该所有者的项目
(Serverless Step Functions
This is the Serverless Framework plugin for AWS Step Functions.
Requirement
Serverless Framework v2.32.0 or later is required.
TOC
- Install
- Setup
- Current Gotcha
- Events
- API Gateway
- Simple HTTP endpoint
- Custom Step Functions Action
- HTTP Endpoint with custom IAM Role
- Share API Gateway and API Resources
- Enabling CORS
- HTTP Endpoints with AWS_IAM Authorizers
- HTTP Endpoints with Custom Authorizers
- Shared Authorizer
- LAMBDA_PROXY request template
- Customizing request body mapping templates
- Customizing response headers and templates
- Send request to an API
- Setting API keys for your Rest API
- Request Schema Validators
- Schedule
- CloudWatch Event
- API Gateway
- Tags
- Commands
- IAM Role
- Tips
- Sample statemachines setting in serverless.yml
Install
Run npm install in your Serverless project.
$ npm install --save-dev serverless-step-functions
Add the plugin to your serverless.yml file
plugins:
- serverless-step-functions
Setup
Specify your state machine definition using Amazon States Language in a definition statement in serverless.yml. You can use CloudFormation intrinsic functions such as Ref and Fn::GetAtt to reference Lambda functions, SNS topics, SQS queues and DynamoDB tables declared in the same serverless.yml. Since Ref returns different things (ARN, ID, resource name, etc.) depending on the type of CloudFormation resource, please refer to this page to see whether you need to use Ref or Fn::GetAtt.
Alternatively, you can also provide the raw ARN, or SQS queue URL, or DynamoDB table name as a string. If you need to construct the ARN by hand, then we recommend to use the serverless-pseudo-parameters plugin together to make your life easier.
In addition, if you want to reference a DynamoDB table managed by an external CloudFormation Stack, as long as that table name is exported as an output from that stack, it can be referenced by importing it using Fn::ImportValue. See the ddbtablestepfunc Step Function definition below for an example.
functions:
hello:
handler: handler.hello
stepFunctions:
stateMachines:
hellostepfunc1:
events:
- http:
path: gofunction
method: GET
- schedule:
rate: rate(10 minutes)
enabled: true
input:
key1: value1
key2: value2
stageParams:
stage: dev
name: myStateMachine
definition:
Comment: "A Hello World example of the Amazon States Language using an AWS Lambda Function"
StartAt: HelloWorld1
States:
HelloWorld1:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
End: true
dependsOn: CustomIamRole
tags:
Team: Atlantis
alarms:
topics:
ok: arn:aws:sns:us-east-1:1234567890:NotifyMe
alarm: arn:aws:sns:us-east-1:1234567890:NotifyMe
insufficientData: arn:aws:sns:us-east-1:1234567890:NotifyMe
metrics:
- executionsTimedOut
- executionsFailed
- executionsAborted
- metric: executionThrottled
treatMissingData: breaching # overrides below default
- executionsSucceeded
treatMissingData: ignore # optional
hellostepfunc2:
definition:
StartAt: HelloWorld2
States:
HelloWorld2:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
End: true
ddbtablestepfunc:
definition:
Comment: Demonstrates how to reference a DynamoDB Table Name exported from an external CloudFormation Stack
StartAt: ImportDDBTableName
States:
ImportDDBTableName:
Type: Task
Resource: "arn:aws:states:::dynamodb:updateItem"
Parameters:
TableName:
Fn::ImportValue: MyExternalStack:ToDoTable:Name # imports a table name from an external stack
Key:
id:
S.$: "$.todoId"
UpdateExpression: "SET #status = :updatedStatus"
ExpressionAttributeNames:
"#status": status
ExpressionAttributeValues:
":updatedStatus":
S: DONE
End: true
dependsOn:
- DynamoDBTable
- KinesisStream
- CustomIamRole
tags:
Team: Atlantis
activities:
- myTask
- yourTask
validate: true # enable pre-deployment definition validation (disabled by default)
plugins:
- serverless-step-functions
- serverless-pseudo-parameters
In the example above, notice that we used Fn::GetAtt: [hello, Arn] to get the ARN for the hello function defined earlier. This means you don't have to know how the Serverless framework converts these local names to CloudFormation logical IDs (e.g. hello-world becomes HelloDashworldLambdaFunction).
However, if you prefer to work with logical IDs, you can. You can also express the above Fn::GetAtt function as Fn::GetAtt: [HelloLambdaFunction, Arn]. If you're unfamiliar with the convention the Serverless framework uses, then the easiest thing to do is to first run sls package then look in the .serverless folder for the generated CloudFormation template. Here you can find the logical resource names for the functions you want to reference.
