Connecting to the cluster¶

Scylla is a distributed database, which means that it operates on multiple nodes running independently. When creating a Session you can specify a few known nodes to which the driver will try connecting:

use scylla::{Session, SessionBuilder};
use std::error::Error;
use std::time::Duration;
use std::net::{IpAddr, Ipv4Addr, SocketAddr};

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let uri = std::env::var("SCYLLA_URI")
        .unwrap_or_else(|_| "127.0.0.1:9042".to_string());

    let session: Session = SessionBuilder::new()
        .known_node(uri)
        .known_node("127.0.0.72:4321")
        .known_node("localhost:8000")
        .connection_timeout(Duration::from_secs(3))
        .cluster_metadata_refresh_interval(Duration::from_secs(10))
        .known_node_addr(SocketAddr::new(
            IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)),
            9000,
        ))
        .build()
        .await?;

    Ok(())
}

After successfully connecting to some specified node the driver will fetch topology information about other nodes in this cluster and connect to them as well.

The driver refreshes the cluster metadata periodically, which contains information about cluster topology as well as the cluster schema. By default, the driver refreshes the cluster metadata every 60 seconds. However, you can set the cluster_metadata_refresh_interval to a non-negative value to periodically refresh the cluster metadata. This is useful when you do not have unexpected amount of traffic or when you have an extra traffic causing topology to change frequently.

Scylla Serverless is an elastic and dynamic deployment model. When creating a Session you need to specify the secure connection bundle as follows:

use std::path::Path;
use std::error::Error;
use scylla::CloudSessionBuilder;

#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
    let session = CloudSessionBuilder::new(Path::new("config_data.yaml"))
        .unwrap()
        .build()
        .await
        .unwrap();

    Ok(())
}

Note that the bundle file will be provided after the serverless cluster is created. Here is an example of a configuration file for a serverless cluster:

datacenters:
  datacenter1:
    certificateAuthorityData: CERTIFICATE_DATA
    server: 127.0.1.1:9142
    nodeDomain: cql.cluster-id.scylla.com
    insecureSkipTlsVerify: false
authInfos:
  default:
    clientCertificateData: CERTIFICATE_DATA
    clientKeyData: KEY_DATA
    username: scylladb
    password: scylladb
contexts:
  default:
    datacenterName: datacenter1
    authInfoName: default
currentContext: default