Retry logic in AWS step function

Question

I am testing the retry logic of the step function. Theoretically following step function should have been retried to execute the lambda 3 times if it fails.

{
  "StartAt": "Bazinga",
  "States": {
    "Bazinga": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "Parameters": {
        "FunctionName": "arn:aws:lambda:ap-southeast-2:518815385770:function:errorTest:$LATEST",
        "Payload": {
          "Input.$": "$"
        }
      },
      "Retry" : [
        {
          "ErrorEquals": [ "States.All", "States.Timeout" ],
          "IntervalSeconds": 1,
          "MaxAttempts": 3,
          "BackoffRate": 1.0
        }
      ],
       "Next": "Fail"
    },
    "Fail": {
      "Type": "Fail"
    }
  }
}

The lambda it calls is set to timeout in 3 seconds. The lambda freezes for 4 seconds. This means the lambda times out and throws States.Timeout error. The code is given below:

function sleep(ms){
    return new Promise(resolve=>{
        setTimeout(resolve,ms)
    })
}

exports.handler = async (event) => {
    console.log('------------> executing ....')
    await sleep(4000)
};

The problem is step function does not retry the task. This can be confirmed from the following CloudWatch logs.


05:59:36
START RequestId: dd1a2ee9-f389-44be-aaa6-07f2ca7983b0 Version: $LATEST

05:59:36
2019-07-24T05:59:36.340Z dd1a2ee9-f389-44be-aaa6-07f2ca7983b0 INFO ------------> executing ....

05:59:39
END RequestId: dd1a2ee9-f389-44be-aaa6-07f2ca7983b0

05:59:39
REPORT RequestId: dd1a2ee9-f389-44be-aaa6-07f2ca7983b0 Duration: 3003.29 ms Billed Duration: 3000 ms Memory Size: 128 MB Max Memory Used: 26 MB

05:59:39
2019-07-24T05:59:39.317Z dd1a2ee9-f389-44be-aaa6-07f2ca7983b0 Task timed out after 3.00 seconds 

Not sure what went wrong. Any help is appreciated, thanks in advance.

Answer 1

To answer my own question, there were 2 problems with the retry logic I placed.

1. States.All should have been States.ALL (notice the case of L)
2. When the lambda timed out, the error being thrown was Lambda.Unknown instead of States.Timeout.

I updated my step function with following code and now it works:

{
  "StartAt": "Bazinga",
  "States": {
    "Bazinga": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "Parameters": {
        "FunctionName": "arn:aws:lambda:ap-southeast-2:518815385770:function:errorTest:$LATEST",
        "Payload": {
          "Input.$": "$"
        }
      },
      "Retry" : [
        {
          "ErrorEquals": [ "States.Timeout", "Lambda.Unknown" ],
          "IntervalSeconds": 1,
          "MaxAttempts": 3,
          "BackoffRate": 1.0
        }
      ],
       "Next": "Fail"
    },
    "Fail": {
      "Type": "Fail"
    }
  }
}

Answer 2

Because you didn't define TimeoutSeconds in the ASL. Example:

"Type": "Task",
"Resource": "${FunctionArn}",
"TimeoutSeconds": 3,

Otherwise it will throw out Lambda.Unknown failure