Automatically detect and sync local changes to the AWS Cloud Customize what local changes are synced to the AWS Cloud Prepare your application in the cloud for testing and validation Options for the sam sync command Troubleshooting Examples Learn more

Introduction to using sam sync to sync to AWS Cloud

The AWS Serverless Application Model Command Line Interface (AWS SAM CLI) sam sync command provides options to quickly sync local application changes to the AWS Cloud. Use sam sync when developing your applications to:

Automatically detect and sync local changes to the AWS Cloud.
Customize what local changes are synced to the AWS Cloud.
Prepare your application in the cloud for testing and validation.

With sam sync, you can create a rapid development workflow that shortens the time it takes to sync your local changes to the cloud for testing and validation.

Note

The sam sync command is recommended for development environments. For production environments, we recommend using sam deploy or configuring a continuous integration and delivery (CI/CD) pipeline. To learn more, see Deploy your application and resources with AWS SAM.

The sam sync command is a part of AWS SAM Accelerate. AWS SAM Accelerate provides tools that you can use to speed up the experience of developing and testing serverless applications in the AWS Cloud.

Topics

Automatically detect and sync local changes to the AWS Cloud
Customize what local changes are synced to the AWS Cloud
Prepare your application in the cloud for testing and validation
Options for the sam sync command
Troubleshooting
Examples
Learn more

Automatically detect and sync local changes to the AWS Cloud

Run sam sync with the --watch option to begin syncing your application to the AWS Cloud. This does the following:

Build your application – This process is similar to using the sam build command.
Deploy your application – The AWS SAM CLI deploys your application to AWS CloudFormation using your default settings. The following default values are used:
1. AWS credentials and general configuration settings found in your .aws user folder.
2. Application deployment settings found in your application’s samconfig.toml file.
If default values can’t be found, the AWS SAM CLI will inform you and exit the sync process.
Watch for local changes – The AWS SAM CLI remains running and watches for local changes to your application. This is what the --watch option provides.

This option may be turned on by default. For default values, see your application’s samconfig.toml file. The following is an example file:
```
...
[default.sync]
[default.sync.parameters]
watch = true
...
```
Sync local changes to the AWS Cloud – When you make local changes, the AWS SAM CLI detects and syncs those changes to the AWS Cloud through the quickest method available. Depending on the type of change, the following may occur:
1. If your updated resource supports AWS service APIs, the AWS SAM CLI will use it to deploy your changes. This results in a quick sync to update your resource in the AWS Cloud.
2. If your updated resource doesn’t support AWS service APIs, the AWS SAM CLI will perform an AWS CloudFormation deployment. This updates your entire application in the AWS Cloud. While not as quick, it does prevent you from having to manually initiate a deployment.

Since the sam sync command automatically updates your application in the AWS Cloud, it is recommended for development environments only. When you run sam sync, you will be asked to confirm:

**The sync command should only be used against a development stack**.

Confirm that you are synchronizing a development stack.

Enter Y to proceed with the command, or enter N to cancel:
 [Y/n]: ENTER

Customize what local changes are synced to the AWS Cloud

Provide options to customize what local changes are synced to the AWS Cloud. This can speed up the time it takes to see your local changes in the cloud for testing and validation.

For example, provide the --code option to sync only code changes, such as AWS Lambda function code. During development, if you are focused specifically on Lambda code, this will get your changes into the cloud quickly for testing and validation. The following is an example:


$ sam sync --code --watch

To sync only code changes for a specific Lambda function or layer, use the --resource-id option. The following is an example:


$ sam sync --code --resource-id HelloWorldFunction --resource-id HelloWorldLayer

Prepare your application in the cloud for testing and validation

The sam sync command automatically finds the quickest method available to update your application in the AWS Cloud. This can speed up your development and cloud testing workflows. By utilizing AWS service APIs, you can quickly develop, sync, and test supported resources. For a hands-on example, see Module 6 - AWS SAM Accelerate in The Complete AWS SAM Workshop.

