mirror of https://github.com/ModernRelay/omnigraph.git synced 2026-06-30 02:49:39 +02:00

Ragnor Comerford 7779b72446

feat(engine): retire commit-graph tables (#311 )

* docs(dev): write-latency roadmap (validated cost model + layered fix)

Records the validated 6-LIST warm-write cost model, the two root causes
(un-GC'd _versions/; re-resolving latest by listing), and the layered fix
(GC + capture-once reuse), plus how commit-graph-table retirement feeds in.
Linked from docs/dev/index.md next to the RFC-013 docs.

* feat(engine)!: strand storage versioning — one internal-schema version, no in-place migration

Set MIN_SUPPORTED == CURRENT == 4: this binary reads exactly one `__manifest`
internal-schema version and refuses any older graph on open with a
rebuild-via-export/import message, instead of migrating it in place. Storage
format changes become a deliberate cutover, not a permanently-carried in-place
migration — the pre-release "complexity must be earned" contract.

Delete the entire in-place migration apparatus and everything that existed only
to support it: the `migrate_vN` arms + dispatcher + stamp-bump helpers + the
schema-version-floor tripwire; `migrate_on_open` (both open modes now refuse);
the legacy `_graph_commits.lance` readers + the v3 test fixtures + migration
tests + `migration.v3_to_v4.*` failpoints + the two surface guards that pinned
Lance variants only the migration matched on; and `state::merge_lineage_rows`.
Keep `read_stamp` / `stamp_current_version` / `set_stamp` /
`refuse_if_stamp_unsupported` — the seam a future one-shot converter plugs into.

`load_commit_cache_for_branch` now reads the `__manifest` projection
unconditionally (sub-v4 graphs are refused at open). Adds
`sub_current_graph_is_refused_on_open_with_rebuild_hint`.

The commit-graph TABLES are still created/used as branch-ref ledgers — their
retirement (CommitGraph -> pure `__manifest` projection) is the next commit.

BREAKING CHANGE: a graph created by omnigraph <= 0.7.2 (internal schema v3) is
refused on open. Rebuild it: `omnigraph export` with the old release, then
`omnigraph init` + `omnigraph load` with this one. Data, vectors, and blobs are
preserved; commit history and branches are not.

* feat(engine)!: retire `_graph_commits.lance` / `_graph_commit_actors.lance` — CommitGraph is a pure `__manifest` projection

Since RFC-013 Phase 7, graph lineage lives in `__manifest` (`graph_commit` /
`graph_head` rows) and branch authority is `__manifest` (branch create forks it
first). The two commit-graph datasets were vestigial: `_graph_commit_actors.lance`
was never written or read; `_graph_commits.lance` carried zero commit rows and
only mirrored the manifest's branch refs (a deny-list "parallel copy"). Retire
both.

- `CommitGraph` collapses to a pure projection: drops its Lance dataset handles
(`dataset`/`actor_dataset`) and all branch methods; `open`/`open_at_branch`/
`refresh`/`init` open NO dataset, building the cache from
`ManifestCoordinator::read_graph_lineage_at`. Removes ~1.4s of cold-open
dataset opens.
- `graph_coordinator`: `commit_graph` is now non-`Option` (always a valid
projection). `branch_create`/`branch_delete` go through `ManifestCoordinator`
only — a single atomic op, replacing the two-step manifest-fork +
commit-graph-fork + rollback. Deleted `create_commit_graph_branch`,
`reclaim_commit_graph_branch`, `ensure_commit_graph_initialized`, and every
`storage.exists(_graph_commits.lance)` gate.
- `optimize`: dropped `reconcile_commit_graph_orphans` and the two tables from
the internal-table compaction set (now `__manifest` only).
- `instrumentation`: `INTERNAL_TABLE_DIRS` no longer lists the two tables.
- Fresh graphs create neither table; `lineage_projection.rs` now asserts both
`.lance` dirs are absent. Deleted the obsolete commit-graph-branch-race
failpoint tests + their failpoint names, and updated the `maintenance`
optimize tests (one internal table, not three).

Review-pass fixes folded in:
- Removed two stale `omnigraph.rs` in-source tests the prior run missed (a
disk-full link failure masked them): one asserting `open` probes
`_graph_commits.lance` (the exists-gate this commit removes) — it was masked
earlier by a disk-full link failure.
- Corrected src comments referencing deleted code (`migrate_v3_to_v4`,
`append_commit`/`append_merge_commit`, the three-internal-table list,
the `_graph_commits` reconcile owner) in publisher/recovery/optimize/recovery_audit.
- Narrowed `set_stamp_for_test` to `cfg(test)` (its only caller is the refusal
test) — removes a dead-code warning in the failpoints build.

