Im trying to do the following at AWS Step Functions:
IF ExampleState fails, do "Next":"Anotherlambda"
IF ExampleState completes successfull, end the execution.
How can i do that? The CHOICE state doesn't support ErrorEquals: States.TaskFailed.
In my case, when ExampleState fails, State Machine STOPS and gives me error, but i want to continue and catch some info from the error and save it with another lambda
Thanks!
All i wanted AWS Step Functions to do is, if a State succeeded, finish the execution, if fails, run another lambda. Like an IF / ELSE on programming.
Step Functions gives this easy to you as a CATCH block that only activates if catches an error and does what you want. Here the solution:
"StartAt": "ExampleLambda",
"States": {
"ExampleLambda": {
"Type": "Task",
"Resource": "xxx:function:ExampleLambda",
"Catch": [
{
"ErrorEquals":["States.TaskFailed"],
"Next": "SendToErrorQueue"
}
],
"End": true
}
Related
I am trying to go to a specific state directly or I want to have the flexibility to start from beginning of the workflow. I am not able to pass the next state as dynamic variable. How can I achieve this please?
workflow:
{
{
"Comment": "A description of my state machine",
"StartAt": "gotochoice",
"States": {
"gotochoice": {
"Type": "Choice",
"Choices": [
{
"Variable": "$$.Execution.Input.initial",
"BooleanEquals": true,
"Next": "$$.Execution.Input.startState"
}
],
"Default": "defaultState"
}
},
//Other states
}
}
From above workflow I want to specify the start state dynamically. But "Next" is not accepting the variable from executionContext. Any workaround or any suggestions to fix this issue please?
Basically i just want to start my state machine from a certain failed state. I know below can be done, but i don’t want to create a new state machine for that.Any other alternative please.
https://aws.amazon.com/blogs/compute/resume-aws-step-functions-from-any-state/
Just in case if anyone is still looking for an answer, this is not possible at this stage. But may be in future according to aws support.
I am executing a Java lambda in a step function. I am throwing any exceptions in lambda code as RuntimeExceptions. I am hoping to retry the lambda execution via below code on getting any Runtime exception(since https://docs.aws.amazon.com/step-functions/latest/dg/concepts-error-handling.html says any unhandled lambda errors come up as Lambda.Unknown). However, this does not retry lambda execution on failure.:
"STATE_NAME": {
"Type": "Task",
"Resource": "arn:aws:states:::lambda:invoke",
"OutputPath": "$.Payload",
"Parameters": {
"FunctionName": "arn:aws:lambda:*:$LATEST",
"Payload": {
...
}
},
"Retry": [
{
"ErrorEquals": [
"Lambda.Unknown"
],
"IntervalSeconds": 2,
"MaxAttempts": 6,
"BackoffRate": 2
}
],
What does work though is if i replace Error condition with States.ALL. However this also would include invalid permissions, state timeouts etc. on which i do Not want to Retry the lambda execution. Is there something i am missing here?
Based on AWS doc (https://docs.aws.amazon.com/step-functions/latest/dg/bp-lambda-serviceexception.html)
Unhandled errors in Lambda are reported as Lambda.Unknown in the error output. These include out-of-memory errors and function timeouts. You can match on Lambda.Unknown, States.ALL, or States.TaskFailed to handle these errors. When Lambda hits the maximum number of invocations, the error is Lambda.TooManyRequestsException. For more information about Lambda Handled and Unhandled errors, see FunctionError in the AWS Lambda Developer Guide.
If you are throwing exception in lambda code, then it will not be classified as Lambda Unhandled errors based on that clasifications.
We are creating a workflow composed of multiple SQL Operations(Aggregations, Transposes etc.) via AWS Step functions. Every operation is modelled as a separate Lambda which houses the SQL query.
Now, every query accepts its input parameters from the state machine, so every lambda task is as below:
"SQLQueryTask": {
"Type": "Task",
"Parameters": {
"param1.$": "$$.Execution.Input.param1",
"param2.$": "$$.Execution.Input.param2"
},
"Resource": "LambdaArn",
"End": true
}
The Parameters block thus repeats for every SQLQuery node.