Adding a custom name for a stateMachine
In case you need to interpolate a specific stage or service layer variable as the
stateMachines name you can add a name property to your yaml.
service: messager
functions:
sendMessage:
handler: handler.sendMessage
stepFunctions:
stateMachines:
sendMessageFunc:
name: sendMessageFunc-${self:custom.service}-${opt:stage}
definition:
<your definition>
plugins:
- serverless-step-functions
Adding a custom logical id for a stateMachine
You can use a custom logical id that is only unique within the stack as opposed to the name that needs to be unique globally. This can make referencing the state machine easier/simpler because you don't have to duplicate the interpolation logic everywhere you reference the state machine.
service: messager
functions:
sendMessage:
handler: handler.sendMessage
stepFunctions:
stateMachines:
sendMessageFunc:
id: SendMessageStateMachine
name: sendMessageFunc-${self:custom.service}-${opt:stage}
definition:
<your definition>
plugins:
- serverless-step-functions
You can then Ref: SendMessageStateMachine in various parts of CloudFormation or serverless.yml
Depending on another logical id
If your state machine depends on another resource defined in your serverless.yml then you can add a dependsOn field to the state machine definition. This would add the DependsOnclause to the generated CloudFormation template.
This dependsOn field can be either a string, or an array of strings.
stepFunctions:
stateMachines:
myStateMachine:
dependsOn: myDB
myOtherStateMachine:
dependsOn:
- myOtherDB
- myStream
Adding retain property for a stateMachine
There are some practical cases when you would like to prevent state machine from deletion on stack delete or update. This can be achieved by adding retain property to the state machine section.
stepFunctions:
stateMachines:
myStateMachine:
retain: true
Configuring in such way adds "DeletionPolicy" : "Retain" to the state machine within CloudFormation template.
CloudWatch Alarms
It's common practice to want to monitor the health of your state machines and be alerted when something goes wrong. You can either:
- do this using the serverless-plugin-aws-alerts, which lets you configure custom CloudWatch Alarms against the various metrics that Step Functions publishes.
- or, you can use the built-in
alarmsconfiguration from this plugin, which gives you an opinionated set of default alarms (see below)
stepFunctions:
stateMachines:
myStateMachine:
alarms:
topics:
ok: arn:aws:sns:us-east-1:1234567890:NotifyMe
alarm: arn:aws:sns:us-east-1:1234567890:NotifyMe
insufficientData: arn:aws:sns:us-east-1:1234567890:NotifyMe
metrics:
- executionsTimedOut
- executionsFailed
- executionsAborted
- executionThrottled
- executionsSucceeded
treatMissingData: missing
Both topics and metrics are required properties. There are 4 supported metrics, each map to the CloudWatch Metrics that Step Functions publishes for your executions.
You can configure how the CloudWatch Alarms should treat missing data:
missing(AWS default): The alarm does not consider missing data points when evaluating whether to change state.ignore: The current alarm state is maintained.breaching: Missing data points are treated as breaching the threshold.notBreaching: Missing data points are treated as being within the threshold.
For more information, please refer to the official documentation.
The generated CloudWatch alarms would have the following configurations:
namespace: 'AWS/States'
metric: <ExecutionsTimedOut | ExecutionsFailed | ExecutionsAborted | ExecutionThrottled>
threshold: 1
period: 60
evaluationPeriods: 1
ComparisonOperator: GreaterThanOrEqualToThreshold
Statistic: Sum
treatMissingData: <missing (default) | ignore | breaching | notBreaching>
Dimensions:
- Name: StateMachineArn
Value: <ArnOfTheStateMachine>
You can also override the default treatMissingData setting for a particular alarm by specifying an override:
alarms:
topics:
ok: arn:aws:sns:us-east-1:1234567890:NotifyMe
alarm: arn:aws:sns:us-east-1:1234567890:NotifyMe
insufficientData: arn:aws:sns:us-east-1:1234567890:NotifyMe
metrics:
- executionsTimedOut
- executionsFailed
- executionsAborted
- metric: executionThrottled
treatMissingData: breaching # override
- executionsSucceeded
treatMissingData: ignore # default
Custom CloudWatch Alarm names
By default, the CloudFormation assigns names to the alarms based on the CloudFormation stack and the resource logical Id, and in some cases and these names could be confusing.
To use custom names to the alarms add nameTemplate property in the alarms object.
example:
service: myservice
plugins:
- serverless-step-functions
stepFunctions:
stateMachines:
main-workflow:
name: main
alarms:
nameTemplate: $[stateMachineName]-$[cloudWatchMetricName]-alarm
topics:
alarm: !Ref AwsAlertsGenericAlarmTopicAlarm
metrics:
- executionsFailed
- executionsAborted
- executionsTimedOut
- executionThrottled
treatMissingData: ignore
definition: ${file(./step-functions/main.asl.yaml)}
Supported variables to the nameTemplate property:
stateMachineNamemetricNamecloudWatchMetricName
Per-Metric Alarm Name
To overwrite the alarm name for a specific metric, add the alarmName property in the metric object.
service: myservice
plugins:
- serverless-step-functions
stepFunctions:
stateMachines:
main-workflow:
name: main
alarms:
nameTemplate: $[stateMachineName]-$[cloudWatchMetricName]-alarm
topics:
alarm: !Ref AwsAlertsGenericAlarmTopicAlarm
metrics:
- metric: executionsFailed
alarmName: mycustom-name-${self:stage.region}-Failed-alarm
- executionsAborted
- executionsTimedOut
- executionThrottled
treatMissingData: ignore
definition: ${file(./step-functions/main.asl.yaml)}
CloudWatch Notifications
You can monitor the execution state of your state machines via CloudWatch Events. It allows you to be alerted when the status of your state machine changes to ABORTED, FAILED, RUNNING, SUCCEEDED or TIMED_OUT.