Branch create/delete atomicity improves (single atomic `__manifest` op). No
behavior change for reads or branches.

Follow-up (separate commit): the now-always-0 `IoCounts::commit_graph_reads` test
counter + its `IOTracker`, threaded through ~11 cost-test files.

* feat: surface the internal-schema (storage-format) version to operators

After stranding storage versioning (a sub-v4 graph is refused on open), operators
could only discover the storage-format version by hitting a refusal. Surface it:

- `omnigraph version` prints an `internal-schema <N>` line (the binary's CURRENT
storage-format version).
- `omnigraph snapshot` includes `internal_schema_version` — the GRAPH's per-branch
on-disk stamp, read via the new `Omnigraph::internal_schema_version_of`.
- `GET /healthz` includes `internal_schema_version` (server-scoped: the binary's
CURRENT, alongside `version`/`source_version`).

Wire: re-expose `INTERNAL_MANIFEST_SCHEMA_VERSION` as `pub` on `db::manifest`;
add `internal_schema_version: u32` to `SnapshotOutput` + `HealthOutput`;
`snapshot_payload` takes the per-graph version (the `Snapshot` does not carry it),
threaded through the embedded CLI + server snapshot callers. `openapi.json`
regenerated (two added int32 properties). Extends the existing healthz / snapshot /
version tests.

* docs(engine): gate internal-schema version at the graph level; record the per-branch read gap

PR reviewers flagged that the open path validates only main's internal-schema stamp, so a branch read could decode a branch stamped outside this binary's range. The stamp is a graph-wide storage-format property (the upgrade path is a whole-graph export/import), so with one binary version every branch is always CURRENT; divergence needs concurrent multi-version writers, an unsupported topology already in one-winner-CAS territory. Gating per-branch would add a second __manifest open per non-main branch read to defend a state we do not support, unearned complexity that regresses the warm-read budget.

Keep the graph-level gate, document it at the code site (refuse_if_internal_schema_unsupported), and record the read-only residual hole as a known gap in invariants.md to close only when multi-version write topologies become supported. Also clarify the sub-floor rebuild message to say "export with the older omnigraph binary that created it."

No behavior change: HEAD already gated at the graph level.

* test(cost): remove the dead commit_graph_reads IO counter

Phase B retired _graph_commits.lance / _graph_commit_actors.lance, so no commit-graph dataset is opened and the commit_graph IOTracker term is structurally always 0. Remove IoCounts::commit_graph_reads, its total_reads() term, the commit_graph IOTracker in OpProbes, and the now-dead commit_graph_wrapper field on QueryIoProbes (it had no accessor — nothing ever attached it). Drop the 7 trivially-true assert_eq!(commit_graph_reads, 0) checks in warm_read_cost.rs and the debug-print refs in write_cost{,_s3}.rs.

Lineage and actor rows now live in __manifest (RFC-013 Phase 7), so the internal_table_scans_are_flat_in_history gate folds into the single manifest_reads flat-assertion — the manifest scan already covers them. Harness-only; no production runtime impact.

* docs: align with the commit-graph retirement + strand storage versioning

Update the always-loaded and user-facing docs to match the landed state: graph lineage lives in __manifest, the _graph_commits.lance / _graph_commit_actors.lance tables are retired, and storage is strict-single-version (no in-place migration — a sub-CURRENT graph is refused with an export/import rebuild).

Fixed stale claims in invariants.md (the migration/atomicity known-gap entry, the Truth Matrix branch-delete row, the read-path/optimize internal-table scope), lance.md (the migrate_v1_to_v2 PK bullet now reflects init-time set; removed the two deleted v3->v4 migration surface guards), testing.md (dropped the deleted migration failpoint tests; manifest-only internal-table term), writes.md (rewrote the Migration-code section to the strand model), storage.md / maintenance.md / constants.md (retired tables out of the layout, internal-table compaction scope, and the constants cheat-sheet), and AGENTS.md. Marked the retirement DONE in the RFC-013 handoff/roadmap and banner-noted the historical RFC analysis.

Added docs/user/operations/upgrade.md (the export/import rebuild recipe) and docs/dev/versioning.md (the four-axis compatibility policy: release lockstep / wire additive / storage strict-single-version / Lance pinned), cross-linked from the audience indexes and the AGENTS.md topic map, and rewrote the in-progress v0.8.0 release note for the strand model + version surfacing. check-agents-md.sh passes (65 links, 62 docs).

* test(manifest): cover the v3-refusal→export/import rebuild cycle and branch stamp inheritance

Two coverage additions from PR review (P1):

(a) sub_current_graph_is_refused_then_rebuilt_via_export_import — the full operator narrative in one flow: load → export → a sub-CURRENT graph (stamp rewound below CURRENT) is refused with the export nudge → fresh init + load(export) → data present and the rebuilt graph opens. The refusal is stamp-only (read before any data), so a stamp-rewound graph is a faithful stand-in for a real older-release graph without a second binary; vector/blob fidelity stays covered by tests/export.rs.

