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fix(transactions): resumable rollback (T-4) and failed-save safety (T-5) - #162
Fixes the two OPEN gaps that #161 found while modelling transaction atomicity. Both are Rust changes; the Agda model is untouched.
T-4: a rollback that fails part-way can now be retried to completion. cmd_rollback undoes operations last-first and stops at the first error, leaving the transaction Active with the later operations already undone. The retry then stopped at the first, already undone, operation (Operation … already undone), so the rollback could never finish and the only way out was jk commit on a half-undone transaction. cmd_rollback now skips operations already marked undone and resumes at the one that failed.
T-5: a failed save no longer leaves memory and disk disagreeing, and the log is replaced atomically. begin, add_operation, commit and mark_rolled_back mutated the in-memory log before save()?, and save was a plain fs::write. Each mutator now builds the successor log on a copy, saves it, and only then makes it the in-memory log. The save writes a sibling .tmp file, fsyncs it, renames it over the log, and fsyncs the directory.
Tests
crates/januskey-cli/tests/rollback_resume_test.rs drives the real jk: copy then modify in a transaction, break the second undo, repair, retry. A second case checks the retry does not undo an operation twice (a hand edit to its file survives).
Four unit tests in transaction.rs, with the save made to fail at its last step (a non-empty directory planted where the log goes, so the temp file is written but the rename is refused; works as root too): begin, add_operation, and commit/rollback each stay unapplied and succeed on retry; a save leaves no temp file and ignores a stale torn one.
Negative controls
Each test was run against the behaviour it guards:
Mutant
Result
old cmd_rollback (no skip)
both rollback tests fail with already undone
in-memory log updated before the save
the three failed_save_* tests fail
plain fs::write instead of write-and-rename
the atomic-replace test fails
failed save leaves its temp file behind
the three failed_save_* tests fail
(An earlier version of the unit tests injected the fault at create_dir_all, which does not distinguish the ordering; that mutant survived, so the fault was moved to the rename step.)
Ledger and dashboards
T-4 and T-5: OPEN → TESTED, six ledger rows, each with its test as the checked command.
Not claimed: crash-safety of the rename itself is by construction (write, fsync, rename), not crash-injected. The Rust is tested, not proved; the Agda model is unchanged.
New T-8 (OPEN): MetadataStore::save has the same plain fs::write, and an undo whose mark_undone fails to persist is still not retryable. Same class of fault, deliberately not widened into this PR.
dashboard-check locally: the new rows pass and the counts match; the same 10 Idris2 rows fail only because idris2 is not installed in this sandbox. CI's pinned image is the gate of record for those.
T-4: `jk rollback` undoes a transaction's operations last-first and stops
at the first error, leaving the transaction Active with the later
operations already undone. The retry then stopped at the first, already
undone, operation ("already undone"), so a failed rollback could never
finish. cmd_rollback now skips operations already marked undone.
T-5: begin, add_operation, commit and mark_rolled_back mutated the
in-memory log before `save()?`, and save was a plain `fs::write`. A failed
save left memory and disk disagreeing; a crash mid-write could corrupt the
log. Each mutator now builds the successor log on a copy, saves it, and
only then makes it the in-memory log; the save writes a sibling temporary
file, fsyncs it, and renames it over the log.
Tests: rollback_resume_test (real `jk`, two cases) and four unit tests in
transaction.rs. Each was checked against the old behaviour: the T-4 tests
fail on the old cmd_rollback; the T-5 tests fail when memory is updated
before the save, when the save is a plain fs::write, and when a failed
save leaves its temporary file behind.
Ledger: T-4 and T-5 move OPEN -> TESTED. Crash-safety of the rename is by
construction (write, fsync, rename), not crash-injected. T-8 (OPEN) records
that the operation metadata log has the same plain-write save, and that an
undo whose `mark_undone` fails to persist is still not retryable.
Dashboards: 119 -> 125 tests.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kjdf4Mf4Z41bNQh2TrsEp9
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Reviewing files that changed from the base of the PR and between e18a4f4 and 6318083.
