Rust Drivers

Rust Smart Driver for YSQL

YugabyteDB Rust smart driver is a Rust driver for YSQL based on rust-postgres, with additional connection load balancing features.

Rust smart drivers offers two different clients similar to rust-postgres:

yb-postgres - native, synchronous YugabyteDB YSQL client based on postgres.
yb-tokio-postgres - native, asynchronous YugabyteDB YSQL client based on tokio-postgres.

For more information on the YugabyteDB Rust smart driver, see the following:

Include the driver dependency

You can use the YugabyteDB Rust driver crates by adding the following statements in the Cargo.toml file of your Rust application.

# For yb-postgres
yb-postgres = "0.19.7-yb-1-beta"

# For yb-tokio-postgres
yb-tokio-postgres = "0.7.10-yb-1-beta"

Or, run the following command from your project directory:

# For yb-postgres
$ cargo add yb-postgres

# For yb-tokio-postgres
$ cargo add yb-tokio-postgres

Fundamentals

Learn how to perform common tasks required for Rust application development using the YugabyteDB Rust smart driver.

Load balancing connection properties

The following connection properties need to be added to enable load balancing:

load_balance - enable cluster-aware load balancing by setting this property to true; disabled by default.
topology_keys - provide comma-separated geo-location values to enable topology-aware load balancing. Geo-locations can be provided as cloud.region.zone. Specify all zones in a region as cloud.region.*. To designate fallback locations for when the primary location is unreachable, specify a priority in the form :n, where n is the order of precedence. For example, cloud1.datacenter1.rack1:1,cloud1.datacenter1.rack2:2.

By default, the driver refreshes the list of nodes every 300 seconds (5 minutes). You can change this value by including the yb_servers_refresh_interval parameter.

Following are other connection properties offered with the Rust smart driver:

fallback_to_topology_keys_only - when set to true, the smart driver does not attempt to connect to servers outside of primary and fallback placements specified by the topology_keys property. By default, the driver falls back to any available server in the cluster. Default is false.
failed_host_reconnect_delay_secs - when the driver is unable to connect to a server, it marks the server using a timestamp. When refreshing the server list via yb_servers(), if the failed server appears in the response, the driver will only mark the server as "up" if failed_host_reconnect_delay_secs time has elapsed since the server was marked as down. Default is 5 seconds.

Use the driver

To use the driver, pass new connection properties for load balancing in the connection string.

To enable uniform load balancing across all servers, you set the load-balance property to true in the connection string, as per the following examples:

let url: String = String::from( "postgresql://localhost:5434/yugabyte?user=yugabyte&password=yugabyte&load_balance=true", );
let conn = yb_postgres::Client::connect(&connection_url,NoTls,)?;

You can specify multiple hosts in the connection string to use as fallbacks in case the primary address fails during the initial connection attempt. After the driver establishes the initial connection, it fetches the list of available servers from the cluster, and load-balances subsequent connection requests across those servers.

To specify topology keys, you set the topology_keys property to comma-separated values in the connection string or dictionary, as per the following example:

let url: String = String::from( "postgresql://localhost:5434/yugabyte?user=yugabyte&password=yugabyte&load_balance=true&topology_keys=cloud1.datacenter1.rack2", );
let conn = yb_postgres::Client::connect(&connection_url,NoTls,)?;

Try it out

This tutorial shows how to use the asynchronous yb-tokio-postgres client with YugabyteDB. It starts by creating a three-node cluster with a replication factor of 3. This tutorial uses the yugabyted utility.

Next, you use a Rust application to demonstrate the driver's load balancing features.

For an example using the synchronous yb-postgres client, see Connect an application.

Create a local cluster

Create a universe with a 3-node RF-3 cluster with some fictitious geo-locations assigned. Place two nodes in one location, and the third in a separate location. The placement values used are just tokens and have nothing to do with actual AWS cloud regions and zones.

cd <path-to-yugabytedb-installation>

To create a multi-zone cluster, do the following:

Start the first node by running the yugabyted start command, passing in the --cloud_location and --fault_tolerance flags to set the node location details, as follows:

./bin/yugabyted start --advertise_address=127.0.0.1 \
    --base_dir=$HOME/yugabyte-2.21.0.0/node1 \
    --cloud_location=aws.us-east-1.us-east-1a \
    --fault_tolerance=zone

