server.go starts listenAndServe in an anonymous function (closes #162)

The server's OnStart hook started the HTTP listener with
`go s.listenAndServe()`; the Go style guide asks for a function called
with `go` to be wrapped in an anonymous function, so it is now
`go func() { s.listenAndServe() }()`. No other go statement in the Go
code called a function directly. Nothing the server does changed.

Model: opus-5-5

.dockerignore

@@ -73,9 +73,12 @@
 
 # This repository's own entries, after the shared content above: the
 # frontend build, the viewport test's output, the binary `make build`
-# writes and the reports `make run` stores, and log files at the root.
+# writes and the reports `make run` stores, and Go test binaries,
+# coverage output and log files at the root.
 /dist
 /tmp
 /netwatch-server
 /data
+/*.test
+/*.out
 /*.log

.editorconfig

@@ -11,7 +11,8 @@ insert_final_newline = true
 [Makefile]
 indent_style = tab
 
-# This repository's own entries, after the shared content above.
-
 [*.go]
 indent_style = tab
+
+# This repository's own sections, such as one for another language it
+# uses, go below this comment, and a re-vendor keeps them.

.gitea/workflows/check.yml

@@ -1,9 +1,20 @@
 name: check
 on: [push]
+# Free the shared runner: a new push cancels only the same branch's older run.
+concurrency:
+    group: ${{ github.workflow }}-${{ github.ref }}
+    cancel-in-progress: true
 jobs:
     check:
         runs-on: ubuntu-latest
+        # Free the shared runner from a hung build.
+        timeout-minutes: 20
         steps:
             # actions/checkout v4.2.2, 2026-02-22
             - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+              # script/cibuild needs no token, so none is left in .git/config.
+              with:
+                  persist-credentials: false
+                  # All history and tags, so git describe finds the version tag.
+                  fetch-depth: 0
             - run: script/cibuild

.gitignore

@@ -27,7 +27,7 @@ node_modules/
 # Environment files. `*.env` covers bare `.env` and the `prod.env`
 # convention. Only the templates `example.env` and `sample.env` are
 # re-included below. A repository that commits any other template adds
-# its own negation after these lines, for example `!.env.example`.
+# its own negation at the end of this file, for example `!.env.example`.
 *.[eE][nN][vV]
 .[eE][nN][vV].*
 .[eE][nN][vV][rR][cC]
@@ -46,7 +46,9 @@ node_modules/
 [iI][dD]_[eE][dD]25519
 [iI][dD]_[eE][dD]25519_[sS][kK]
 
-# This repository's own entries, after the shared content above.
+# This repository's own entries, such as its build outputs, go below
+# this comment, and a re-vendor keeps them. Anchor a binary built at the
+# root: `/myapp`, never `myapp`, which also ignores `cmd/myapp/`.
 
 # Build output
 dist/

.golangci.yml

@@ -25,6 +25,8 @@ linters:
     # silenced by disabling that name, not by enabling the successor.
     - wsl              # Deprecated, replaced by wsl_v5
     - gomodguard       # Deprecated, replaced by gomodguard_v2
+    # Misses findings at random in v2.14.0; back once a pinned release fixes it
+    - canonicalheader
   settings:
     lll:
       line-length: 88

README.md

@@ -55,7 +55,8 @@ either one is broken. We provide:
 - `script/build` — build the frontend for production into `dist/`, then the
   static `netwatch-server` binary into the repo root with its version stamped
   in: `VERSION` from the environment, or when that is unset or empty,
-  `git describe` inside a git checkout, then `dev`
+  `git describe --tags --always --dirty` inside a git checkout, as
+  `script/docker` does, then `dev`
 - `script/run` — build with `script/build`, then run `netwatch-server` with its
   defaults (see [Settings](#settings))
 - `script/clean` — remove what `script/build` writes
@@ -207,7 +208,9 @@ stops. Its routes:
   address may send a limited number a minute, and the report files are capped in
   size, the oldest deleted first
 - `GET /.well-known/healthcheck` — answers 200 with `"status":"ok"`, the
-  server's version and its uptime
+  server's version and its uptime; while reports cannot be stored, as the last
+  write of a report file failed, it answers 503 with `"status":"error"` and the
+  same fields (see [Report storage](#report-storage))
 - `GET /metrics` — Prometheus metrics behind basic auth, only when
   `METRICS_USERNAME` and `METRICS_PASSWORD` are set; each client address may
   make a limited number of requests to it a minute
@@ -215,6 +218,10 @@ stops. Its routes:
 It is an `fx`-wired Go application: `cmd/netwatch-server/` starts it, and its
 packages are in `internal/`:
 
+- **`cli`**: Runs `netwatch-server` from its command line: the `check-cidr` and
+  `prepare-data-dir` subcommands, which `bin/entrypoint.sh` runs before it
+  starts the server, and, given no arguments, the server, with the `fx` wiring.
+  It refuses any other arguments with a usage message and exit code 2.
 - **`config`**: Loads configuration from environment variables and config files
   via Viper.
 - **`handlers`**: HTTP request handlers for the API (health check, report
@@ -282,10 +289,11 @@ The reports of a failed write stay in memory, and the next flush, within a
 minute, tries again to write them. The server writes one file at a time, so a
 file holds its reports in the order they arrived, those of a failed write
 included. From the failed write until a write succeeds, `POST /api/v1/reports`
-refuses every report with 500 and keeps nothing of it. The page sends the
+refuses every report with 500 and keeps nothing of it, and the health check
-refused samples again in its next report, as long as it still holds them: at the
+answers 503 with `"status":"error"`. The page sends the refused samples again in
-1-second interval one refused report already loses some of those in the history
+its next report, as long as it still holds them: at the 1-second interval one
-(see [Reporting](#reporting)). Reports already answered 200 are lost only if the
+refused report already loses some of those in the history (see
+[Reporting](#reporting)). Reports already answered 200 are lost only if the
 server stops before a write succeeds; the final flush at stop tries them too,
 and if it fails, the process exits non-zero.
 
@@ -559,9 +567,16 @@ What the [upaas](https://git.eeqj.de/sneak/upaas) app for netwatch needs:
       stops the container. Empty, the backend sends nothing to Sentry
 - **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
+  both nginx and the backend answer. It also fails while reports cannot be
-  seconds after a deploy and fails the deploy unless it is `healthy`. The
+  stored, as when the volume is full or `DATA_DIR` cannot be written: the health
-  container also stops when either process exits.
+  check answers 503 from a failed write of a report file until a write succeeds,
+  and the backend tries the write again every minute. Three failed checks in a
+  row make the container `unhealthy`, and one that passes makes it `healthy`
+  again. upaas reads the container's health once, 60 seconds after a deploy, and
+  fails the deploy unless it is `healthy`. A container that turns `unhealthy`
+  after that is neither restarted nor reported by upaas, whose `unless-stopped`
+  restart policy ignores health; only `docker ps` and `docker inspect` show it.
+  The container also stops when either process exits.
 