You can configure CloudWatch Events to send notification to a number of targets. Currently this plugin supports sns, sqs, kinesis, firehose, lambda and stepFunctions.
To configure status change notifications to your state machine, you can add a notifications like below:
stepFunctions:
stateMachines:
hellostepfunc1:
name: test
definition:
...
notifications:
ABORTED:
- sns: SNS_TOPIC_ARN
- sqs: SQS_TOPIC_ARN
- sqs: # for FIFO queues, which requires you to configure the message group ID
arn: SQS_TOPIC_ARN
messageGroupId: 12345
- lambda: LAMBDA_FUNCTION_ARN
- kinesis: KINESIS_STREAM_ARN
- kinesis:
arn: KINESIS_STREAM_ARN
partitionKeyPath: $.id # used to choose the parition key from payload
- firehose: FIREHOSE_STREAM_ARN
- stepFunctions: STATE_MACHINE_ARN
FAILED:
... # same as above
... # other status
As you can see from the above example, you can configure different notification targets for each type of status change. If you want to configure the same targets for multiple status changes, then consider using YML anchors to keep your YML succinct.
CloudFormation intrinsic functions such as Ref and Fn::GetAtt are supported.
When setting up a notification target against a FIFO SQS queue, the queue must enable the content-based deduplication option and you must configure the messageGroupId.
Blue green deployment
To implement a blue-green deployment with Step Functions you need to reference the exact versions of the functions.
To do this, you can specify useExactVersion: true in the state machine.
stepFunctions:
stateMachines:
hellostepfunc1:
useExactVersion: true
definition:
...
Pre-deployment validation
By default, your state machine definition will be validated during deployment by StepFunctions. This can be cumbersome when developing because you have to upload your service for every typo in your definition. In order to go faster, you can enable pre-deployment validation using asl-validator which should detect most of the issues (like a missing state property).
stepFunctions:
validate: true
Disable Output Cloudformation Outputs section
Disables the generation of outputs in the CloudFormation Outputs section. If you define many state machines in serverless.yml you may reach the CloudFormation limit of 60 outputs. If you define noOutput: true then this plugin will not generate outputs automatically.
stepFunctions:
noOutput: true
Express Workflow
At re:invent 2019, AWS introduced Express Workflows as a cheaper, more scalable alternative (but with a cut-down set of features). See this page for differences between standard and express workflows.
To declare an express workflow, specify type as EXPRESS and you can specify the logging configuration:
stepFunctions:
stateMachines:
hellostepfunc1:
type: EXPRESS
loggingConfig:
level: ERROR
includeExecutionData: true
destinations:
- Fn::GetAtt: [MyLogGroup, Arn]
CloudWatch Logs
You can enable CloudWatch Logs for standard Step Functions, the syntax is
exactly like with Express Workflows.
stepFunctions:
stateMachines:
hellostepfunc1:
loggingConfig:
level: ERROR
includeExecutionData: true
destinations:
- Fn::GetAtt: [MyLogGroup, Arn]
X-Ray
You can enable X-Ray for your state machine, specify tracingConfig as shown below.
stepFunctions:
stateMachines:
hellostepfunc1:
tracingConfig:
enabled: true
Current Gotcha
Please keep this gotcha in mind if you want to reference the name from the resources section. To generate Logical ID for CloudFormation, the plugin transforms the specified name in serverless.yml based on the following scheme.
- Transform a leading character into uppercase
- Transform
-into Dash - Transform
_into Underscore
If you want to use variables system in name statement, you can't put the variables as a prefix like this:${self:service}-${opt:stage}-myStateMachine since the variables are transformed within Output section, as a result, the reference will be broken.
The correct sample is here.
stepFunctions:
stateMachines:
myStateMachine:
name: myStateMachine-${self:service}-${opt:stage}
...
resources:
Outputs:
myStateMachine:
Value:
Ref: MyStateMachineDash${self:service}Dash${opt:stage}
Events
API Gateway
To create HTTP endpoints as Event sources for your StepFunctions statemachine
Simple HTTP Endpoint
This setup specifies that the hello state machine should be run when someone accesses the API gateway at hello via a GET request.
Here's an example:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: hello
method: GET
definition:
Here You can define an POST endpoint for the path posts/create.
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
definition:
Custom Step Functions Action
Step Functions have custom actions like DescribeExecution or StopExecution to fetch and control them. You can use custom actions like this:
stepFunctions:
stateMachines:
start:
events:
- http:
path: action/start
method: POST
definition:
...
status:
events:
- http:
path: action/status
method: POST
action: DescribeExecution
definition:
...
stop:
events:
- http:
path: action/stop
method: POST
action: StopExecution
definition:
...
Request template is not used when action is set because there're a bunch of actions. However if you want to use request template you can use Customizing request body mapping templates.
