AWS::Serverless::Function - AWS Serverless Application Model
SyntaxPropertiesReturn ValuesExamples

AWS::Serverless::Function

Creates an AWS Lambda function, an AWS Identity and Access Management (IAM) execution role, and event source mappings that trigger the function.

The AWS::Serverless::Function resource also supports the Metadata resource attribute, so you can instruct AWS SAM to build custom runtimes that your application requires. For more information about building custom runtimes, see Building custom runtimes.

Note

When you deploy to AWS CloudFormation, AWS SAM transforms your AWS SAM resources into AWS CloudFormation resources. For more information, see Generated AWS CloudFormation resources.

Syntax

To declare this entity in your AWS Serverless Application Model (AWS SAM) template, use the following syntax.

Properties

Architectures

The instruction set architecture for the function.

For more information about this property, see Lambda instruction set architectures in the AWS Lambda Developer Guide.

Valid values: One of x86_64 or arm64

Type: List

Required: No

Default: x86_64

AWS CloudFormation compatibility: This property is passed directly to the Architectures property of an AWS::Lambda::Function resource.

AssumeRolePolicyDocument

Adds an AssumeRolePolicyDocument for the default created Role for this function. If this property isn't specified, AWS SAM adds a default assume role for this function.

Type: JSON

Required: No

AWS CloudFormation compatibility: This property is similar to the AssumeRolePolicyDocument property of an AWS::IAM::Role resource. AWS SAM adds this property to the generated IAM role for this function. If a role's Amazon Resource Name (ARN) is provided for this function, this property does nothing.

AutoPublishAlias

The name of the Lambda alias. For more information about Lambda aliases, see Lambda function aliases in the AWS Lambda Developer Guide. For examples that use this property, see Deploying serverless applications gradually.

AWS SAM generates AWS::Lambda::Version and AWS::Lambda::Alias resources when this property is set. For information about this scenario, see AutoPublishAlias property is specified. For general information about generated AWS CloudFormation resources, see Generated AWS CloudFormation resources.

Type: String

Required: No

AWS CloudFormation compatibility: This property is unique to AWS SAM and doesn't have an AWS CloudFormation equivalent.

AutoPublishAliasAllProperties

Specifies when a new AWS::Lambda::Version is created. When true, a new Lambda version is created when any property in the Lambda function is modified. When false, a new Lambda version is created only when any of the following properties are modified:

  • Environment, MemorySize, or SnapStart.

  • Any change that results in an update to the Code property, such as CodeDict, ImageUri, or InlineCode.

This property requires AutoPublishAlias to be defined.

If AutoPublishSha256 is also specified, its behavior takes precedence over AutoPublishAliasAllProperties: true.

Type: Boolean

Required: No

Default value: false

AWS CloudFormation compatibility: This property is unique to AWS SAM and doesn't have an AWS CloudFormation equivalent.

AutoPublishCodeSha256

The string value that is used, along with the value in CodeUri, to determine whether a new Lambda version should be published. This property is only used when AutoPublishAlias is also defined.

This property addresses a problem that occurs when an AWS SAM template has the following characteristics: the DeploymentPreference object is configured for gradual deployments (as described in Deploying serverless applications gradually), the AutoPublishAlias property is set and doesn't change between deployments, and the CodeUri property is set and doesn't change between deployments.

This scenario can occur when the deployment package stored in an Amazon Simple Storage Service (Amazon S3) location is replaced by a new deployment package that contains updated Lambda function code, but the CodeUri property remains unchanged (as opposed to the new deployment package being uploaded to a new Amazon S3 location and the CodeUri being changed to the new location).

In this scenario, to trigger the gradual deployment successfully, you must provide a unique value for AutoPublishCodeSha256.

Type: String

Required: No

AWS CloudFormation compatibility: This property is unique to AWS SAM and doesn't have an AWS CloudFormation equivalent.

CodeSigningConfigArn

The ARN of the AWS::Lambda::CodeSigningConfig resource, used to enable code signing for this function. For more information about code signing, see Configuring code signing for AWS SAM applications.

Type: String

Required: No

AWS CloudFormation compatibility: This property is passed directly to the CodeSigningConfigArn property of an AWS::Lambda::Function resource.

