jcoffey-dev
a0f846a31b
`run --dry-run` cloned the data directory into a sandbox, migrated the copy,
booted it, and compared content before and after. Running that design
against a real 0.15.5 instance and a real production settings corpus
retired it:
* The mechanics were never the risk. Backup, dump, convert and the
recovery-mode store migration all worked essentially first time.
* Its final comparison cannot work at all. It needs the migrated sandbox
to answer an API, and server.listener is not among the settings
migrate_v016.py carries - so a migrated instance has no listeners and
answers on nothing. That is the true post-migration state, not a
sandbox artifact to engineer around.
* The expensive half bought the least: against a 3.6 GB production store
it copies the data twice, reading a live mail store, to prove RocksDB
files copy and recovery mode can open them.
Meanwhile the cheap half found every problem that would have derailed a
real migration - an empty defaultHostname v0.16 rejects, passwords v0.16
refuses to create, and a 12,182-key reconstruction worklist - and needs no
data copy at all.
So `stalwart-migrate rehearse`: preflight, dump, convert, report. It copies
nothing, starts no server, and never writes to the store, so it is safe to
run against production repeatedly without a maintenance window. It needs no
target binary either, since convert is pure Python.
The scratch directory is cleaned up as before, with the rehearsal's two
conclusions lifted out first and recorded as artifacts: export.json (what
will carry over) and unmigrated.txt (what will not). Recording an artifact
whose path was about to be deleted was a bug in the first cut of this;
both now resolve.
`run` keeps its refusal and explains where rehearse went. `--dry-run` is
kept as a flag purely to say what replaced it.
Verified against the smoke VM end to end: rehearsal completes read-only in
seconds and reports 3505 unmigrated settings on a default install,
listeners included.
206 lines
8.6 KiB
Markdown
206 lines
8.6 KiB
Markdown
# stalwart-migrator
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In-place upgrade tool for Stalwart Mail Server, 0.15.5 → latest: no data
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loss, a checkpoint at every step so an interrupted run resumes instead of
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restarting, and automated validation that the server still works afterwards.
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**Recovery from a failed migration is your own snapshot or backup — this
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tool does not undo a migration.** See [Recovery is your
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job](#recovery-is-your-job) before using it on anything you care about.
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Go, standard library only — no external dependencies.
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## Status
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Partially implemented. Roughly 8,800 lines of tested code. Every phase
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except staging now exists as a package, including cutover, but nothing wires
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them into a production run yet, so `run` still refuses.
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| Command | State |
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| `stalwart-migrate preflight` | **Works** — read-only checks and a migration plan |
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| `stalwart-migrate rehearse` | **Works** — read-only; converts your settings and reports what won't carry over |
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| `stalwart-migrate run` | **Refuses on purpose** — see below |
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| `stalwart-migrate status <id>` | **Works** |
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| `stalwart-migrate report <id>` | Not implemented |
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**`run` deliberately refuses to proceed.** Cutover (ARCHITECTURE.md §4.5) is
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implemented, but nothing calls it: the staging phase (§4.3) and the pipeline
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that would run preflight → backup → stage → recovery-mode → cutover →
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validate against real paths don't exist yet. `run` stops rather than going
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partway. That refusal is the correct behaviour today, not a bug.
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**Start with `rehearse` instead.** It is read-only, needs no maintenance
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window, and answers the question that actually shapes a migration plan —
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see below.
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Package state:
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| Package | Lines | Tests |
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| `internal/backup` | 1806 | yes |
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| `internal/preflight` | 1329 | yes |
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| `internal/stalwartapi` | 1276 | yes |
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| `internal/cutover` | 1186 | yes |
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| `internal/validate` | 792 | yes |
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| `internal/recovery` | 702 | yes |
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| `internal/checkpoint` | 556 | yes |
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| `internal/service` | 467 | yes |
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| `internal/plan` | 195 | yes |
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| `internal/config` | stub | — |
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## Why not a shell script
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Stalwart's 0.15 → 0.16 boundary is not a drop-in binary swap: settings move,
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and the data directory has to be migrated rather than merely copied. The
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failure mode that matters is a half-migrated mail store with no way back —
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which is why backup verification and checkpointing are the design centre
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rather than conveniences bolted on afterwards — and why the tool refuses to
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cut over until you confirm you have a way back.
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[`ARCHITECTURE.md`](ARCHITECTURE.md) covers this in full: §1 on why a thin
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wrapper is insufficient, §4 on the migration phases, §5 on the checkpoint
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state machine, §6 on the CLI surface, and §8 on what is still open.
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## Build and test
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```sh
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go build ./...
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go test ./...
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```
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Requires Go 1.26 or newer.
