# Building Rust Lambda functions with Cargo Lambda in AWS SAM | | | --- | | This feature is in preview release for AWS SAM and is subject to change. | Use the AWS Serverless Application Model Command Line Interface (AWS SAM CLI) with your Rust AWS Lambda functions. **Topics** + [ ## Prerequisites ](#building-rust-prerequisites) + [ ## Configuring AWS SAM to use with Rust Lambda functions ](#building-rust-configure) + [ ## Examples ](#building-rust-examples) ## Prerequisites **Rust language** To install Rust, see [Install Rust](https://www.rust-lang.org/tools/install) in the *Rust language website*. **Cargo Lambda** The AWS SAM CLI requires installation of [https://www.cargo-lambda.info/guide/what-is-cargo-lambda.html](https://www.cargo-lambda.info/guide/what-is-cargo-lambda.html), a subcommand for Cargo. For installation instructions, see [Installation](https://www.cargo-lambda.info/guide/installation.html) in the *Cargo Lambda documentation*. **Docker** Building and testing Rust Lambda functions requires Docker. For installation instructions, see [Installing Docker](install-docker.md). **Opt in to AWS SAM CLI beta feature** Since this feature is in preview, you must opt in using one of the following methods: 1. Use the environment variable: `SAM_CLI_BETA_RUST_CARGO_LAMBDA=1`. 1. Add the following to your `samconfig.toml` file: ``` [default.build.parameters] beta_features = true [default.sync.parameters] beta_features = true ``` 1. Use the `--beta-features` option when using a supported AWS SAM CLI command. For example: ``` $ sam build --beta-features ``` 1. Choose option `y` when the AWS SAM CLI prompts you to opt in. The following is an example: ``` $ sam build Starting Build use cache Build method "rust-cargolambda" is a beta feature. Please confirm if you would like to proceed You can also enable this beta feature with "sam build --beta-features". [y/N]: y ``` ## Configuring AWS SAM to use with Rust Lambda functions ### Step 1: Configure your AWS SAM template Configure your AWS SAM template with the following: + **Binary** – Optional. Specify when your template contains multiple Rust Lambda functions. + **BuildMethod** – `rust-cargolambda`. + **CodeUri** – path to your `Cargo.toml` file. + **Handler** – `bootstrap`. + **Runtime** – `provided.al2`. To learn more about custom runtimes, see [Custom AWS Lambda runtimes](https://docs.aws.amazon.com/lambda/latest/dg/runtimes-custom.html) in the *AWS Lambda Developer Guide*. Here is an example of a configured AWS SAM template: ``` AWSTemplateFormatVersion: '2010-09-09' Transform: AWS::Serverless-2016-10-31 ... Resources: MyFunction: Type: AWS::Serverless::Function Metadata: BuildMethod: rust-cargolambda BuildProperties: function_a Properties: CodeUri: ./rust_app Handler: bootstrap Runtime: provided.al2 ... ``` ### Step 2: Use the AWS SAM CLI with your Rust Lambda function Use any AWS SAM CLI command with your AWS SAM template. For more information, see [AWS SAM CLI](using-sam-cli.md). ## Examples ### Hello World example **In this example, we build the sample Hello World application using Rust as our runtime.** First, we initialize a new serverless application using `sam init`. During the interactive flow, we select the **Hello World application** and choose the **Rust** runtime. ``` $ sam init ... Which template source would you like to use? 1 - AWS Quick Start Templates 2 - Custom Template Location Choice: 1 Choose an AWS Quick Start application template 1 - Hello World Example 2 - Multi-step workflow 3 - Serverless API ... Template: 1 Use the most popular runtime and package type? (Python and zip) [y/N]: ENTER Which runtime would you like to use? 1 - dotnet8 2 - dotnet6 3 - go (provided.al2) ... 18 - python3.11 19 - python3.10 20 - ruby3.3 21 - ruby3.2 22 - rust (provided.al2) 23 - rust (provided.al2023) Runtime: 22 Based on your selections, the only Package type available is Zip. We will proceed to selecting the Package type as Zip. Based on your selections, the only dependency manager available is cargo. We will proceed copying the template using cargo. Would you like to enable X-Ray tracing on the function(s) in your application? [y/N]: ENTER Would you like to enable monitoring using CloudWatch Application Insights? For more info, please view https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/cloudwatch-application-insights.html [y/N]: ENTER Project name [sam-app]: hello-rust ----------------------- Generating application: ----------------------- Name: hello-rust Runtime: rust (provided.al2) Architectures: x86_64 Dependency Manager: cargo Application Template: hello-world Output Directory: . Configuration file: hello-rust/samconfig.toml Next steps can be found in the README file at hello-rust/README.md Commands you can use next ========================= [*] Create pipeline: cd hello-rust && sam pipeline init --bootstrap [*] Validate SAM template: cd hello-rust && sam validate [*] Test Function