tokio-postgres

tokio-postgres is an async PostgreSQL client for Rust.

Read-only transactions

Use build_transaction().read_only(true):

main.rs

let tx = client.build_transaction().read_only(true).start().await?;
// Sends: BEGIN READ ONLY

Halephant detects BEGIN READ ONLY and routes the transaction to a replica.

Connection parameters

You can pass startup parameters through the options config field:

main.rs

let mut config = tokio_postgres::Config::new();
config.host("halephant");
config.port(6432);
config.dbname("myapp");
config.user("myapp_ro");
config.options("-c default_transaction_read_only=on");

Or use a dedicated read-only user configured in halephant. See the read replica guide.