ConnectOptions

with_options attaches async_nats::ConnectOptions to the broker: the client's name, pings, reconnects, no_echo and the inbox prefix.

ConnectOptions is the builder of the async-nats client this crate runs on. Building it does no I/O, and the broker applies it when the runtime connects. A service that names it adds async-nats to its own dependencies, in the version this crate uses. An option the service leaves unset keeps the client's default.

The options a service sets most often:

Option	What it does	Default
`name`	the name the server's monitoring lists the connection under	none
`ping_interval`	how often the client checks that the server still answers	60 s
`max_reconnects`	how many failed reconnects in a row the client makes before it gives up	no limit
`connection_timeout`	how long the connect at startup waits	5 s
`subscription_capacity`	how many messages a subscription buffers before the client drops them as a slow consumer	65 536
`no_echo`	the connection's own publishes skip its own subscriptions	off
`custom_inbox_prefix`	the subject prefix of the inboxes requests are answered on	`_INBOX`

Credentials and TLS are options too, on the Security page.

no_echo and the inbox prefix change what the server delivers, so the in-process mode of a TestApp test reads them as the server would. With no_echo a reply or a publish of the service never reaches a handler of the same service, while a message from another connection does. The other options shape the client's own connection, which the in-process mode has none of.

Example

The dependency line:

async-nats = "0.50"

The service names its connection pricing-svc and bounds its reconnects. It publishes cache invalidations to a subject it also reads, and no_echo keeps its own invalidations from coming back to it.

Macros
Manual

examples/nats_broker_options.rs
/// The servers at `addrs`, with the client settings this service relies on.
fn broker(addrs: &str) -> NatsBroker {
    NatsBroker::new(addrs).with_options(
        ConnectOptions::new()
            // The name the server's monitoring lists this connection under.
            .name("pricing-svc")
            .ping_interval(Duration::from_secs(20))
            // Give up after ten failed reconnects in a row.
            .max_reconnects(10)
            // This connection's own publishes skip its own subscriptions.
            .no_echo()
            .custom_inbox_prefix("_INBOX_pricing"),
    )
}

#[ruststream::app]
fn app() -> impl App {
    RustStream::new(AppInfo::new("pricing", "0.1.0")).with_broker(
        broker("nats://localhost:4222"),
        |b| {
            b.include(reprice);
            b.include(evict);
        },
    )
}

examples/manual/nats_broker_options.rs
/// The servers at `addrs`, with the client settings this service relies on.
fn broker(addrs: &str) -> NatsBroker {
    NatsBroker::new(addrs).with_options(
        ConnectOptions::new()
            // The name the server's monitoring lists this connection under.
            .name("pricing-svc")
            .ping_interval(Duration::from_secs(20))
            // Give up after ten failed reconnects in a row.
            .max_reconnects(10)
            // This connection's own publishes skip its own subscriptions.
            .no_echo()
            .custom_inbox_prefix("_INBOX_pricing"),
    )
}

fn app() -> impl App {
    RustStream::new(AppInfo::new("pricing", "0.1.0")).with_broker(
        broker("nats://localhost:4222"),
        |b| {
            b.include(subscriber("prices.updated", Reprice).reply().build());
            b.include(subscriber("cache.invalidate", Evict).build());
        },
    )
}

Example​

Example