Deploy Ruby Lambda functions with container images

There are three ways to build a container image for a Ruby Lambda function:

• Using an AWS base image for Ruby

  The AWS base images are preloaded with a language runtime, a runtime interface client to manage the interaction between Lambda and your function code, and a runtime interface emulator for local testing.

• Using an AWS OS-only base image

  AWS OS-only base images contain an Amazon Linux distribution and the runtime interface emulator. These images are commonly used to create container images for compiled languages, such as Go and Rust, and for a language or language version that Lambda doesn't provide a base image for, such as Node.js 19. You can also use OS-only base images to implement a custom runtime. To make the image compatible with Lambda, you must include the runtime interface client for Ruby in the image.

• Using a non-AWS base image

  You can use an alternative base image from another container registry, such as Alpine Linux or Debian. You can also use a custom image created by your organization. To make the image compatible with Lambda, you must include the runtime interface client for Ruby in the image.

Tip

To reduce the time it takes for Lambda container functions to become active, see Use multi-stage builds in the Docker documentation. To build efficient container images, follow the Best practices for writing Dockerfiles.

This page explains how to build, test, and deploy container images for Lambda.

AWS base images for Ruby

AWS provides the following base images for Ruby:

Tags	Runtime	Operating system	Dockerfile	Deprecation
3.3	Ruby 3.3	Amazon Linux 2023	Dockerfile for Ruby 3.3 on GitHub	Not scheduled
3.2	Ruby 3.2	Amazon Linux 2	Dockerfile for Ruby 3.2 on GitHub	Not scheduled

Amazon ECR repository: gallery.ecr.aws/lambda/ruby

Using an AWS base image for Ruby

Prerequisites

To complete the steps in this section, you must have the following:

• AWS Command Line Interface (AWS CLI) version 2

• Docker

• Ruby

Creating an image from a base image

To create a container image for Ruby

1. Create a directory for the project, and then switch to that directory.

   mkdir example
   cd example

2. Create a new file called Gemfile. This is where you list your application's required RubyGems packages. The AWS SDK for Ruby is available from RubyGems. You should choose specific AWS service gems to install. For example, to use the Ruby gem for Lambda, your Gemfile should look like this:

   source 'https://rubygems.org'
   
   gem 'aws-sdk-lambda'

   Alternatively, the aws-sdk gem contains every available AWS service gem. This gem is very large. We recommend that you use it only if you depend on many AWS services.

3. Install the dependencies specified in the Gemfile using bundle install.

   bundle install

4. Create a new file called lambda_function.rb. You can add the following sample function code to the file for testing, or use your own.

   Example Ruby function

   module LambdaFunction
     class Handler
       def self.process(event:,context:)
         "Hello from Lambda!"
       end
     end
   end

5. Create a new Dockerfile. The following is an example Dockerfile that uses an AWS base image. This Dockerfiles uses the following configuration:

   • Set the FROM property to the URI of the base image.

   • Use the COPY command to copy the function code and runtime dependencies to {LAMBDA_TASK_ROOT}, a Lambda-defined environment variable.

   • Set the CMD argument to the Lambda function handler.

   Note that the example Dockerfile does not include a USER instruction. When you deploy a container image to Lambda, Lambda automatically defines a default Linux user with least-privileged permissions. This is different from standard Docker behavior which defaults to the root user when no USER instruction is provided.

   Example Dockerfile

   FROM public.ecr.aws/lambda/ruby:3.2
   
   # Copy Gemfile and Gemfile.lock
   COPY Gemfile Gemfile.lock ${LAMBDA_TASK_ROOT}/
   
   # Install Bundler and the specified gems
   RUN gem install bundler:2.4.20 && \
       bundle config set --local path 'vendor/bundle' && \
       bundle install
   
   # Copy function code
   COPY lambda_function.rb ${LAMBDA_TASK_ROOT}/    
   
   # Set the CMD to your handler (could also be done as a parameter override outside of the Dockerfile)
   CMD [ "lambda_function.LambdaFunction::Handler.process" ]

6. Build the Docker image with the docker build command. The following example names the image docker-image and gives it the test tag.

   docker build --platform linux/amd64 -t docker-image:test .

