How to Access Full HTTP Response Details in Step Functions' HTTP Invoke Errors?

Question

Hello AWS Community,

I am working with AWS Step Functions and facing a challenge related to handling errors in [HTTP Invoke steps](https://docs.aws.amazon.com/step-functions/latest/dg/connect-third-party-apis.html). When an HTTP request results in an error (e.g., HTTP 400 Bad Request), the information I receive is quite limited, typically including only the `error` and `cause` fields:

```json
{
    "error": "States.Http.StatusCode.400",
    "cause": "Bad Request"
}
```

However, the full HTTP response contains much more detail (obtained from the trace logs of "Test Step"- feature), which is crucial for our error resolution processes:

```json
{
    "body": "{\"code\":\"400\",\"details\":\"Detailed error information here.\"}",
    "headers": { /* headers omitted for brevity */ },
    "statusCode": "400",
    "statusMessage": "Bad Request"
}
```

I've attempted to capture these details using a catch block in the step function, hoping to pass the detailed error message through to my error handling logic. Unfortunately, it seems that the error handler only receives the limited information:

```javascript
// Catch block setup in AWS Step Functions
this.addCatch(errorHandler, {
    errors: [
        'States.Http.StatusCode.400',
        'States.Http.StatusCode.404',
        'States.Http.StatusCode.500',
        // Additional relevant HTTP status codes
    ]
});
```

**My Question**: Is there a way to configure the HTTP Invoke step or modify the catch block to capture and utilize the entire HTTP response, especially the error details contained in the body? Accessing this detailed information is essential for troubleshooting and dynamically responding to issues within our workflows.

I'm interested in any configuration options, workarounds, or best practices that could help in accessing the full error details from HTTP responses in Step Functions. Your insights would be invaluable and greatly appreciated!

Thank you in advance for your help!

Answer

Unfortunately there is no direct way to access the full HTTP response details in the error object passed to the catch block in Step Functions. The error object contains only the basic error code and message.

However, there are a couple potential workarounds:

1. Enable detailed CloudWatch logging for Step Functions. This will log the full HTTP response details in the CloudWatch logs for each state. You can then search the logs using the executionId to find the response details for a failed execution.

2. Handle HTTP errors within the state machine logic. Rather than using a catch block, check the HTTP status code in the response and handle errors inline. For example:

```
"Check HTTP Response": {
  "Type": "Task",
  "Resource": "arn:aws:states:::lambda:invoke",
  "Parameters": {
    "FunctionName": "myFunction", 
    "Payload": {
      "statusCode": $.statusCode,
      "response": $
    }
  },
  "Next": "HTTP 200 Success State",
  "Catch": [
    {
      "ErrorEquals": ["States.ALL"],
      "Next": "HTTP Error Handling State"
    }
  ]
}
```

Then in "HTTP Error Handling State" you have access to the full response to handle errors.

3. Surface the full response in the exception. In the Lambda function called by the HTTP invoke, you could catch errors and throw a custom exception containing the full response object. This custom exception will propagate to the catch block.

So in summary, while not straightforward, there are some options to get the HTTP response details you need for error handling in Step Functions. Enabling detailed CloudWatch logging is probably the simplest approach.

How to Access Full HTTP Response Details in Step Functions' HTTP Invoke Errors?

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