Options for the sam sync command

The following are some of the main options you can use to modify the sam sync command. For a list of all options, see sam sync.

Perform a one-time AWS CloudFormation deployment

Use the --no-watch option to turn off automatic syncing. The following is an example:


$ sam sync --no-watch

The AWS SAM CLI will perform a one-time AWS CloudFormation deployment. This command groups together the actions performed by the sam build and sam deploy commands.

Skip the initial AWS CloudFormation deployment

You can customize whether an AWS CloudFormation deployment is required each time sam sync is run.

Provide --no-skip-deploy-sync to require an AWS CloudFormation deployment each time sam sync is run. This ensures that your local infrastructure is synced to AWS CloudFormation, preventing drift. Using this option does add additional time to your development and testing workflow.
Provide --skip-deploy-sync to make AWS CloudFormation deployment optional. The AWS SAM CLI will compare your local AWS SAM template with your deployed AWS CloudFormation template and will skip the initial AWS CloudFormation deployment if a change isn't detected. Skipping AWS CloudFormation deployment can save you time when syncing local changes to the AWS Cloud.

If no change is detected, the AWS SAM CLI will still perform an AWS CloudFormation deployment in the following scenarios:
- If its been 7 days or more since your last AWS CloudFormation deployment.
- If a large number of Lambda function code changes are detected, making AWS CloudFormation deployment the quickest method to update your application.

The following is an example:


$ sam sync --skip-deploy-sync

Sync a resource from a nested stack

To sync a resource from a nested stack

Provide the root stack using --stack-name.
Identify the resource in the nested stack using the following format: nestedStackId/resourceId.

Provide the resource in the nested stack using --resource-id.

The following is an example:


$ sam sync --code --stack-name sam-app --resource-id myNestedStack/HelloWorldFunction

For more information about creating nested applications, see Reuse code and resources using nested applications in AWS SAM.

Specify a specific AWS CloudFormation stack to update

To specify a specific AWS CloudFormation stack to update, provide the --stack-name option. The following is an example:


$ sam sync --stack-name dev-sam-app

Speed up build times by building your project in the source folder

For supported runtimes and build methods, you can use the --build-in-source option to build your project directly in the source folder. By default, the AWS SAM CLI builds in a temporary directory, which involves copying over source code and project files. With --build-in-source, the AWS SAM CLI builds directly in your source folder, which speeds up the build process by removing the need to copy files to a temporary directory.

For a list of supported runtimes and build methods, see --build-in-source.

Specify files and folders that won't initiate a sync

Use the --watch-exclude option to specify any file or folder that won't initiate a sync when updated. For more information about this option, see --watch-exclude.

The following is an example that excludes the package-lock.json file associated with our HelloWorldFunction function:


$ sam sync --watch --watch-exclude HelloWorldFunction=package-lock.json

When this command is run, the AWS SAM CLI will initiate the sync process. This includes the following:

Run sam build to build your functions and prepare your application for deployment.
Run sam deploy to deploy your application.
Watch for changes to your application.

When we modify the package-lock.json file, the AWS SAM CLI won't initiate a sync. When another file is updated, the AWS SAM CLI will initiate a sync, which will include the package-lock.json file.

The following is an example of specifying a Lambda function of a child stack:


$ sam sync --watch --watch-exclude ChildStackA/MyFunction=database.sqlite3

Troubleshooting

To troubleshoot the AWS SAM CLI, see AWS SAM CLI troubleshooting.

Examples

Using sam sync to update the Hello World application

In this example, we start by initializing the sample Hello World application. To learn more about this application, see Tutorial: Deploy a Hello World application with AWS SAM.

Running sam sync begins the build and deployment process.


$ sam sync
				
The SAM CLI will use the AWS Lambda, Amazon API Gateway, and AWS StepFunctions APIs to upload your code without
performing a CloudFormation deployment. This will cause drift in your CloudFormation stack.
**The sync command should only be used against a development stack**.