   Note

   The command specifies the --platform linux/amd64 option to ensure that your container is compatible with the Lambda execution environment regardless of the architecture of your build machine. If you intend to create a Lambda function using the ARM64 instruction set architecture, be sure to change the command to use the --platform linux/arm64 option instead.

(Optional) Test the image locally

1. Start the Docker image with the docker run command. In this example, docker-image is the image name and test is the tag.

   docker run --platform linux/amd64 -p 9000:8080 --read-only docker-image:test

   This command runs the image as a container and creates a local endpoint at localhost:9000/2015-03-31/functions/function/invocations.

   Note

   If you built the Docker image for the ARM64 instruction set architecture, be sure to use the --platform linux/arm64 option instead of --platform linux/amd64.

2. From a new terminal window, post an event to the local endpoint.

   Linux/macOS

   In Linux and macOS, run the following curl command:

   curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{}'

   This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:

   curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{"payload":"hello world!"}'

   PowerShell

   In PowerShell, run the following Invoke-WebRequest command:

   Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{}' -ContentType "application/json"

   This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:

   Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{"payload":"hello world!"}' -ContentType "application/json"

3. Get the container ID.

   docker ps

4. Use the docker kill command to stop the container. In this command, replace 3766c4ab331c with the container ID from the previous step.

   docker kill 3766c4ab331c

Deploying the image

To upload the image to Amazon ECR and create the Lambda function

1. Run the get-login-password command to authenticate the Docker CLI to your Amazon ECR registry.

   • Set the --region value to the AWS Region where you want to create the Amazon ECR repository.

   • Replace 111122223333 with your AWS account ID.

   aws ecr get-login-password --region us-east-1 | docker login --username AWS --password-stdin 111122223333.dkr.ecr.us-east-1.amazonaws.com

2. Create a repository in Amazon ECR using the create-repository command.

   aws ecr create-repository --repository-name hello-world --region us-east-1 --image-scanning-configuration scanOnPush=true --image-tag-mutability MUTABLE

   Note

   The Amazon ECR repository must be in the same AWS Region as the Lambda function.

   If successful, you see a response like this:

   {
       "repository": {
           "repositoryArn": "arn:aws:ecr:us-east-1:111122223333:repository/hello-world",
           "registryId": "111122223333",
           "repositoryName": "hello-world",
           "repositoryUri": "111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world",
           "createdAt": "2023-03-09T10:39:01+00:00",
           "imageTagMutability": "MUTABLE",
           "imageScanningConfiguration": {
               "scanOnPush": true
           },
           "encryptionConfiguration": {
               "encryptionType": "AES256"
           }
       }
   }

3. Copy the repositoryUri from the output in the previous step.

4. Run the docker tag command to tag your local image into your Amazon ECR repository as the latest version. In this command:

   • docker-image:test is the name and tag of your Docker image. This is the image name and tag that you specified in the docker build command.

   • Replace <ECRrepositoryUri> with the repositoryUri that you copied. Make sure to include :latest at the end of the URI.

   docker tag docker-image:test <ECRrepositoryUri>:latest

   Example:

   docker tag docker-image:test 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest

5. Run the docker push command to deploy your local image to the Amazon ECR repository. Make sure to include :latest at the end of the repository URI.

   docker push 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest

6. Create an execution role for the function, if you don't already have one. You need the Amazon Resource Name (ARN) of the role in the next step.

7. Create the Lambda function. For ImageUri, specify the repository URI from earlier. Make sure to include :latest at the end of the URI.

   aws lambda create-function \
     --function-name hello-world \
     --package-type Image \
     --code ImageUri=111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest \
     --role arn:aws:iam::111122223333:role/lambda-ex

   Note

   You can create a function using an image in a different AWS account, as long as the image is in the same Region as the Lambda function. For more information, see Amazon ECR cross-account permissions.