 ## Browser Compatibility
 

TODO.md

@@ -9,10 +9,12 @@
 
 # Status
 
-pre-1.0. No git tags. `main` is the stable branch and `next` the development
+pre-1.0. Release candidates are tagged on `next`, the first being `v1.0.0-rc1`;
-branch, which every PR targets. The frontend and the Go backend ship as one
+`git tag --merged origin/next` lists them. `main` is the stable branch and
-Docker image, and the Gitea workflow `.gitea/workflows/check.yml` runs
+`next` the development branch, which every PR targets. The frontend and the Go
-`script/cibuild` on every push. Working toward 1.0.0.
+backend ship as one Docker image, and the Gitea workflow
+`.gitea/workflows/check.yml` runs `script/cibuild` on every push, and cancels
+the older run on the same branch. Working toward 1.0.0.
 
 # Next Step
 
@@ -21,6 +23,72 @@ Run `make frontend-viewport-test` in CI as its own step; it is not part of
 
 # Completed Steps
 
+- 2026-10-19: the server's `OnStart` hook in `internal/server/server.go` starts
+  `listenAndServe` with `go func() { s.listenAndServe() }()`, as the Go style
+  guide asks ([#162](https://git.eeqj.de/sneak/netwatch/issues/162)); it was
+  `go s.listenAndServe()`. No other `go` statement in the Go code called a
+  function directly. Nothing the server does changed
+- 2026-10-19: `.gitignore`, `.editorconfig` and `.golangci.yml` are the
+  sneak/prompts copies at `0653579`
+  ([#174](https://git.eeqj.de/sneak/netwatch/issues/174)). `.gitignore` is the
+  standard file followed by this repository's own entries; `.editorconfig` is
+  the standard file alone, which now carries the `[*.go]` section.
+  `.golangci.yml` disables `canonicalheader`, as the canonical copy does,
+  because golangci-lint v2.14.0 misses its findings at random
+- 2026-10-19: `package.json` has no `version` field and is marked
+  `"private": true` ([#158](https://git.eeqj.de/sneak/netwatch/issues/158)). It
+  said `1.0.0`, a release that has not been made, and nothing read it; the git
+  tag is the one version, which the image and `make build` take from
+  `git describe --tags`. The package is never published
+- 2026-10-19: Status names `v1.0.0-rc1`, the first release candidate, and says
+  release candidates are tagged on `next`, where it said there were no git tags
+  ([#157](https://git.eeqj.de/sneak/netwatch/issues/157)). The rest of Status
+  matches the tree
+- 2026-10-19: `netwatch-server` starts the server only when given no arguments
+  ([#179](https://git.eeqj.de/sneak/netwatch/issues/179)). `check-cidr CIDR` and
+  `prepare-data-dir DATA_DIR` behave as before; any other arguments, such as a
+  subcommand with no value or two, or a misspelt one, print a one-line usage
+  message naming both forms to stderr and exit 2. They used to start the server.
+  Unit tests call `cli.Main` with no arguments and check that it starts the
+  server, and with each subcommand given no value and two values and with a
+  misspelt subcommand, and check the exit code, the message and that the server
+  does not start
+- 2026-10-19: `main()` in `cmd/netwatch-server/main.go` is one call into a new
+  package, `internal/cli`, as the Go style guide asks
+  ([#160](https://git.eeqj.de/sneak/netwatch/issues/160)). `internal/cli` runs
+  the `check-cidr` and `prepare-data-dir` subcommands, with the same arguments,
+  messages and exit codes, and otherwise the server, with the `fx` wiring.
+  `Appname` and `Version` stay in `main`, where the build sets `Version`, and
+  `main` gives `cli.Main` stderr and the function that runs the server, which
+  the tests replace with a buffer and a function that fails them. Unit tests
+  call `cli.Main` with `check-cidr` and a CIDR the server takes and one it
+  refuses, and check the exit code and what it writes to stderr, and with
+  `prepare-data-dir` and a path outside `/data`, and check that it exits 1 with
+  the error from looking up the `netwatch` user, which the test image does not
+  have. Others give the functions behind the subcommands input they take and
+  input they refuse, and check the exit code and what they write to stderr
+- 2026-10-19: when `VERSION` is unset or empty, `script/build` stamps the
+  version from `git describe --tags --always --dirty`, as `script/docker` does
+  ([#156](https://git.eeqj.de/sneak/netwatch/issues/156)). Without `--tags` it
+  skipped lightweight tags, so `make run` could report a commit where the image
+  built from the same tree reported the tag. Checked once with a lightweight tag
+  on a scratch clone: `make build` stamped it
+- 2026-10-19: `.dockerignore` keeps Go test binaries and coverage output at the
+  root out of the build context, with `/*.test` and `/*.out` in the repository's
+  own section ([#155](https://git.eeqj.de/sneak/netwatch/issues/155)). Such
+  files went into the build context of every `docker build` in `script/` and
+  were copied into the lint, test and build stages. Checked with a probe image
+  that copies the whole context: `x.test` and `x.out` planted at the root no
+  longer land in it, and nothing else changed. The entries match only at the
+  root, so the same files in a subdirectory still reach the image
+- 2026-10-19: `.gitea/workflows/check.yml` is the sneak/prompts copy at
+  `0653579` ([#153](https://git.eeqj.de/sneak/netwatch/issues/153)). Its
+  checkout step sets `fetch-depth: 0`, so CI clones all history and tags, and
+  `git describe` in `script/cibuild` gives the image built from a tagged commit
+  the tag as its version; it gave the short commit. The checkout step also sets
+  `persist-credentials: false`, so the job's token is not left in `.git/config`.
+  A new push cancels the older run on the same branch, and a run stops after 20
+  minutes
 - 2026-10-19: `script/bootstrap` keeps the `yarn` on `PATH` only when
   `yarn --version` is exactly `YARN_VERSION`, and otherwise installs that
   version as it did when no yarn was installed
@@ -35,6 +103,22 @@ Run `make frontend-viewport-test` in CI as its own step; it is not part of
   script puts `~/.local/bin` first on `PATH`, uses the first `node` on that
   `PATH` when it passes the same test, and otherwise runs yarn under the pinned
   node in nvm; `make build` ran yarn under whatever node was first on `PATH`
+- 2026-10-19: `bin/entrypoint.sh` has each of its steps in a function, and a
+  `main` at the end calls them in order, as the shell section of the code style
+  guide asks ([#163](https://git.eeqj.de/sneak/netwatch/issues/163)). It is
+  still POSIX sh with no `set -e`, and does what it did, with the same messages
+  and exit codes. Checked by running the image with each script: a normal start,
+  bad `PORT`, `TRUSTED_PROXIES` and `DATA_DIR` values, `docker stop`, INT, and
+  nginx exiting on its own
+- 2026-10-19: while report files cannot be written, the health check answers 503
+  with `"status":"error"` and the same fields, so the image's `HEALTHCHECK`
+  reports the container `unhealthy`
+  ([#142](https://git.eeqj.de/sneak/netwatch/issues/142)). It answered 200
+  `"status":"ok"` whatever happened, so the platform saw a healthy container
+  while every report was refused with 500. It answers 200 at start, before any
+  write has failed, and again from the first write that succeeds. A unit test
+  removes `DATA_DIR` to make a write fail and checks the 503, then puts it back
+  and checks the 200 after the next write
 - 2026-10-19: report file writes no longer overlap
   ([#150](https://git.eeqj.de/sneak/netwatch/issues/150)), so the reports of
   failed writes are written in the order they arrived. Two writes that failed at