CodeUri

The function code's Amazon S3 URI, path to local folder, or FunctionCode object. This property only applies if the PackageType property is set to Zip, otherwise it is ignored.

Notes:

1. If the PackageType property is set to Zip (default), then one of CodeUri or InlineCode is required.

2. If an Amazon S3 URI or FunctionCode object is provided, the Amazon S3 object referenced must be a valid Lambda deployment package.

3. If the path to a local folder is provided, for the code to be transformed properly the template must go through the workflow that includes sam build followed by either sam deploy or sam package. By default, relative paths are resolved with respect to the AWS SAM template's location.

Type: String | FunctionCode

Required: Conditional

AWS CloudFormation compatibility: This property is similar to the Code property of an AWS::Lambda::Function resource. The nested Amazon S3 properties are named differently.

DeadLetterQueue

Configures an Amazon Simple Notification Service (Amazon SNS) topic or Amazon Simple Queue Service (Amazon SQS) queue where Lambda sends events that it can't process. For more information about dead-letter queue functionality, see AWS Lambda function dead letter queues in the AWS Lambda Developer Guide.

Note

If your Lambda function's event source is an Amazon SQS queue, configure a dead-letter queue for the source queue, not for the Lambda function. The dead-letter queue that you configure for a function is used for the function's asynchronous invocation queue, not for event source queues.

Type: Map | DeadLetterQueue

Required: No

AWS CloudFormation compatibility: This property is similar to the DeadLetterConfig property of an AWS::Lambda::Function resource. In AWS CloudFormation the type is derived from the TargetArn, whereas in AWS SAM you must pass the type along with the TargetArn.

DeploymentPreference

The settings to enable gradual Lambda deployments.

If a DeploymentPreference object is specified, AWS SAM creates an AWS::CodeDeploy::Application called ServerlessDeploymentApplication (one per stack), an AWS::CodeDeploy::DeploymentGroup called <function-logical-id>DeploymentGroup, and an AWS::IAM::Role called CodeDeployServiceRole.

Type: DeploymentPreference

Required: No

AWS CloudFormation compatibility: This property is unique to AWS SAM and doesn't have an AWS CloudFormation equivalent.

See also: For more information about this property, see Deploying serverless applications gradually.

Description

A description of the function.

Type: String

Required: No

AWS CloudFormation compatibility: This property is passed directly to the Description property of an AWS::Lambda::Function resource.

Environment

The configuration for the runtime environment.

Type: Environment

Required: No

AWS CloudFormation compatibility: This property is passed directly to the Environment property of an AWS::Lambda::Function resource.

EphemeralStorage

An object that specifies the disk space, in MB, available to your Lambda function in /tmp.

For more information about this property, see Lambda execution environment in the AWS Lambda Developer Guide.

Type: EphemeralStorage

Required: No

AWS CloudFormation compatibility: This property is passed directly to the EphemeralStorage property of an AWS::Lambda::Function resource.

EventInvokeConfig

The object that describes event invoke configuration on a Lambda function.

Type: EventInvokeConfiguration

Required: No

AWS CloudFormation compatibility: This property is unique to AWS SAM and doesn't have an AWS CloudFormation equivalent.

Events

Specifies the events that trigger this function. Events consist of a type and a set of properties that depend on the type.

Type: EventSource

Required: No

AWS CloudFormation compatibility: This property is unique to AWS SAM and doesn't have an AWS CloudFormation equivalent.

FileSystemConfigs

List of FileSystemConfig objects that specify the connection settings for an Amazon Elastic File System (Amazon EFS) file system.

If your template contains an AWS::EFS::MountTarget resource, you must also specify a DependsOn resource attribute to ensure that the mount target is created or updated before the function.

Type: List

Required: No

AWS CloudFormation compatibility: This property is passed directly to the FileSystemConfigs property of an AWS::Lambda::Function resource.

FunctionName

A name for the function. If you don't specify a name, a unique name is generated for you.

Type: String

Required: No

AWS CloudFormation compatibility: This property is passed directly to the FunctionName property of an AWS::Lambda::Function resource.

FunctionUrlConfig

The object that describes a function URL. A function URL is an HTTPS endpoint that you can use to invoke your function.