HTTP Endpoint with custom IAM Role
The plugin would generate an IAM Role for you by default. However, if you wish to use an IAM role that you have provisioned separately, then you can override the IAM Role like this:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
iamRole: arn:aws:iam::<accountId>:role/<roleName>
definition:
Share API Gateway and API Resources
You can share the same API Gateway between multiple projects by referencing its REST API ID and Root Resource ID in serverless.yml as follows:
service: service-name
provider:
name: aws
apiGateway:
# REST API resource ID. Default is generated by the framework
restApiId: xxxxxxxxxx
# Root resource, represent as / path
restApiRootResourceId: xxxxxxxxxx
functions:
...
If your application has many nested paths, you might also want to break them out into smaller services.
However, Cloudformation will throw an error if we try to generate an existing path resource. To avoid that, we reference the resource ID:
service: service-a
provider:
apiGateway:
restApiId: xxxxxxxxxx
restApiRootResourceId: xxxxxxxxxx
# List of existing resources that were created in the REST API. This is required or the stack will be conflicted
restApiResources:
/users: xxxxxxxxxx
functions:
...
Now we can define endpoints using existing API Gateway ressources
stepFunctions:
stateMachines:
hello:
events:
- http:
path: users/create
method: POST
Enabling CORS
To set CORS configurations for your HTTP endpoints, simply modify your event configurations as follows:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
cors: true
definition:
Setting cors to true assumes a default configuration which is equivalent to:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
cors:
origin: '*'
headers:
- Content-Type
- X-Amz-Date
- Authorization
- X-Api-Key
- X-Amz-Security-Token
- X-Amz-User-Agent
allowCredentials: false
definition:
Configuring the cors property sets Access-Control-Allow-Origin, Access-Control-Allow-Headers, Access-Control-Allow-Methods,Access-Control-Allow-Credentials headers in the CORS preflight response.
To enable the Access-Control-Max-Age preflight response header, set the maxAge property in the cors object:
stepFunctions:
stateMachines:
SfnApiGateway:
events:
- http:
path: /playground/start
method: post
cors:
origin: '*'
maxAge: 86400
HTTP Endpoints with AWS_IAM Authorizers
If you want to require that the caller submit the IAM user's access keys in order to be authenticated to invoke your Lambda Function, set the authorizer to AWS_IAM as shown in the following example:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
authorizer: aws_iam
definition:
HTTP Endpoints with Custom Authorizers
Custom Authorizers allow you to run an AWS Lambda Function before your targeted AWS Lambda Function. This is useful for Microservice Architectures or when you simply want to do some Authorization before running your business logic.
You can enable Custom Authorizers for your HTTP endpoint by setting the Authorizer in your http event to another function in the same service, as shown in the following example:
stepFunctions:
stateMachines:
hello:
- http:
path: posts/create
method: post
authorizer: authorizerFunc
definition:
If the Authorizer function does not exist in your service but exists in AWS, you can provide the ARN of the Lambda function instead of the function name, as shown in the following example:
stepFunctions:
stateMachines:
hello:
- http:
path: posts/create
method: post
authorizer: xxx:xxx:Lambda-Name
definition:
Shared Authorizer
Auto-created Authorizer is convenient for conventional setup. However, when you need to define your custom Authorizer, or use COGNITO_USER_POOLS authorizer with shared API Gateway, it is painful because of AWS limitation. Sharing Authorizer is a better way to do.
stepFunctions:
stateMachines:
createUser:
...
events:
- http:
path: /users
...
authorizer:
# Provide both type and authorizerId
type: COGNITO_USER_POOLS # TOKEN, CUSTOM or COGNITO_USER_POOLS, same as AWS Cloudformation documentation
authorizerId:
Ref: ApiGatewayAuthorizer # or hard-code Authorizer ID
# [Optional] you can also specify the OAuth scopes for Cognito
scopes:
- scope1
...
LAMBDA_PROXY request template
The plugin generates default body mapping templates for application/json and application/x-www-form-urlencoded content types. The default template would pass the request body as input to the state machine. If you need access to other contextual information about the HTTP request such as headers, path parameters, etc. then you can also use the lambda_proxy request template like this:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
request:
template: lambda_proxy
This would generate the normal LAMBDA_PROXY template used for API Gateway integration with Lambda functions.
Customizing request body mapping templates
If you'd like to add content types or customize the default templates, you can do so by including your custom API Gateway request mapping template in serverless.yml like so:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
request:
template:
application/json: |
#set( $body = $util.escapeJavaScript($input.json('$')) )
#set( $name = $util.escapeJavaScript($input.json('$.data.attributes.order_id')) )
{
"input": "$body",
"name": "$name",
"stateMachineArn":"arn:aws:states:#{AWS::Region}:#{AWS::AccountId}:stateMachine:processOrderFlow-${opt:stage}"
}
name: processOrderFlow-${opt:stage}
definition:
Customizing response headers and templates
If you'd like to add custom headers in the HTTP response, or customize the default response template (which just returns the response from Step Function's StartExecution API), then you can do so by including your custom headers and API Gateway response mapping template in serverless.yml like so:
stepFunctions:
stateMachines:
hello:
events:
- http:
path: posts/create
method: POST
response:
headers:
Content-Type: "'application/json'"
X-Application-Id: "'my-app'"
template:
application/json: |
{
"status": 200,
"info": "OK"
}
definition:
Send request to an API
You can input an value as json in request body, the value is passed as the input value of your statemachine
$ curl -XPOST https://xxxxxxxxx.execute-api.us-east-1.amazonaws.com/dev/posts/create -d '{"foo":"bar"}'
Setting API keys for your Rest API
You can specify a list of API keys to be used by your service Rest API by adding an apiKeys array property to the apiGateway subsection of the provider object in serverless.yml. You'll also need to explicitly specify which endpoints are private and require one of the api keys to be included in the request by adding a private boolean property to the http event object you want to set as private. API Keys are created globally, so if you want to deploy your service to different stages make sure your API key contains a stage variable as defined below. When using API keys, you can optionally define usage plan quota and throttle, using usagePlan object.