bin/entrypoint.sh

@@ -13,24 +13,27 @@ set -u
 # address and start anyway, and reports a bad port without naming
 # PORT, so a value that is not a usable port stops the container here,
 # before either process starts.
-export PORT="${PORT:-8080}"
+check_port() {
-case "$PORT" in
+    export PORT="${PORT:-8080}"
-    *[!0-9]*)
+    case "$PORT" in
-        echo "entrypoint: PORT must be a port number, not '$PORT'" >&2
+        *[!0-9]*)
+            echo "entrypoint: PORT must be a port number, not '$PORT'" >&2
+            exit 1
+            ;;
+    esac
+    # The length is checked first because, for a number too big for it,
+    # the shell's test prints an error and is false, so the range checks
+    # alone would let it through.
+    if [ "${#PORT}" -gt 5 ] || [ "$PORT" -lt 1 ] || [ "$PORT" -gt 65535 ]; then
+        echo "entrypoint: PORT must be from 1 to 65535, not '$PORT'" >&2
         exit 1
-        ;;
+    fi
-esac
+    if [ "$PORT" -eq 8081 ]; then
-# The length is checked first because, for a number too big for it,
+        echo "entrypoint: PORT cannot be 8081, netwatch-server" \
-# the shell's test prints an error and is false, so the range checks
+            "listens there" >&2
-# alone would let it through.
+        exit 1
-if [ "${#PORT}" -gt 5 ] || [ "$PORT" -lt 1 ] || [ "$PORT" -gt 65535 ]; then
+    fi
-    echo "entrypoint: PORT must be from 1 to 65535, not '$PORT'" >&2
+}
-    exit 1
-fi
-if [ "$PORT" -eq 8081 ]; then
-    echo "entrypoint: PORT cannot be 8081, netwatch-server listens there" >&2
-    exit 1
-fi
 
 # TRUSTED_PROXIES names the reverse proxies in front of the container,
 # as IP addresses or CIDRs separated by commas. nginx takes the client
@@ -47,21 +50,23 @@ fi
 # TRUSTED_PROXIES. Its error, naming the CIDR, is dropped for the one
 # below, naming the entry as written. set -f keeps a * in an entry from
 # becoming a list of file names.
-TRUSTED_PROXIES="${TRUSTED_PROXIES-10.0.0.0/8,172.16.0.0/12,192.168.0.0/16}"
+write_trusted_proxies() {
-set -f
+    TRUSTED_PROXIES="${TRUSTED_PROXIES-10.0.0.0/8,172.16.0.0/12,192.168.0.0/16}"
-for proxy in $(printf '%s' "$TRUSTED_PROXIES" | tr ',' ' '); do
+    set -f
-    case "$proxy" in
+    for proxy in $(printf '%s' "$TRUSTED_PROXIES" | tr ',' ' '); do
-        */*) cidr="$proxy" ;;
+        case "$proxy" in
-        *:*) cidr="$proxy/128" ;;
+            */*) cidr="$proxy" ;;
-        *) cidr="$proxy/32" ;;
+            *:*) cidr="$proxy/128" ;;
-    esac
+            *) cidr="$proxy/32" ;;
-    if ! netwatch-server check-cidr "$cidr" 2> /dev/null; then
+        esac
-        echo "entrypoint: TRUSTED_PROXIES must be IP addresses or CIDRs" \
+        if ! netwatch-server check-cidr "$cidr" 2> /dev/null; then
-            "separated by commas; '$proxy' is neither" >&2
+            echo "entrypoint: TRUSTED_PROXIES must be IP addresses or CIDRs" \
-        exit 1
+                "separated by commas; '$proxy' is neither" >&2
-    fi
+            exit 1
-    echo "set_real_ip_from $cidr;"
+        fi
-done > /etc/nginx/trusted-proxies.conf
+        echo "set_real_ip_from $cidr;"
+    done > /etc/nginx/trusted-proxies.conf
+}
 
 # netwatch-server keeps its report files in DATA_DIR, on the /data
 # volume, which may be a host directory owned by root or by another
@@ -73,12 +78,10 @@ done > /etc/nginx/trusted-proxies.conf
 # naming DATA_DIR, unless DATA_DIR is /data or a path below it, and it
 # acts on nothing outside /data, whatever symbolic or hard links it
 # meets there.
-export DATA_DIR="${DATA_DIR:-/data/reports}"
+prepare_data_dir() {
-netwatch-server prepare-data-dir "$DATA_DIR" || exit 1
+    export DATA_DIR="${DATA_DIR:-/data/reports}"
-
+    netwatch-server prepare-data-dir "$DATA_DIR" || exit 1
-# A stop signal is only noted here; the loop below acts on it.
+}
-stop_requested=""
-trap 'stop_requested=yes' TERM INT
 
 # netwatch-server runs as the netwatch user and listens on loopback
 # only, on a port other than the public one; configs/nginx.conf proxies
@@ -87,9 +90,11 @@ trap 'stop_requested=yes' TERM INT
 # the container has. The netwatch user has no login shell, hence -s
 # /bin/sh. busybox su replaces itself with the command instead of
 # staying on as its parent, so $! is the server's own PID.
-BIND_ADDRESS=127.0.0.1 PORT=8081 TRUSTED_PROXIES=127.0.0.1/32 \
+start_backend() {
-    su -s /bin/sh netwatch -c 'exec netwatch-server' &
+    BIND_ADDRESS=127.0.0.1 PORT=8081 TRUSTED_PROXIES=127.0.0.1/32 \
-backend=$!
+        su -s /bin/sh netwatch -c 'exec netwatch-server' &
+    backend=$!
+}
 