Files selected for processing: 6
PROOF-NEEDS.adoc
READINESS.adoc
TOPOLOGY.adoc
crates/januskey-cli/src/main.rs
crates/januskey-cli/tests/rollback_resume_test.rs
crates/reversible-core/src/transaction.rs
📝 Summary
Summary by CodeRabbit
Bug Fixes
Rollback retries now skip operations that have already been undone, allowing a retry to continue after a partial failure. Changes made to restored files between attempts are preserved.
Failed transaction-log saves no longer change the in-memory transaction state. Log updates are written using atomic file replacement.
Documentation
Updated the readiness and testing documentation to report 125 tests and clarify which transaction-safety claims are tested, proved, assumed or still open.
Transaction mutations now persist a cloned successor log through temporary-file replacement and update in-memory state only after persistence succeeds. CLI rollback skips operations already marked undone. Tests cover failed saves and rollback retries, while project records update proof statuses and the test count.
Transaction mutations persist a cloned successor log through a temporary file and rename. In-memory state changes only after persistence succeeds. Tests cover failed saves and retries. The records mark T-4 and T-5 as tested, T-8 as open, and update the test count from 119 to 125.
CLI rollback skips operations already marked undone. Integration tests cover completing rollback after a failed attempt and preserving an edit made before retry.
hyperpolymath/januskey#161: Records the T-4 and T-5 gaps that this pull request updates with tested Rust fixes.
Merge Risk: Low · previous review e18a4
A transaction log opened by a bare filename may lack the intended rename durability. The gap is narrow, but worth fixing before relying on that path for crash recovery.
Pre-merge checks: 4 · 1
Failed checks: 1 warning
Check name
Status
Explanation
Resolution
Docstring Coverage
Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Documentation-only edits and deletions within surv…
Write docstrings for the functions missing them to satisfy the coverage threshold.
Passed checks: 4 passed
Check name
Status
Explanation
Title check
The title clearly and concisely identifies the two main changes: resumable rollback and failed-save safety. It matches the changeset.
Description check
The description directly explains the T-4 and T-5 changes, implementation details, tests, verification results, and remaining T-8 scope. It is related to the changeset.
Linked Issues check
Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check
Check skipped because no linked issues were found for this pull request.
Full details: Docstring Coverage
Explanation
Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 18 functions across 3 files. (3 skipped: 3 unsupported.)
Resolution
Write docstrings for the functions missing them to satisfy the coverage threshold.
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Actionable comments posted: 1
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Inline comments:
Review comments at @crates/reversible-core/src/transaction.rs:
- Around line 131-135: Update the post-rename directory sync logic using
path.parent() so an empty parent for a bare relative filename resolves to the
current directory before fs::File::open; preserve the existing best-effort
sync_all behaviour.
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PROOF-NEEDS.adoc
READINESS.adoc
TOPOLOGY.adoc
crates/januskey-cli/src/main.rs
crates/januskey-cli/tests/rollback_resume_test.rs
crates/reversible-core/src/transaction.rs
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Additional comments: 6
crates/reversible-core/src/transaction.rs: 1
16-17: LGTM!
Also applies to: 109-128, 172-211, 221-224, 250-250, 256-256, 264-264, 369-496
PROOF-NEEDS.adoc: 1
73-77: LGTM!
Also applies to: 141-141, 192-197, 203-203, 216-216
…e rename
`Path::new("transactions.json").parent()` is `Some("")`, which cannot be
opened, so the post-rename directory fsync was silently skipped for a log
given as a bare filename. A bare filename now syncs the current directory.
Adds a unit test for the helper, a doc comment on each new test, and moves
the dashboard test count 125 -> 126.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kjdf4Mf4Z41bNQh2TrsEp9
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Propagate directory-sync failures
When the directory opens successfully but sync_all() reports an I/O error (for example on a failing or unusual filesystem), swallowing the error makes persist update the in-memory log and report success even though the rename is not known to be durable. A crash can then restore the previous transaction log while the corresponding filesystem operation remains applied, defeating the crash-safety this write path is intended to provide; the directory-sync result needs to participate in the persistence outcome.
