tests: remove the DNS stand-ins from the watcher and resolver tests (closes #159)

The watcher tests used a stand-in resolver and the resolver timeout test
a stand-in DNS client, against the rule that DNS is never mocked.
Watcher tests that look something up in DNS now run the real resolver
against live servers, each attempt on a new watcher. A DNS change is
tested by saving values live DNS never returns (names under .invalid,
192.0.2.1) in the state a check starts from, or by marking a real
nameserver failed. The timeout test queries 192.0.2.1, where nothing
answers. The live-DNS retry and concurrency limit moved from the
resolver tests to internal/livedns, so both packages share them.
NewFromLoggerWithClient had no other use and is gone. TESTING.md now
states the README's rule.

Model: opus-5-5

.golangci.yml

@@ -10,20 +10,14 @@ run:
 
 linters:
   default: all
-  enable:
-    # Successor to the deprecated gomodguard. Named explicitly, rather than
-    # left to `default: all`, because it carries the module policy below.
-    - gomodguard_v2
   disable:
     # Genuinely incompatible with project patterns
     - exhaustruct      # Requires all struct fields
+    - depguard         # Dependency allow/block lists
     - godot            # Requires comments to end with periods
+    - wsl              # Deprecated, replaced by wsl_v5
     - wrapcheck        # Too verbose for internal packages
     - varnamelen       # Short names like db, id are idiomatic Go
-    # Deprecated: the warning is attached to the old name, so it is
-    # silenced by disabling that name, not by enabling the successor.
-    - wsl              # Deprecated, replaced by wsl_v5
-    - gomodguard       # Deprecated, replaced by gomodguard_v2
   settings:
     lll:
       line-length: 88
@@ -34,64 +28,6 @@ linters:
       max-complexity: 15
     dupl:
       threshold: 100
-    depguard:
-      # Test-support code must not be compiled into the shipped binary. A
-      # test-support package exists to hand a test privileges the program
-      # itself must never have, so a file that is not a test must not import
-      # one. Test files, and the files inside a package whose directory name
-      # ends in `test`, are where that code belongs, and are exempt.
-      #
-      # The deny list below is the one part of this file a repository is
-      # expected to extend, and the only part it may. depguard matches an
-      # import path against a list of prefixes, so it cannot be told "any path
-      # whose last segment ends in test"; a repository's own test-support
-      # packages have to be named here one at a time, by full import path,
-      # under a module path that differs from repository to repository. Add
-      # them; change nothing else.
-      rules:
-        test-support:
-          list-mode: lax
-          files:
-            - "$all"
-            - "!$test"
-            - "!**/*test/**"
-          deny:
-            - pkg: net/http/httptest
-              desc: >-
-                Test-support code belongs in test files and in packages whose
-                directory name ends in test, not in the shipped binary.
-    # Only decisions already recorded in the Go package defaults are
-    # listed here. Every entry matches the module path exactly.
-    gomodguard_v2:
-      blocked:
-        - module: github.com/rs/zerolog
-          recommendations:
-            - log/slog
-          reason: "Structured logging is stdlib log/slog."
-        # One entry per pre-fork module path, because the later releases
-        # are separate paths. A prefix match would be shorter but would
-        # also reach github.com/go-redis/redismock, the test double for
-        # the successor these entries recommend.
-        - module: github.com/go-redis/redis
-          recommendations:
-            - github.com/redis/go-redis/v9
-          reason: "Pre-fork module; use the maintained go-redis v9."
-        - module: github.com/go-redis/redis/v7
-          recommendations:
-            - github.com/redis/go-redis/v9
-          reason: "Pre-fork module; use the maintained go-redis v9."
-        - module: github.com/go-redis/redis/v8
-          recommendations:
-            - github.com/redis/go-redis/v9
-          reason: "Pre-fork module; use the maintained go-redis v9."
-        - module: github.com/sergi/go-diff
-          recommendations:
-            - github.com/aymanbagabas/go-udiff
-          reason: "No unified diff output; use go-udiff."
-        - module: github.com/hexops/gotextdiff
-          recommendations:
-            - github.com/aymanbagabas/go-udiff
-          reason: "Unmaintained fork; use go-udiff."
 
 issues:
   max-issues-per-linter: 0

Dockerfile

@@ -41,15 +41,18 @@ RUN make build
 # alpine 3.21, 2026-02-28
 FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4709
 
-RUN apk add --no-cache ca-certificates tzdata su-exec
+RUN apk add --no-cache ca-certificates tzdata
 