8. Invoke the function.

   aws lambda invoke --function-name hello-world response.json

   You should see a response like this:

   {
     "ExecutedVersion": "$LATEST", 
     "StatusCode": 200
   }

9. To see the output of the function, check the response.json file.

To update the function code, you must build the image again, upload the new image to the Amazon ECR repository, and then use the update-function-code command to deploy the image to the Lambda function.

Lambda resolves the image tag to a specific image digest. This means that if you point the image tag that was used to deploy the function to a new image in Amazon ECR, Lambda doesn't automatically update the function to use the new image.

To deploy the new image to the same Lambda function, you must use the update-function-code command, even if the image tag in Amazon ECR remains the same. In the following example, the --publish option creates a new version of the function using the updated container image.

aws lambda update-function-code \
  --function-name hello-world \
  --image-uri 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest \
  --publish

Using an alternative base image with the runtime interface client

If you use an OS-only base image or an alternative base image, you must include the runtime interface client in your image. The runtime interface client extends the Using the Lambda runtime API for custom runtimes, which manages the interaction between Lambda and your function code.

Install the Lambda runtime interface client for Ruby using the RubyGems.org package manager:

gem install aws_lambda_ric

You can also download the Ruby runtime interface client from GitHub. The runtime interface client supports Ruby versions 2.5.x to 2.7.x.

The following example demonstrates how to build a container image for Ruby using a non-AWS base image. The example Dockerfile uses an official Ruby base image. The Dockerfile includes the runtime interface client.

Prerequisites

To complete the steps in this section, you must have the following:

• AWS Command Line Interface (AWS CLI) version 2

• Docker

• Ruby

Creating an image from an alternative base image

To create a container image for Ruby using an alternative base image

1. Create a directory for the project, and then switch to that directory.

   mkdir example
   cd example

2. Create a new file called Gemfile. This is where you list your application's required RubyGems packages. The AWS SDK for Ruby is available from RubyGems. You should choose specific AWS service gems to install. For example, to use the Ruby gem for Lambda, your Gemfile should look like this:

   source 'https://rubygems.org'
   
   gem 'aws-sdk-lambda'

   Alternatively, the aws-sdk gem contains every available AWS service gem. This gem is very large. We recommend that you use it only if you depend on many AWS services.

3. Install the dependencies specified in the Gemfile using bundle install.

   bundle install

4. Create a new file called lambda_function.rb. You can add the following sample function code to the file for testing, or use your own.

   Example Ruby function

   module LambdaFunction
     class Handler
       def self.process(event:,context:)
         "Hello from Lambda!"
       end
     end
   end

5. Create a new Dockerfile. The following Dockerfile uses a Ruby base image instead of an AWS base image. The Dockerfile includes the runtime interface client for Ruby, which makes the image compatible with Lambda. Alternatively, you can add the runtime interface client to your application's Gemfile.

   • Set the FROM property to the Ruby base image.

   • Create a directory for the function code and an environment variable that points to that directory. In this example, the directory is /var/task, which mirrors the Lambda execution environment. However, you can choose any directory for the function code because the Dockerfile doesn't use an AWS base image.

   • Set the ENTRYPOINT to the module that you want the Docker container to run when it starts. In this case, the module is the runtime interface client.

   • Set the CMD argument to the Lambda function handler.

   Note that the example Dockerfile does not include a USER instruction. When you deploy a container image to Lambda, Lambda automatically defines a default Linux user with least-privileged permissions. This is different from standard Docker behavior which defaults to the root user when no USER instruction is provided.

