AWS Textract InvalidParameterException

Question

I have a .Net core client application using amazon Textract with S3,SNS and SQS as per the AWS Document , Detecting and Analyzing Text in Multipage Documents(https://docs.aws.amazon.com/textract/latest/dg/async.html)

Created an AWS Role with AmazonTextractServiceRole Policy and added the Following Trust relation ship as per the documentation (https://docs.aws.amazon.com/textract/latest/dg/api-async-roles.html) { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Principal": { "Service": "textract.amazonaws.com" }, "Action": "sts:AssumeRole" } ] }

Subscribed SQS to the topic and Given Permission to the Amazon SNS Topic to Send Messages to the Amazon SQS Queue as per the aws documentation .

All Resources including S3 Bucket, SNS ,SQS are in the same us-west2 region

The following method shows a generic error "InvalidParameterException" Request has invalid parameters

But If the NotificationChannel section is commented the code is working fine and returning the correct job id.

Error message is not giving a clear picture about the parameter. Highly appreciated any help .

public async Task<string> ScanDocument()
{
            string roleArn = "aws:iam::xxxxxxxxxxxx:instance-profile/MyTextractRole";
            string topicArn = "aws:sns:us-west-2:xxxxxxxxxxxx:AmazonTextract-My-Topic";
            string bucketName = "mybucket";
            string filename = "mytestdoc.pdf";

            var request = new StartDocumentAnalysisRequest();
            var notificationChannel = new NotificationChannel();
            notificationChannel.RoleArn = roleArn;
            notificationChannel.SNSTopicArn = topicArn;

            var s3Object = new S3Object
            {
                Bucket = bucketName,
                Name = filename
            };
            request.DocumentLocation = new DocumentLocation
            {
                S3Object = s3Object
            };
            request.FeatureTypes = new List<string>() { "TABLES", "FORMS" };
            request.NotificationChannel = channel; /* Commenting this line work the code*/
            var response = await this._textractService.StartDocumentAnalysisAsync(request);
            return response.JobId;

        }

Answer 1

Debugging Invalid AWS Requests

The AWS SDK validates your request object locally, before dispatching it to the AWS servers. This validation will fail with unhelpfully opaque errors, like the OP.

As the SDK is open source, you can inspect the source to help narrow down the invalid parameter.

Before we look at the code: The SDK (and documentation) are actually generated from special JSON files that describe the API, its requirements and how to validate them. The actual code is generated based on these JSON files.

I'm going to use the Node.js SDK as an example, but I'm sure similar approaches may work for the other SDKs, including .NET

In our case (AWS Textract), the latest Api version is 2018-06-27. Sure enough, the JSON source file is on GitHub, here.

In my case, experimentation narrowed the issue down to the ClientRequestToken. The error was an opaque InvalidParameterException. I searched for it in the SDK source JSON file, and sure enough, on line 392:

"ClientRequestToken": {
  "type": "string",
  "max": 64,
  "min": 1,
  "pattern": "^[a-zA-Z0-9-_]+$"
},

A whole bunch of undocumented requirements!

In my case the token I was using violated the regex (pattern in the above source code). Changing my token code to satisfy the regex solved the problem.

I recommend this approach for these sorts of opaque type errors.