypoints section
@@ -13,11 +13,7 @@ setup:
 	@script/setup
 
 dev:
-	@script/dev
-
-# The frontend only; backend/Makefile's build target builds the Go server.
-build:
-	@script/build
+	yarn dev
 
 test:
 	@script/test

README.md

@@ -46,10 +46,6 @@ halves, so the root `make check` fails if either one is broken. We provide:
   both linters in Docker
 - `script/setup` — make a fresh clone ready for development: bootstrap plus the
   git pre-commit hook
-- `script/dev` — run the Vite dev server, which proxies `/api` to a locally
-  running `netwatch-server`
-- `script/build` — build the frontend for production into `dist/`;
-  `backend/script/build` builds the Go server
 - `script/projectname` — print the project name (used for the Docker image tag)
 - `script/test` — run `script/frontend-test`, then `backend/script/test`, the
   backend's Go tests with the race detector and coverage
@@ -65,8 +61,7 @@ halves, so the root `make check` fails if either one is broken. We provide:
 - `script/frontend-lint` — run eslint with the rules in `eslint.config.js`; it
   runs inside the `frontend-lint` stage of `Dockerfile`, which `make lint`
   builds
-- `script/frontend-fmt` — format everything prettier understands (writes), the
-  markdown in `backend/` included
+- `script/frontend-fmt` — format everything prettier understands (writes)
 - `script/frontend-fmt-check` — check prettier formatting (read-only)
 - `script/frontend-check` — run `script/frontend-test` and
   `script/frontend-fmt-check`, for the frontend stage of `Dockerfile`, which has
@@ -255,8 +250,8 @@ What the [upaas](https://git.eeqj.de/sneak/upaas) app for netwatch needs:
       the backend records Prometheus metrics of its requests and serves them at
       `/metrics` on the container port, to requests with this user name and
       password as their basic auth credentials. With neither set, there are no
-      metrics and `/metrics` is not found. One set without the other, or a user
-      name containing `:`, stops the container
+      metrics and `/metrics` is not found. One set without the other stops the
+      container
 - **Health check:** the image's `HEALTHCHECK` requests
   `/.well-known/healthcheck` through nginx every 30 seconds, so it fails unless
   both nginx and the backend answer. upaas reads the container's health 60

TODO.md

@@ -29,23 +29,12 @@ latest run passes.
   Go's runtime and process metrics, at `GET /metrics` behind basic auth with
   those credentials; nginx passes `/metrics` to it as it does `/api/`. With
   neither set there are no metrics and `/metrics` is 404; one without the other
-  stops the start with an error naming both, and so does a `METRICS_USERNAME`
-  containing `:`, with an error naming it. Only requests that reach the health
+  stops the start with an error naming both. Only requests that reach the health
   check or `POST /api/v1/reports` are recorded, not `/metrics` itself and not
   every request as `GO_HTTP_SERVER_CONVENTIONS.md` shows, because the labels are
   the request's path and method, which clients can make up without end. For
   that, `POST /api/v1/reports` is now registered by its full path instead of
   inside a `/api/v1` route group; it answers as before
-- 2026-10-04: `script/` and `Makefile` follow the org models (issue #28):
-  `make dev` shims to the new `script/dev`, the Vite dev server, and the new
-  `make build` to `script/build`, the frontend production build.
-  `.prettierignore` no longer leaves out `backend/`, so `make fmt` and
-  `make fmt-check` cover `backend/README.md`; it leaves out
-  `backend/.golangci.yml` by name, the org standard file whose sha256
-  `backend/script/lint` checks. `script/install-precommit` and the date on
-  `script/bootstrap`'s pins are the org model again; `script/bootstrap`,
-  `script/fmt` and `script/fmt-check` each say in a comment why they differ from
-  it
 - 2026-10-04: a frontend build on Node 26 or newer, such as `make test` on a
   host with Node 26, no longer prints Node's warning that `module.register()` is
   deprecated (issue #32); the build in `Dockerfile` runs on Node 22, which never

backend/README.md

@@ -32,16 +32,17 @@ pattern as the repo root: the targets in `backend/Makefile` are thin shims over
 `test`, `fmt` and `fmt-check`:
 