   Example Dockerfile

   FROM ruby:2.7
   
   # Install the runtime interface client for Ruby
   RUN gem install aws_lambda_ric
   
   # Add the runtime interface client to the PATH
   ENV PATH="/usr/local/bundle/bin:${PATH}"
   
   # Create a directory for the Lambda function
   ENV LAMBDA_TASK_ROOT=/var/task
   RUN mkdir -p ${LAMBDA_TASK_ROOT}
   WORKDIR ${LAMBDA_TASK_ROOT}
   
   # Copy Gemfile and Gemfile.lock
   COPY Gemfile Gemfile.lock ${LAMBDA_TASK_ROOT}/
   
   # Install Bundler and the specified gems
   RUN gem install bundler:2.4.20 && \
       bundle config set --local path 'vendor/bundle' && \
       bundle install
   
   # Copy function code
   COPY lambda_function.rb ${LAMBDA_TASK_ROOT}/    
   
   # Set runtime interface client as default command for the container runtime
   ENTRYPOINT [ "aws_lambda_ric" ]
   
   # Set the CMD to your handler (could also be done as a parameter override outside of the Dockerfile)
   CMD [ "lambda_function.LambdaFunction::Handler.process" ]

6. Build the Docker image with the docker build command. The following example names the image docker-image and gives it the test tag.

   docker build --platform linux/amd64 -t docker-image:test .

   Note

   The command specifies the --platform linux/amd64 option to ensure that your container is compatible with the Lambda execution environment regardless of the architecture of your build machine. If you intend to create a Lambda function using the ARM64 instruction set architecture, be sure to change the command to use the --platform linux/arm64 option instead.

(Optional) Test the image locally

Use the runtime interface emulator to locally test the image. You can build the emulator into your image or use the following procedure to install it on your local machine.

To install and run the runtime interface emulator on your local machine

1. From your project directory, run the following command to download the runtime interface emulator (x86-64 architecture) from GitHub and install it on your local machine.

   Linux/macOS

   mkdir -p ~/.aws-lambda-rie && \
       curl -Lo ~/.aws-lambda-rie/aws-lambda-rie https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie && \
       chmod +x ~/.aws-lambda-rie/aws-lambda-rie

   To install the arm64 emulator, replace the GitHub repository URL in the previous command with the following:

   https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie-arm64

   PowerShell

   $dirPath = "$HOME\.aws-lambda-rie"
   if (-not (Test-Path $dirPath)) {
       New-Item -Path $dirPath -ItemType Directory
   }
         
   $downloadLink = "https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie"
   $destinationPath = "$HOME\.aws-lambda-rie\aws-lambda-rie"
   Invoke-WebRequest -Uri $downloadLink -OutFile $destinationPath

   To install the arm64 emulator, replace the $downloadLink with the following:

   https://github.com/aws/aws-lambda-runtime-interface-emulator/releases/latest/download/aws-lambda-rie-arm64

2. Start the Docker image with the docker run command. Note the following:

   • docker-image is the image name and test is the tag.

   • aws_lambda_ric lambda_function.LambdaFunction::Handler.process is the ENTRYPOINT followed by the CMD from your Dockerfile.

   Linux/macOS

   docker run --platform linux/amd64 -d -v ~/.aws-lambda-rie:/aws-lambda -p 9000:8080 \
       --entrypoint /aws-lambda/aws-lambda-rie \
       --read-only \
       docker-image:test \
           aws_lambda_ric lambda_function.LambdaFunction::Handler.process

   PowerShell

   docker run --platform linux/amd64 -d -v "$HOME\.aws-lambda-rie:/aws-lambda" -p 9000:8080 `
   --entrypoint /aws-lambda/aws-lambda-rie `
   --read-only `
   docker-image:test `
       aws_lambda_ric lambda_function.LambdaFunction::Handler.process

   This command runs the image as a container and creates a local endpoint at localhost:9000/2015-03-31/functions/function/invocations.

   Note

   If you built the Docker image for the ARM64 instruction set architecture, be sure to use the --platform linux/arm64 option instead of --platform linux/amd64.