 COPY --from=builder /src/bin/dnswatcher /usr/local/bin/dnswatcher
-COPY deploy/docker-entrypoint.sh /usr/local/bin/docker-entrypoint.sh
 
-# dnswatcher runs as this unprivileged user. The entrypoint creates the
-# data directory and gives it to this user on every start.
+# Run as an unprivileged user that owns the data directory. A fresh named
+# volume inherits this ownership; a bind-mounted host directory must be
+# owned by uid 10001 (see "Running under upaas" in README.md), or startup
+# fails.
 RUN addgroup -S -g 10001 dnswatcher \
-    && adduser -S -G dnswatcher -u 10001 dnswatcher
+    && adduser -S -G dnswatcher -u 10001 dnswatcher \
+    && mkdir -p /var/lib/dnswatcher \
+    && chown dnswatcher:dnswatcher /var/lib/dnswatcher
 
 ENV DNSWATCHER_DATA_DIR=/var/lib/dnswatcher
 
@@ -59,8 +62,7 @@ ENV DNSWATCHER_DATA_DIR=/var/lib/dnswatcher
 # data directory, or the binary's directory, the working directory.
 WORKDIR /
 
-# No USER: the entrypoint must start as root to set up the data
-# directory; it then runs dnswatcher as the dnswatcher user.
+USER dnswatcher
 
 EXPOSE 8080
 
@@ -70,4 +72,4 @@ EXPOSE 8080
 HEALTHCHECK --interval=10s --timeout=5s --start-period=10s --retries=3 \
     CMD wget -q -O /dev/null "http://127.0.0.1:${PORT:-8080}/.well-known/healthcheck" || exit 1
 
-ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
+ENTRYPOINT ["/usr/local/bin/dnswatcher"]

README.md

@@ -533,7 +533,17 @@ repository's `Dockerfile` and runs it. The app needs:
 - **Branch:** `prod`. `prod` is cut from `main`, and merging a `main` to
   `prod` pull request is a deploy.
 - **Volume:** one host directory mounted at `/var/lib/dnswatcher`, where
-  the state file lives.
+  the state file lives. upaas bind-mounts the host path it is given and
+  does not create it. The container runs as uid 10001 and does not start
+  unless it can write there. Create the directory before the first
+  deploy:
+
+  ```sh
+  mkdir -p /path/to/data
+  chown 10001:10001 /path/to/data
+  chmod 700 /path/to/data
+  ```
+
 - **Network and port:** the dashboard is unauthenticated and shows every
   watched name and recent alert, and upaas publishes every mapped port on
   all interfaces of the host

TODO.md

@@ -19,17 +19,6 @@ Rationale, Design, TODO, License, Author) if any are still missing.
 
 # Completed Steps
 
-- 2026-09-29: the image sets up its own data directory. Its entrypoint,
-  `deploy/docker-entrypoint.sh`, starts as root, creates the data directory if
-  needed, gives it and everything in it to the `dnswatcher` user with mode 700
-  on the directory, then runs dnswatcher as that user with `su-exec`. A
-  bind-mounted host directory no longer has to be chowned first (closes #166).
-- 2026-09-29: `.golangci.yml` re-fetched unchanged from `sneak/prompts`. It
-  replaces the deprecated `gomodguard` with `gomodguard_v2`, so `make lint` no
-  longer warns about it, and turns on `depguard` with the org `test-support`
-  rule, which rejects `net/http/httptest` except in test files and in files
-  under a directory whose name ends in `test`. This repo had no `deny` entries
-  of its own to carry forward (closes #123).
 - 2026-09-29: nothing stands in for DNS any more. Watcher tests that look
   something up in DNS use the real resolver against live DNS servers and test
   record and nameserver changes by preparing the saved state a check starts

deploy/docker-entrypoint.sh

@@ -1,17 +0,0 @@
-#!/bin/sh
-# deploy/docker-entrypoint.sh: the Docker image's ENTRYPOINT. It runs as
-# root only to give the data directory to the dnswatcher user: a host
-# directory bind-mounted there keeps its host owner, often root, and may
-# hold a state file left by another uid, which dnswatcher could neither
-# read nor replace. dnswatcher itself always runs as the dnswatcher user.
-set -eu
-
-main() {
-    dir="${DNSWATCHER_DATA_DIR:-/var/lib/dnswatcher}"
-    mkdir -p "$dir"
-    chown -R dnswatcher:dnswatcher "$dir"
-    chmod 700 "$dir"
-    exec su-exec dnswatcher /usr/local/bin/dnswatcher "$@"
-}
-
-main "$@"