Build a Rust App with CockroachDB and the Rust-Postgres Driver

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This tutorial shows you how build a simple Rust application with CockroachDB and the Rust-Postgres driver.

Before you begin

You must have Rust and Cargo installed. For instructions on installing Rust and Cargo, see the Cargo documentation.

Step 1. Start CockroachDB

Choose your installation method

You can install a CockroachDB Serverless cluster using either the CockroachDB Cloud Console, a web-based graphical user interface (GUI) tool, or ccloud, a command-line interface (CLI) tool.

Create a free cluster

Note:

Organizations without billing information on file can only create one CockroachDB Basic cluster.

If you haven't already, sign up for a CockroachDB Cloud account.
Log in to your CockroachDB Cloud account.
On the Clusters page, click Create cluster.
On the Select a plan page, select Basic.
On the Cloud & Regions page, select a cloud provider (GCP or AWS) in the Cloud provider section.
In the Regions section, select a region for the cluster. Refer to CockroachDB Cloud Regions for the regions where CockroachDB Basic clusters can be deployed. To create a multi-region cluster, click Add region and select additional regions.
Click Next: Capacity.
On the Capacity page, select Start for free. Click Next: Finalize.
On the Finalize page, click Create cluster.

Your cluster will be created in a few seconds and the Create SQL user dialog will display.

Create a SQL user

The Create SQL user dialog allows you to create a new SQL user and password.

Enter a username in the SQL user field or use the one provided by default.
Click Generate & save password.
Copy the generated password and save it in a secure location.
Click Next.

Currently, all new SQL users are created with admin privileges. For more information and to change the default settings, see Manage SQL users on a cluster.

Get the connection string

The Connect to cluster dialog shows information about how to connect to your cluster.

Select General connection string from the Select option dropdown.
Open the General connection string section, then copy the connection string provided and save it in a secure location.

The sample application used in this tutorial uses system CA certificates for server certificate verification, so you can skip the Download CA Cert instructions.

Note:

The connection string is pre-populated with your username, password, cluster name, and other details. Your password, in particular, will be provided only once. Save it in a secure place (Cockroach Labs recommends a password manager) to connect to your cluster in the future. If you forget your password, you can reset it by going to the SQL Users page for the cluster, found at https://cockroachlabs.cloud/cluster/<CLUSTER ID>/users.

Follow these steps to create a CockroachDB Serverless cluster using the ccloud CLI tool.

Note:

The ccloud CLI tool is in Preview.

Install `ccloud`

Choose your OS:

You can install ccloud using either Homebrew or by downloading the binary.

Use Homebrew

Install Homebrew.
Install using the ccloud tap:
```
brew install cockroachdb/tap/ccloud
```

Download the binary

In a terminal, enter the following command to download and extract the ccloud binary and add it to your PATH:

curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-amd64_0.6.12.tar.gz | tar -xJ && cp -i ccloud /usr/local/bin/

Use the ARM 64 binary if you have an M-series Mac:

curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-arm64_0.6.12.tar.gz | tar -xJ && cp -i ccloud /usr/local/bin/

In a terminal, enter the following command to download and extract the ccloud binary and add it to your PATH:

curl https://binaries.cockroachdb.com/ccloud/ccloud_linux-amd64_0.6.12.tar.gz | tar -xz && cp -i ccloud /usr/local/bin/

In a PowerShell window, enter the following command to download and extract the ccloud binary and add it to your PATH:

$ErrorActionPreference = "Stop"; [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; $ProgressPreference = 'SilentlyContinue'; $null = New-Item -Type Directory -Force $env:appdata/ccloud; Invoke-WebRequest -Uri https://binaries.cockroachdb.com/ccloud/ccloud_windows-amd64_0.6.12.zip -OutFile ccloud.zip; Expand-Archive -Force -Path ccloud.zip; Copy-Item -Force ccloud/ccloud.exe -Destination $env:appdata/ccloud; $Env:PATH += ";$env:appdata/ccloud"; # We recommend adding ";$env:appdata/ccloud" to the Path variable for your system environment. See https://docs.microsoft.com/powershell/module/microsoft.powershell.core/about/about_environment_variables#saving-changes-to-environment-variables for more information.