 # nginx starts through the nginx image's own entrypoint, which applies
 # the image's start-up configuration and then replaces itself with
@@ -98,9 +103,11 @@ backend=$!
 # that rendering to PORT: a variable nginx itself uses, such as $uri,
 # would otherwise be replaced by an environment variable of the same
 # name.
-NGINX_ENVSUBST_FILTER='^PORT$' \
+start_nginx() {
-    /docker-entrypoint.sh nginx -g 'daemon off;' &
+    NGINX_ENVSUBST_FILTER='^PORT$' \
-nginx=$!
+        /docker-entrypoint.sh nginx -g 'daemon off;' &
+    nginx=$!
+}
 
 running() {
     kill -0 "$1" 2>/dev/null
@@ -109,26 +116,47 @@ running() {
 # POSIX sh cannot wait for whichever of two children exits first, so
 # look once a second. The shell collects a child that has exited while
 # it runs sleep, and running() is false for that child from then on.
-while [ -z "$stop_requested" ] && running "$backend" && running "$nginx"; do
+wait_for_stop_or_exit() {
-    sleep 1
+    while [ -z "$stop_requested" ] && running "$backend" && running "$nginx"; do
-done
+        sleep 1
+    done
+}
 
 # Stop both, then wait until neither is left.
-kill -TERM "$backend" "$nginx" 2>/dev/null
+stop_both() {
-while running "$backend" || running "$nginx"; do
+    kill -TERM "$backend" "$nginx" 2>/dev/null
-    sleep 1
+    while running "$backend" || running "$nginx"; do
-done
+        sleep 1
-
+    done
-wait "$backend"
+}
-backend_status=$?
-wait "$nginx"
-nginx_status=$?
-echo "entrypoint: netwatch-server exited $backend_status," \
-    "nginx exited $nginx_status"
 
 # Success is a requested stop that both processes exited cleanly from.
-if [ -n "$stop_requested" ] && [ "$backend_status" -eq 0 ] &&
+exit_with_status() {
-    [ "$nginx_status" -eq 0 ]; then
+    wait "$backend"
-    exit 0
+    backend_status=$?
-fi
+    wait "$nginx"
-exit 1
+    nginx_status=$?
+    echo "entrypoint: netwatch-server exited $backend_status," \
+        "nginx exited $nginx_status"
+    if [ -n "$stop_requested" ] && [ "$backend_status" -eq 0 ] &&
+        [ "$nginx_status" -eq 0 ]; then
+        exit 0
+    fi
+    exit 1
+}
+
+main() {
+    check_port
+    write_trusted_proxies
+    prepare_data_dir
+    # A stop signal is only noted here; wait_for_stop_or_exit acts on it.
+    stop_requested=""
+    trap 'stop_requested=yes' TERM INT
+    start_backend
+    start_nginx
+    wait_for_stop_or_exit
+    stop_both
+    exit_with_status
+}
+
+main "$@"

cmd/netwatch-server/main.go

@@ -1,22 +1,11 @@
-// Package main is the entry point for netwatch-server.
+// Package main is the entry point for netwatch-server; package cli
+// does the work.
 package main
 
 import (
-	"fmt"
 	"os"
-	"os/user"
 
-	"sneak.berlin/go/netwatch/internal/config"
+	"sneak.berlin/go/netwatch/internal/cli"
-	"sneak.berlin/go/netwatch/internal/globals"
-	"sneak.berlin/go/netwatch/internal/handlers"
-	"sneak.berlin/go/netwatch/internal/healthcheck"
-	"sneak.berlin/go/netwatch/internal/logger"
-	"sneak.berlin/go/netwatch/internal/middleware"
-	"sneak.berlin/go/netwatch/internal/reportbuf"
-	"sneak.berlin/go/netwatch/internal/server"
-
-	"go.uber.org/fx"
-	"go.uber.org/fx/fxevent"
 )
 
 //nolint:gochecknoglobals // set via ldflags at build time
@@ -26,64 +15,5 @@ var (
 )
 
 func main() {
-	// "netwatch-server check-cidr CIDR" exits 1, with the error, if
+	os.Exit(cli.Main(os.Stderr, Appname, Version, os.Args[1:], cli.RunServer))
-	// this server would refuse CIDR in its TRUSTED_PROXIES.
-	// bin/entrypoint.sh runs it on each entry it gives nginx.
-	if len(os.Args) == 3 && os.Args[1] == "check-cidr" {
-		_, err := middleware.ParseTrustedProxies(os.Args[2:])
-		if err != nil {
-			fmt.Fprintln(os.Stderr, err)
-			os.Exit(1)
-		}
-
-		return
-	}
-
-	// "netwatch-server prepare-data-dir DATA_DIR" gets DATA_DIR ready
-	// for the netwatch user, or exits 1 with the error; see
-	// reportbuf.PrepareDataDir. bin/entrypoint.sh runs it as root
-	// before it starts this server as that user.
-	if len(os.Args) == 3 && os.Args[1] == "prepare-data-dir" {
-		netwatch, err := user.Lookup("netwatch")
-		if err != nil {
-			fmt.Fprintln(os.Stderr, err)
-			os.Exit(1)
-		}
-
-		err = reportbuf.PrepareDataDir("/data", os.Args[2], netwatch)
-		if err != nil {
-			fmt.Fprintf(os.Stderr, "DATA_DIR '%s': %v\n", os.Args[2], err)
-			os.Exit(1)
-		}
-
-		return
-	}
-
-	globals.Appname = Appname
-	globals.Version = Version
-
-	fx.New(
-		// fx logs each step of starting and stopping through the
-		// server's own logger, so off a terminal those lines are
-		// JSON like every other line.
-		fx.WithLogger(func(log *logger.Logger) fxevent.Logger {
-			return &fxevent.SlogLogger{Logger: log.Get()}
-		}),
-		fx.Provide(
-			config.New,
-			globals.New,
-			handlers.New,
-			healthcheck.New,
-			logger.New,
-			middleware.New,
-			reportbuf.New,
-			server.New,
-		),
-		fx.Invoke(
-			// First, so the name and version are logged even when
-			// a setting stops the start.
-			func(log *logger.Logger) { log.Identify() },
-			func(*server.Server) {},
-		),
-	).Run()
 }