For more information, see Function URLs in the AWS Lambda Developer Guide.

Type: FunctionUrlConfig

Required: No

AWS CloudFormation compatibility: This property is unique to AWS SAM and doesn't have an AWS CloudFormation equivalent.

Handler

The function within your code that is called to begin execution. This property is only required if the PackageType property is set to Zip.

Type: String

Required: Conditional

AWS CloudFormation compatibility: This property is passed directly to the Handler property of an AWS::Lambda::Function resource.

ImageConfig

The object used to configure Lambda container image settings. For more information, see Using container images with Lambda in the AWS Lambda Developer Guide.

Type: ImageConfig

Required: No

AWS CloudFormation compatibility: This property is passed directly to the ImageConfig property of an AWS::Lambda::Function resource.

ImageUri

The URI of the Amazon Elastic Container Registry (Amazon ECR) repository for the Lambda function's container image. This property only applies if the PackageType property is set to Image, otherwise it is ignored. For more information, see Using container images with Lambda in the AWS Lambda Developer Guide.

Note

If the PackageType property is set to Image, then either ImageUri is required, or you must build your application with necessary Metadata entries in the AWS SAM template file. For more information, see Building applications.

Building your application with necessary Metadata entries takes precedence over ImageUri, so if you specify both then ImageUri is ignored.

Type: String

Required: No

AWS CloudFormation compatibility: This property is passed directly to the ImageUri property of the AWS::Lambda::Function Code data type.

InlineCode

The Lambda function code that is written directly in the template. This property only applies if the PackageType property is set to Zip, otherwise it is ignored.

Note

If the PackageType property is set to Zip (default), then one of CodeUri or InlineCode is required.

Type: String

Required: Conditional

AWS CloudFormation compatibility: This property is passed directly to the ZipFile property of the AWS::Lambda::Function Code data type.

KmsKeyArn

The ARN of an AWS Key Management Service (AWS KMS) key that Lambda uses to encrypt and decrypt your function's environment variables.

Type: String

Required: No

AWS CloudFormation compatibility: This property is passed directly to the KmsKeyArn property of an AWS::Lambda::Function resource.

Layers

The list of LayerVersion ARNs that this function should use. The order specified here is the order in which they will be imported when running the Lambda function.

Type: List

Required: No

AWS CloudFormation compatibility: This property is passed directly to the Layers property of an AWS::Lambda::Function resource.

MemorySize

The size of the memory in MB allocated per invocation of the function.

Type: Integer

Required: No

AWS CloudFormation compatibility: This property is passed directly to the MemorySize property of an AWS::Lambda::Function resource.

PackageType

The deployment package type of the Lambda function. For more information, see Lambda deployment packages in the AWS Lambda Developer Guide.

Notes:

1. If this property is set to Zip (default), then either CodeUri or InlineCode applies, and ImageUri is ignored.

2. If this property is set to Image, then only ImageUri applies, and both CodeUri and InlineCode are ignored. The Amazon ECR repository required to store the functionsl container image can be auto created by the AWS SAM CLI. For more information, see sam deploy.

Valid values: Zip or Image

Type: String

Required: No

Default: Zip

AWS CloudFormation compatibility: This property is passed directly to the PackageType property of an AWS::Lambda::Function resource.

PermissionsBoundary

The ARN of a permissions boundary to use for this function's execution role. This property works only if the role is generated for you.

Type: String

Required: No

AWS CloudFormation compatibility: This property is passed directly to the PermissionsBoundary property of an AWS::IAM::Role resource.

Policies

One or more policies that this function needs. They will be appended to the default role for this function.

This property accepts a single string or a list of strings, and can be the name of AWS managed policies or AWS SAM policy templates, or inline IAM policy documents formatted in YAML.

For more information about AWS managed policies, see AWS managed policies in the IAM User Guide. For more information about AWS SAM policy templates, see AWS SAM policy templates in the AWS Serverless Application Model Developer Guide. For more information about inline policies, see Inline policies in the IAM User Guide.

Note

If the Role property is set, this property is ignored.

Type: String | List | Map

Required: No

AWS CloudFormation compatibility: This property is similar to the Policies property of an AWS::IAM::Role resource. AWS SAM supports AWS managed policy names and AWS SAM policy templates, in addition to JSON policy documents. AWS CloudFormation accepts only JSON policy documents.

