Crate x_pipe_rs 

Composable recommendation and feed pipeline framework.

x-pipe-rs provides a typed, composable pipeline for assembling ranked feeds, inspired by the X algorithm’s candidate-pipeline architecture. Every pipeline stage is a Kleisli arrow in the Io monad from comp_cat_rs; composition is Kleisli composition, which by comp-cat-rs’s collapse hierarchy is a Kan extension.

Architecture

A pipeline assembles six kinds of stages:

1. Source – produce candidate items from backends
2. Hydrator – enrich candidates with additional data
3. Filter – remove candidates that fail criteria
4. Scorer – assign relevance scores
5. Selector – choose final candidates (dedup, diversity, budget)
6. SideEffect – observe without modifying (logging, metrics)

Each trait converts to a Stage, the universal Kleisli arrow type. Stages compose via Stage::then (Kleisli composition). The final Pipeline is itself a single Stage from query to scored results.

Categorical justification

Stage forms a category whose morphisms are Kleisli arrows A -> Io<E, B>. Composition is associative with identity, and by collapse::monad_is_kan every such composition is a pair of Kan extensions. Score implements JoinSemilattice, making score merging a colimit (left Kan extension).

Re-exports

pub use error::PipelineError;

pub use filter::Filter;

pub use hydrator::Hydrator;

pub use pipeline::Pipeline;

pub use score::Score;

pub use score::ScoredCandidate;

pub use scorer::Scorer;

pub use selector::Budget;

pub use selector::MaxItems;

pub use selector::Selector;

pub use side_effect::SideEffect;

pub use source::Source;

pub use stage::Stage;

Modules

error

Pipeline error types.

filter

Candidate filtering: removing items that fail criteria.

hydrator

Candidate hydration: enriching items with additional data.

pipeline

Pipeline composition: wiring stages into a complete pipeline.

score

Score and scored candidate types.

scorer

Candidate scoring: assigning relevance scores.

selector

Candidate selection: choosing final results.

side_effect

Side effects: observing candidates without modifying them.

source

Candidate sources.

stage

The Kleisli arrow type: the categorical heart of the pipeline.