 - `script/build` — compile the static `netwatch-server` binary with its version
-  stamped in. The version is `VERSION` from the environment; when that is unset
-  or empty, it falls back to `git describe` inside a git checkout, then to `dev`
+  stamped in. The version is `VERSION` from the environment;
+  when that is unset or empty, it falls back to `git describe` inside a git
+  checkout, then to `dev`
 - `script/test` — run the Go tests with the race detector and coverage. Go's
   `-timeout 30s` bounds the tests, not their compile. If they fail, they run
   again with `-v` for the details, and the script fails. The race detector needs
   a C compiler
 - `script/lint` — check `.golangci.yml` against its pinned sha256, then run
-  golangci-lint. It runs inside the golangci-lint image of the lint stage of the
-  root `Dockerfile`; from a checkout, run `make lint` at the repo root, which
-  builds that stage
+  golangci-lint. It runs inside the golangci-lint image of the lint stage of
+  the root `Dockerfile`; from a checkout, run `make lint` at the repo root,
+  which builds that stage
 - `script/fmt` — format the Go sources (writes)
 - `script/fmt-check` — check Go formatting (read-only)
 - `script/run` — build and run the server locally
@@ -60,9 +61,8 @@ flushes them to compressed files on disk for later analysis.
 
 ## Design
 
-The server is structured as an `fx`-wired Go application under
-`cmd/netwatch-server/`. Internal packages in `internal/` follow standard Go
-project layout:
+The server is structured as an `fx`-wired Go application under `cmd/netwatch-server/`.
+Internal packages in `internal/` follow standard Go project layout:
 
 - **`config`**: Loads configuration from environment variables and config files
   via Viper.
@@ -91,12 +91,11 @@ project layout:
 | `METRICS_USERNAME`     | empty                | Basic auth user name for `/metrics`; see [Metrics](#metrics)                                             |
 | `METRICS_PASSWORD`     | empty                | Basic auth password for `/metrics`; see [Metrics](#metrics)                                              |
 
-`TRUSTED_PROXIES` defaults to
-`127.0.0.1/32,::1/128,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16`. The loopback
-entries cover a reverse proxy on the same host. A request whose direct peer is
-outside this set has its forwarded headers ignored, and the direct peer is
-logged and rate-limited instead. The container image does not use this default;
-see [Container image](#container-image).
+`TRUSTED_PROXIES` defaults to `127.0.0.1/32,::1/128,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16`.
+The loopback entries cover a reverse proxy on the same host. A request whose
+direct peer is outside this set has its forwarded headers ignored, and the
+direct peer is logged and rate-limited instead. The container image does not use
+this default; see [Container image](#container-image).
 
 A variable set to a value the server cannot use, such as `PORT=abc`,
 `DEBUG=maybe` or a `BIND_ADDRESS` that is not an IP address, stops it from
@@ -165,7 +164,8 @@ credentials, so it is bounded instead. Both refusals below answer with the same
   to be written fill the cap on their own, and then no file is deleted. At
   start, report files past the cap, as after lowering it, are deleted the same
   way. So the cap is how much of the newest reports is kept: the default of 1
-  GiB is small enough for any host; set it to the space you can give `DATA_DIR`.
+  GiB is small enough for any host; set it to the space you can give
+  `DATA_DIR`.
 
 ### CORS
 
@@ -189,14 +189,11 @@ method and status; they also count those requests in progress, and include Go's
 runtime and process metrics. No other request is recorded: not those to
 `/metrics` itself, and not those answered before they reach either route, such
 as a CORS preflight, or a request refused with 404 for a path no route has, 405
-for a method its route does not take, or 413 for declaring a body length over
-the 1 MiB limit. A report whose body goes over the limit without declaring its
-length reaches the route, is answered 413 there, and is recorded with that
-status. Clients can make up any number of paths and methods, and each would add
-labels to the metrics for as long as the server runs. With neither set, nothing
-is recorded and `/metrics` answers 404. One without the other stops the server
-from starting, with an error naming both; so does a `METRICS_USERNAME`
-containing `:`, which basic auth cannot carry, with an error naming it.
+for a method its route does not take, or 413 for a body over the 1 MiB limit.
+Clients can make up any number of paths and methods, and each would add labels
+to the metrics for as long as the server runs. With neither set, nothing is
+recorded and `/metrics` answers 404. One without the other stops the server
+from starting, with an error naming both.
 
