Module outbox 

The transactional outbox: what a service publishes is recorded in its own table until a consumer has processed it, and what was not processed is published again at startup.

A struct deriving Outbox, or implementing OutboxTable by hand, describes the table; outbox!, Outbox::register or Outbox::track registers it under the names it tracks, and the registry hands out the two middlewares and the republish. The events below are what the record’s statements do; a service implements the ones it names as its own (#[outbox(custom(..))], or OutboxSpec::own), and always Publish, which has no default.

The crate overview’s transactional outbox section shows a whole service and states the guarantee, the test switch and the costs.

Re-exports

pub use events::Ack;

pub use events::Discard;

pub use events::Fetch;

pub use events::Publish;

pub use events::Recover;

pub use events::Retry;

pub use spec::OutboxSpec;

pub use spec::OutboxTable;

Modules

spec

The settings of an outbox table described by hand, as types.

Structs

Checked

A name tracked by type, kept in the registry’s type for the compile-time check; it holds no record and forwards every call. Machinery behind Outbox::track.

Nil

The end of the registrations.

Outbox

The outbox of a service: the record type of each name it tracks, and the pool their records live in.

PoolAlreadySet

The outbox’s pool was set already: by Outbox::new or by an earlier set_pool.

Registered

A name the outbox tracks with Record, in front of the registrations Rest.

Republishing

The body of the startup republish, which republish hands to after_startup: it resolves once every unprocessed record went out again, and fails startup with the first record that did not.

TrackedPublisher

A publisher that records what it publishes under a registered name, from wrap.

TrackingLayer

The subscription middleware of an Outbox, from layer.

TrackingPublishLayer

The publish middleware of an Outbox, from publish_layer.

Enums

OutboxError

A failure of the outbox: a record it could not write or read, or a republish that did not reach the broker.

TrackedPublishError

A publish through wrap that failed: the outbox did not record the message, or the publisher it wraps did not send it.

Constants

OUTBOX_ID_HEADER

The header a tracked message carries its record’s id in: written with the id’s Display, read back with its FromStr.

Traits

Ack

Marks the record processed once its handler acknowledged the message.

Discard

Runs when the handler dropped the message.

Fetch

Takes the record id into work when its message reaches a subscription.

OutboxDatabase

A sqlx database the default events of an outbox record run on.

OutboxRow

A record of an outbox table: a struct deriving Outbox or implementing OutboxTable.

Publish

Creates the record of a message a handler publishes under a registered name, and returns its id, which the message then carries in OUTBOX_ID_HEADER.

Recover

Selects the unprocessed records of one name, for the republish at startup.

Retry

Runs when the handler asked for the message again.

TrackedName

A name the outbox tracks, as a type: Outbox::track refuses a name tracked twice while the service compiles.