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`JobBuilder::node(payload)` hands back a `NodeRef` handle obtainable no other way, and edges are handle -> handle. `insert_into(graph, root_parent)` consumes the builder, inserts in declaration order, and returns the id each handle was minted as. There is no intermediate node-description type: the builder inserts through `Graph::insert` directly, so nothing has to stay in sync with that signature. `root_parent` is the group's attachment point — a node that declared no parent hangs there. That is what makes a job a self-contained sub-DAG: a template is written without knowing which container node it will live under, and the same builder serves a runtime-emitted subgraph hanging off its emitting node. Generic over the same `N`/`R` as `Graph`, so it belongs to the library rather than to any one caller's node kind. `.needs(name)` / `.needs_units(name, count)` declare resource deps at the construction site, next to the node that needs them. `Scheduler::insert_job` is the same over a scheduler, via the shared `insert_with` sink, so a caller building a job never reaches past the scheduler at the graph underneath. Declaration order is enforced rather than papered over: a node referencing one declared later is a named `BuildError::ForwardEdge` / `ForwardParent`. Sorting for the caller would silently accept a shape the graph cannot express, and would put ordering logic in a second place. Additive — `Graph` is untouched. |
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| Cargo.toml | ||
| README.md | ||
hive-jobq
A persistent job-DAG scheduler, extracted from hive-c0re's in-tree job_queue
as a domain-agnostic library. It schedules a single persistent graph of
nodes over named resources; it knows nothing about containers, rebuilds, or any
hyperhive type — the node payload N and resource name R are both generic, so
the caller supplies its own domain.
When to use it
Reach for this crate whenever you need to run a DAG of interdependent work items under bounded, named concurrency — the hive-c0re rebuild/lifecycle queue is the first consumer, but nothing here is specific to it. The caller defines the node kinds, wires deps, and supplies a runner; the scheduler decides what can start.
Model
One persistent graph for the whole system, not a DAG per job. Enqueuing inserts a self-contained sub-DAG and returns the new node ids; the scheduler runs a continuous loop, starting every node whose deps are satisfied:
- Resource deps are named counting semaphores over a caller-chosen type
R— e.g.build-slot(capacity N),agent/<name>(capacity 1), or any unconfigured name (capacity 1, created on use). A node acquires all its resource deps atomically at start (all-or-nothing) — no hold-and-wait, so no deadlock. - Node deps wait on another node per
DepWhen:AfterOkneeds success (a failed dep cancels the dependent),AfterAnyonly needs terminal.
A node carries two independent axes: its Deps (ordering + resource needs) and
its parent (structural grouping). The parent chain, not the node edges, is
what the scheduler consults for resource re-entrancy: a resource unit is held
for the acquiring node plus its whole parent subtree, and a descendant needing
a resource an ancestor already holds re-uses that grant (a re-entrant borrow,
one branch at a time) rather than taking a fresh unit.
A NodeId is opaque, stable, and monotonic (safe to persist). The scheduler is
single-threaded — it owns the resource table and mutates it directly.
Shape
Graph<N, R>— the persistent node store.insertmints ids and validates dep/parent references;set_stateis the single state-transition choke point (and where each node's lifecycle timestamps —started_at/finished_at,DateTime<Utc>— are stamped).Node<N, R>—{ id, parent, payload, deps, state, started_at, finished_at, error }. All fields public; derives serde for persistence + the wire.Scheduler<N, R>— drives the graph:settle()starts every ready node (acquiring resources atomically),complete(id, outcome)reports a finished node's result and rolls terminality up the parent chain, releasing grants once a subtree is done.Outcome::{Done, Failed(String)}— the failure reason ridesFailedonto the node'serror.ResourceTable<R>— per-name capacities; unconfigured names default to capacity 1.
See the crate-root and scheduler module //! docs for the full borrow/release
model.