> ## Documentation Index > Fetch the complete documentation index at: https://cockroachlabs.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # Build a Rust App with CockroachDB and the Rust-Postgres Driver export const InternalLink = ({version, path = "", children, ...props}) => { let detectedVersion = version || "stable"; if (typeof window !== 'undefined' && !version) { const match = window.location.pathname.match(/\/docs\/([^/]+)/); if (match) { detectedVersion = match[1]; } } const normalizedPath = path.startsWith("/") ? path.slice(1) : path; return {children} ; }; export const InternalLink = ({version, path = "", children, ...props}) => { let detectedVersion = version || "stable"; if (typeof window !== 'undefined' && !version) { const match = window.location.pathname.match(/\/docs\/([^/]+)/); if (match) { detectedVersion = match[1]; } } const normalizedPath = path.startsWith("/") ? path.slice(1) : path; return {children} ; }; This tutorial shows you how build a simple Rust application with CockroachDB and the [Rust-Postgres driver](https://github.com/sfackler/rust-postgres). ## Before you begin You must have Rust and Cargo installed. For instructions on installing Rust and Cargo, see the [Cargo documentation](https://doc.rust-lang.org/cargo/getting-started/installation). ## Step 1. Start CockroachDB ### Choose your installation method You can create a CockroachDB Basic 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 Organizations without billing information on file can only create one CockroachDB Basic cluster. 1. If you haven't already, [sign up for a CockroachDB Cloud account](https://cockroachlabs.cloud/signup?referralId=docs_rust). 2. [Log in](https://cockroachlabs.cloud/) to your CockroachDB Cloud account. 3. On the **Clusters** page, click **Create cluster**. 4. On the **Select a plan** page, select **Basic**. 5. On the **Cloud & Regions** page, select a cloud provider (GCP or AWS) in the **Cloud provider** section. 6. 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. 7. Click **Next: Capacity**. 8. On the **Capacity** page, select **Start for free**. Click **Next: Finalize**. 9. 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. 1. Enter a username in the **SQL user** field or use the one provided by default. 2. Click **Generate & save password**. 3. Copy the generated password and save it in a secure location. 4. 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. 1. Select **General connection string** from the **Select option** dropdown. 2. 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. 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//users`. Follow these steps to create a CockroachDB Basic cluster using the `ccloud` CLI tool. The `ccloud` CLI tool is in Preview. ### Install `ccloud` You can install `ccloud` using either Homebrew or by downloading the binary. #### Use Homebrew 1. [Install Homebrew](http://brew.sh/). 2. Install using the `ccloud` tap: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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`: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-amd64_.tar.gz | tar -xJ && cp -i ccloud /usr/local/bin/ ``` Use the ARM 64 binary if you have an M-series Mac: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} curl https://binaries.cockroachdb.com/ccloud/ccloud_darwin-arm64_.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`: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} curl https://binaries.cockroachdb.com/ccloud/ccloud_linux-amd64_.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`: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $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_.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 Basic cluster, and connecting to the new cluster. Run `ccloud quickstart` and follow the instructions: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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 ``` 1. If you haven't already, download the CockroachDB binary. 2. Run the `cockroach start-single-node` command: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ cockroach start-single-node --advertise-addr 'localhost' --insecure ``` This starts an insecure, single-node cluster. 3. 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. 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: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ git clone https://github.com/cockroachdb/example-app-rust-postgres ``` The project has the following structure: ```text theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} ├── 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. ```toml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} [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](https://wikipedia.org/wiki/Exponential_backoff), until the maximum number of retries is reached (by default, 15). 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. ```rust theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} /// 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(client: &mut Client, op: F) -> Result where F: Fn(&mut Transaction) -> Result, { 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. ```rust theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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 1. In a terminal go to the `example-app-rust-postgres` directory. ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cd example-app-rust-postgres ``` 2. Set the `DATABASE_URL` environment variable to the connection string to your CockroachDB Cloud cluster: 1. Edit the connection string you copied earlier and replace `sslmode=verify-full` with `sslmode=require`. 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: ```text theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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. ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ 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. 3. Run the code to create a table and insert some rows: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cargo run ``` The output should look similar to the following: ```text theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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 ``` 4. If you haven't already, download the CockroachDB binary. 5. Run the `cockroach start-single-node` command: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ cockroach start-single-node --advertise-addr 'localhost' --insecure ``` This starts an insecure, single-node cluster. 6. Take note of the following connection information in the SQL shell welcome text: ```text theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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. 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: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ git clone https://github.com/cockroachdb/example-app-rust-postgres ``` The project has the following structure: ```text theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} ├── 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. ```toml theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} [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](https://wikipedia.org/wiki/Exponential_backoff), until the maximum number of retries is reached (by default, 15). 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. ```rust theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} /// 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(client: &mut Client, op: F) -> Result where F: Fn(&mut Transaction) -> Result, { 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. ```rust theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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 1. In a terminal go to the `example-app-rust-postgres` directory. ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cd example-app-rust-postgres ``` 2. Set the `DATABASE_URL` environment variable to the connection string to your CockroachDB Cloud cluster: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} $ export DATABASE_URL="postgresql://root@localhost:26257/defaultdb?sslmode=disable" ``` The app uses the connection string saved to the `DATABASE_URL` environment variable to connect to your cluster and execute the code. 3. Run the code to create a table and insert some rows: ```shell theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} cargo run ``` The output should look similar to the following: ```text theme={"theme":{"light":"catppuccin-mocha","dark":"catppuccin-mocha"}} 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](https://crates.io/crates/postgres). You might also be interested in the following pages: * [Client Connection Parameters](connection-parameters) * [Connection Pooling](connection-pooling) * [Data Replication](demo-replication-and-rebalancing) * [CockroachDB Resilience](demo-cockroachdb-resilience) * [Replication & Rebalancing](demo-replication-and-rebalancing) * [Cross-Cloud Migration](demo-automatic-cloud-migration) * [Automated Operations](orchestrate-a-local-cluster-with-kubernetes-insecure)