Crate datum 

Datum

🪼 - Just “Stream” anything :]

Datum is a Rust stream processing library scaffolded around Ractor actors and a push-based stream abstraction. The compatibility target is Akka/Pekko Streams Typed API shape and behavior, with Rust-native ownership, async, and benchmarking constraints.

Install

Add Datum to your project from crates.io:

cargo add datum-core

Or in Cargo.toml:

[dependencies]
datum-core = "0.4"

Note: The package is published as datum-core (the name datum is taken on crates.io), but the import path stays use datum::… — the crate’s library name is datum.

To track an unreleased commit instead:

[dependencies]
datum-core = { git = "https://github.com/Aethergrids/Datum", tag = "v0.4.0" }

Upstream References

• Ractor crate: 0.15.13
• Optional Ractor cluster crate: 0.15.13, enabled with --features cluster
• Akka source submodule: third_party/akka, tracking upstream main and pinned in this repository at commit 58f1f6db2e505e87f5dc115ee9476833872e7ae0
• Latest stable Akka tag observed during setup: v2.10.18

Feature highlights (v0.4.0)

• Graph cycles — MergePreferred/Broadcast feedback loops supported; unbuffered cycles surface EventLimitExceeded instead of hanging.
• StreamRefs — StreamRefs::source_ref() / sink_ref(), Ractor-backed one-shot streaming handles for actor/process boundary crossing.
• IO adapters — StreamConverters::as_input_stream / as_output_stream bridging Datum streams to std::io::Read / Write.
• Performance — the typed graph executor now covers all major junction shapes and cyclic feedback; nearly every benchmarked hot path meets or beats warmed Akka/Pekko (see benchmark tables linked below for honest per-row numbers, including below-parity rows).
• #![forbid(unsafe_code)] on the datum crate itself; new safe deps crossbeam-queue and arc-swap handle lock-free queues and hub snapshots without adding unsafe to the crate.

Development

cargo test
cargo check --benches
cargo bench --bench push_baseline
cargo bench --bench source_flow
cargo bench --bench materialization
cargo bench --bench graph
cargo bench --bench actor_ask
benches/actor_ask_compare/run.sh

use datum::{Sink, Source};

let sum = Source::from_iter(0_u64..1_000)
    .map(|item| item + 1)
    .filter(|item| item % 2 == 0)
    .run_with(Sink::fold(0_u64, |acc, item| acc + item))
    .unwrap()
    .wait()
    .unwrap();

Benchmarks

Datum is benchmarked head-to-head against warmed Akka/Pekko Streams across seven areas — Source/Flow, materialization, graph/junctions, actor ask, dynamic streams, streaming IO, and substreams. As of v0.4.0, Datum is at or above Akka on the large majority of benchmarked paths. Honest per-path numbers (including remaining below-parity rows) are in the result tables under roadmap/benchmarks/. The harness adds a Datum CPU us/op column on purpose: some wins come partly from busy-spinning while Akka parks — a real cost the wall-clock number hides.

Qualitative summary of the current state:

• Fused linear path: 13–44x Akka (typed plan; all common sink shapes).
• Junctions: 1–340x, with most shapes well above parity; typed kernels now cover concat, merge, broadcast/zip, balance/merge, partition, prioritized merge, merge-preferred, merge-sorted, merge-sequence, and merge-latest.
• Graph cycles (typed feedback kernel): ~29x Akka on the MergePreferred/Broadcast feedback shape.
• BidiFlow: 3.7–5x Akka.
• Dynamic hubs: MergeHub p16 13x, p4 2.1x (p1 below parity — remaining lever documented in roadmap/benchmarks/dynamic-streams.md); BroadcastHub 1.3–2x; PartitionHub 1.4–2.7x.
• Bounded queue: ~parity (0.96x wall) with ~112x less allocation than Akka.
• map_async: ≥2x at p4/p32 (Tokio dispatch).
• flat_map_merge: 1.4–1.8x.
• Streaming IO adapters: ~7.4x on the round-trip scenario.
• StreamRefs: 0.24–0.26x (Ractor-bound; levers documented).
• Actor ask: ~1.3x at p1; allocation dominated by upstream Ractor boxing (~848 B/element, upstream-blocked).
• Materialization: at parity.

Run a comparison (requires a JDK + sbt); each runner writes a rendered table under target/<area>-comparison/:

benches/source_flow_compare/run.sh
benches/materialization_compare/run.sh
benches/graph_compare/run.sh
benches/actor_ask_compare/run.sh
benches/dynamic_streams_compare/run.sh
benches/streaming_io_compare/run.sh
benches/substreams_compare/run.sh

Current result tables, the per-operator coverage matrix, and apples-to-apples caveats:

• roadmap/benchmarks/source-flow.md
• roadmap/benchmarks/materialization.md
• roadmap/benchmarks/graph.md
• roadmap/benchmarks/actor-ask.md
• roadmap/benchmarks/dynamic-streams.md
• roadmap/benchmarks/streaming-io.md
• roadmap/benchmarks/substreams.md
• roadmap/M1-v0.1.0-foundation.md — coverage matrix, optimization status & apples-to-apples caveats
• roadmap/M4-v0.4.0-completeness-hardening.md — M4 work packages and exit criteria

See roadmap/ for the full milestone roadmap. User documentation is the published VitePress site (Cloudflare Pages); docs/ holds its source. roadmap/ holds internal planning and benchmark records.

