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route

SqlxBroker::route leads a name into a row type's table in both directions; Routed, the default for replies and slots, looks each name up.

.route::<Job>("orders") on the broker serves two directions. A publish to orders writes a row of Job's table through the row's Publish. #[subscriber("orders")] opens a subscription by that name on the same table. A name ending in * leads every name that starts with what precedes it: reports.* takes reports.daily and reports.weekly. An exact name wins over a prefix, and a longer prefix over a shorter one. A name routed twice leads to the last row type.

Routed is the broker's default publish policy. A reply or an Out slot that names no policy of its own publishes through it, and so does a test's input through the harness. A publish looks its name up in the route table: one hash lookup for an exact name, the prefixes scanned only when none matches, then one dynamic call into the row's Publish. That call's future stays in place in 1024 bytes, so a routed publish allocates what a repository publish does. A row whose Publish future is larger is boxed: one allocation per publish on its route. A name no route leads anywhere fails the publish with SqlxBrokerError::NoRoute, which names the route to add.

A route asks of the broker's dialect what an InboxQueue of the row asks: the table's form and the isolation level or SQLite mode the struct declares. A routed publish wakes the subscriptions of its table and group in the same process, as a repository publish does.

Example​

The prefix route reports.* leads the daily report a client publishes and the weekly report the service replies with into one table. The reply names no policy, so it goes through the routes.

examples/sqlx_publishing_route.rs
use ruststream::OutgoingMessage;
use sqlx::{Sqlite, SqliteConnection};

/// One row of `report_jobs`: the group column holds the name a message was published to.
#[derive(Inbox, sqlx::FromRow)]
#[inbox(table = "report_jobs")]
struct Report {
    #[field(id, generated)]
    id: i64,
    #[field(group)]
    name: String,
    #[field(locked_until)]
    locked_until: Option<DateTime<Utc>>,
    #[field(payload)]
    payload: Vec<u8>,
}

/// The service's own insert: the name goes to the group column, the bytes to the payload.
impl Publish<Sqlite> for Report {
    async fn publish(
        conn: &mut SqliteConnection,
        message: &OutgoingMessage<'_>,
    ) -> Result<(), sqlx::Error> {
        sqlx::query("INSERT INTO report_jobs (name, payload) VALUES (?, ?)")
            .bind(message.name())
            .bind(message.payload())
            .execute(conn)
            .await?;
        Ok(())
    }
}

#[subscriber(InboxQueue::<Report>::new("reports.daily"), reply)]
async fn roll_up(daily: &Daily) -> Weekly {
    Weekly {
        week: daily.day / 7 + 1,
    }
}

#[subscriber(InboxQueue::<Report>::new("reports.weekly"))]
async fn file(weekly: &Weekly) -> HandlerOutcome {
    tracing::info!(week = weekly.week, "filing the weekly report");
    HandlerOutcome::ack()
}

/// The service on the database `url` names.
fn service(url: &str) -> RustStream {
    let schema_url = url.to_owned();
    // Nothing connects here: the broker builds its pool when the service starts.
    let broker = SqlxBroker::from_url(url, SqlitePoolOptions::new());
    // `reports.daily` and `reports.weekly` both lead into `report_jobs`.
    let broker = broker.route::<Report>("reports.*");
    RustStream::new(AppInfo::new("reports", "0.1.0"))
        // The table, created before the subscription checks it.
        .on_startup(async move |()| {
            let mut conn = SqliteConnection::connect(&schema_url).await?;
            sqlx::raw_sql(SCHEMA).execute(&mut conn).await?;
            conn.close().await
        })
        .with_broker(broker, |b| {
            // A reply without a policy of its own publishes through the routes.
            b.include(roll_up);
            b.include(file);
        })
}