internal/cli/cli.go

@@ -0,0 +1,143 @@
+// Package cli runs netwatch-server from its command line: the
+// check-cidr and prepare-data-dir subcommands, which bin/entrypoint.sh
+// runs before it starts the server, and, given no arguments, the
+// server, with the fx wiring.
+package cli
+
+import (
+	"fmt"
+	"io"
+	"os/user"
+
+	"sneak.berlin/go/netwatch/internal/config"
+	"sneak.berlin/go/netwatch/internal/globals"
+	"sneak.berlin/go/netwatch/internal/handlers"
+	"sneak.berlin/go/netwatch/internal/healthcheck"
+	"sneak.berlin/go/netwatch/internal/logger"
+	"sneak.berlin/go/netwatch/internal/middleware"
+	"sneak.berlin/go/netwatch/internal/reportbuf"
+	"sneak.berlin/go/netwatch/internal/server"
+
+	"go.uber.org/fx"
+	"go.uber.org/fx/fxevent"
+)
+
+// usageExitCode is what Main returns for a command line it does not
+// understand, the usual exit code for a usage error.
+const usageExitCode = 2
+
+// Main runs netwatch-server with args, its command line after the
+// program's name, and returns the exit code. With no args, Main runs
+// the server by calling serve with appname and version, the name and
+// version the server logs and reports. With "check-cidr CIDR" or
+// "prepare-data-dir DATA_DIR" it runs that subcommand, which writes its
+// errors to stderr. Any other args get a one-line usage message on
+// stderr and exit code 2. main passes os.Stderr and RunServer; the
+// tests pass a buffer and a function of their own, so that no test
+// starts the server. When serve is RunServer and the server fails to
+// start, to listen or to stop, fx's Run exits the process with status 1
+// and Main never returns.
+func Main(
+	stderr io.Writer,
+	appname, version string,
+	args []string,
+	serve func(appname, version string),
+) int {
+	// "netwatch-server check-cidr CIDR" exits 1, with the error, if
+	// this server would refuse CIDR in its TRUSTED_PROXIES.
+	// bin/entrypoint.sh runs it on each entry it gives nginx.
+	if len(args) == 2 && args[0] == "check-cidr" {
+		return checkCIDR(stderr, args[1])
+	}
+
+	// "netwatch-server prepare-data-dir DATA_DIR" gets DATA_DIR ready
+	// for the netwatch user, or exits 1 with the error; see
+	// reportbuf.PrepareDataDir. bin/entrypoint.sh runs it as root
+	// before it starts this server as that user.
+	if len(args) == 2 && args[0] == "prepare-data-dir" {
+		return prepareDataDir(stderr, "/data", args[1], "netwatch")
+	}
+
+	// Any other command line is refused, so that a mistyped one does
+	// not start the server.
+	if len(args) > 0 {
+		_, _ = fmt.Fprintln(stderr,
+			"usage: netwatch-server [check-cidr CIDR | prepare-data-dir DATA_DIR]")
+
+		return usageExitCode
+	}
+
+	serve(appname, version)
+
+	return 0
+}
+
+// checkCIDR returns 0 if the server would take cidr in its
+// TRUSTED_PROXIES, and otherwise writes the error to stderr and
+// returns 1.
+func checkCIDR(stderr io.Writer, cidr string) int {
+	_, err := middleware.ParseTrustedProxies([]string{cidr})
+	if err != nil {
+		_, _ = fmt.Fprintln(stderr, err)
+
+		return 1
+	}
+
+	return 0
+}
+
+// prepareDataDir gets dataDir ready for the user named username with
+// reportbuf.PrepareDataDir, volume being where the data volume is
+// mounted, and returns 0. Otherwise it writes the error to stderr and
+// returns 1.
+func prepareDataDir(stderr io.Writer, volume, dataDir, username string) int {
+	owner, err := user.Lookup(username)
+	if err != nil {
+		_, _ = fmt.Fprintln(stderr, err)
+
+		return 1
+	}
+
+	err = reportbuf.PrepareDataDir(volume, dataDir, owner)
+	if err != nil {
+		_, _ = fmt.Fprintf(stderr, "DATA_DIR '%s': %v\n", dataDir, err)
+
+		return 1
+	}
+
+	return 0
+}
+
+// RunServer runs the server until it is told to stop, with appname and
+// version as the name and version it logs and reports. If the server
+// fails to start, to listen or to stop, fx's Run exits the process
+// with status 1 itself.
+func RunServer(appname, version string) {
+	globals.Appname = appname
+	globals.Version = version
+
+	fx.New(
+		// fx logs each step of starting and stopping through the
+		// server's own logger, so off a terminal those lines are
+		// JSON like every other line.
+		fx.WithLogger(func(log *logger.Logger) fxevent.Logger {
+			return &fxevent.SlogLogger{Logger: log.Get()}
+		}),
+		fx.Provide(
+			config.New,
+			globals.New,
+			handlers.New,
+			healthcheck.New,
+			logger.New,
+			middleware.New,
+			reportbuf.New,
+			server.New,
+		),
+		fx.Invoke(
+			// First, so the name and version are logged even when
+			// a setting stops the start.
+			func(log *logger.Logger) { log.Identify() },
+			func(*server.Server) {},
+		),
+	).Run()
+}

