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Bwrap build runtime und Installation in Hostsharing Managed Webspace (#4)

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* Add the bubblewrap build runtime (step 17, ADR 0007)

BwrapBuildRunner: third runtime behind BuildRunner for hosts without root
and without Docker (e.g. Hostsharing managed webspaces). Shells out to the
bwrap CLI, unpacks a prepared rootfs on demand into
.git/werkator/buildenv/<envKey>/rootfs, reuses the Docker runner's git
metadata mounts, and returns the attached bwrap process for streaming and
cancellation.

Config: bwrap.enabled/rootfs/env on BranchConfig and BwrapOverrides on
BuildDefinition; enabled/rootfs are pinned like the docker sandbox policy.
Docker and bwrap are mutually exclusive per build, rejected in
buildSettings instead of picked silently. DispatchingBuildRunner routes
bwrap; InitCommand template, docs/configuration.md and AGENTS.md in sync.

* bwrap rollout tooling: remote script, prerequisites disk/quota check, absolute workspace binds

- tools/remote: central remote control script with check-prerequisites, install and build commands
- tools/werkator-build-prerequisites.sh: compact PASS/FAIL output, target-dir parameter, free-space and
  group-quota headroom checks against the ~5 GiB build footprint, home-filesystem reference
- BwrapBuildRunner: bind workspace and home at absolute paths resolved against repoDir — a relative
  path made bwrap create mountpoints inside the read-only rootfs (seen on the webspace); regression test
- TestcontainersSmokeTest: gated with enabledIf docker available (skip, never fail, without a daemon)
- docs: configuration reference, step-17 plan notes, PR-doc

* bwrap: bind the repo read-write before the workspace so mountpoints are creatable

bwrap creates mountpoints for bind destinations inside the sandbox; with only a
read-only rootfs bound at /, creating them for the workspace under .git/werkator/
worktrees failed with 'Read-only file system' (seen on the webspace). Binding the
repo dir read-write first provides the base; the git metadata mounts then layer
the usual isolation on top (read-only .git, tmpfs mask over .git/werkator,
read-write worktree admin dir).

* bwrap: pre-create bind mountpoints inside the unpacked rootfs

bwrap mkdirs mountpoints for bind destinations against the sandbox view; with the
rootfs ro-bound at / every destination missing from the rootfs (the repo dir under
/home/storage/... on the webspace) fails with 'Read-only file system'. The rootfs
directory is a plain host dir, so create the mountpoints there before launching
bwrap; it then finds them and has nothing left to create.

* bwrap: skip existing rootfs files when pre-creating bind mountpoints

/etc/resolv.conf is a file the rootfs already ships; createDirectories threw on it.
Only missing directories are created now.

* bwrap: pre-create proc/dev/tmpfs mountpoints in the rootfs too

The rootfs archive ships no /proc or /dev (excluded when packed), so bwrap failed
mkdir'ing their mountpoints against the read-only root.

* bwrap: bind the workspace after the git metadata mounts

The tmpfs mask over .git/werkator shadowed the earlier workspace bind, because the
worktree lives under .git/werkator/worktrees — chdir then failed with ENOENT. The
workspace bind now comes last and shadows the mask at exactly its own path.

* systemd resource limits and webspace start command (step 17, web access)

- server.systemd.memoryMax/tasksMax (empty = directive omitted): on platforms where
  the service runs in a shared memory slice (Hostsharing Managed Webspaces) a
  runaway Gradle build must not starve the whole package; init --systemd reads the
  effective config and bakes the values into the generated unit
- tools/remote werkator start: writes server settings (assigned port, loopback
  bind, publicBaseUrl, nginx off) plus the Apache reverse-proxy .htaccess into
  ~/doms/<domain>/subs/www, runs init --systemd and enables the user unit
- docs/configuration.md documents the new keys

* tools/remote: env-based configuration and background port-forward

All connection and deployment values come from .env in the repository root
(WERKATOR_REMOTE, WERKATOR_PATH, WERKATOR_PORT, WERKATOR_DOMAIN,
WERKATOR_LOCAL_PORT, optional WERKATOR_BRANCH/MEMORY_MAX/TASKS_MAX/ROOTFS);
missing values fail with a pointing error instead of positional parameters.