ProvisionedConcurrencyConfig

The provisioned concurrency configuration of a function's alias.

Note

ProvisionedConcurrencyConfig can be specified only if the AutoPublishAlias is set. Otherwise, an error results.

Type: ProvisionedConcurrencyConfig

Required: No

AWS CloudFormation compatibility: This property is passed directly to the ProvisionedConcurrencyConfig property of an AWS::Lambda::Alias resource.

ReservedConcurrentExecutions

The maximum number of concurrent executions that you want to reserve for the function.

For more information about this property, see Lambda Function Scaling in the AWS Lambda Developer Guide.

Type: Integer

Required: No

AWS CloudFormation compatibility: This property is passed directly to the ReservedConcurrentExecutions property of an AWS::Lambda::Function resource.

Role

The ARN of an IAM role to use as this function's execution role.

Type: String

Required: No

AWS CloudFormation compatibility: This property is similar to the Role property of an AWS::Lambda::Function resource. This is required in AWS CloudFormation but not in AWS SAM. If a role isn't specified, one is created for you with a logical ID of <function-logical-id>Role.

RolePath

The path to the function's IAM execution role.

Use this property when the role is generated for you. Do not use when the role is specified with the Role property.

Type: String

Required: Conditional

AWS CloudFormation compatibility: This property is passed directly to the Path property of an AWS::IAM::Role resource.

Runtime

The identifier of the function's runtime. This property is only required if the PackageType property is set to Zip.

Note

If you specify the provided identifier for this property, you can use the Metadata resource attribute to instruct AWS SAM to build the custom runtime that this function requires. For more information about building custom runtimes, see Building custom runtimes.

Type: String

Required: Conditional

AWS CloudFormation compatibility: This property is passed directly to the Runtime property of an AWS::Lambda::Function resource.

RuntimeManagementConfig

Configure runtime management options for your Lambda functions such as runtime environment updates, rollback behavior, and selecting a specific runtime version. To learn more, see Lambda runtime updates in the AWS Lambda Developer Guide.

Note

If AutoPublishAlias is configured, RuntimeManagementConfig will apply to both $LATEST and to the newly created version of the function.

Type: RuntimeManagementConfig

Required: No

AWS CloudFormation compatibility: This property is passed directly to the RuntimeManagementConfig property of an AWS::Lambda::Function resource.

SnapStart

Create a snapshot of any new Lambda function version. A snapshot is a cached state of your initialized function, including all of its dependencies. The function is initialized just once and the cached state is reused for all future invocations, improving application performance by reducing the number of times your function must be initialized. To learn more, see Improving startup performance with Lambda SnapStart in the AWS Lambda Developer Guide.

Type: SnapStart

Required: No

AWS CloudFormation compatibility: This property is passed directly to the SnapStart property of an AWS::Lambda::Function resource.

Tags

A map (string to string) that specifies the tags added to this function. For details about valid keys and values for tags, see Tag Key and Value Requirements in the AWS Lambda Developer Guide.

When the stack is created, AWS SAM automatically adds a lambda:createdBy:SAM tag to this Lambda function, and to the default roles that are generated for this function.

Type: Map

Required: No

AWS CloudFormation compatibility: This property is similar to the Tags property of an AWS::Lambda::Function resource. The Tags property in AWS SAM consists of key-value pairs (whereas in AWS CloudFormation this property consists of a list of Tag objects). Also, AWS SAM automatically adds a lambda:createdBy:SAM tag to this Lambda function, and to the default roles that are generated for this function.

Timeout

The maximum time in seconds that the function can run before it is stopped.

Type: Integer

Required: No

Default: 3

AWS CloudFormation compatibility: This property is passed directly to the Timeout property of an AWS::Lambda::Function resource.

Tracing

The string that specifies the function's X-Ray tracing mode. For more information about X-Ray, see Using AWS Lambda with AWS X-Ray in the AWS Lambda Developer Guide.

Valid values: Active or PassThrough

Type: String

Required: No

AWS CloudFormation compatibility: This property is similar to the TracingConfig property of an AWS::Lambda::Function resource. If the Tracing property is set to Active and the Role property is not specified, then AWS SAM adds the arn:aws:iam::aws:policy/AWSXrayWriteOnlyAccess policy to the Lambda execution role that it creates for you.

