docs(arch): A-2 + A-6 — async-trait trait family, pinned execution model
Resolves review 001 findings A-2 (critical) and A-6 (major) — the same signature surface: - ADR-012 §1: registry traits amended to #[async_trait] (bare async fn in traits is not dyn-compatible, E0038; ops sit behind Arc<dyn GitRegistryStore>). Desugared boxed Future form pinned in OQ-03's freeze inventory. async-trait = "0.1" added to the manifest. - backend.md concurrency model: the five-trait family is #[async_trait] Send + Sync dyn-compatible; the wire layer enforces ADR-009's pipeline-concurrency budget itself (permit acquired around each GitPackGen/GitPackIngest call — the concrete admission point); impls must not block the async executor and own their internal threading (gix impls run spawn_blocking inside the impl — POC-2's shape restated at its true layer). - transport.md §fetch: spawn_blocking sentence rephrased to the trait-contract version (the wire spec stops speaking gix). - ADR-009: enforcement point of the blocking-pool budget made concrete. - ADR-013 §6: ingestion spawn_blocking line aligned. - review 001: A-2, A-6 marked resolved. Verification: cargo test, clippy -D warnings, fmt --check, doc --no-deps, check --no-default-features, check --all-features — all clean.
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@@ -38,6 +38,11 @@ sha256 = ["gix-hash/sha256"]
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[dependencies]
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alkcall = "0.8"
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# Trait-family dyn-compatibility (ADR-012 §1: all backend traits are
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# #[async_trait] — bare `async fn` in a trait is not dyn-compatible,
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# review 001 A-2; the family-wide pattern: alktty TtyBackend, alkcall
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# ProtocolHandler).
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async-trait = "0.1"
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gix-odb = { version = "0.84", optional = true, default-features = false, features = ["sha1"] }
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gix-pack = { version = "0.74", optional = true, features = ["sha1"] }
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gix-ref = { version = "0.67", optional = true }
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@@ -1,6 +1,6 @@
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---
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status: draft
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last_updated: 2026-09-25
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last_updated: 2026-09-29
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---
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# Backend traits: the storage seam
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@@ -52,7 +52,8 @@ gix types:
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validated ref updates; the transaction itself is applied by `GitRefs`
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(single CAS home — ingest validates, refs commits; one transaction per
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push is what makes `atomic` correct — ADR-013 §7). Budgeted (ADR-009
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max pack size); blocking-thread friendly.
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max pack size); the impl runs its blocking work off the async
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executor (concurrency model below).
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Minimal-vs-full was the open sub-question; resolved as **full family** —
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each trait is one or two methods plus types, and collapsing them (e.g.
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@@ -96,13 +97,31 @@ Two independent seams, two default-on features:
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## Concurrency model
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- `gix` structures: `parking_lot` short-held locks; per-session handles
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moved into `spawn_blocking` tasks (POC-2's shape: store shared, handle
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per session, generation on blocking threads).
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and `spawn_blocking` live inside the gix impls (POC-2's shape: store
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shared, handle per session, generation on blocking threads).
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- Poisoned locks: `unwrap_or_else(|e| e.into_inner())` (convention 2).
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- The traits are `Send + Sync` object-safe; impls run under the
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adapter's tokio context. `GitRegistry::resolve` is async (one call per
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session/request, before the first protocol byte — ADR-011 §6); no
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sync-hot-path constraint exists here, unlike alkcall's accept loop.
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- **Trait execution model** (review 001 A-6): all five traits are
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`#[async_trait]` — `Send + Sync`, dyn-compatible (E0038 forbids bare
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`async fn`), signatures per ADR-012 §1. `GitRegistry::resolve` is
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async (one call per session/request, before the first protocol byte —
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ADR-011 §6); no sync-hot-path constraint exists here, unlike alkcall's
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accept loop. The execution model the signatures imply:
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- **The wire layer enforces the pipeline-concurrency budget itself**
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(ADR-009's "max concurrent blocking pipeline tasks" — a permit
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acquired in the wire layer around each `GitPackGen`/`GitPackIngest`
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call; the admission point of "enforced at assembly/acceptance
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time"). The wire layer is backend-trait-only (ADR-010) and knows
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nothing of stores, handles, or threads — so the permit, not
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`spawn_blocking`, is its entire concurrency contract.
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- **Implementations must not block the async executor** and own their
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internal threading: the gix impls run pack generation/ingestion on
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`spawn_blocking` with the owned handle moved in *inside the trait
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impl* (POC-2's shape, restated at its true layer — it is the impl's
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internal structure, invisible from the wire layer).
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- The traits are async so an embedder whose storage is async (DB
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registries, network object stores) implements them natively; the
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gix impl's blocking work is an internal detail, not part of the
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seam.
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## Public API surface
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@@ -58,6 +58,9 @@ gets the hard cap.
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*aggregate* work, not internal buffering.
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- The blocking-pool budget is enforced at assembly/acceptance time
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(reject/slow-path excess concurrent generations), not per-byte.
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Enforcement point (review 001 A-6): the wire layer — a permit
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acquired around each `GitPackGen`/`GitPackIngest` call; impls own
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their internal `spawn_blocking` (backend.md concurrency model).
