Use a service client in the AWS SDK for Rust - AWS SDK for Rust

Use a service client in the AWS SDK for Rust

Create a client

This section describes how to create a client, including one in a specific Region.

In most cases, you'll want to create a client that uses the default search path, which looks for credentials and Region in the order described in Specify your credentials and default Region. After it finds a value for an access key, secret key, or Region, it stops searching for that value.

You can also supply a Region with an argument to the client object. Most of the SDK for Rust code examples use the following construct, which searches for the Region in the search path described previously. If a Region isn't found, this sets the Region to us-east-1. SERVICENAME is the name of the service, such as s3 for Amazon Simple Storage Service (Amazon S3).

use aws_config::meta::region::RegionProviderChain; use aws_sdk_SERVICENAME::Client; let region_provider = RegionProviderChain::default_provider().or_else("us-east-1"); let config = aws_config::from_env_with_version(aws_config::BehaviorVersion::latest()) .region(region_provider) .load() .await; let client = Client::new(&config);

Specify default configuration behavior

Rust developers expect and rely upon the robust and predictable behavior the language and its major libraries offer. To help developers using the AWS SDK for Rust get the expected behavior from the SDK, SDK and client configurations are required to include a BehaviorVersion. The BehaviorVersion specifies the version of the SDK whose defaults are expected. This lets the SDK evolve over time, changing best practices to match new standards and support new features without unexpected adverse impact on your application's behavior.


If you try to configure the SDK or create a client without explicitly specifying a BehaviorVersion, the constructor will panic.

For example, imagine that a new version of the SDK is released using a new default retry policy. If your application uses a BehaviorVersion matching a previous version of the SDK that used a different default configuration, that configuration is used instead of the new default configuration.

Each time a new version of the AWS SDK for Rust is released, the previous version in BehaviorVersion is marked with the Rust deprecated attribute and the new version is added. This causes warnings to occur at compile time, but otherwise lets the build continue as usual. BehaviorVersion::latest() is also updated to indicate the new version's default behavior.

In most cases, you should use BehaviorVersion::latest() in code or the feature flag behavior-version-latest in the Cargo.toml file.

Set the behavior version in Cargo.toml

You can specify the behavior version for the SDK and individual modules (such as aws-sdk-s3 or aws-sdk-iam) by including an appropriate feature flag in the Cargo.toml file. At this time, only the latest version of the SDK is supported in Cargo.toml:

[dependencies] aws-config = { version = "1", features = ["behavior-version-latest"] } aws-sdk-s3 = { version = "1", features = ["behavior-version-latest"] }

This snippet from Cargo.toml indicates that the project depends on the aws-config and aws-sdk-s3 crates, which both need to be version 1, and should use the latest defaults.

Set the behavior version in code

Your code can change the behavior version as needed by specifying it when configuring the SDK or a client:

let config = aws_config::from_env_with_version(aws_config::BehaviorVersion::v2023_11_09());

This example creates a configuration that uses the environment to configure the SDK but sets the BehaviorVersion to v2023_11_09().