Run `ccloud quickstart` to create a new cluster, create a SQL user, and retrieve the connection string.

The easiest way of getting started with CockroachDB Cloud is to use ccloud quickstart. The ccloud quickstart command guides you through logging in to CockroachDB Cloud, creating a new CockroachDB Serverless cluster, and connecting to the new cluster. Run ccloud quickstart and follow the instructions:

ccloud quickstart

The ccloud quickstart command will open a browser window to log you in to CockroachDB Cloud. If you are new to CockroachDB Cloud, you can register using one of the single sign-on (SSO) options, or create a new account using an email address.

The ccloud quickstart command will prompt you for the cluster name, cloud provider, and cloud provider region, then ask if you want to connect to the cluster. Each prompt has default values that you can select, or change if you want a different option.

Select General connection string, then copy the connection string displayed and save it in a secure location. The connection string is the line starting postgresql://.

? How would you like to connect? General connection string
Retrieving cluster info: succeeded
 Downloading cluster cert to /Users/maxroach/.postgresql/root.crt: succeeded
postgresql://maxroach:ThisIsNotAGoodPassword@blue-dog-147.6wr.cockroachlabs.cloud:26257/defaultdb?sslmode=verify-full&sslrootcert=%2FUsers%2Fmaxroach%2F.postgresql%2Froot.crt

If you haven't already, download the CockroachDB binary.
Run the cockroach start-single-node command:
```
$ cockroach start-single-node --advertise-addr 'localhost' --insecure
```
This starts an insecure, single-node cluster.

Take note of the following connection information in the SQL shell welcome text:

CockroachDB node starting at 2021-08-30 17:25:30.06524 +0000 UTC (took 4.3s)
build:               CCL v21.1.6 @ 2021/07/20 15:33:43 (go1.15.11)
webui:               http://localhost:8080
sql:                 postgresql://root@localhost:26257?sslmode=disable

You'll use the sql connection string to connect to the cluster later in this tutorial.

Warning:

The --insecure flag used in this tutorial is intended for non-production testing only. To run CockroachDB in production, use a secure cluster instead.

Step 2. Get the code

Clone the code's GitHub repo:

$ git clone https://github.com/cockroachdb/example-app-rust-postgres

The project has the following structure:

├── Cargo.toml
├── LICENSE
├── README.md
└── src
    └── main.rs

The Cargo.toml file is the configuration file for the example, and sets the dependencies for the project.

[package]
name = "bank"
version = "0.1.0"
edition = "2021"

[dependencies]
openssl = "0.10.41"
postgres-openssl = "0.5.0"
chrono = "0.4.22"

[dependencies.postgres]
version = "0.19.3"
features = [
    "with-uuid-1"
]

[dependencies.uuid]
version = "1.1.2"

The main function is the entry point for the application, with the code for connecting to the cluster, creating the accounts table, creating accounts in that table, and transferring money between two accounts.

The execute_txn function wraps database operations in the context of an explicit transaction. If a retry error is thrown, the function will retry committing the transaction, with exponential backoff, until the maximum number of retries is reached (by default, 15).

Note:

CockroachDB may require the client to retry a transaction in case of read/write contention. CockroachDB provides a generic retry function that runs inside a transaction and retries it as needed. You can copy and paste the retry function from here into your code.


/// Runs op inside a transaction and retries it as needed.
/// On non-retryable failures, the transaction is aborted and
/// rolled back; on success, the transaction is committed.
fn execute_txn<T, F>(client: &mut Client, op: F) -> Result<T, Error>
where
    F: Fn(&mut Transaction) -> Result<T, Error>,
{
    let mut txn = client.transaction()?;
    loop {
        // Set a retry savepoint 
        // See https://www.cockroachlabs.com/docs/stable/advanced-client-side-transaction-retries
        let mut sp = txn.savepoint("cockroach_restart")?;
        match op(&mut sp).and_then(|t| sp.commit().map(|_| t)) {
            Err(ref err)
                if err
                    .code()
                    .map(|e| *e == SqlState::T_R_SERIALIZATION_FAILURE)
                    .unwrap_or(false) => {}
            r => break r,
        }
    }
    .and_then(|t| txn.commit().map(|_| t))
}
//