Added to this since Lambdas can fail intermittently and we would like to retry for them ; we also need to have below retry block in every State:
"Retry": [ {
"ErrorEquals": [ "Lambda.ServiceException", "Lambda.AWSLambdaException", "Lambda.SdkClientException"],
"IntervalSeconds": 2,
"MaxAttempts": 6,
"BackoffRate": 2
} ]
This is making the state definition very complex. Is there No way to extract out the common part of state definition to a reusable piece?
One solution could be using AWS CDK (https://aws.amazon.com/cdk/)
This allows developers to define higher-level abstractions of resources, which can easily be reused.
There are some example here that could be helpful: https://docs.aws.amazon.com/cdk/api/latest/docs/aws-stepfunctions-readme.html
I'm constructing my first state machine using AWS Step Functions and inside the state machine I'm invoking Go Lambdas. I'm starting the execution of the state machine from another Lambda that passes some input I'd like to reference inside different parts of the state machine. I notice I'm losing that input between the LambdaFunctionScheduled stage and the LambdaFunctionStarted stage and as a result I don't seem to have an event in my Lambda where I can grab the pieces of info I need. Am I missing a step?
Here is the state machine I'm creating in Terraform:
resource "aws_sfn_state_machine" "bulk_state_machine" {
name = "bulk_state_machine"
role_arn = "${aws_iam_role.bulk_state_machine_role.arn}"
definition = <<EOF
{
"Comment": "A state machine to orchestrate a series of Lambdas that complete the bulk provisioning process",
"StartAt": "CreateBuckets",
"States": {
"CreateBuckets": {
"Type": "Task",
"Resource": "${aws_lambda_function.createBulkProvisionBuckets.arn}",
"End": true
}
}
}
EOF
}
And this is the struct of input I'm marshalling into JSON and sending along as input in the Lambda that begins execution of the Step Function:
sfnInput := models.BulkSFNInput{
DefaultRegion: brand.DefaultRegion,
OtherRegions: brand.OtherRegions,
ACMARN: brand.ACMARN,
}
I have created a simple AWS state machine with lambda functions. Like below
{
"Comment":"Validates data",
"StartAt": "ChooseDocumentType",
"States": {
"ChooseDocumentType": {
"Type": "Choice",
"Choices":[
{
"Variable":"$.documentType",
"StringEquals":"RETURN",
"Next":"ValidateReturn"
},
{
"Variable":"$.documentType",
"StringEquals":"ASSESSMENT",
"Next":"ValidateAssessment"
}
],
"Default":"DefaultState"
},
"ValidateReturn":{
"Type":"Task",
"Resource":"arn:aws:lambda:us-west-2:111111111:function:ValidateReturn",
"Next":"DefaultState"
},
"ValidateAssessment":{
"Type":"Task",
"Resource":"arn:aws:lambda:us-west-2:111111111:function:ValidateAssessment",
"Next":"DefaultState"
},
"DefaultState":{
"Type":"Pass",
"End":true
}
}
}
Questions
1> How do i create stages for this state machine. (like production, development etc)?
2>Each lambda function has alias pointing to different versions. So development alias always point to $latest version and production alias point to, lets say, version 2. How do i dynamically associate state machine's stages with these lambda alias? So state machine in development stage should use lambda function with alias development and so on.
I am using AWS console to manage state machines and lambdas, and i don't see any action to create stages for state machine
You can declare the alias and the version in the Lambda ARN:
# default, $LATEST
arn:aws:lambda:us-west-2:111111111:function:ValidateAssessment
# using alias
arn:aws:lambda:us-west-2:111111111:function:ValidateAssessment:development
# using version
arn:aws:lambda:us-west-2:111111111:function:ValidateAssessment:2
Use these in the Step Function definition according to your needs.
Re: # 2, if your main concern is controlling which Lambda alias gets invoked, there is a way you can do that via a single step function.
Your step function state definition would be something like:
{
"Type": "Task",
"Resource": "arn:aws:states:::lambda:invoke",
"Parameters": {
"InvocationType": "RequestResponse",
"FunctionName": "someFunction",
"Qualifier.$": "$.lambdaAlias",
"Payload": {}
},
}
So where you execute the step function and would specify the stage if there was such a thing, you'd pass a lambdaAlias parameter. (There's nothing magical about that name, you can pull it from whatever step function input parameter you want.)
The request payload to your Lambda would go in Parameters.Payload.
https://docs.aws.amazon.com/step-functions/latest/dg/connect-lambda.html