bind_with

bind_with binds a queue to a headers exchange by x-match and the headers to match, all of them or any one.

A headers exchange ignores the routing key and routes on the message's headers. bind_with(exchange, routing_key, arguments) gives the binding an argument table, a FieldTable of AMQPValue entries. The entry x-match decides the rule: all takes a message that carries every other entry of the table with the same value, and any takes a message that carries at least one. The other entries are the headers to match, and the routing key of the binding is usually empty. A plain bind to a headers exchange sends an empty table, and all of no headers is true of every message, so such a queue gets everything the exchange gets.

The publishing side sets the headers on the message, and they ride the AMQP header table the exchange reads. bind_with also serves a plugin exchange that routes on binding arguments.

Example

The EU gold queue matches both headers, and the EU-or-gold queue matches either one.

Macros
Manual

examples/lapin_exchanges_headers.rs
/// The binding arguments: how to match, then the headers matched on.
fn gold_in_eu(x_match: &str) -> FieldTable {
    let mut arguments = FieldTable::default();
    arguments.insert("x-match".into(), AMQPValue::LongString(x_match.into()));
    arguments.insert("region".into(), AMQPValue::LongString("eu".into()));
    arguments.insert("tier".into(), AMQPValue::LongString("gold".into()));
    arguments
}

/// Gold orders from the EU: both headers have to match.
#[subscriber(RabbitQueue::new("orders.eu-gold")
    .bind_with(RabbitExchange::headers("orders"), "", gold_in_eu("all")))]
async fn expedite(order: &Order) -> HandlerOutcome {
    tracing::info!(order.id, "expedited");
    HandlerOutcome::ack()
}

/// Orders from the EU or of the gold tier: one header is enough.
#[subscriber(RabbitQueue::new("orders.eu-or-gold")
    .bind_with(RabbitExchange::headers("orders"), "", gold_in_eu("any")))]
async fn review(order: &Order) -> HandlerOutcome {
    tracing::info!(order.id, "reviewed");
    HandlerOutcome::ack()
}

examples/manual/lapin_exchanges_headers.rs
/// The binding arguments: how to match, then the headers matched on.
fn gold_in_eu(x_match: &str) -> FieldTable {
    let mut arguments = FieldTable::default();
    arguments.insert("x-match".into(), AMQPValue::LongString(x_match.into()));
    arguments.insert("region".into(), AMQPValue::LongString("eu".into()));
    arguments.insert("tier".into(), AMQPValue::LongString("gold".into()));
    arguments
}

struct Expedite;

impl Handle<Order> for Expedite {
    fn handle(
        &self,
        order: &Order,
        _outs: &(),
        _ctx: &mut Context<'_>,
    ) -> impl Future<Output = Result<(), HandlerOutcome>> {
        tracing::info!(order.id, "expedited");
        ready(Ok(()))
    }
}

struct Review;

impl Handle<Order> for Review {
    fn handle(
        &self,
        order: &Order,
        _outs: &(),
        _ctx: &mut Context<'_>,
    ) -> impl Future<Output = Result<(), HandlerOutcome>> {
        tracing::info!(order.id, "reviewed");
        ready(Ok(()))
    }
}

/// Gold orders from the EU, where both headers have to match, and orders from the EU or of the
/// gold tier, where one header is enough.
fn bound() -> (RabbitQueue, RabbitQueue) {
    let orders = RabbitExchange::headers("orders");
    let all = RabbitQueue::new("orders.eu-gold").bind_with(orders.clone(), "", gold_in_eu("all"));
    let any = RabbitQueue::new("orders.eu-or-gold").bind_with(orders, "", gold_in_eu("any"));
    (all, any)
}

Example​

Example