The transfer_funds function calls execute_txn to perform the actual transfer of funds from one account to the other.


fn transfer_funds(txn: &mut Transaction, from: Uuid, to: Uuid, amount: i64) -> Result<(), Error> {
    // Read the balance.
    let from_balance: i64 = txn
        .query_one("SELECT balance FROM accounts WHERE id = $1", &[&from])?
        .get(0);

    assert!(from_balance >= amount);

    // Perform the transfer.
    txn.execute(
        "UPDATE accounts SET balance = balance - $1 WHERE id = $2",
        &[&amount, &from],
    )?;
    txn.execute(
        "UPDATE accounts SET balance = balance + $1 WHERE id = $2",
        &[&amount, &to],
    )?;
    Ok(())
}
//

Step 3. Run the code

In a terminal go to the example-app-rust-postgres directory.
```
cd example-app-rust-postgres
```
Set the DATABASE_URL environment variable to the connection string to your CockroachDB Cloud cluster:
```
$ export DATABASE_URL="postgresql://root@localhost:26257/defaultdb?sslmode=disable"
```
1. Edit the connection string you copied earlier and replace sslmode=verify-full with sslmode=require.
  
  Warning:
  
  You must change the sslmode in your connection string to sslmode=require, as the Rust postgres driver does not recognize sslmode=verify-full. This example uses postgres-openssl, which will perform host verification when the sslmode=require option is set, so require is functionally equivalent to verify-full.
  
  For example:
```
postgresql://maxroach:ThisIsNotAGoodPassword@blue-dog-147.6wr.cockroachlabs.cloud:26257/bank?sslmode=require
```
2. Set the DATABASE_URL environment variable to the modified connection string.
```
$ export DATABASE_URL="{connection-string}"
```
  Where {connection-string} is the modified connection string.
The app uses the connection string saved to the DATABASE_URL environment variable to connect to your cluster and execute the code.

Run the code to create a table and insert some rows:

cargo run

The output should look similar to the following:

  Compiling bank v0.1.0 (/Users/maxroach/go/src/github.com/cockroachdb/example-app-rust-postgres)
    Finished dev [unoptimized + debuginfo] target(s) in 8.00s
     Running `target/debug/bank`
Creating accounts table if it doesn't already exist.
Deleted existing accounts.
Balances before transfer:
account id: 8e88f765-b532-4071-a23d-1b33729d01cb  balance: $250
account id: c6de70e2-78e0-484b-ae5b-6ac2aa43d9ec  balance: $1000
Final balances:
account id: 8e88f765-b532-4071-a23d-1b33729d01cb  balance: $350
account id: c6de70e2-78e0-484b-ae5b-6ac2aa43d9ec  balance: $900

What's next?

Read more about using the Rust-Postgres driver.

You might also be interested in the following pages:

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Build a Rust App with CockroachDB and the Rust-Postgres Driver

Before you begin

Step 1. Start CockroachDB

Choose your installation method

Create a free cluster

Create a SQL user

Get the connection string

Install `ccloud`

Use Homebrew

Download the binary

Run `ccloud quickstart` to create a new cluster, create a SQL user, and retrieve the connection string.

Step 2. Get the code

Step 3. Run the code

What's next?

Build a Rust App with CockroachDB and the Rust-Postgres Driver

Before you begin

Step 1. Start CockroachDB

Choose your installation method

Create a free cluster

Create a SQL user

Get the connection string

Install ccloud

Use Homebrew

Download the binary

Run ccloud quickstart to create a new cluster, create a SQL user, and retrieve the connection string.

Step 2. Get the code

Step 3. Run the code

What's next?

Install `ccloud`

Run `ccloud quickstart` to create a new cluster, create a SQL user, and retrieve the connection string.