- port-forward is now 'tools/remote port-forward start|stop' with a detached
  ssh tunnel, pid file under /tmp, and idempotent start
- start restarts the systemd unit after updating the machine config
- control-token generates the token in place when the server has not yet
- the rootfs archive default moves to build/ (already gitignored)
This commit is contained in:
Michael Hönnig
2026-08-31 19:56:04 +02:00
committed by GitHub
parent 516765a717
commit 71f1fc62c6
21 changed files with 1564 additions and 37 deletions
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docs/configuration.md
+28 -4
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@@ -63,7 +63,7 @@ above, giving the precedence **branch > repo install > project**. It takes prece
everything that describes how this branch is built: the whole `builds` section — its own
definitions and its overrides of the definitions from the project config, with
`buildCommand`, `cleanCommand`, `artifactDirs`, log file names, and
`docker.image`/`dockerfile`/`context`/`env` inside them. That is how a new configuration is tried out: change it on a branch, and
`docker.image`/`dockerfile`/`context`/`env` and `bwrap.env` inside them. That is how a new configuration is tried out: change it on a branch, and
no other branch's builds are affected.
The branch layer is used in both places where it matters: the watcher reads the committed
@@ -90,7 +90,8 @@ single branch may decide it:
- the repository-side settings: the whole `gitea`, `executor`, and `watcher` sections;
- the trust gate: `requirePullRequest`, and the Gitea status context: `statusContext`;
- the container sandbox policy: `docker.enabled` and `docker.network` — host-pinned as
- the container sandbox policy: `docker.enabled`/`docker.network` and
`bwrap.enabled`/`bwrap.rootfs` — host-pinned as
long as only the host's configuration sets them, master-pinned once the committed
configuration does.
@@ -138,6 +139,12 @@ server:
bindAddress: 127.0.0.1
# optional Impressum (legal disclosure) link in the web UI footer; empty hides the link
impressumUrl: ""
# Resource limits of the systemd user unit generated by `init --systemd`; empty = directive omitted.
# Needed where the service shares a memory slice, e.g. Hostsharing Managed Webspaces, where a
# runaway Gradle build would starve everything else in the package.
systemd:
memoryMax: "" # e.g. 1G — written as `MemoryMax=` into the unit
tasksMax: "" # e.g. 512 — written as `TasksMax=` into the unit
# Opt-in managed nginx+certbot Docker container for HTTPS, for hosts without
# a usable reverse proxy (ADR 0005; see notes below and deployment.md).
nginx:
@@ -342,9 +349,9 @@ That is how a branch gets a build of its own without being built by the default
`activeWithin` (e.g. `24h`) additionally keeps only branches whose origin head commit is younger than the duration — useful to run a nightly deep check over all recently active branches.
Both parts combine as an intersection.
Settings: `buildCommand`, `cleanCommand`, `artifactDirs`, `stdoutLog`/`stderrLog`, `requirePullRequest`, `statusContext`, and `docker` with all its keys.
Settings: `buildCommand`, `cleanCommand`, `artifactDirs`, `stdoutLog`/`stderrLog`, `requirePullRequest`, `statusContext`, and `docker` and `bwrap` with all their keys.
A definition carries the complete description of its build; unset keys fall back to `builds.default` and then to Werkator's own defaults.
`requirePullRequest`, `statusContext`, `docker.enabled`, and `docker.network` are pinned (master-pinned, see [the branch layer](#the-branch-layer-a-branch-describes-its-own-ci)): they are read from the repo install/project config even when a branch sets them in its own committed config.
`requirePullRequest`, `statusContext`, `docker.enabled`, `docker.network`, `bwrap.enabled`, and `bwrap.rootfs` are pinned (master-pinned, see [the branch layer](#the-branch-layer-a-branch-describes-its-own-ci)): they are read from the repo install/project config even when a branch sets them in its own committed config.
Inheritance from `builds.default` covers the settings only — the `trigger` block says when and where *this* build runs and is never inherited.
Definitions are part of the branch layer: a branch may add its own and override those from the project config, for its own builds only.
Because the inheritance is applied after all layers are merged, a build a branch invents still inherits the host's `builds.default` — its sandbox policy included, which is what keeps the pinning effective for a build the host has never heard of.
@@ -400,6 +407,23 @@ Note that the rest of `.git` — including `.git/config` — is visible to build
The Docker socket is mounted into the container and `DOCKER_HOST`/`TESTCONTAINERS_*` variables are set, so Testcontainers-based builds work inside the container.
All Werkator containers carry `org.hoennig.werkator` labels; stale build containers of the repository are removed before the first Docker build after a restart.
### Notes on `builds.<name>.bwrap`
With `bwrap.enabled`, Werkator shells out to the `bwrap` CLI (bubblewrap) instead of native execution.
This is the third runtime, for hosts without root and without a Docker daemon (e.g. Hostsharing managed webspaces); see `docs/plan/17-bwrap-build-runtime.md` and ADR 0007.
`bwrap` must be on the `PATH`.
`bwrap.rootfs` names the prepared root filesystem archive — a Debian-base rootfs with the build tools (JDK, git, locales, project-specific tooling) built elsewhere, since `debootstrap` is unavailable on the target.
It is a local path or an `http(s)` URL; a URL is downloaded once.
Build the archive with `tools/build-bwrap-rootfs.sh` on any machine with Docker; verify the host's user-namespace capability first with `tools/werkator-build-prerequisites.sh`.
The archive is unpacked on demand (`tar --no-same-owner`) into `.git/werkator/buildenv/<envKey>/rootfs`, shared across all branch worktrees like the Docker Gradle cache volume; `<envKey>` derives from a hash of the source, so a changed `rootfs` unpacks a fresh environment and stale ones can be pruned.
Per-branch Gradle caches persist in `.git/werkator/buildenv/home`, bound as `/root`.
`bwrap.env` adds environment variables inside the sandbox.
Files created inside the sandbox are owned by the host user, because uid 0 maps back to the unprivileged webspace user.
`docker` and `bwrap` are mutually exclusive per branch: enabling both is rejected at start, not silently picked.
Git works inside the sandbox exactly as inside the Docker container: the primary `.git` is mounted read-only with `.git/werkator/` masked, so builds can run read-only git commands but never reach the machine config or the control token.
## `.git/werkator/.werkator.yml` (not committed)
```yaml