Here's an example configuration for setting API keys for your service Rest API:
service: my-service
provider:
name: aws
apiGateway:
apiKeys:
- myFirstKey
- ${opt:stage}-myFirstKey
- ${env:MY_API_KEY} # you can hide it in a serverless variable
usagePlan:
quota:
limit: 5000
offset: 2
period: MONTH
throttle:
burstLimit: 200
rateLimit: 100
functions:
hello:
handler: handler.hello
stepFunctions:
stateMachines:
statemachine1:
name: ${self:service}-${opt:stage}-statemachine1
events:
- http:
path: /hello
method: post
private: true
definition:
Comment: "A Hello World example of the Amazon States Language using an AWS Lambda Function"
StartAt: HelloWorld1
States:
HelloWorld1:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
End: true
plugins:
- serverless-step-functions
- serverless-pseudo-parameters
Please note that those are the API keys names, not the actual values. Once you deploy your service, the value of those API keys will be auto generated by AWS and printed on the screen for you to use. The values can be concealed from the output with the --conceal deploy option.
Clients connecting to this Rest API will then need to set any of these API keys values in the x-api-key header of their request. This is only necessary for functions where the private property is set to true.
Request Schema Validators
To use request schema validation with API gateway, add the JSON Schema for your content type. Since JSON Schema is represented in JSON, it's easier to include it from a file.
stepFunctions:
stateMachines:
create:
events:
- http:
path: posts/create
method: post
request:
schemas:
application/json: ${file(create_request.json)}
In addition, you can also customize created model with name and description properties.
stepFunctions:
stateMachines:
create:
events:
- http:
path: posts/create
method: post
request:
schemas:
application/json:
schema: ${file(create_request.json)}
name: PostCreateModel
description: 'Validation model for Creating Posts'
To reuse the same model across different events, you can define global models on provider level. In order to define global model you need to add its configuration to provider.apiGateway.request.schemas. After defining a global model, you can use it in the event by referencing it by the key. Provider models are created for application/json content type.
provider:
...
apiGateway:
request:
schemas:
post-create-model:
name: PostCreateModel
schema: ${file(api_schema/post_add_schema.json)}
description: "A Model validation for adding posts"
stepFunctions:
stateMachines:
create:
events:
- http:
path: posts/create
method: post
request:
schemas:
application/json: post-create-model
A sample schema contained in create_request.json might look something like this:
{
"definitions": {},
"$schema": "http://json-schema.org/draft-04/schema#",
"type": "object",
"title": "The Root Schema",
"required": ["username"],
"properties": {
"username": {
"type": "string",
"title": "The Foo Schema",
"default": "",
"pattern": "^[a-zA-Z0-9]+$"
}
}
}
NOTE: schema validators are only applied to content types you specify. Other content types are not blocked. Currently, API Gateway supports JSON Schema draft-04.
Schedule
The following config will attach a schedule event and causes the stateMachine crawl to be called every 2 hours. The configuration allows you to attach multiple schedules to the same stateMachine. You can either use the rate or cron syntax. Take a look at the AWS schedule syntax documentation for more details.
stepFunctions:
stateMachines:
crawl:
events:
- schedule: rate(2 hours)
- schedule: cron(0 12 * * ? *)
definition:
Enabling / Disabling
Note: schedule events are enabled by default.
This will create and attach a schedule event for the aggregate stateMachine which is disabled. If enabled it will call
the aggregate stateMachine every 10 minutes.
stepFunctions:
stateMachines:
aggregate:
events:
- schedule:
rate: rate(10 minutes)
enabled: false
input:
key1: value1
key2: value2
stageParams:
stage: dev
- schedule:
rate: cron(0 12 * * ? *)
enabled: false
inputPath: '$.stageVariables'
Specify Name and Description
Name and Description can be specified for a schedule event. These are not required properties.
events:
- schedule:
name: your-scheduled-rate-event-name
description: 'your scheduled rate event description'
rate: rate(2 hours)
Scheduled Events IAM Role
By default, the plugin will create a new IAM role that allows AWS Events to start your state machine. Note that this role is different than the role assumed by the state machine. You can specify your own role instead (it must allow events.amazonaws.com to assume it, and it must be able to run states:StartExecution on your state machine):
events:
- schedule:
rate: rate(2 hours)
role: arn:aws:iam::xxxxxxxx:role/yourRole
Specify InputTransformer
You can specify input values to the Lambda function.
stepFunctions:
stateMachines:
stateMachineScheduled:
events:
- schedule:
rate: cron(30 12 ? * 1-5 *)
inputTransformer:
inputPathsMap:
time: '$.time'
stage: '$.stageVariables'
inputTemplate: '{"time": <time>, "stage" : <stage> }'
definition:
...