Confirm that you are synchronizing a development stack.

Enter Y to proceed with the command, or enter N to cancel:
 [Y/n]:
Queued infra sync. Waiting for in progress code syncs to complete...
Starting infra sync.
Manifest file is changed (new hash: 3298f13049d19cffaa37ca931dd4d421) or dependency folder (.aws-sam/deps/0663e6fe-a888-4efb-b908-e2344261e9c7) is missing for (HelloWorldFunction), downloading dependencies and copying/building source
Building codeuri: /Users/.../Demo/sync/sam-app/hello_world runtime: python3.9 metadata: {} architecture: x86_64 functions: HelloWorldFunction
Running PythonPipBuilder:CleanUp
Running PythonPipBuilder:ResolveDependencies
Running PythonPipBuilder:CopySource

Build Succeeded

Successfully packaged artifacts and wrote output template to file /var/folders/45/5ct135bx3fn2551_ptl5g6_80000gr/T/tmpx_5t4u3f.
Execute the following command to deploy the packaged template
sam deploy --template-file /var/folders/45/5ct135bx3fn2551_ptl5g6_80000gr/T/tmpx_5t4u3f --stack-name <YOUR STACK NAME>


    Deploying with following values
    ===============================
    Stack name                   : sam-app
    Region                       : us-west-2
    Disable rollback             : False
    Deployment s3 bucket         : aws-sam-cli-managed-default-samcliamzn-s3-demo-bucket-1a4x26zbcdkqr
    Capabilities                 : ["CAPABILITY_NAMED_IAM", "CAPABILITY_AUTO_EXPAND"]
    Parameter overrides          : {}
    Signing Profiles             : null

Initiating deployment
=====================


2023-03-17 11:17:19 - Waiting for stack create/update to complete

CloudFormation events from stack operations (refresh every 0.5 seconds)
---------------------------------------------------------------------------------------------------------------------------------------------
ResourceStatus                      ResourceType                        LogicalResourceId                   ResourceStatusReason
---------------------------------------------------------------------------------------------------------------------------------------------
CREATE_IN_PROGRESS                  AWS::CloudFormation::Stack          sam-app                             Transformation succeeded
CREATE_IN_PROGRESS                  AWS::CloudFormation::Stack          AwsSamAutoDependencyLayerNestedSt   -
                                                                        ack
CREATE_IN_PROGRESS                  AWS::IAM::Role                      HelloWorldFunctionRole              -
CREATE_IN_PROGRESS                  AWS::IAM::Role                      HelloWorldFunctionRole              Resource creation Initiated
CREATE_IN_PROGRESS                  AWS::CloudFormation::Stack          AwsSamAutoDependencyLayerNestedSt   Resource creation Initiated
                                                                        ack
CREATE_COMPLETE                     AWS::IAM::Role                      HelloWorldFunctionRole              -
CREATE_COMPLETE                     AWS::CloudFormation::Stack          AwsSamAutoDependencyLayerNestedSt   -
                                                                        ack
CREATE_IN_PROGRESS                  AWS::Lambda::Function               HelloWorldFunction                  -
CREATE_IN_PROGRESS                  AWS::Lambda::Function               HelloWorldFunction                  Resource creation Initiated
CREATE_COMPLETE                     AWS::Lambda::Function               HelloWorldFunction                  -
CREATE_IN_PROGRESS                  AWS::ApiGateway::RestApi            ServerlessRestApi                   -
CREATE_IN_PROGRESS                  AWS::ApiGateway::RestApi            ServerlessRestApi                   Resource creation Initiated
CREATE_COMPLETE                     AWS::ApiGateway::RestApi            ServerlessRestApi                   -
CREATE_IN_PROGRESS                  AWS::ApiGateway::Deployment         ServerlessRestApiDeployment47fc2d   -
                                                                        5f9d
CREATE_IN_PROGRESS                  AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   -
                                                                        ssionProd
CREATE_IN_PROGRESS                  AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   Resource creation Initiated
                                                                        ssionProd
CREATE_IN_PROGRESS                  AWS::ApiGateway::Deployment         ServerlessRestApiDeployment47fc2d   Resource creation Initiated
                                                                        5f9d
CREATE_COMPLETE                     AWS::ApiGateway::Deployment         ServerlessRestApiDeployment47fc2d   -
                                                                        5f9d
CREATE_IN_PROGRESS                  AWS::ApiGateway::Stage              ServerlessRestApiProdStage          -
CREATE_IN_PROGRESS                  AWS::ApiGateway::Stage              ServerlessRestApiProdStage          Resource creation Initiated
CREATE_COMPLETE                     AWS::ApiGateway::Stage              ServerlessRestApiProdStage          -
CREATE_COMPLETE                     AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   -
                                                                        ssionProd
CREATE_COMPLETE                     AWS::CloudFormation::Stack          sam-app                             -
---------------------------------------------------------------------------------------------------------------------------------------------