 ## TODO
 

backend/internal/config/config.go

@@ -49,10 +49,6 @@ var (
 		"METRICS_USERNAME and METRICS_PASSWORD must be set together, " +
 			"or neither",
 	)
-	errMetricsUsernameColon = errors.New(
-		"METRICS_USERNAME must not contain \":\", " +
-			"which basic auth cannot carry in a user name",
-	)
 )
 
 // Params defines the dependencies for Config.
@@ -193,12 +189,6 @@ func (s *Config) check() error {
 		return errMetricsCredentials
 	}
 
-	// Basic auth splits the credentials at the first ":", so with one
-	// in the user name every request to /metrics would get 401.
-	if strings.Contains(s.MetricsUsername, ":") {
-		return errMetricsUsernameColon
-	}
-
 	return checkOrigins(s.CORSAllowedOrigins)
 }
 

backend/internal/config/config_test.go

@@ -119,16 +119,6 @@ func TestMetricsCredentialsGoTogether(t *testing.T) {
 	}
 }
 
-// TestMetricsUsernameMustNotContainColon: basic auth splits the
-// credentials at the first ":", so such a user name would get 401 on
-// every request to /metrics.
-func TestMetricsUsernameMustNotContainColon(t *testing.T) {
-	t.Setenv("METRICS_USERNAME", "prom:etheus")
-	t.Setenv("METRICS_PASSWORD", "secret")
-
-	requireConfigError(t, "METRICS_USERNAME")
-}
-
 // TestCORSAllowedOriginsMustBeOrigins: "*" would let every origin in,
 // and an entry that is not a plain origin would match no page.
 func TestCORSAllowedOriginsMustBeOrigins(t *testing.T) {

script/bootstrap

@@ -17,13 +17,11 @@
 #
 # golangci-lint is not installed: make lint runs it in Docker, which
 # this script does not install either.
-#
-# Unlike the org model: Go and gcc for backend/, a newer node for eslint.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 
-# Pinned versions, 2026-07-06
+# Pinned versions, 2026-07-07
 NODE_VERSION="22.17.0"
 # The oldest node the frontend's dependencies accept: the "engines"
 # field of eslint 10.12.0, the most demanding of them, asks for 22.13.0

script/build

@@ -1,13 +0,0 @@
-#!/bin/sh
-# script/build: build the frontend for production into dist/. The Go
-# backend is built by backend/script/build.
-set -eu
-
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-
-main() {
-    cd "$ROOT"
-    yarn build
-}
-
-main "$@"

script/dev

@@ -1,13 +0,0 @@
-#!/bin/sh
-# script/dev: run the frontend's Vite dev server. It proxies /api to a
-# netwatch-server running locally (see vite.config.js).
-set -eu
-
-ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
-
-main() {
-    cd "$ROOT"
-    yarn dev
-}
-
-main "$@"

script/fmt

@@ -1,7 +1,6 @@
 #!/bin/sh
 # script/fmt: format the whole repo (writes): prettier over everything
 # it understands, then gofmt over the Go backend.
-# The org model formats only markdown; this repo also has JS and Go.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"

script/fmt-check

@@ -1,7 +1,6 @@
 #!/bin/sh
 # script/fmt-check: check formatting across the whole repo (read-only).
 # Same scope as script/fmt, but fails instead of writing.
-# The org model checks only markdown; this repo also has JS and Go.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"

script/frontend-fmt

@@ -1,7 +1,7 @@
 #!/bin/sh
 # script/frontend-fmt: format the frontend and every other file prettier
-# understands, repo-wide (writes), the markdown in backend/ included.
-# Prettier does not read Go; backend/script/fmt formats the Go sources.
+# understands, repo-wide (writes). backend/ is in .prettierignore; Go
+# sources are formatted by backend/script/fmt.
 set -eu
 
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"

script/install-precommit

@@ -8,8 +8,8 @@ ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 main() {
     cd "$ROOT"
     hook=".git/hooks/pre-commit"
-    printf '#!/bin/sh\nset -e\nscript/precommit\n' > .git/hooks/pre-commit
-    chmod +x .git/hooks/pre-commit
+    printf '#!/bin/sh\nset -e\nscript/precommit\n' > "$hook"
+    chmod +x "$hook"
     echo "pre-commit hook installed: runs script/precommit"
 }