Use EventBridge Scheduler instead of EventBridge rules
AWS has account-wide limits on the number of AWS::Event::Rule triggers per bus (300 events), and all Lambda schedules go into a single bus with no way to override it. This can lead to a situation where large projects hit the limit with no ability to schedule more events.
However, AWS::Scheduler::Schedule has much higher limits (1,000,000 events), and is configured identically. method can be set in order to migrate to this trigger type seamlessly. It also allows you to specify a timezone to run your event based on local time.
stepFunctions:
stateMachines:
stateMachineScheduled:
events:
- schedule:
method: scheduler
rate: cron(30 12 ? * 1-5 *)
enabled: true
timezone: America/New_York
definition:
...
CloudWatch Event / EventBridge
Simple event definition
This will enable your Statemachine to be called by an EC2 event rule.
Please check the page of Event Types for CloudWatch Events.
stepFunctions:
stateMachines:
first:
events:
- cloudwatchEvent:
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
definition:
...
You can alternatively use EventBridge:
stepFunctions:
stateMachines:
first:
events:
- eventBridge:
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
definition:
...
All the configurations in this section applies to both cloudwatchEvent and eventBridge.
Enabling / Disabling
Note: cloudwatchEvent and eventBridge events are enabled by default.
This will create and attach a disabled cloudwatchEvent event for the myCloudWatch statemachine.
stepFunctions:
stateMachines:
cloudwatchEvent:
events:
- cloudwatchEvent:
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
enabled: false
definition:
...
Specify Input or Inputpath or InputTransformer
You can specify input values to the Lambda function.
stepFunctions:
stateMachines:
cloudwatchEvent:
events:
- cloudwatchEvent:
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
input:
key1: value1
key2: value2
stageParams:
stage: dev
- cloudwatchEvent:
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
inputPath: '$.stageVariables'
- cloudwatchEvent:
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
inputTransformer:
inputPathsMap:
stage: '$.stageVariables'
inputTemplate: '{ "stage": <stage> }'
definition:
...
Specifying a Description
You can also specify a CloudWatch Event description.
stepFunctions:
stateMachines:
cloudwatchEvent:
events:
- cloudwatchEvent:
description: 'CloudWatch Event triggered on EC2 Instance pending state'
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
definition:
...
Specifying a Name
You can also specify a CloudWatch Event name. Keep in mind that the name must begin with a letter; contain only ASCII letters, digits, and hyphens; and not end with a hyphen or contain two consecutive hyphens. More infomation here.
stepFunctions:
stateMachines:
cloudwatchEvent:
events:
- cloudwatchEvent:
name: 'my-cloudwatch-event-name'
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
definition:
...
Specifying a RoleArn
You can also specify a CloudWatch Event RoleArn.
The Amazon Resource Name (ARN) of the role that is used for target invocation.
Required: No
stepFunctions:
stateMachines:
cloudwatchEvent:
events:
- cloudwatchEvent:
name: 'my-cloudwatch-event-name'
iamRole: 'arn:aws:iam::012345678910:role/Events-InvokeStepFunctions-Role'
event:
source:
- "aws.ec2"
detail-type:
- "EC2 Instance State-change Notification"
detail:
state:
- pending
definition:
...
Specifying a custom CloudWatch EventBus
You can choose which CloudWatch Event bus:
stepFunctions:
stateMachines:
exampleCloudwatchEventStartsMachine:
events:
- cloudwatchEvent:
eventBusName: 'my-custom-event-bus'
event:
source:
- "my.custom.source"
detail-type:
- "My Event Type"
detail:
state:
- pending
definition:
...
Specifying a custom EventBridge EventBus
You can choose which EventBridge Event bus:
stepFunctions:
stateMachines:
exampleEventBridgeEventStartsMachine:
events:
- eventBridge:
eventBusName: 'my-custom-event-bus'
event:
source:
- "my.custom.source"
detail-type:
- "My Event Type"
detail:
state:
- pending
definition:
...
Specifying a DeadLetterQueue
You can configure a target queue to send dead-letter queue events to:
stepFunctions:
stateMachines:
exampleEventBridgeEventStartsMachine:
events:
- eventBridge:
eventBusName: 'my-custom-event-bus'
event:
source:
- "my.custom.source"
detail-type:
- "My Event Type"
detail:
state:
- pending
deadLetterConfig: 'arn:aws:sqs:us-east-1:012345678910:my-dlq' # SQS Arn
definition:
...
Important point
Don't forget to Grant permissions to the dead-letter queue, to do that you may need to have the ARN of the generated EventBridge Rule.