internal/cli/cli_test.go

@@ -0,0 +1,219 @@
+package cli_test
+
+import (
+	"bytes"
+	"os"
+	"os/user"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+
+	"sneak.berlin/go/netwatch/internal/cli"
+	"sneak.berlin/go/netwatch/internal/reportbuf"
+)
+
+// TestMainRunsCheckCIDR: Main given check-cidr returns 0, writing
+// nothing, for a CIDR the server takes in its TRUSTED_PROXIES, and 1,
+// with an error naming TRUSTED_PROXIES and the CIDR, for one it
+// refuses, and does not start the server.
+func TestMainRunsCheckCIDR(t *testing.T) {
+	t.Parallel()
+
+	var stderr bytes.Buffer
+
+	code := cli.Main(&stderr, "netwatch", "test",
+		[]string{"check-cidr", "10.0.0.0/8"}, failIfServerStarts(t))
+	if code != 0 || stderr.Len() != 0 {
+		t.Errorf("check-cidr 10.0.0.0/8: exit %d, stderr %q; want exit 0 and no output",
+			code, stderr.String())
+	}
+
+	stderr.Reset()
+
+	code = cli.Main(&stderr, "netwatch", "test",
+		[]string{"check-cidr", "1.2.3/32"}, failIfServerStarts(t))
+
+	want := `TRUSTED_PROXIES "1.2.3/32": `
+	if code != 1 || !strings.HasPrefix(stderr.String(), want) {
+		t.Errorf("check-cidr 1.2.3/32: exit %d, stderr %q; want exit 1 and %q...",
+			code, stderr.String(), want)
+	}
+}
+
+// TestMainRunsPrepareDataDir: Main given prepare-data-dir runs the
+// prepare-data-dir subcommand for the netwatch user, and does not start
+// the server. The test image has no netwatch user, so that subcommand
+// exits 1 with the error from looking the user up;
+// TestPrepareDataDirRefusesPathOutsideVolume checks the path.
+func TestMainRunsPrepareDataDir(t *testing.T) {
+	t.Parallel()
+
+	var stderr bytes.Buffer
+
+	code := cli.Main(&stderr, "netwatch", "test",
+		[]string{"prepare-data-dir", "/etc"}, failIfServerStarts(t))
+
+	want := user.UnknownUserError("netwatch").Error() + "\n"
+	if code != 1 || stderr.String() != want {
+		t.Errorf("prepare-data-dir /etc: exit %d, stderr %q; want exit 1 and %q",
+			code, stderr.String(), want)
+	}
+}
+
+// TestMainRunsServerWithNoArguments: Main given no arguments starts the
+// server with the name and version it was given, writes nothing and
+// returns 0.
+func TestMainRunsServerWithNoArguments(t *testing.T) {
+	t.Parallel()
+
+	var (
+		stderr                 bytes.Buffer
+		gotAppname, gotVersion string
+	)
+
+	code := cli.Main(&stderr, "netwatch", "test", []string{},
+		func(appname, version string) {
+			gotAppname, gotVersion = appname, version
+		})
+	if code != 0 || stderr.Len() != 0 {
+		t.Errorf("exit %d, stderr %q; want exit 0 and no output",
+			code, stderr.String())
+	}
+
+	if gotAppname != "netwatch" || gotVersion != "test" {
+		t.Errorf("server started with %q %q; want %q %q",
+			gotAppname, gotVersion, "netwatch", "test")
+	}
+}
+
+// TestMainRefusesOtherCommandLines: Main given a subcommand with too
+// few or too many values, or a misspelt subcommand, writes the usage
+// message to stderr, returns 2 and does not start the server.
+func TestMainRefusesOtherCommandLines(t *testing.T) {
+	t.Parallel()
+
+	want := "usage: netwatch-server " +
+		"[check-cidr CIDR | prepare-data-dir DATA_DIR]\n"
+
+	for _, commandLine := range []string{
+		"netwatch-server check-cidr",
+		"netwatch-server check-cidr 192.0.2.0/24 198.51.100.0/24",
+		"netwatch-server prepare-data-dir",
+		"netwatch-server prepare-data-dir /data/reports /data/other",
+		"netwatch-server check-cdir 192.0.2.0/24",
+	} {
+		var stderr bytes.Buffer
+
+		// Main takes the command line after the program's name.
+		args := strings.Fields(commandLine)[1:]
+
+		code := cli.Main(&stderr, "netwatch", "test", args, failIfServerStarts(t))
+		if code != 2 || stderr.String() != want {
+			t.Errorf("%q: exit %d, stderr %q; want exit 2 and %q",
+				commandLine, code, stderr.String(), want)
+		}
+	}
+}
+
+// TestCheckCIDRTakesCIDR: check-cidr exits 0, writing nothing, for a
+// CIDR the server takes in its TRUSTED_PROXIES.
+func TestCheckCIDRTakesCIDR(t *testing.T) {
+	t.Parallel()
+
+	for _, cidr := range []string{"10.0.0.0/8", "192.0.2.1/32", "2001:db8::/32"} {
+		var stderr bytes.Buffer
+
+		code := cli.CheckCIDR(&stderr, cidr)
+		if code != 0 || stderr.Len() != 0 {
+			t.Errorf("%q: exit %d, stderr %q; want exit 0 and no output",
+				cidr, code, stderr.String())
+		}
+	}
+}
+
+// TestCheckCIDRRefusesOtherInput: check-cidr exits 1, with an error
+// naming TRUSTED_PROXIES and the input, for anything the server would
+// refuse in its TRUSTED_PROXIES, such as 1.2.3/32, which nginx would
+// look up as a hostname.
+func TestCheckCIDRRefusesOtherInput(t *testing.T) {
+	t.Parallel()
+
+	for _, cidr := range []string{
+		"1.2.3/32", "example.com/32", "10.0.0.0/33", "10.0.0.1", "",
+	} {
+		var stderr bytes.Buffer
+
+		code := cli.CheckCIDR(&stderr, cidr)
+
+		want := "TRUSTED_PROXIES " + strconv.Quote(cidr) + ": "
+		if code != 1 || !strings.HasPrefix(stderr.String(), want) {
+			t.Errorf("%q: exit %d, stderr %q; want exit 1 and %q...",
+				cidr, code, stderr.String(), want)
+		}
+	}
+}
+
+// TestPrepareDataDirTakesPathInVolume: prepare-data-dir exits 0,
+// writing nothing, for a DATA_DIR below the volume, and creates it.
+func TestPrepareDataDirTakesPathInVolume(t *testing.T) {
+	t.Parallel()
+
+	volume := t.TempDir()
+	dataDir := filepath.Join(volume, "reports")
+
+	var stderr bytes.Buffer
+
+	code := cli.PrepareDataDir(&stderr, volume, dataDir, currentUsername(t))
+	if code != 0 || stderr.Len() != 0 {
+		t.Errorf("exit %d, stderr %q; want exit 0 and no output",
+			code, stderr.String())
+	}
+
+	info, err := os.Stat(dataDir)
+	if err != nil || !info.IsDir() {
+		t.Errorf("DATA_DIR not created: %v", err)
+	}
+}
+
+// TestPrepareDataDirRefusesPathOutsideVolume: prepare-data-dir exits
+// 1, with an error naming DATA_DIR and its value, for a DATA_DIR
+// outside the volume.
+func TestPrepareDataDirRefusesPathOutsideVolume(t *testing.T) {
+	t.Parallel()
+
+	volume := t.TempDir()
+
+	var stderr bytes.Buffer
+
+	code := cli.PrepareDataDir(&stderr, volume, "/etc", currentUsername(t))
+
+	want := "DATA_DIR '/etc': " + reportbuf.ErrDataDirOutsideVolume.Error() + "\n"
+	if code != 1 || stderr.String() != want {
+		t.Errorf("exit %d, stderr %q; want exit 1 and %q",
+			code, stderr.String(), want)
+	}
+}
+
+// currentUsername is the name of the user the test runs as, the only
+// owner a test not run as root can give files to.
+func currentUsername(t *testing.T) string {
+	t.Helper()
+
+	current, err := user.Current()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return current.Username
+}
+
+// failIfServerStarts is what the tests give Main in place of
+// cli.RunServer: it fails the test instead of starting the server.
+func failIfServerStarts(t *testing.T) func(appname, version string) {
+	t.Helper()
+
+	return func(string, string) {
+		t.Error("Main started the server")
+	}
+}

internal/cli/export_test.go

@@ -0,0 +1,16 @@
+package cli
+
+import "io"
+
+// CheckCIDR exposes the check-cidr subcommand to the external tests,
+// which read what it writes to stderr.
+func CheckCIDR(stderr io.Writer, cidr string) int {
+	return checkCIDR(stderr, cidr)
+}
+
+// PrepareDataDir exposes the prepare-data-dir subcommand to the
+// external tests, which give it a volume and a user of their own in
+// place of /data and netwatch.
+func PrepareDataDir(stderr io.Writer, volume, dataDir, username string) int {
+	return prepareDataDir(stderr, volume, dataDir, username)
+}

internal/config/config_test.go

@@ -13,8 +13,8 @@ import (
 	"go.uber.org/fx"
 )
 