Start the second and the third node on two separate VMs using the --join flag, as follows:

./bin/yugabyted start --advertise_address=127.0.0.2 \
    --join=127.0.0.1 \
    --base_dir=$HOME/yugabyte-2.21.0.0/node2 \
    --cloud_location=aws.us-east-1.us-east-1a \
    --fault_tolerance=zone

./bin/yugabyted start --advertise_address=127.0.0.3 \
    --join=127.0.0.1 \
    --base_dir=$HOME/yugabyte-2.21.0.0/node3 \
    --cloud_location=aws.us-east-1.us-east-1b \
    --fault_tolerance=zone

Check uniform load balancing

To check uniform load balancing, do the following:

Create a Rust project using the following command:
```
cargo new try-it-out
```
This creates the project "try-it-out" which consists of a Cargo.toml file (project metadata) and a src directory containing the main code file, main.rs.

Add yb-tokio-postgres = "0.7.10-yb-1-beta" dependency in the Cargo.toml file as follows:

[package]
name = "try-it-out"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
yb-tokio-postgres = "0.7.10-yb-1-beta"

Replace the existing code in the file src/main.rs with the following code:

use isahc::ReadResponseExt;
use tokio::task::JoinHandle;
use yb_tokio_postgres::{Client, Error, NoTls};

#[tokio::main]
async fn main() -> Result<(), Error> {
   println!("Starting the example ...");

   let url: String = String::from(
   "postgresql://127.0.0.1:5433/yugabyte?user=yugabyte&password=yugabyte&load_balance=true",
   );
   println!("Using connection url: {}", url);
   let (_clients, _connections) = createconn(30, url).await.unwrap();
   //Check and print number of connections on each node.
   num_of_connections();

   println!("End of Example");
   Ok(())
}

async fn createconn(
   numconn: usize,
   url: String,
) -> Result<(Vec<Client>, Vec<JoinHandle<()>>), Error> {
   let mut connectionstored: Vec<JoinHandle<()>> = Vec::with_capacity(numconn);
   let mut clientstored: Vec<Client> = Vec::with_capacity(numconn);
   for _i in 0..numconn {
       let connectionresult = createconnection(url.clone()).await;
       match connectionresult {
          Err(error) => return Err(error),
          Ok((connection, client)) => {
              clientstored.push(client);
              connectionstored.push(connection);
          }
       }
   }
   return Ok((clientstored, connectionstored));
}

async fn createconnection(url: String) -> Result<(tokio::task::JoinHandle<()>, Client), Error> {
   let (client, connection) = yb_tokio_postgres::connect(&url, NoTls).await?;

   // The connection object performs the actual communication with the database,
   // so spawn it off to run on its own.
   let handle = tokio::spawn(async move {
       if let Err(e) = connection.await {
           eprintln!("connection error: {}", e);
       }
   });

   Ok((handle, client))
}

pub(crate) fn num_of_connections() {
   for i in 1..4 {
       let url = "http://127.0.0.".to_owned() + &i.to_string() + ":13000/rpcz";
       let response = isahc::get(url);
       if response.is_err() {
           println!("127.0.0.{} = {}",i, 0);
       } else {
           let body = response.unwrap().text().unwrap();
           let c = body.matches("client backend").count();
           println!("127.0.0.{} = {}", i, c);
       }
   }
}

Run the example:
```
cargo run
```

The application creates 30 connections and displays a key value pair map where the keys are the host, and the values are the number of connections on them. (The application gets the number of connections from http://<host>:13000/rpcz for each node. This URL presents a list of connections where each element of the list has some information about the connection.) Each node should have 10 connections.

Check topology-aware load balancing

For topology-aware load balancing, run the application with the topology_keys property set to aws.us-east-1.us-east-1a. Only two nodes are used in this case.