in the Cloud: cd hello-rust && sam sync --stack-name {stack-name} --watch ``` The following is the structure of our Hello World application: ``` hello-rust ├── README.md ├── events │ └── event.json ├── rust_app │ ├── Cargo.toml │ └── src │ └── main.rs ├── samconfig.toml └── template.yaml ``` In our AWS SAM template, our Rust function is defined as the following: ``` AWSTemplateFormatVersion: '2010-09-09' Transform: AWS::Serverless-2016-10-31 ... Resources: HelloWorldFunction: Type: AWS::Serverless::Function Metadata: BuildMethod: rust-cargolambda Properties: CodeUri: ./rust_app Handler: bootstrap Runtime: provided.al2 Architectures: - x86_64 Events: HelloWorld: Type: Api Path: /hello Method: get ``` Next, we run `sam build` to build our application and prepare for deployment. The AWS SAM CLI creates a `.aws-sam` directory and organizes our build artifacts there. Our function is built using Cargo Lambda and stored as an executable binary at `.aws-sam/build/HelloWorldFunction/bootstrap`. **Note** If you plan on running the **sam local invoke** command in MacOS, you need to build functions different before invoking. To do this, use the following command: **SAM\$1BUILD\$1MODE=debug sam build** This command is only needed if local testing will be done. This is not recommended when building for deployment. ``` hello-rust$ sam build Starting Build use cache Build method "rust-cargolambda" is a beta feature. Please confirm if you would like to proceed You can also enable this beta feature with "sam build --beta-features". [y/N]: y Experimental features are enabled for this session. Visit the docs page to learn more about the AWS Beta terms https://aws.amazon.com/service-terms/. Cache is invalid, running build and copying resources for following functions (HelloWorldFunction) Building codeuri: /Users/.../hello-rust/rust_app runtime: provided.al2 metadata: {'BuildMethod': 'rust-cargolambda'} architecture: x86_64 functions: HelloWorldFunction Running RustCargoLambdaBuilder:CargoLambdaBuild Running RustCargoLambdaBuilder:RustCopyAndRename Build Succeeded Built Artifacts : .aws-sam/build Built Template : .aws-sam/build/template.yaml Commands you can use next ========================= [*] Validate SAM template: sam validate [*] Invoke Function: sam local invoke [*] Test Function in the Cloud: sam sync --stack-name {{stack-name}} --watch [*] Deploy: sam deploy --guided ``` Next, we deploy our application using `sam deploy --guided`. ``` hello-rust$ sam deploy --guided Configuring SAM deploy ====================== Looking for config file [samconfig.toml] : Found Reading default arguments : Success Setting default arguments for 'sam deploy' ========================================= Stack Name [hello-rust]: ENTER AWS Region [us-west-2]: ENTER #Shows you resources changes to be deployed and require a 'Y' to initiate deploy Confirm changes before deploy [Y/n]: ENTER #SAM needs permission to be able to create roles to connect to the resources in your template Allow SAM CLI IAM role creation [Y/n]: ENTER #Preserves the state of previously provisioned resources when an operation fails Disable rollback [y/N]: ENTER HelloWorldFunction may not have authorization defined, Is this okay? [y/N]: y Save arguments to configuration file [Y/n]: ENTER SAM configuration file [samconfig.toml]: ENTER SAM configuration environment [default]: ENTER Looking for resources needed for deployment: ... Uploading to hello-rust/56ba6585d80577dd82a7eaaee5945c0b 817973 / 817973 (100.00%) Deploying with following values =============================== Stack name : hello-rust Region : us-west-2 Confirm changeset : True Disable rollback : False Deployment s3 bucket : aws-sam-cli-managed-default-samclisam-s3-demo-bucket-1a4x26zbcdkqr Capabilities : ["CAPABILITY_IAM"] Parameter overrides : {} Signing Profiles : {} Initiating deployment ===================== Uploading to hello-rust/a4fc54cb6ab75dd0129e4cdb564b5e89.template 1239 / 1239 (100.00%) Waiting for changeset to be created.. CloudFormation stack changeset --------------------------------------------------------------------------------------------------------- Operation LogicalResourceId ResourceType Replacement --------------------------------------------------------------------------------------------------------- + Add HelloWorldFunctionHelloW AWS::Lambda::Permission N/A orldPermissionProd ... --------------------------------------------------------------------------------------------------------- Changeset created successfully. arn:aws:cloudformation:us-west-2:012345678910:changeSet/samcli-deploy1681427201/f0ef1563-5ab6-4b07-9361-864ca3de6ad6 Previewing CloudFormation changeset before deployment ====================================================== Deploy this changeset? [y/N]: y 2023-04-13 13:07:17 - Waiting for stack create/update to complete CloudFormation events from stack operations (refresh every 5.0 