-// requireConfigError builds the config as main does and fails the
+// requireConfigError builds the config as cli.RunServer does and fails
-// test unless that fails with an error naming setting. It uses
+// the test unless that fails with an error naming setting. It uses
 // fx.New, because fxtest.New fails the test itself on an error.
 func requireConfigError(t *testing.T, setting string) {
 	t.Helper()
@@ -31,8 +31,8 @@ func requireConfigError(t *testing.T, setting string) {
 	}
 }
 
-// requireTrustedProxies builds the config as main does and fails the
+// requireTrustedProxies builds the config as cli.RunServer does and
-// test unless its TrustedProxies are want.
+// fails the test unless its TrustedProxies are want.
 func requireTrustedProxies(t *testing.T, want []string) {
 	t.Helper()
 

internal/globals/globals.go

@@ -4,7 +4,7 @@ package globals
 
 import "go.uber.org/fx"
 
-//nolint:gochecknoglobals // set from main before fx starts
+//nolint:gochecknoglobals // set by cli.RunServer before fx starts
 var (
 	// Appname is the application name.
 	Appname string

internal/handlers/healthcheck.go

@@ -3,9 +3,17 @@ package handlers
 import "net/http"
 
 // HandleHealthCheck returns a handler for the health check
-// endpoint.
+// endpoint. It answers 200 while the status is "ok" and 503 otherwise,
+// so that the image's HEALTHCHECK fails.
 func (s *Handlers) HandleHealthCheck() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		s.respondJSON(w, r, s.hc.Healthcheck(), http.StatusOK)
+		resp := s.hc.Healthcheck()
+
+		code := http.StatusOK
+		if resp.Status != "ok" {
+			code = http.StatusServiceUnavailable
+		}
+
+		s.respondJSON(w, r, resp, code)
 	}
 }

internal/handlers/healthcheck_test.go

@@ -9,17 +9,19 @@ import (
 	"testing"
 	"time"
 
+	"sneak.berlin/go/netwatch/internal/config"
 	"sneak.berlin/go/netwatch/internal/globals"
 	"sneak.berlin/go/netwatch/internal/handlers"
 	"sneak.berlin/go/netwatch/internal/healthcheck"
 	"sneak.berlin/go/netwatch/internal/logger"
+	"sneak.berlin/go/netwatch/internal/reportbuf"
 
 	"go.uber.org/fx/fxtest"
 )
 
 // newStartedHandlers builds Handlers with a real health check for the
-// server named in g, and starts them, which records the time the
+// server named in g, and a report buffer in a temporary directory, and
-// uptime counts from.
+// starts them, which records the time the uptime counts from.
 func newStartedHandlers(t *testing.T, g *globals.Globals) *handlers.Handlers {
 	t.Helper()
 
@@ -30,14 +32,23 @@ func newStartedHandlers(t *testing.T, g *globals.Globals) *handlers.Handlers {
 		t.Fatalf("logger: %v", err)
 	}
 
+	buf, err := reportbuf.New(lc, reportbuf.Params{
+		Config: &config.Config{DataDir: t.TempDir(), DataDirMaxBytes: 1 << 20},
+		Logger: log,
+	})
+	if err != nil {
+		t.Fatalf("report buffer: %v", err)
+	}
+
 	hc, err := healthcheck.New(lc,
-		healthcheck.Params{Globals: g, Logger: log})
+		healthcheck.Params{Buffer: buf, Globals: g, Logger: log})
 	if err != nil {
 		t.Fatalf("health check: %v", err)
 	}
 
-	h, err := handlers.New(lc,
+	h, err := handlers.New(lc, handlers.Params{
-		handlers.Params{Globals: g, Healthcheck: hc, Logger: log})
+		Buffer: buf, Globals: g, Healthcheck: hc, Logger: log,
+	})
 	if err != nil {
 		t.Fatalf("handlers: %v", err)
 	}
@@ -48,10 +59,12 @@ func newStartedHandlers(t *testing.T, g *globals.Globals) *handlers.Handlers {
 	return h
 }
 
-// TestHandleHealthCheck checks the health check's answer: 200, a JSON
+// TestHandleHealthCheck checks the health check's answer at start, when
-// content type, and a JSON object with exactly the fields of
+// no write of a report file has failed: 200, a JSON content type, and a
-// healthcheck.HealthcheckResponse, carrying this server's name and
+// JSON object with exactly the fields of healthcheck.HealthcheckResponse,
-// version and an uptime counted from its start.
+// carrying "status":"ok", this server's name and version and an uptime
+// counted from its start. The answer while writes fail is checked in
+// internal/reportbuf, whose tests can make a write fail.
 func TestHandleHealthCheck(t *testing.T) {
 	t.Parallel()
 

internal/healthcheck/healthcheck.go

@@ -10,6 +10,7 @@ import (
 	"sneak.berlin/go/netwatch/internal/config"
 	"sneak.berlin/go/netwatch/internal/globals"
 	"sneak.berlin/go/netwatch/internal/logger"
+	"sneak.berlin/go/netwatch/internal/reportbuf"
 
 	"go.uber.org/fx"
 )
@@ -18,6 +19,7 @@ import (
 type Params struct {
 	fx.In
 
+	Buffer  *reportbuf.Buffer
 	Config  *config.Config
 	Globals *globals.Globals
 	Logger  *logger.Logger
@@ -68,12 +70,18 @@ func New(
 	return s, nil
 }
 
