ruststream-sqlx 0.7.1

//! A newsletter queue on SQLite read in batches: one claim is the batch, and each email settles
//! its own row.
//!
//! ```text
//! cargo run -p ruststream-sqlx --example sqlx_subscriptions_batches --features inbox,sqlite,chrono,testing
//! ```

use chrono::{DateTime, Utc};
use serde::{Deserialize, Serialize};

// --8<-- [start:batches]
use ruststream_sqlx::prelude::*;
use sqlx::sqlite::SqlitePoolOptions;
use sqlx::{Connection, SqliteConnection};

/// One row of `newsletter_jobs`, claimed under a lease.
#[derive(Inbox, sqlx::FromRow)]
#[inbox(table = "newsletter_jobs")]
struct SendNewsletter {
    #[field(id, generated)]
    id: i64,
    #[field(locked_until)]
    locked_until: Option<DateTime<Utc>>,
    #[field(payload)]
    payload: Vec<u8>,
}

/// Up to fifty emails per claim; an address that cannot receive mail is dropped, and only its
/// own row is.
#[subscriber(InboxQueue::<SendNewsletter>::new("newsletter"))]
async fn send_all(emails: &[Email]) -> Vec<HandlerOutcome> {
    tracing::info!(count = emails.len(), "sending a batch");
    emails
        .iter()
        .map(|email| {
            if email.to.contains('@') {
                HandlerOutcome::ack()
            } else {
                HandlerOutcome::drop()
            }
        })
        .collect()
}

/// 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());
    RustStream::new(AppInfo::new("newsletter", "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| {
            b.include(send_all.batch(nonzero!(50)));
        })
}
// --8<-- [end:batches]

#[ruststream::app]
fn app() -> impl App {
    service("sqlite:newsletter.db?mode=rwc")
}

const SCHEMA: &str = "CREATE TABLE IF NOT EXISTS newsletter_jobs (
    id INTEGER PRIMARY KEY,
    locked_until TEXT,
    payload BLOB NOT NULL
)";

#[derive(Debug, PartialEq, Deserialize, Serialize)]
struct Email {
    to: String,
}

#[cfg(test)]
mod tests {
    use std::error::Error;
    use std::time::Duration;

    use ruststream::testing::TestApp;
    use ruststream_sqlx::prelude::*;
    use sqlx::sqlite::{SqliteConnectOptions, SqlitePoolOptions};
    use sqlx::{Connection, Sqlite, SqliteConnection, SqlitePool};

    use super::{Email, SCHEMA, service};

    // An in-memory database every connection naming it shares, alive while one of them is open:
    // the test holds one beside the pool it reads the table through.
    async fn database(
        name: &str,
    ) -> Result<(String, SqlitePool, SqliteConnection), Box<dyn Error>> {
        let url = format!("sqlite:file:{name}?mode=memory&cache=shared");
        let options: SqliteConnectOptions = url.parse()?;
        let keeper = SqliteConnection::connect_with(&options).await?;
        let pool = SqlitePoolOptions::new()
            .min_connections(1)
            .idle_timeout(None)
            .connect_with(options)
            .await?;
        sqlx::raw_sql(SCHEMA).execute(&pool).await?;
        Ok((url, pool, keeper))
    }

    // The rows wait in the table before the service starts, so its first claim takes them
    // together; the harness counts a row once a claim takes it, so the test runs on the real
    // clock and lets the claim happen.
    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
    async fn one_claim_is_the_batch_and_each_row_settles_on_its_own() -> Result<(), Box<dyn Error>>
    {
        let (url, pool, _keeper) = database("sqlx_subscriptions_batches").await?;
        for to in ["ada@example.com", "no-address", "grace@example.com"] {
            sqlx::query("INSERT INTO newsletter_jobs (payload) VALUES (?)")
                .bind(serde_json::to_vec(&Email { to: to.to_owned() })?)
                .execute(&pool)
                .await?;
        }
        let tb = TestApp::start_live(service(&url)).await?;
        tb.advance(Duration::from_millis(500)).await?;

        tb.broker::<SqlxBroker<Sqlite>>()
            .subscriber("newsletter")
            .assert_called_once()
            .assert_batch_sizes(&[3]);
        let left: i64 = sqlx::query_scalar("SELECT count(*) FROM newsletter_jobs")
            .fetch_one(&pool)
            .await?;
        assert_eq!(
            left, 0,
            "the acknowledged rows and the dropped one are deleted"
        );
        Ok(())
    }
}