In order to get the ARN you can use intrinsic functions against the logicalId, this plugin generates logicalIds following this format:
`${StateMachineName}EventsRuleCloudWatchEvent${index}`
Given this example 👇
stepFunctions:
stateMachines:
hellostepfunc1: # <---- StateMachineName
events:
- eventBridge:
eventBusName: 'my-custom-event-bus'
event:
source:
- "my.custom.source"
- eventBridge:
eventBusName: 'my-custom-event-bus'
event:
source:
- "my.custom.source"
deadLetterConfig: 'arn:aws:sqs:us-east-1:012345678910:my-dlq'
name: myStateMachine
definition:
Comment: "A Hello World example of the Amazon States Language using an AWS Lambda Function"
StartAt: HelloWorld1
States:
HelloWorld1:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
End: true
Then
# to get the Arn of the 1st EventBridge rule
!GetAtt Hellostepfunc1EventsRuleCloudWatchEvent1.Arn
# to get the Arn of the 2nd EventBridge rule
!GetAtt Hellostepfunc1EventsRuleCloudWatchEvent2.Arn
Tags
You can specify tags on each state machine. Additionally any global tags (specified under provider section in your serverless.yml) would be merged in as well.
If you don't want for global tags to be merged into your state machine, you can include the inheritGlobalTags property for your state machine.
provider:
tags:
app: myApp
department: engineering
stepFunctions:
stateMachines:
hellostepfunc1:
name: myStateMachine
inheritGlobalTags: false
tags:
score: 42
definition: something
As a result, hellostepfunc1 will only have the tag of score: 42, and not the tags at the provider level
Commands
deploy
Run sls deploy, the defined Stepfunctions are deployed.
invoke
$ sls invoke stepf --name <stepfunctionname> --data '{"foo":"bar"}'
options
- --name or -n The name of the step function in your service that you want to invoke. Required.
- --stage or -s The stage in your service you want to invoke your step function.
- --region or -r The region in your stage that you want to invoke your step function.
- --data or -d String data to be passed as an event to your step function.
- --path or -p The path to a json file with input data to be passed to the invoked step function.
IAM Role
The IAM roles required to run Statemachine are automatically generated for each state machine in the serverless.yml, with the IAM role name of StatesExecutionPolicy-<environment>. These roles are tailored to the services that the state machine integrates with, for example with Lambda the InvokeFunction is applied. You can also specify a custom ARN directly to the step functions lambda.
Here's an example:
stepFunctions:
stateMachines:
hello:
role: arn:aws:iam::xxxxxxxx:role/yourRole
definition:
It is also possible to use the CloudFormation intrinsic functions to reference resources from elsewhere. This allows for an IAM role to be created, and applied to the state machines all within the serverless file.
The below example shows the policy needed if your step function needs the ability to send a message to an sqs queue. To apply the role either the RoleName can be used as a reference in the state machine, or the role ARN can be used like in the example above. It is important to note that if you want to store your state machine role at a certain path, this must be specified on the Path property on the new role.
stepFunctions:
stateMachines:
hello:
role:
Fn::GetAtt: ["StateMachineRole", "Arn"]
definition:
...
resources:
Resources:
StateMachineRole:
Type: AWS::IAM::Role
Properties:
RoleName: RoleName
Path: /path_of_state_machine_roles/
AssumeRolePolicyDocument:
Statement:
- Effect: Allow
Principal:
Service:
- states.amazonaws.com
Action:
- sts:AssumeRole
Policies:
- PolicyName: statePolicy
PolicyDocument:
Version: "2012-10-17"
Statement:
- Effect: Allow
Action:
- lambda:InvokeFunction
Resource:
- arn:aws:lambda:lambdaName
- Effect: Allow
Action:
- sqs:SendMessage
Resource:
- arn:aws:sqs::xxxxxxxx:queueName
The short form of the intrinsic functions (i.e. !Sub, !Ref) is not supported at the moment.
Tips
How to specify the stateMachine ARN to environment variables
Here is serverless.yml sample to specify the stateMachine ARN to environment variables.
This makes it possible to trigger your statemachine through Lambda events
functions:
hello:
handler: handler.hello
environment:
statemachine_arn: ${self:resources.Outputs.MyStateMachine.Value}
stepFunctions:
stateMachines:
hellostepfunc:
name: myStateMachine
definition:
<your definition>
resources:
Outputs:
MyStateMachine:
Description: The ARN of the example state machine
Value:
Ref: MyStateMachine
plugins:
- serverless-step-functions
How to split up state machines into files
When you have a large serverless project with lots of state machines
your serverless.yml file can grow to a point where it is unmaintainable.
You can split step functions into external files and import them
into your serverless.yml file.
There are two ways you can do this:
Single external file
You can define the entire stateMachines block in a separate file
and import it in its entirety.
includes/state-machines.yml:
stateMachines:
hellostepfunc1:
name: myStateMachine1
definition:
<your definition>
hellostepfunc2:
name: myStateMachine2
definition:
<your definition>
serverless.yml:
stepFunctions:
${file(includes/state-machines.yml)}
plugins:
- serverless-step-functions
Separate Files
You can split up the stateMachines block into separate files.