Replace the existing code in src/main.rs with the following sample code:

use isahc::ReadResponseExt;
use tokio::task::JoinHandle;
use yb_tokio_postgres::{Client, Error, NoTls};

#[tokio::main]
async fn main() -> Result<(), Error> {
   println!("Starting the example ...");

   let url: String = String::from(
       "postgresql://127.0.0.1:5433/yugabyte?user=yugabyte&password=yugabyte&load_balance=true&topology_keys=aws.us-east-1.us-east-1a",
   );
   println!("Using connection url: {}", url);
   let (_clients, _connections) = createconn(30, url).await.unwrap();
   //Check and print number of connections on each node.
   num_of_connections();

   println!("End of Example");
   Ok(())
}

async fn createconn(
   numconn: usize,
   url: String,
) -> Result<(Vec<Client>, Vec<JoinHandle<()>>), Error> {
   let mut connectionstored: Vec<JoinHandle<()>> = Vec::with_capacity(numconn);
   let mut clientstored: Vec<Client> = Vec::with_capacity(numconn);
   for _i in 0..numconn {
       let connectionresult = createconnection(url.clone()).await;
       match connectionresult {
           Err(error) => return Err(error),
           Ok((connection, client)) => {
               clientstored.push(client);
               connectionstored.push(connection);
           }
       }
   }
   return Ok((clientstored, connectionstored));
}

async fn createconnection(url: String) -> Result<(tokio::task::JoinHandle<()>, Client), Error> {
   let (client, connection) = yb_tokio_postgres::connect(&url, NoTls).await?;

   // The connection object performs the actual communication with the database,
   // so spawn it off to run on its own.
   let handle = tokio::spawn(async move {
       if let Err(e) = connection.await {
           eprintln!("connection error: {}", e);
       }
   });

   Ok((handle, client))
}

pub(crate) fn num_of_connections() {
   for i in 1..4 {
       let url = "http://127.0.0.".to_owned() + &i.to_string() + ":13000/rpcz";
       let response = isahc::get(url);
       if response.is_err() {
           println!("127.0.0.{} = {}",i, 0);
       } else {
           let body = response.unwrap().text().unwrap();
           let c = body.matches("client backend").count();
           println!("127.0.0.{} = {}", i, c);
       }
   }
}

In this case the first two nodes should have 15 connections each, and the third node should have zero connections.

Clean up

After you're done experimenting, run the following command to destroy the local cluster:

./bin/yugabyted destroy --base_dir=$HOME/yugabyte-2.21.0.0/node1
./bin/yugabyted destroy --base_dir=$HOME/yugabyte-2.21.0.0/node2
./bin/yugabyted destroy --base_dir=$HOME/yugabyte-2.21.0.0/node3

Configure SSL/TLS

The YugabyteDB Rust smart driver support for SSL is the same as for the upstream driver.

The following table describes the additional parameters the YugabyteDB Rust smart driver requires as part of the connection string when using SSL.

rust-postgres parameter	Description	default
sslmode	SSL Mode	prefer

The rust-postgres driver supports the following SSL modes.

SSL Mode	Description
disable	TLS is not used.
prefer (default)	Use TLS is if available, but not otherwise.
require	Require TLS to be used.

Currently, the rust-postgres driver and YugabyteDB Rust smart driver do not support verify-full or verify-ca SSL modes.

YugabyteDB Managed requires SSL/TLS, and connections using SSL mode disable will fail.

The following is an example connection URL for connecting to a YugabyteDB cluster with SSL encryption enabled:

"postgresql://127.0.0.1:5434/yugabyte?user=yugabyte&password=yugabyte&load_balance=true&sslmode=require"

If you created a cluster on YugabyteDB Managed, use the cluster credentials and download the SSL Root certificate.

The following is an example application for connecting to a YugabyteDB cluster with SSL enabled:

Add yb-postgres-openssl = "0.5.0-yb-1", yb-postgres = "0.19.7-yb-1-beta", and openssl = "0.10.61" dependencies in the Cargo.toml file before executing the application.

use openssl::ssl::{SslConnector, SslMethod};
use yb_postgres_openssl::MakeTlsConnector;
use yb_postgres::{Client};

fn main()  {
   let mut builder = SslConnector::builder(SslMethod::tls()).expect("unable to create sslconnector builder");
   builder.set_ca_file("/path/to/root/certificate").expect("unable to load root certificate");
   let connector: MakeTlsConnector = MakeTlsConnector::new(builder.build());

   let mut connection = Client::connect( "host=? port=5433 dbname=yugabyte user=? password=? sslmode=require",
       connector,
       ).expect("failed to create tls ysql connection");

   let result = connection.query_one("select 1", &[]).expect("failed to execute select 1 ysql");
   let value: i32 = result.get(0);
   println!("result of query_one call: {}", value);
}