CloudFormation outputs from deployed stack
----------------------------------------------------------------------------------------------------------------------------------------------
Outputs
----------------------------------------------------------------------------------------------------------------------------------------------
Key                 HelloWorldFunctionIamRole
Description         Implicit IAM Role created for Hello World function
Value               arn:aws:iam::012345678910:role/sam-app-HelloWorldFunctionRole-BUFVMO2PJIYF

Key                 HelloWorldApi
Description         API Gateway endpoint URL for Prod stage for Hello World function
Value               https://pcrx5gdaof.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:sam-app-HelloWorldFunction-2PlN6TPTQoco
----------------------------------------------------------------------------------------------------------------------------------------------
Stack creation succeeded. Sync infra completed.

Infra sync completed.
CodeTrigger not created as CodeUri or DefinitionUri is missing for ServerlessRestApi.

Once deployment is complete, we modify the HelloWorldFunction code. The AWS SAM CLI detects this change and syncs our application to the AWS Cloud. Since AWS Lambda supports AWS service APIs, a quick sync is performed.

Syncing Lambda Function HelloWorldFunction...
Manifest is not changed for (HelloWorldFunction), running incremental build
Building codeuri: /Users/.../Demo/sync/sam-app/hello_world runtime: python3.9 metadata: {} architecture: x86_64 functions: HelloWorldFunction
Running PythonPipBuilder:CopySource
Finished syncing Lambda Function HelloWorldFunction.

Next, we modify our API endpoint in the application’s AWS SAM template. We change /hello to /helloworld.


AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
...
Resources:
  HelloWorldFunction:
    ...
    Properties:
      ...
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /helloworld
            Method: get

Since the Amazon API Gateway resource doesn’t support the AWS service API, the AWS SAM CLI automatically performs an AWS CloudFormation deployment. The following is an example output:


Queued infra sync. Waiting for in progress code syncs to complete...
Starting infra sync.
Manifest is not changed for (HelloWorldFunction), running incremental build
Building codeuri: /Users/.../Demo/sync/sam-app/hello_world runtime: python3.9 metadata: {} architecture: x86_64 functions: HelloWorldFunction
Running PythonPipBuilder:CopySource

Build Succeeded

Successfully packaged artifacts and wrote output template to file /var/folders/45/5ct135bx3fn2551_ptl5g6_80000gr/T/tmpuabo0jb9.
Execute the following command to deploy the packaged template
sam deploy --template-file /var/folders/45/5ct135bx3fn2551_ptl5g6_80000gr/T/tmpuabo0jb9 --stack-name <YOUR STACK NAME>


    Deploying with following values
    ===============================
    Stack name                   : sam-app
    Region                       : us-west-2
    Disable rollback             : False
    Deployment s3 bucket         : aws-sam-cli-managed-default-samcliamzn-s3-demo-bucket-1a4x26zbcdkqr
    Capabilities                 : ["CAPABILITY_NAMED_IAM", "CAPABILITY_AUTO_EXPAND"]
    Parameter overrides          : {}
    Signing Profiles             : null