Re-exports

pub use actor::ActorFlow;

pub use actor::ActorPubSub;

pub use actor::ActorSink;

pub use actor::ActorSinkBackpressureMessage;

pub use actor::ActorSinkMessage;

pub use actor::ActorSource;

pub use actor::ActorSourceMessage;

pub use actor::ActorStatus;

pub use actor::ReplyPort;

pub use actor::ReplySendError;

pub use actor::SinkRef;

pub use actor::SourceRef;

pub use actor::StreamRefSettings;

pub use actor::StreamRefs;

pub use actor::WatchEvent;

pub use context::FlowWithContext;

pub use context::SourceWithContext;

pub use dynamic::BroadcastHub;

pub use dynamic::BroadcastHubConsumerSource;

pub use dynamic::KillSwitches;

pub use dynamic::MergeHub;

pub use dynamic::MergeHubDrainingControl;

pub use dynamic::PartitionConsumerInfo;

pub use dynamic::PartitionHub;

pub use dynamic::PartitionHubConsumerSource;

pub use dynamic::SharedKillSwitch;

pub use dynamic::UniqueKillSwitch;

pub use graph::AnyInlet;

pub use graph::AnyOutlet;

pub use graph::AsyncBoundary;

pub use graph::AsyncBoundaryExecutionConfig;

pub use graph::Balance;

pub use graph::BidiShape;

pub use graph::Broadcast;

pub use graph::Buffer;

pub use graph::Concat;

pub use graph::FanInShape;

pub use graph::FanOutShape;

pub use graph::FanOutShape2;

pub use graph::FlowShape;

pub use graph::FlowShape as GraphFlowShape;

pub use graph::FusedExecutionConfig;

pub use graph::FusedExecutionReport;

pub use graph::FusedTerminalReport;

pub use graph::Graph;

pub use graph::GraphBlueprint;

pub use graph::GraphBuilder;

pub use graph::GraphDsl;

pub use graph::GraphStage;

pub use graph::GraphStageLogic;

pub use graph::Identity;

pub use graph::ImportedGraph;

pub use graph::InHandler;

pub use graph::Inlet;

pub use graph::Interleave;

pub use graph::MapStage;

pub use graph::Merge;

pub use graph::MergeLatest;

pub use graph::MergePreferred;

pub use graph::MergePreferredShape;

pub use graph::MergePrioritized;

pub use graph::MergeSequence;

pub use graph::MergeSorted;

pub use graph::OrElse;

pub use graph::OutHandler;

pub use graph::Outlet;

pub use graph::PartialGraph;

pub use graph::Partition;

pub use graph::PortId;

pub use graph::PortKind;

pub use graph::SinkShape;

pub use graph::SourceShape;

pub use graph::StageSpec;

pub use graph::TakeWhile;

pub use graph::Unzip;

pub use graph::UnzipWith;

pub use graph::Zip;

pub use graph::ZipShape;

pub use io::Compression;

pub use io::FileIO;

pub use io::Framing;

pub use io::FramingByteOrder;

pub use io::InputStreamHandle;

pub use io::IoResult;

pub use io::OutputStreamHandle;

pub use io::StreamConverters;

pub use io::TcpBinding;

pub use io::TcpConnection;

pub use io::TcpIncomingConnection;

pub use io::TokioByteSink;

pub use io::TokioByteSource;

pub use io::TokioFileIO;

pub use io::TokioTcp;

pub use queue::BoundedSourceQueue;

pub use queue::QueueOfferResult;

pub use queue::SinkQueue;

pub use queue::SourceQueue;

pub use stream::AggregateTimer;

pub use stream::BidiFlow;

pub use stream::Cancellable;

pub use stream::DelayOverflowStrategy;

pub use stream::Demand;

pub use stream::Flow;

pub use stream::Keep;

pub use stream::Materializer;

pub use stream::MaybeHandle;

pub use stream::NotUsed;

pub use stream::OverflowStrategy;

pub use stream::PushOutlet;

pub use stream::RestartFlow;

pub use stream::RestartSettings;

pub use stream::RestartSink;

pub use stream::RestartSource;

pub use stream::RetryFlow;

pub use stream::RunnableGraph;

pub use stream::Runtime;

pub use stream::Sink;

pub use stream::SinkCombineStrategy;

pub use stream::Source;

pub use stream::SourceCombineStrategy;

pub use stream::StreamCompletion;

pub use stream::StreamError;

pub use stream::StreamResult;

pub use stream::Supervision;

pub use stream::SupervisionDecider;

pub use stream::SupervisionDirective;

pub use stream::ThrottleMode;

Modules

actor

Actor interop APIs backed by Ractor for local execution.

context

Context-aware stream wrappers.

dynamic

Dynamic stream controls and attachment points modeled after Akka Streams.

graph

Runtime-checked graph, shape, port, and junction primitives.

io

Streaming I/O — file sources and sinks, TCP, byte framing, and compression.

queue

Bounded and unbounded queues that bridge external producers into a Datum stream.

stream

Core push-stream vocabulary and the first reusable Source/Flow API slice.

testkit

Stream testing probes built on Datum’s normal runtime.

Structs

ActorRef

An ActorRef is a strongly-typed wrapper over an ActorCell to provide some syntactic wrapping on the requirement to pass the actor’s message type everywhere.

Attributes

Enums

Attribute