-// Healthcheck returns the current health status of the application.
+// Healthcheck returns the current health status of the application:
+// "ok", or "error" while report files cannot be written.
 func (s *Healthcheck) Healthcheck() *HealthcheckResponse {
+	status := "ok"
+	if s.params.Buffer.LastWriteFailed() {
+		status = "error"
+	}
+
 	return &HealthcheckResponse{
 		Appname:       s.params.Globals.Appname,
 		Now:           time.Now().UTC().Format(time.RFC3339Nano),
-		Status:        "ok",
+		Status:        status,
 		UptimeHuman:   s.uptime().String(),
 		UptimeSeconds: int64(s.uptime().Seconds()),
 		Version:       s.params.Globals.Version,

internal/reportbuf/reportbuf.go

@@ -255,6 +255,16 @@ func (b *Buffer) Append(v any) error {
 	return nil
 }
 
+// LastWriteFailed reports whether the last write of a report file to
+// finish failed: false at start until a write fails, and false again
+// once a write succeeds. While it is true, Append refuses reports.
+func (b *Buffer) LastWriteFailed() bool {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.writeErr != nil
+}
+
 // deleteOldestFiles deletes report files, oldest first, until n more
 // bytes fit under maxBytes. It deletes none when the reports waiting
 // to be written leave no room for n even with every file gone, since

internal/reportbuf/reportbuf_test.go

@@ -334,9 +334,9 @@ func stopWhileHeld(
 	return <-stopped
 }
 
-// startApp starts a Buffer through fx, as main does, with the DATA_DIR
+// startApp starts a Buffer through fx, as cli.RunServer does, with the
-// and DATA_DIR_MAX_BYTES the calling test has set, and returns it with
+// DATA_DIR and DATA_DIR_MAX_BYTES the calling test has set, and returns
-// the app, for tests that stop the app themselves.
+// it with the app, for tests that stop the app themselves.
 func startApp(t *testing.T) (*reportbuf.Buffer, *fxtest.App) {
 	t.Helper()
 
@@ -358,8 +358,8 @@ func startApp(t *testing.T) (*reportbuf.Buffer, *fxtest.App) {
 	return buf, app
 }
 
-// startBuffer starts a Buffer through fx, as main does, with the
+// startBuffer starts a Buffer through fx, as cli.RunServer does, with
-// DATA_DIR and DATA_DIR_MAX_BYTES the calling test has set.
+// the DATA_DIR and DATA_DIR_MAX_BYTES the calling test has set.
 func startBuffer(t *testing.T) *reportbuf.Buffer {
 	t.Helper()
 
@@ -1074,9 +1074,54 @@ func TestReportsRefusedWhileWritesFail(t *testing.T) {
 	}
 }
 
+// TestHealthCheckFailsWhileWritesFail asks the health check handler
+// for its answer around a failed write. It answers 200 with
+// "status":"ok" at start, 503 with "status":"error" from the failed
+// write until a write succeeds, and 200 with "status":"ok" again after.
+func TestHealthCheckFailsWhileWritesFail(t *testing.T) {
+	dir := t.TempDir()
+	t.Setenv("DATA_DIR", dir)
+
+	buf, h := startBufferWithHandlers(t)
+
+	checkHealthCheck(t, h, "at start", http.StatusOK, "ok")
+
+	// A flush writes a file only when a report is waiting.
+	err := buf.Append(map[string]string{"id": "kept"})
+	if err != nil {
+		t.Fatalf("append: %v", err)
+	}
+
+	// With the data directory gone, the write has nowhere to go.
+	err = os.Remove(dir)
+	if err != nil {
+		t.Fatalf("remove data dir: %v", err)
+	}
+
+	err = buf.Flush()
+	if err == nil {
+		t.Fatal("flush succeeded with the data directory gone")
+	}
+
+	checkHealthCheck(t, h, "after the failed write",
+		http.StatusServiceUnavailable, "error")
+
+	err = os.Mkdir(dir, 0o750)
+	if err != nil {
+		t.Fatalf("make data dir: %v", err)
+	}
+
+	err = buf.Flush()
+	if err != nil {
+		t.Fatalf("flush with the data directory back: %v", err)
+	}
+
+	checkHealthCheck(t, h, "after a write succeeded", http.StatusOK, "ok")
+}
+
 // startBufferWithHandlers starts a Buffer and the Handlers that store
-// reports in it through fx, as main does, with the DATA_DIR the calling
+// reports in it through fx, as cli.RunServer does, with the DATA_DIR
-// test has set.
+// the calling test has set.
 func startBufferWithHandlers(
 	t *testing.T,
 ) (*reportbuf.Buffer, *handlers.Handlers) {
@@ -1121,6 +1166,39 @@ func postReport(t *testing.T, h *handlers.Handlers, clientID string) int {
 	return rec.Code
 }
 
+// checkHealthCheck asks the health check handler for its answer, and
+// fails the test, saying when it asked, unless the answer has status
+// code wantCode and a "status" field of wantStatus.
+func checkHealthCheck(
+	t *testing.T,
+	h *handlers.Handlers,
+	when string,
+	wantCode int,
+	wantStatus string,
+) {
+	t.Helper()
+
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequestWithContext(t.Context(),
+		http.MethodGet, "/.well-known/healthcheck", http.NoBody)
+	h.HandleHealthCheck().ServeHTTP(rec, req)
+
+	var body struct {
+		Status string `json:"status"`
+	}
+
+	err := json.Unmarshal(rec.Body.Bytes(), &body)
+	if err != nil {
+		t.Fatalf("health check %s: body not JSON: %v (%q)",
+			when, err, rec.Body.String())
+	}
+
+	if rec.Code != wantCode || body.Status != wantStatus {
+		t.Fatalf("health check %s: %d with status %q, want %d with %q",
+			when, rec.Code, body.Status, wantCode, wantStatus)
+	}
+}
+
 // TestConcurrentAppendsStopAtCap appends from many goroutines at once
 // with room for exactly roomFor reports: exactly that many must be
 // taken, which holds only if Append checks and counts each report

internal/server/routes_test.go

@@ -22,9 +22,9 @@ import (
 	"go.uber.org/fx/fxtest"
 )
 
-// newServer builds a Server from the same constructors as main,
+// newServer builds a Server from the same constructors as
-// configured from the environment. It is never started, so nothing
+// cli.RunServer, configured from the environment. It is never started,
-// listens.
+// so nothing listens.
 func newServer(t *testing.T) *server.Server {
 	t.Helper()
 

internal/server/server.go

@@ -79,7 +79,7 @@ func New(
 			s.SetupRoutes()
 			s.httpServer = s.newHTTPServer()
 
-			go s.listenAndServe()
+			go func() { s.listenAndServe() }()
 
 			return nil
 		},

package.json

@@ -1,6 +1,6 @@
 {
     "name": "netwatch",
-    "version": "1.0.0",
+    "private": true,
     "description": "Real-time network latency monitor SPA",
     "type": "module",
     "scripts": {

script/build

@@ -10,9 +10,10 @@ main() {
     cd "$ROOT"
     "$ROOT/script/yarn" build
 
-    # VERSION comes from the environment. Unset or empty, it is git
+    # VERSION comes from the environment. Unset or empty, it is
-    # describe, or "dev" where there is no git or no repository history.
+    # `git describe --tags --always --dirty`, as in script/docker, or
-    version="${VERSION:-$(git describe --always --dirty 2>/dev/null || echo dev)}"
+    # "dev" where there is no git or no repository history.
+    version="${VERSION:-$(git describe --tags --always --dirty 2>/dev/null || echo dev)}"
 
     CGO_ENABLED=0 go build -trimpath \
         -ldflags "-s -w -X main.Version=$version" \