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## Trying it safely
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`preflight` is the sensible starting point — its checks against the Stalwart
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installation are read-only:
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```sh
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sudo go run ./cmd/stalwart-migrate preflight
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```
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It still needs write access, because it records the run as a checkpoint
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before doing anything else:
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```
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create run: checkpoint: create run directory:
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mkdir /var/lib/stalwart-migrator: permission denied
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```
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That path is `checkpoint.DefaultBaseDir`, a compile-time constant with no
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flag or environment override — so preflight needs either root or a
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pre-created writable `/var/lib/stalwart-migrator`. (`run` takes `--work-dir`
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for its scratch space, but that is a different directory and does not move
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the checkpoint store.)
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`rehearse` is the next step, and unlike everything else here it is worth
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running today — see the next section.
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## Rehearse before you migrate
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```sh
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stalwart-migrate rehearse --admin-url https://mail.example.com \
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--admin-user admin --target 0.16.14
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```
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It runs preflight, dumps your settings and principals, converts them with
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Stalwart's own `migrate_v016.py`, and reports **both halves** of the result:
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the apply plan of what will carry over, and the worklist of what will not.
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It copies no data, clones nothing, starts no server, and never writes to the
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store, so it is safe to run against production repeatedly and without a
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maintenance window.
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Expect the worklist to be long. Measured against a real production instance,
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`migrate_v016.py` carried **219 of 12,401 settings — 1.8%**. The rest,
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including `server.listener`, has to be rebuilt by hand; until it is, a
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migrated instance answers on no ports at all. Both outputs are preserved
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under `<state-dir>/runs/<run-id>/` (`export.json` and `unmigrated.txt`) even
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though the rest of the scratch directory is cleaned up, because they are the
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conclusions.
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This replaced an earlier `run --dry-run` that cloned the data directory into
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a sandbox and migrated the copy. That proved the store opens, at the cost of
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copying it twice — while the half that found every real problem needed no
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copy at all. ARCHITECTURE.md §4.9 has the reasoning.
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## Recovery is your job
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**This tool does not undo a migration.** There is no `rollback` command.
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Recovery from a failed migration is your own snapshot or backup, taken by
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whatever method you already trust and know how to restore — a ZFS, LVM or
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btrfs snapshot, a VM or volume snapshot, or a restorable backup. Choosing
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that method, taking it, and verifying you can actually restore from it is
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out of scope for this tool: it does not take one, does not check that one
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exists, and cannot restore from one.
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Cutover refuses to start until you confirm a recovery point exists. That
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confirmation is an acknowledgement, not a check — nothing here can verify
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your snapshot. Its only purpose is that nobody migrates a production mail
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server having never been asked the question.
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**Take the snapshot with the service stopped** if you want a clean one. A
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snapshot of a running Stalwart is crash-consistent rather than clean; RocksDB
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will usually recover from its WAL, but "usually" is doing real work in that
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sentence.
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### Restoring from a snapshot loses mail delivered since
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Reverting to any pre-migration recovery point discards mail delivered
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between taking it and restoring it. This is inherent to restoring a point in
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time and this tool cannot solve it — plan your migration window with that in
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mind, and consider holding inbound mail at a secondary MX for the duration
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if the gap matters to you.
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### What the tool does to make a manual restore easier
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- **The old binary is preserved**, never deleted, next to the new one as
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`<binary>.v<old-version>` — so putting things back doesn't depend on
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re-downloading a specific old release under pressure.
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- **The original service definition is preserved** as `<unit>.pre-<run-id>`
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before cutover rewrites it, so you aren't reconstructing a unit file from
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memory.
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- **The settings and principals dumps** taken during backup stay on disk.
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- **Every artifact path and checksum is in the checkpoint**, and
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`stalwart-migrate status <run-id>` prints exactly which steps completed
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and which failed — which is the first thing you want when deciding what to
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restore.
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None of this is a substitute for the snapshot. It's what makes the twenty
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minutes after restoring one less unpleasant.
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### Why it works this way
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An earlier version of this tool implemented rollback itself: it restored the
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filesystem backup, verified every restored file against a manifest, replayed
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SQL dumps, reinstalled the old binary, and re-validated the result. It was
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tested and it looked good. It was removed, because restoring bytes correctly
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is not the hard part — it copied contents and permissions but not
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*ownership*, so run as root it would have produced a byte-perfect,
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checksum-verified, root-owned data directory that Stalwart, running as its
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own user, could not open, and it would have reported success. A filesystem
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snapshot has no such failure mode, because it never lost the metadata to
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begin with. ARCHITECTURE.md §4.8 records the full reasoning.
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## License
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Copyright (C) 2026 LINUXexpert-org
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This program is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the Free
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Software Foundation, either version 3 of the License, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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You should have received a copy of the GNU General Public License along with
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this program. If not, see <https://www.gnu.org/licenses/>.
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The full text is in [`LICENSE`](LICENSE). No third-party code is vendored —
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this tool is standard library only, and the `migrate_v016.py` it downloads
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at runtime is Stalwart's own script, fetched rather than redistributed.
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