147 lines
6.2 KiB
Markdown
147 lines
6.2 KiB
Markdown
# M7.6 — Sync framework
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| Field | Value |
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|---|---|
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| Phase | M7 — Source connectors |
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| Size | L — 3–5 days |
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| Status | ⬜ Not started |
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| Flags | — |
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| Spec | inlined below |
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| Blocks | M7.7, M7.10 |
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| Depends | M7.1 |
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## Goal
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Build the shared sync engine that handles change detection, tombstoning, drift
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reporting, and resumable sync for **all** connectors — so individual connector
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implementations only fetch documents and everything else is handled once.
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## Facts (inlined — no spec read needed)
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Every connector faces the same sync problems:
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1. **What changed?** Compare content hashes from `list_documents()` against a
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manifest of last-known hashes. Only fetch and process changed documents.
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2. **What disappeared?** Documents in the manifest but not in `list_documents()`
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need tombstone records in the log. Append-only — never delete.
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3. **What if sync crashes midway?** Track progress per-document. Restart
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processes only unseen documents.
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4. **How much will this cost?** Drift report shows counts without mutating
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anything.
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This is the generalization of M3.6.3's `mem ref sync/list/rm` logic, applied to
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any `SourceConnector` instead of just `DocCorpusSource`.
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**Manifest storage.** Per-connector manifest in `log/connectors/<name>.manifest.jsonl`:
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```jsonl
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{"doc_id":"abc","source_uri":"file:///vault/k8s.md","content_hash":"sha256:...","chunk_count":12,"synced_at":"..."}
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{"doc_id":"def","source_uri":"paperless://doc/42","content_hash":"sha256:...","chunk_count":3,"synced_at":"..."}
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```
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**Sync algorithm:**
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```
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current = connector.list_documents()
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previous = load_manifest(connector.name)
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for doc in current:
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if doc.content_hash == previous[doc.doc_id].content_hash:
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skip (unchanged)
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else if doc.doc_id in previous:
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tombstone previous chunks, fetch + chunk + embed new (changed)
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else:
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fetch + chunk + embed (new)
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for doc_id in previous not in current:
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tombstone all chunks (removed)
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save_manifest(connector.name, current)
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```
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**Chunking delegation.** The sync framework owns the chunking step. It routes
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fetched `DocumentContent` through the appropriate `ChunkPolicy`:
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- Markdown → heading-boundary chunking (reuse `DocCorpusSource` logic)
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- Plain text → paragraph-boundary chunking
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- Configurable per connector kind in `connectors.yaml`
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**Level routing.** Session connectors → RecordSource → gated loop (L0/L1/L2).
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Document connectors → Reference records (Level R). The `source_type()` method
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on the connector determines the pipeline.
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## Steps
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1. Define `SyncEngine` struct in `mem-ingest/src/sync.rs`.
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2. Implement manifest loading/saving (JSONL per connector).
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3. Implement diff algorithm: `(new, changed, unchanged, removed)` from
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`list_documents()` vs manifest.
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4. Implement sync loop: for each `new`/`changed` doc, fetch → chunk → emit
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records. For each `removed` doc, emit tombstones.
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5. Implement drift reporting: same diff algorithm, print counts, no mutations.
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6. Implement resume: track synced doc_ids in a progress file. On restart,
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skip already-synced docs.
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7. Implement rate limiting: configurable max concurrent fetches per connector.
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8. Integrate with `mem-store` for writing Reference records to the log.
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9. Integrate with `mem-llm` for embedding new chunks.
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## Acceptance
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- Sync of unchanged connector produces zero embedding calls.
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- Changed document: old chunks tombstoned, new chunks embedded and stored.
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- Removed document: chunks tombstoned, manifest updated.
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- Drift report matches actual changes without mutating anything.
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- Crash mid-sync → restart processes only remaining documents.
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- Rate limiting: never exceeds configured concurrent fetch limit.
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- Log remains append-only (tombstones are records, not deletions).
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## Verify
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**Harness:** `VecConnector` with mutable document list, counting embedder.
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**Integration test** — `tests/it_sync_framework.rs`:
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1. `a1_initial_sync_all_new` — 3 docs, no manifest; assert all 3 fetched and
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embedded, manifest written with 3 entries.
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2. `a2_unchanged_skipped` — sync again with same content; assert zero fetch
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calls, zero embed calls.
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3. `a3_changed_doc_replaced` — modify one doc's content; sync; assert old chunks
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tombstoned, new chunks embedded, embed count equals changed doc's chunk count.
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4. `a4_removed_doc_tombstoned` — remove a doc from connector; sync; assert
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tombstone records emitted, manifest entry removed.
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5. `a5_new_doc_added` — add a doc to connector; sync; assert only new doc
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fetched and embedded.
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6. `a6_drift_report_read_only` — modify docs, run drift report; assert correct
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counts (1 new, 1 changed, 1 unchanged, 1 removed); assert no mutations to
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manifest or log.
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7. `a7_resume_after_crash` — sync 5 docs, simulate crash after 3; restart;
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assert only 2 remaining docs processed.
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8. `a8_tombstone_is_append` — count log lines before and after remove; assert
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count only grew.
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9. `a9_manifest_roundtrip` — save manifest, load it; assert field-for-field
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equality.
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10. `a10_rebuild_parity` — after full sync, `mem rebuild --from-log` produces
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identical state.
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**Command:** `cargo test --test it_sync_framework`
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**False pass:**
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- Asserting "no duplicate rows" instead of counting embed calls. A sync that
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re-embeds everything and upserts by sha produces correct rows and wasted
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compute.
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- Testing drift report without actually changing documents first.
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## Traps
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- Comparing document-level hashes instead of chunk-level. A doc that changed
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one paragraph should re-embed only the affected chunks, not all of them.
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However, heading-boundary chunking means changing one heading can shift all
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subsequent chunks. Accept document-level granularity for now; chunk-level
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optimization is a future refinement.
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- Making the manifest a database table instead of JSONL. The manifest must
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survive `mem rebuild --from-log` — it is metadata about the sync process,
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not a projection of the log.
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- Running fetch + embed serially. A connector with 500 docs at 200ms per embed
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takes 100s serially. Concurrent fetch + sequential embed is the right shape.
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- Ignoring the derived filter (M4.2). Document connectors produce Level R content
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that must register in the artifact manifest so it cannot re-enter as evidence.
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---
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Background: [DESIGN.md](../DESIGN.md) — source connectors, sync framework
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