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## References
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- `docs/research/vision.md` §"Guiding principles" 7
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@@ -42,11 +42,21 @@ and with the registry store (which needs no gitoxide at all).
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### 1. Read/write split on the record family
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*(Signatures amended per review 001 A-2: bare `async fn` in a trait is
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not dyn-compatible (E0038), and §3's ops sit behind `Arc<dyn
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GitRegistryStore>`. All five backend traits carry `#[async_trait]` —
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the family-wide pattern (alktty `TtyBackend`, alkcall
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`ProtocolHandler`); `async-trait = "0.1"` is in the manifest. The
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desugared `Pin<Box<dyn Future + Send>>` boxed form is the published
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vtable shape — pinned deliberately here, in OQ-03's freeze inventory.)*
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```
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#[async_trait]
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pub trait GitRegistry: Send + Sync {
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async fn resolve(&self, repo_id: &str) -> Result<RepoRecord, RegistryError>;
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}
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#[async_trait]
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pub trait GitRegistryStore: GitRegistry {
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async fn put_repo(&self, record: &RepoRecord) -> Result<(), RegistryError>;
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async fn update_repo(&self, record: &RepoRecord) -> Result<(), RegistryError>;
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@@ -115,7 +115,9 @@ verification of the ingestion composition. Captures are recorded in
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concurrency budget apply (the generation budget covers ingestion —
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same `spawn_blocking` pool, amended in ADR-009's table).
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- Ingestion runs on `spawn_blocking` (POC-2's shape: store shared,
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handle per session).
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handle per session — inside the gix impl; the wire layer's
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pipeline-concurrency permit wraps the trait call per ADR-009,
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backend.md concurrency model).
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- fsck/connectivity: `gix-fsck::Connectivity` over the odb handle
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after indexing, for each new tip reachable from the pushed refs;
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missing objects → `unpack ng <reason>`.
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@@ -1,6 +1,6 @@
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---
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status: draft
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last_updated: 2026-09-25
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last_updated: 2026-09-29
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---
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# alkgit: Git Smart Protocol (wire layer)
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@@ -70,9 +70,10 @@ substrate property (per-request state), not a protocol fork.
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re-sends wants + commons each round — negotiation-captures.md).
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Advertisement text is unchanged: `fetch=wait-for-done`.
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- Pack generation via `GitPackGen` (ADR-004), streamed over sideband on
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duplex / sideband-in-response on http; generation runs on
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`spawn_blocking` with the owned handle moved in (POC-2's shape: store
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shared, handle per session, generation on blocking threads).
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duplex / sideband-in-response on http; the call is async-trait, with
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the pipeline-concurrency permit acquired around the call by the wire
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layer (ADR-009's enforcement point — backend.md concurrency model;
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the gix impl's internal `spawn_blocking` is its own detail).
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- Round/haves budgets enforced here (ADR-009); an empty resulting pack
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(client already has everything) is a valid zero-object packfile.
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@@ -759,11 +759,11 @@ criticals are ADR-writing work, not code):
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| ID | Finding | Recommended fix | Effort | Risk | Status |
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|----|---------|----------------|--------|------|--------|
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| A-1 | op-gate OR not expressible in `AccessControl` | new ADR (or ADR-012 §3 amendment): handler-side two-tier check, create keeps static scope gate | small | none | **resolved (ADR-015)** — option (a) shape with the OR-term generalized to the `manage` grant |
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| A-2 | `async fn` traits not dyn-compatible | ADR-012 §1 + backend.md amendment: `#[async_trait]`; add `async-trait = "0.1"` to manifest | small | none | open |
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| A-2 | `async fn` traits not dyn-compatible | ADR-012 §1 + backend.md amendment: `#[async_trait]`; add `async-trait = "0.1"` to manifest | small | none | **resolved** — all five traits `#[async_trait]`, desugared boxed form pinned in the freeze inventory (OQ-03), dep in manifest |
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| A-3 | native preamble / service dimension unpinned | new ADR: open-op params `{repo, service}`, session tuple + stateless entry gain the service selector, `GitAdapter` preamble pinned | moderate | wire-format (freeze inventory) | open |
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| A-4 | done-round boundary set unverified | ADR-014 §2 + transport.md clause: boundary = `common_haves`-filtered haves | trivial | none | open |
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| A-5 | consumer half unspecified | user scope decision, then amendment or small ADR (recommended: thin wrapper, deps carried with purpose) | small | scope | open |
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| A-6 | trait execution model unspecified | backend.md paragraph + transport.md rephrase: async traits, wire-layer permit, impl-internal spawn_blocking | small | none | open |
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| A-6 | trait execution model unspecified | backend.md paragraph + transport.md rephrase: async traits, wire-layer permit, impl-internal spawn_blocking | small | none | **resolved** — backend.md concurrency model: wire layer enforces the ADR-009 permit around gen/ingest trait calls; impls own internal `spawn_blocking` (ADR-009/ADR-013 aligned) |
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| D-1 | stale Internal-ops + OQ-list text | supersession notes (vision, alk-stack, AGENTS) | trivial | none | open |
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| D-2 | ADR-007 step-3 mechanism superseded | amendment note on ADR-007 | trivial | none | open |
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| D-3 | authorized-repo marker missing from tuples | add to transport.md tuples + backend.md API list | trivial | none | open |
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