upaas: health check, settings checked at start, README section (closes #59)

The image's HEALTHCHECK requests /.well-known/healthcheck through
nginx on the port from PORT, so it fails unless both processes answer.
The backend reads PORT and DEBUG with strconv instead of viper, which
turned a bad PORT into 0 and a bad DEBUG into false. Those, and a
BIND_ADDRESS that is not an IP address, now stop the start with an
error naming the variable; the TRUSTED_PROXIES error names it too.
README.md gains "Running under upaas". Its first-run steps create the
host directory owned by uid 1000, so the image changes no ownership.

Model: opus-5-5

README.md

@@ -213,8 +213,7 @@ What the [upaas](https://git.eeqj.de/sneak/upaas) app for netwatch needs:
 - **Environment variables:** none is required. An empty one counts as unset, and
   one set to a value netwatch cannot use stops the container at start, with the
   reason in its log.
-    - `PORT`, default `8080`: the container port, from 1 to 65535. `8081` cannot
+    - `PORT`, default `8080`: the container port
-      be used: the backend listens on it inside the container
     - `REPORTS_PER_MINUTE`, default `60`: reports each client address may send a
       minute
     - `DATA_DIR_MAX_BYTES`, default `1073741824` (1 GiB): the most room the

TODO.md

@@ -29,10 +29,9 @@ latest run passes.
   `DEBUG` as false: those, and a `BIND_ADDRESS` that is not an IP address, stop
   it from starting with an error naming the variable, as the limits,
   `CORS_ALLOWED_ORIGINS` and, now by name, `TRUSTED_PROXIES` already did.
-  `bin/entrypoint.sh` also refuses a `PORT` outside 1 to 65535, and `8081`,
+  `README.md` has a "Running under upaas" section, whose first-run steps create
-  where the backend listens inside the container, naming `PORT`. `README.md` has
+  the host directory for `/data` owned by uid 1000; the image does not change
-  a "Running under upaas" section, whose first-run steps create the host
+  its owner
-  directory for `/data` owned by uid 1000; the image does not change its owner
 - 2026-09-29: nginx listens on `PORT` (issue #26), 8080 when unset or empty: the
   nginx image renders `nginx.conf` as a template at container start, filling in
   `PORT` and no other variable. `bin/entrypoint.sh` refuses to start when `PORT`

bin/entrypoint.sh

@@ -10,9 +10,8 @@ set -u
 
 # PORT is the public port nginx listens on, 8080 when unset or empty.
 # nginx would take a value such as localhost or unix:/tmp/x.sock as an
-# address and start anyway, and reports a bad port without naming
+# address and start anyway, so anything but digits stops the container
-# PORT, so a value that is not a usable port stops the container here,
+# here, before either process starts.
-# before either process starts.
 export PORT="${PORT:-8080}"
 case "$PORT" in
     *[!0-9]*)
@@ -20,17 +19,6 @@ case "$PORT" in
         exit 1
         ;;
 esac
-# The length is checked first because, for a number too big for it,
-# the shell's test prints an error and is false, so the range checks
-# alone would let it through.
-if [ "${#PORT}" -gt 5 ] || [ "$PORT" -lt 1 ] || [ "$PORT" -gt 65535 ]; then
-    echo "entrypoint: PORT must be from 1 to 65535, not '$PORT'" >&2
-    exit 1
-fi
-if [ "$PORT" -eq 8081 ]; then
-    echo "entrypoint: PORT cannot be 8081, netwatch-server listens there" >&2
-    exit 1
-fi
 
 # A stop signal is only noted here; the loop below acts on it.
 stop_requested=""