Initiating deployment
=====================


2023-03-17 14:41:18 - Waiting for stack create/update to complete

CloudFormation events from stack operations (refresh every 0.5 seconds)
---------------------------------------------------------------------------------------------------------------------------------------------
ResourceStatus                      ResourceType                        LogicalResourceId                   ResourceStatusReason
---------------------------------------------------------------------------------------------------------------------------------------------
UPDATE_IN_PROGRESS                  AWS::CloudFormation::Stack          sam-app                             Transformation succeeded
UPDATE_IN_PROGRESS                  AWS::CloudFormation::Stack          AwsSamAutoDependencyLayerNestedSt   -
                                                                        ack
UPDATE_COMPLETE                     AWS::CloudFormation::Stack          AwsSamAutoDependencyLayerNestedSt   -
                                                                        ack
UPDATE_IN_PROGRESS                  AWS::ApiGateway::RestApi            ServerlessRestApi                   -
UPDATE_COMPLETE                     AWS::ApiGateway::RestApi            ServerlessRestApi                   -
CREATE_IN_PROGRESS                  AWS::ApiGateway::Deployment         ServerlessRestApiDeployment8cf30e   -
                                                                        d3cd
UPDATE_IN_PROGRESS                  AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   Requested update requires the
                                                                        ssionProd                           creation of a new physical
                                                                                                            resource; hence creating one.
UPDATE_IN_PROGRESS                  AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   Resource creation Initiated
                                                                        ssionProd
CREATE_IN_PROGRESS                  AWS::ApiGateway::Deployment         ServerlessRestApiDeployment8cf30e   Resource creation Initiated
                                                                        d3cd
CREATE_COMPLETE                     AWS::ApiGateway::Deployment         ServerlessRestApiDeployment8cf30e   -
                                                                        d3cd
UPDATE_IN_PROGRESS                  AWS::ApiGateway::Stage              ServerlessRestApiProdStage          -
UPDATE_COMPLETE                     AWS::ApiGateway::Stage              ServerlessRestApiProdStage          -
UPDATE_COMPLETE                     AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   -
                                                                        ssionProd
UPDATE_COMPLETE_CLEANUP_IN_PROGRE   AWS::CloudFormation::Stack          sam-app                             -
SS
DELETE_IN_PROGRESS                  AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   -
                                                                        ssionProd
DELETE_IN_PROGRESS                  AWS::ApiGateway::Deployment         ServerlessRestApiDeployment47fc2d   -
                                                                        5f9d
DELETE_COMPLETE                     AWS::ApiGateway::Deployment         ServerlessRestApiDeployment47fc2d   -
                                                                        5f9d
UPDATE_COMPLETE                     AWS::CloudFormation::Stack          AwsSamAutoDependencyLayerNestedSt   -
                                                                        ack
DELETE_COMPLETE                     AWS::Lambda::Permission             HelloWorldFunctionHelloWorldPermi   -
                                                                        ssionProd
UPDATE_COMPLETE                     AWS::CloudFormation::Stack          sam-app                             -
---------------------------------------------------------------------------------------------------------------------------------------------

CloudFormation outputs from deployed stack
----------------------------------------------------------------------------------------------------------------------------------------------
Outputs
----------------------------------------------------------------------------------------------------------------------------------------------
Key                 HelloWorldFunctionIamRole
Description         Implicit IAM Role created for Hello World function
Value               arn:aws:iam::012345678910:role/sam-app-HelloWorldFunctionRole-BUFVMO2PJIYF

Key                 HelloWorldApi
Description         API Gateway endpoint URL for Prod stage for Hello World function
Value               https://pcrx5gdaof.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:sam-app-HelloWorldFunction-2PlN6TPTQoco
----------------------------------------------------------------------------------------------------------------------------------------------


Stack update succeeded. Sync infra completed.

Infra sync completed.

Learn more

For a description of all sam sync options, see sam sync.

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