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Not changing this, deliberately. By the time the directory sync runs, the rename has already happened, so the disk holds the new log. If the sync error were returned, persist would not swap the new log into memory: disk new, memory old, which is the disagreement this PR sets out to remove (T-5). A rename whose durability is unconfirmed is a weaker guarantee on an unusual filesystem; a save that reports failure after it took effect is a wrong answer on every filesystem. I've kept the sync best effort, documented why in the code (a56cbde), and recorded it in the ledger as not claimed. If you'd rather fail the save and accept that mismatch, or retry the sync, that's your call; I've left this thread open for it.
…sions
Review findings on the atomic save:
- Every save used the one `<log>.tmp`, so two writers could truncate, rename
or delete each other's file, and a rename could carry the other writer's
bytes. Each save now writes `<log>.<pid>.<n>.tmp`, opened with create_new so
it can never adopt an existing file.
- Replacing the log by rename gave it the umask default, widening a log the
user had restricted (the old in-place write kept the inode's mode). The new
file now takes the replaced log's permissions before the rename.
The directory fsync stays best effort and is now documented as such: by then
the rename has happened, so failing the save would leave disk on the new log
and memory on the old, the disagreement T-5 exists to prevent.
Tests: each_save_uses_its_own_temporary_file and
save_preserves_the_logs_permissions, each checked against a mutant (shared
name, truncating open, no permission copy). Ledger T-5 gains two TESTED rows
and states what is not claimed. Dashboards: 126 -> 128 tests.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kjdf4Mf4Z41bNQh2TrsEp9
main gained #163 (content-store fixes, +4 tests), which edits the same
test-count lines as this branch. The merged total is 123 + 9 = 132, checked
against `cargo test --workspace --locked -- --list`.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kjdf4Mf4Z41bNQh2TrsEp9
The remote merge of main (42cacae) kept this branch's 128 tests, but main's
#163 adds 4, so the declared total is 132 (checked against
`cargo test --workspace --locked -- --list`). dashboard-check would have
failed on the stale 128.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Kjdf4Mf4Z41bNQh2TrsEp9
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Only remove temporary files created by this save
When writers in separate PID namespaces share this repository, they can have the same PID and sequence number and therefore select the same temporary path. If one writer creates it first, the other's create_new fails, but this unconditional cleanup deletes the first writer's live file, causing its later rename to fail as well; filesystem operations may then be applied without being added to the transaction. Fresh evidence beyond the earlier review is that the follow-up's PID-plus-counter naming is not unique across PID namespaces and cleanup runs even when this invocation never created the file. Track whether creation succeeded before removing the path, and retry AlreadyExists with a new candidate.
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Valid: #162 merged before this was fixed. Fixed in #164 (3b99d42): the name now has a random component, only a file this call created is removed, and a failed create leaves the path alone and fails the save cleanly. I did not add a retry on AlreadyExists: with a random 128-bit name a collision is not a practical case, and the clean failure leaves memory unchanged so the caller can retry. Covered by a_save_never_removes_a_temporary_file_it_did_not_create.
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Restrict the temporary file before writing log contents
When an existing transaction log has been restricted to a mode such as 0600 but .januskey remains its default searchable directory, the new temporary file is initially created using the process umask and receives the log's restrictive permissions only after write_all. During that window, another local user can open the predictable temporary pathname and read transaction names, paths, and user data. Apply the existing file's permissions before writing any content, or create the temporary file with a restrictive mode from the outset.
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Valid: #162 merged before this was fixed. Fixed in #164 (3b99d42): the temporary file takes the log's permissions at creation, while still empty, and the_temporary_file_is_restricted_before_any_content_is_written covers it.
… remove another writer's (#164)
## What
Follow-up to #162, which merged at 02:17 UTC while Codex's last two
review findings on its final commit were still unfixed. Both are real
defects in the atomic save I added, so this fixes them. Rust only; no
behaviour change outside the transaction-log save.
**1. The temp file was readable before it was restricted.** It was
created with the umask default and took the log's restrictive mode only
after the content was written, so for a log restricted to its owner (say
`0600`) another local user could read the new content through the
temporary file during that window. The file now takes the replaced log's
permissions at creation, while it is still empty.
**2. Cleanup could delete another writer's live file.** The temp name
was PID plus a counter, and cleanup ran even when this save had not
created the file. Writers in different PID namespaces that share a
repository (containers on a shared volume) can pick the same name; the
loser's cleanup then deleted the winner's live file and the winner's
rename failed. The name now carries a random component, and only a file
this call created is removed. If the create fails, the save fails
cleanly with memory unchanged (it can be retried) and the other file is
left alone.