(b) branch_inherits_main_internal_schema_stamp — proves a branch cannot diverge from main's stamp under single-binary operation (create_branch forks main's __manifest, the publisher does not re-stamp), which is why the graph-level (main-only) stamp gate is sufficient for supported inputs. A divergent branch stamp needs concurrent multi-version writers, the unsupported topology recorded as a known gap.

2026-06-28 16:49:49 +02:00

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Versioning & compatibility policy

Audience: engine / storage / release maintainers Status: living document

Omnigraph has four independent version axes. They have different compatibility contracts because they fail in different ways and at different costs. Conflating them (for example, treating a storage-format change like a wire change) is how you either ship an unsafe silent-misread or carry migration code you do not need.

Axis	Policy	Mechanism
Release (semver)	All published crates move in lockstep.	Maintenance-contract rule 4 in AGENTS.md: a release bump updates every crate manifest, `Cargo.lock`, `openapi.json`, and the surveyed version line together.
CLI ↔ server wire	Additive and rolling-safe; no version gate. New fields are optional; old clients ignore unknown fields and omit new ones.	Additive JSON DTOs in `omnigraph-api-types`; the OpenAPI-drift test (`crates/omnigraph-server/tests/openapi.rs`) catches an unintended wire change.
Storage (internal manifest schema)	Strict single version; upgrade is a cutover via export/import, never an in-place migration.	A stamp (`omnigraph:internal_schema_version`) in `__manifest`'s schema metadata + `refuse_if_stamp_unsupported`, with `MIN_SUPPORTED == CURRENT`.
Lance on-disk format	Pinned to one Lance version; bumped deliberately with the engine.	`data_storage_version: V2_2` at every write site + the surface guards in lance.md, re-run on every Lance bump.

Why storage is strict-single-version (the strand model)

The internal-schema stamp gates the on-disk shape of __manifest. The contract is: this binary reads exactly one internal-schema version. Omnigraph::open (both read-write and read-only) reads main's stamp before any data and refuses anything it cannot serve:

a stamp below CURRENT → refused with a rebuild-via-export/import message (see the upgrade guide);
a stamp above CURRENT → refused with "upgrade omnigraph", so an old binary cannot silently misread a newer format.

There is no in-place migration dispatcher. The single source file db/manifest/migrations.rs holds only the version constant, the stamp read/write, and refuse_if_stamp_unsupported.

This is a liability decision, not a limitation we have not gotten around to. In-place migration code is permanent surface: every future format change has to write, test, and keep working a vN → vN+1 step, plus the legacy readers and crash-recovery paths each step needs, for a storage format that is still pre-release and changing. The strand model trades that ongoing cost for a one-time operator action (export + import) when a format changes. Per "engineering is programming integrated over time" (see AGENTS.md), the lower-liability option is to not carry the machinery until a concrete graph demands it.

The stamp + refuse_if_stamp_unsupported floor is exactly the seam a future in-place migration would re-introduce: re-add a dispatcher and lower MIN_SUPPORTED below CURRENT for the versions it can actually walk forward. Until then that machinery is deliberately absent.

Gating altitude

The stamp is validated at the graph (main) level: Omnigraph::open checks main once, and branch reads trust it. The stamp is a graph-wide storage-format property (the upgrade path is a whole-graph export/import), so with one binary version every branch is always CURRENT — init stamps main, create_branch forks the stamp, and the publisher writes rows without re-stamping. A branch stamped out of range while main stays in range is only reachable with concurrent multi-version writers, an unsupported topology; the residual is recorded as a known gap in invariants.md.

Why the wire is additive-rolling-safe instead

The CLI↔server boundary is the opposite case: clients and servers are deployed independently and a hard gate there would force lockstep redeploys for every field addition. So that axis is additive — old and new coexist — and the OpenAPI-drift test is the guard that a change stayed additive rather than breaking the shape.

When you change each axis

Storage format: bump INTERNAL_MANIFEST_SCHEMA_VERSION, keep MIN_SUPPORTED == CURRENT (unless you are re-introducing migration), update the stamp history on the constant's doc-comment, and add a release note pointing at the upgrade guide. The change is breaking by construction — pre-bump graphs are refused.
Wire: keep it additive; regenerate openapi.json (OMNIGRAPH_UPDATE_OPENAPI=1); do not add a version gate.
Lance: follow the Lance-bump checklist in lance.md — re-run the surface guards first, then cargo test --workspace (a clean build is not a clean alignment).
Release: lockstep per the maintenance contract.

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