includes/state-machine-1.yml:
name: myStateMachine1
definition:
<your definition>
includes/state-machine-2.yml:
name: myStateMachine2
definition:
<your definition>
serverless.yml:
stepFunctions:
stateMachines:
hellostepfunc1:
${file(includes/state-machine-1.yml)}
hellostepfunc2:
${file(includes/state-machine-2.yml)}
plugins:
- serverless-step-functions
Sample statemachines setting in serverless.yml
Wait State
functions:
hello:
handler: handler.hello
stepFunctions:
stateMachines:
yourWateMachine:
definition:
Comment: "An example of the Amazon States Language using wait states"
StartAt: FirstState
States:
FirstState:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
Next: wait_using_seconds
wait_using_seconds:
Type: Wait
Seconds: 10
Next: wait_using_timestamp
wait_using_timestamp:
Type: Wait
Timestamp: '2015-09-04T01:59:00Z'
Next: wait_using_timestamp_path
wait_using_timestamp_path:
Type: Wait
TimestampPath: "$.expirydate"
Next: wait_using_seconds_path
wait_using_seconds_path:
Type: Wait
SecondsPath: "$.expiryseconds"
Next: FinalState
FinalState:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
End: true
plugins:
- serverless-step-functions
- serverless-pseudo-parameters
Retry Failure
functions:
hello:
handler: handler.hello
stepFunctions:
stateMachines:
yourRetryMachine:
definition:
Comment: "A Retry example of the Amazon States Language using an AWS Lambda Function"
StartAt: HelloWorld
States:
HelloWorld:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
Retry:
- ErrorEquals:
- HandledError
IntervalSeconds: 1
MaxAttempts: 2
BackoffRate: 2
- ErrorEquals:
- States.TaskFailed
IntervalSeconds: 30
MaxAttempts: 2
BackoffRate: 2
- ErrorEquals:
- States.ALL
IntervalSeconds: 5
MaxAttempts: 5
BackoffRate: 2
End: true
plugins:
- serverless-step-functions
- serverless-pseudo-parameters
Parallel
functions:
hello:
handler: handler.hello
stepFunctions:
stateMachines:
yourParallelMachine:
definition:
Comment: "An example of the Amazon States Language using a parallel state to execute two branches at the same time."
StartAt: Parallel
States:
Parallel:
Type: Parallel
Next: Final State
Branches:
- StartAt: Wait 20s
States:
Wait 20s:
Type: Wait
Seconds: 20
End: true
- StartAt: Pass
States:
Pass:
Type: Pass
Next: Wait 10s
Wait 10s:
Type: Wait
Seconds: 10
End: true
Final State:
Type: Pass
End: true
plugins:
- serverless-step-functions
- serverless-pseudo-parameters
Catch Failure
functions:
hello:
handler: handler.hello
stepFunctions:
stateMachines:
yourCatchMachine:
definition:
Comment: "A Catch example of the Amazon States Language using an AWS Lambda Function"
StartAt: HelloWorld
States:
HelloWorld:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
Catch:
- ErrorEquals: ["HandledError"]
Next: CustomErrorFallback
- ErrorEquals: ["States.TaskFailed"]
Next: ReservedTypeFallback
- ErrorEquals: ["States.ALL"]
Next: CatchAllFallback
End: true
CustomErrorFallback:
Type: Pass
Result: "This is a fallback from a custom lambda function exception"
End: true
ReservedTypeFallback:
Type: Pass
Result: "This is a fallback from a reserved error code"
End: true
CatchAllFallback:
Type: Pass
Result: "This is a fallback from a reserved error code"
End: true
plugins:
- serverless-step-functions
- serverless-pseudo-parameters
Choice
functions:
hello1:
handler: handler.hello1
hello2:
handler: handler.hello2
hello3:
handler: handler.hello3
hello4:
handler: handler.hello4
stepFunctions:
stateMachines:
yourChoiceMachine:
definition:
Comment: "An example of the Amazon States Language using a choice state."
StartAt: FirstState
States:
FirstState:
Type: Task
Resource:
Fn::GetAtt: [hello, Arn]
Next: ChoiceState
ChoiceState:
Type: Choice
Choices:
- Variable: "$.foo"
NumericEquals: 1
Next: FirstMatchState
- Variable: "$.foo"
NumericEquals: 2
Next: SecondMatchState
Default: DefaultState
FirstMatchState:
Type: Task
Resource:
Fn::GetAtt: [hello2, Arn]
Next: NextState
SecondMatchState:
Type: Task
Resource:
Fn::GetAtt: [hello3, Arn]
Next: NextState
DefaultState:
Type: Fail
Cause: "No Matches!"
NextState:
Type: Task
Resource:
Fn::GetAtt: [hello4, Arn]
End: true
plugins:
- serverless-step-functions
- serverless-pseudo-parameters
Map
functions:
entry:
handler: handler.entry
mapTask:
handler: handler.mapTask
stepFunctions:
stateMachines:
yourMapMachine:
definition:
Comment: "A Map example of the Amazon States Language using an AWS Lambda Function"
StartAt: FirstState
States:
FirstState:
Type: Task
Resource:
Fn::GetAtt: [entry, Arn]
Next: mapped_task
mapped_task:
Type: Map
Iterator:
StartAt: FirstMapTask
States:
FirstMapTask:
Type: Task
Resource:
Fn::GetAtt: [mapTask, Arn]
End: true
End: true
plugins:
- serverless-step-functions