Crate aspero_engine 

Routing, caching, merging and resilience over registered providers.

The engine owns what providers deliberately don’t: retries and backoff (retry), request pacing and the real HTTP client (transport), and choosing which provider answers what.

• Lookup is interchangeable across providers: each ID goes to the providers that accept its kind, in priority order, until one finds it. A provider that doesn’t know an ID or fails falls through to the next; every attempt is reported.

• Search is not interchangeable (rankings differ), so it runs against one provider: the one named, or the first capable one. Filters that provider doesn’t declare are stripped and reported as ignored, never silently dropped.

• Resolve / verify turn a citation claim into scored candidates and a verdict (see resolve).

• Caching: provider answers (records, “not found”, search pages) are cached with per-kind TTLs (CachePolicy) and served stale if a provider fails; every answer says how it was Served.

• Sharing: one engine serves many callers at once. Lookups already in flight are joined rather than repeated, and each caller sets its own patience with CallOptions. Providers that can’t answer (a spent quota, a rejected key, repeated failures) are skipped until they can (Engine::unavailable).

Not yet: fan-out search.

Modules

retry

Retrying one provider operation under its ResiliencePolicy.

transport

The engine’s side of the HttpClient seam: a real client, and pacing.

Structs

Abstract

An abstract and the provider it came from.

AbstractsReport

Attempt

Budget

What a provider last said was left of its budget.

CachePolicy

How long cached answers are trusted (DESIGN §5). Past these, a provider is asked again; if it then fails, the old answer is served as stale.

CacheStats

CallOptions

How patient a caller is. The default is a batch caller’s: providers’ own policies, retries and all. Set on an engine view with Engine::with_options; views share the cache, pacing and requests in flight.

Candidate

Checked

One checked claim.

CrossrefConfig

DataciteConfig

Difference

A cited field the work disagrees with, and the work’s value if it’s worth showing.

Disagreement

One field on which a record and the registry’s record of the same DOI disagree.

DoiConfig

Engine

Cheap to clone: clones, and views made with with_options, share the cache, providers’ pacing and requests in flight. Hold one per process.

EngineBuilder

EuropePmcConfig

Extras

What to add to each record found.

InputsReport

Looked

LookupReport

LookupResult

OpenAlexConfig

OpenLibraryConfig

ResolveReport

SearchReport

Sighting

One provider surfacing a candidate.

SqliteCache

StandardConfig

Settings for the compiled-in providers. None disables a provider.

Verification

VersionsReport

Enums

CitedField

EngineError

Finding

Something to fix or know about one entry.

InputLookup

One input’s lookup.

Outcome

The outcome of one provider’s attempt at one ID.

Reason

Why a verdict was reached. “The work” is the verdict’s candidate (Verification::best); “the identifiers” are those the claim gave.

Served

Where an answer came from.

Severity

StoreError

Verdict

Via

How a candidate was found.

Traits

Cache

What the engine needs from a cache; it depends on this, not on SQLite.

Pacing

Request slots shared between processes, so parallel agents (and any other process using the same file) keep to one rate limit per provider.

Functions

describe_update

“RETRACTED (2010-02-06, notice doi:…, via retraction-watch)”.

disagreements

Where record contradicts registry’s record of the same DOI. Dates compare by year, any of either record’s years counting (online-first and print years differ legitimately); pages by first page.

duplicates

For each match, the earliest other match that is the same work (shares an identifier).

findings

Findings for one claim from its verification (not duplicates, which need the whole set).

standard

Builds an engine with each enabled provider behind its own paced reqwest client.

Type Aliases

Clock

A clock, injectable so cache expiry is testable.

SecretString

Re-exported for credentials in provider configs. Secret string type.