seconds) --------------------------------------------------------------------------------------------------------- ResourceStatus ResourceType LogicalResourceId ResourceStatusReason --------------------------------------------------------------------------------------------------------- CREATE_IN_PROGRESS AWS::IAM::Role HelloWorldFunctionRole - CREATE_IN_PROGRESS AWS::IAM::Role HelloWorldFunctionRole Resource creation ... --------------------------------------------------------------------------------------------------------- CloudFormation outputs from deployed stack --------------------------------------------------------------------------------------------------------- Outputs --------------------------------------------------------------------------------------------------------- Key HelloWorldFunctionIamRole Description Implicit IAM Role created for Hello World function Value arn:aws:iam::012345678910:role/hello-rust-HelloWorldFunctionRole-10II2P13AUDUY Key HelloWorldApi Description API Gateway endpoint URL for Prod stage for Hello World function Value https://ggdxec9le9.execute-api.us-west-2.amazonaws.com/Prod/hello/ Key HelloWorldFunction Description Hello World Lambda Function ARN Value arn:aws:lambda:us-west-2:012345678910:function:hello-rust-HelloWorldFunction- yk4HzGzYeZBj --------------------------------------------------------------------------------------------------------- Successfully created/updated stack - hello-rust in us-west-2 ``` To test, we can invoke our Lambda function using the API endpoint. ``` $ curl https://ggdxec9le9.execute-api.us-west-2.amazonaws.com/Prod/hello/ Hello World!% ``` To test our function locally, first we ensure our function’s `Architectures` property matches our local machine. ``` ... Resources: HelloWorldFunction: Type: AWS::Serverless::Function # More info about Function Resource: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#awsserverlessfunction Metadata: BuildMethod: rust-cargolambda # More info about Cargo Lambda: https://github.com/cargo-lambda/cargo-lambda Properties: CodeUri: ./rust_app # Points to dir of Cargo.toml Handler: bootstrap # Do not change, as this is the default executable name produced by Cargo Lambda Runtime: provided.al2 Architectures: - arm64 ... ``` Since we modified our architecture from `x86_64` to `arm64` in this example, we run `sam build` to update our build artifacts. We then run `sam local invoke` to locally invoke our function. ``` hello-rust$ sam local invoke Invoking bootstrap (provided.al2) Local image was not found. Removing rapid images for repo public.ecr.aws/sam/emulation-provided.al2 Building image..................................................................................................................................... Using local image: public.ecr.aws/lambda/provided:al2-rapid-arm64. Mounting /Users/.../hello-rust/.aws-sam/build/HelloWorldFunction as /var/task:ro,delegated, inside runtime container START RequestId: fbc55e6e-0068-45f9-9f01-8e2276597fc6 Version: $LATEST {"statusCode":200,"body":"Hello World!"}END RequestId: fbc55e6e-0068-45f9-9f01-8e2276597fc6 REPORT RequestId: fbc55e6e-0068-45f9-9f01-8e2276597fc6 Init Duration: 0.68 ms Duration: 130.63 ms Billed Duration: 131 ms Memory Size: 128 MB Max Memory Used: 128 MB ``` ### Single Lambda function project **Here is an example of a serverless application containing one Rust Lambda function. ** Project directory structure: ``` . ├── Cargo.lock ├── Cargo.toml ├── src │ └── main.rs └── template.yaml ``` AWS SAM template: ``` AWSTemplateFormatVersion: '2010-09-09' Transform: AWS::Serverless-2016-10-31 ... Resources: MyFunction: Type: AWS::Serverless::Function Metadata: BuildMethod: rust-cargolambda Properties: CodeUri: ./ Handler: bootstrap Runtime: provided.al2 ... ``` ### Multiple Lambda function project **Here is an example of a serverless application containing multiple Rust Lambda functions.** Project directory structure: ``` . ├── Cargo.lock ├── Cargo.toml ├── src │ ├── function_a.rs │ └── function_b.rs └── template.yaml ``` AWS SAM template: ``` AWSTemplateFormatVersion: '2010-09-09' Transform: AWS::Serverless-2016-10-31 ... Resources: FunctionA: Type: AWS::Serverless::Function Metadata: BuildMethod: rust-cargolambda BuildProperties: Binary: function_a Properties: CodeUri: ./ Handler: bootstrap Runtime: provided.al2 FunctionB: Type: AWS::Serverless::Function Metadata: BuildMethod: rust-cargolambda BuildProperties: Binary: function_b Properties: CodeUri: ./ Handler: bootstrap Runtime: provided.al2 ``` `Cargo.toml` file: ``` [package] name = "test-handler" version = "0.1.0" edition = "2021" [dependencies] lambda_runtime = "0.6.0" serde = "1.0.136" tokio = { version = "1", features = ["macros"] } tracing = { version = "0.1", features = ["log"] } tracing-subscriber = { version = "0.3", default-features = false, features = ["fmt"] } [[bin]] name = "function_a" path = "src/function_a.rs" [[bin]] name = "function_b" path = "src/function_b.rs" ```