VersionDescription

Specifies the Description field that is added on the new Lambda version resource.

Type: String

Required: No

AWS CloudFormation compatibility: This property is passed directly to the Description property of an AWS::Lambda::Version resource.

VpcConfig

The configuration that enables this function to access private resources within your virtual private cloud (VPC).

Type: VpcConfig

Required: No

AWS CloudFormation compatibility: This property is passed directly to the VpcConfig property of an AWS::Lambda::Function resource.

Return Values

Ref

When the logical ID of this resource is provided to the Ref intrinsic function, it returns the resource name of the underlying Lambda function.

For more information about using the Ref function, see Ref in the AWS CloudFormation User Guide.

Fn::GetAtt

Fn::GetAtt returns a value for a specified attribute of this type. The following are the available attributes and sample return values.

For more information about using Fn::GetAtt, see Fn::GetAtt in the AWS CloudFormation User Guide.

Arn

The ARN of the underlying Lambda function.

Examples

Simple function

The following is a basic example of an AWS::Serverless::Function resource of package type Zip (default) and function code in an Amazon S3 bucket.

YAML

Type: AWS::Serverless::Function
Properties:
  Handler: index.handler
  Runtime: python3.9
  CodeUri: s3://bucket-name/key-name

Function properties example

The following is an example of an AWS::Serverless::Function of package type Zip (default) that uses InlineCode, Layers, Tracing, Policies, Amazon EFS, and an Api event source.

YAML

Type: AWS::Serverless::Function
DependsOn: MyMountTarget        # This is needed if an AWS::EFS::MountTarget resource is declared for EFS
Properties:
  Handler: index.handler
  Runtime: python3.9
  InlineCode: |
    def handler(event, context):
      print("Hello, world!")
  ReservedConcurrentExecutions: 30
  Layers:
    - Ref: MyLayer
  Tracing: Active
  Timeout: 120
  FileSystemConfigs:
    - Arn: !Ref MyEfsFileSystem
      LocalMountPath: /mnt/EFS
  Policies:
    - AWSLambdaExecute
    - Version: '2012-10-17' 
      Statement:
        - Effect: Allow
          Action:
            - s3:GetObject
            - s3:GetObjectACL
          Resource: 'arn:aws:s3:::my-bucket/*'
  Events:
    ApiEvent:
      Type: Api
      Properties:
        Path: /path
        Method: get

ImageConfig example

The following is an example of an ImageConfig for a Lambda function of package type Image.

YAML

HelloWorldFunction:
  Type: AWS::Serverless::Function
  Properties:
    PackageType: Image
    ImageUri: account-id.dkr.ecr.region.amazonaws.com/ecr-repo-name:image-name
    ImageConfig:
      Command:
        - "app.lambda_handler"
      EntryPoint:
        - "entrypoint1"
      WorkingDirectory: "workDir"

RuntimeManagementConfig examples

A Lambda function configured to update its runtime environment according to current behavior:

TestFunction
  Type: AWS::Serverless::Function
  Properties:
    ...
    Runtime: python3.9
    RuntimeManagementConfig:
      UpdateRuntimeOn: Auto

A Lambda function configured to update its runtime environment when the function is updated:

TestFunction
  Type: AWS::Serverless::Function
  Properties:
    ...
    Runtime: python3.9
    RuntimeManagementConfig:
      UpdateRuntimeOn: FunctionUpdate

A Lambda function configured to update its runtime environment manually:

TestFunction
  Type: AWS::Serverless::Function
  Properties:
    ...
    Runtime: python3.9
    RuntimeManagementConfig:
      RuntimeVersionArn: arn:aws:lambda:us-east-1::runtime:4c459dd0104ee29ec65dcad056c0b3ddbe20d6db76b265ade7eda9a066859b1e
      UpdateRuntimeOn: Manual

SnapStart examples

Example of a Lambda function with SnapStart turned on for future versions:

TestFunc
  Type: AWS::Serverless::Function
  Properties:
    ...
    SnapStart:
      ApplyOn: PublishedVersions