## Deliberately not changed
Codex's third finding on #162, that a directory-`fsync` error should
fail the save, is still not taken. By then the rename has happened, so
failing the save would leave disk on the new log and memory on the old
one, the disagreement T-5 exists to remove. The sync stays best-effort,
commented in the code and recorded in the ledger as not claimed. That
thread was left open for the owner's decision and it is unchanged.
## Tests and negative controls
- `the_temporary_file_is_restricted_before_any_content_is_written`: a
`0640` log's temp file is `0640` and still empty at creation. Mutant
with the permissions applied after the write: fails (this test, and
`save_preserves_the_logs_permissions`).
- `a_save_never_removes_a_temporary_file_it_did_not_create`: a save onto
a name already taken fails, leaves that file intact and writes no log.
Mutant with unconditional cleanup: fails.
- Each mutant was confirmed applied (diffed against the unmutated file)
before its result was trusted.
## Ledger and dashboards
T-5 gains two TESTED rows and its status-table row is updated.
Dashboards: 132 → 134 tests (TOPOLOGY, READINESS), checked against
`cargo test --workspace --locked -- --list`.
## Verification
`cargo fmt --all -- --check`, `cargo clippy --workspace --all-targets
--locked -- -D warnings`, `cargo test --workspace --locked` and
`tests/aspect/cross_cutting_test.sh` (32 pass) are clean.
`dashboard-check` locally shows only the same 10 Idris2 rows that fail
because `idris2` is not installed in this sandbox; CI's pinned image is
the gate of record for those.
---
_Generated by [Claude
Code](https://claude.ai/code/session_01Kjdf4Mf4Z41bNQh2TrsEp9)_
---------
Co-authored-by: Claude <noreply@anthropic.com>
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What
Fixes the two OPEN gaps that #161 found while modelling transaction atomicity. Both are Rust changes; the Agda model is untouched.
T-4: a rollback that fails part-way can now be retried to completion.
cmd_rollbackundoes operations last-first and stops at the first error, leaving the transaction Active with the later operations already undone. The retry then stopped at the first, already undone, operation (Operation … already undone), so the rollback could never finish and the only way out wasjk commiton a half-undone transaction.cmd_rollbacknow skips operations already marked undone and resumes at the one that failed.T-5: a failed save no longer leaves memory and disk disagreeing, and the log is replaced atomically.
begin,add_operation,commitandmark_rolled_backmutated the in-memory log beforesave()?, andsavewas a plainfs::write. Each mutator now builds the successor log on a copy, saves it, and only then makes it the in-memory log. The save writes a sibling.tmpfile, fsyncs it, renames it over the log, and fsyncs the directory.Tests
crates/januskey-cli/tests/rollback_resume_test.rsdrives the realjk: copy then modify in a transaction, break the second undo, repair, retry. A second case checks the retry does not undo an operation twice (a hand edit to its file survives).transaction.rs, with the save made to fail at its last step (a non-empty directory planted where the log goes, so the temp file is written but the rename is refused; works as root too): begin, add_operation, and commit/rollback each stay unapplied and succeed on retry; a save leaves no temp file and ignores a stale torn one.Negative controls
Each test was run against the behaviour it guards:
cmd_rollback(no skip)already undonefailed_save_*tests failfs::writeinstead of write-and-renamefailed_save_*tests fail(An earlier version of the unit tests injected the fault at
create_dir_all, which does not distinguish the ordering; that mutant survived, so the fault was moved to the rename step.)Ledger and dashboards
MetadataStore::savehas the same plainfs::write, and an undo whosemark_undonefails to persist is still not retryable. Same class of fault, deliberately not widened into this PR.Verification
cargo fmt --all -- --check,cargo clippy --workspace --all-targets --locked -- -D warnings,cargo test --workspace --locked,tests/aspect/cross_cutting_test.sh(32 pass): all clean.dashboard-checklocally: the new rows pass and the counts match; the same 10 Idris2 rows fail only becauseidris2is not installed in this sandbox. CI's pinned image is the gate of record for those.Generated by Claude Code