3. Post an event to the local endpoint.

   Linux/macOS

   In Linux and macOS, run the following curl command:

   curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{}'

   This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:

   curl "http://localhost:9000/2015-03-31/functions/function/invocations" -d '{"payload":"hello world!"}'

   PowerShell

   In PowerShell, run the following Invoke-WebRequest command:

   Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{}' -ContentType "application/json"

   This command invokes the function with an empty event and returns a response. If you're using your own function code rather than the sample function code, you might want to invoke the function with a JSON payload. Example:

   Invoke-WebRequest -Uri "http://localhost:9000/2015-03-31/functions/function/invocations" -Method Post -Body '{"payload":"hello world!"}' -ContentType "application/json"

4. Get the container ID.

   docker ps

5. Use the docker kill command to stop the container. In this command, replace 3766c4ab331c with the container ID from the previous step.

   docker kill 3766c4ab331c

Deploying the image

To upload the image to Amazon ECR and create the Lambda function

1. Run the get-login-password command to authenticate the Docker CLI to your Amazon ECR registry.

   • Set the --region value to the AWS Region where you want to create the Amazon ECR repository.

   • Replace 111122223333 with your AWS account ID.

   aws ecr get-login-password --region us-east-1 | docker login --username AWS --password-stdin 111122223333.dkr.ecr.us-east-1.amazonaws.com

2. Create a repository in Amazon ECR using the create-repository command.

   aws ecr create-repository --repository-name hello-world --region us-east-1 --image-scanning-configuration scanOnPush=true --image-tag-mutability MUTABLE

   Note

   The Amazon ECR repository must be in the same AWS Region as the Lambda function.

   If successful, you see a response like this:

   {
       "repository": {
           "repositoryArn": "arn:aws:ecr:us-east-1:111122223333:repository/hello-world",
           "registryId": "111122223333",
           "repositoryName": "hello-world",
           "repositoryUri": "111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world",
           "createdAt": "2023-03-09T10:39:01+00:00",
           "imageTagMutability": "MUTABLE",
           "imageScanningConfiguration": {
               "scanOnPush": true
           },
           "encryptionConfiguration": {
               "encryptionType": "AES256"
           }
       }
   }

3. Copy the repositoryUri from the output in the previous step.

4. Run the docker tag command to tag your local image into your Amazon ECR repository as the latest version. In this command:

   • docker-image:test is the name and tag of your Docker image. This is the image name and tag that you specified in the docker build command.

   • Replace <ECRrepositoryUri> with the repositoryUri that you copied. Make sure to include :latest at the end of the URI.

   docker tag docker-image:test <ECRrepositoryUri>:latest

   Example:

   docker tag docker-image:test 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest

5. Run the docker push command to deploy your local image to the Amazon ECR repository. Make sure to include :latest at the end of the repository URI.

   docker push 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest

6. Create an execution role for the function, if you don't already have one. You need the Amazon Resource Name (ARN) of the role in the next step.

7. Create the Lambda function. For ImageUri, specify the repository URI from earlier. Make sure to include :latest at the end of the URI.

   aws lambda create-function \
     --function-name hello-world \
     --package-type Image \
     --code ImageUri=111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest \
     --role arn:aws:iam::111122223333:role/lambda-ex

   Note

   You can create a function using an image in a different AWS account, as long as the image is in the same Region as the Lambda function. For more information, see Amazon ECR cross-account permissions.

8. Invoke the function.

   aws lambda invoke --function-name hello-world response.json

   You should see a response like this:

   {
     "ExecutedVersion": "$LATEST", 
     "StatusCode": 200
   }

9. To see the output of the function, check the response.json file.

To update the function code, you must build the image again, upload the new image to the Amazon ECR repository, and then use the update-function-code command to deploy the image to the Lambda function.

Lambda resolves the image tag to a specific image digest. This means that if you point the image tag that was used to deploy the function to a new image in Amazon ECR, Lambda doesn't automatically update the function to use the new image.

To deploy the new image to the same Lambda function, you must use the update-function-code command, even if the image tag in Amazon ECR remains the same. In the following example, the --publish option creates a new version of the function using the updated container image.

aws lambda update-function-code \
  --function-name hello-world \
  --image-uri 111122223333.dkr.ecr.us-east-1.amazonaws.com/hello-world:latest \
  --publish