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type mismatch in nested functions

Time:05-15

Objective:- Retrieve json object from aws s3 bucket. Retry on failure. If retry attempts are exhausted, send the error message to azure's event hub.

//Retry function

def retry[T](n: Int, id: String)(fn: => T): Option[T]  = { 
        Try(fn) match {
        case Success(x) => Some(x)
        case Failure(e) => {
        Thread.sleep(1000)
          if (n > 1) {
           retry(n - 1, id)(fn)
          } else {
            val eMessage = "TransactionId ="   id   " : ".concat(e.toString())
            SendMessage(eMessage, event_hub_client)
            None
            }
          }    
        }
      }

//Main function (with above retry) to retrieve objects from aws s3 bucket

 def getS3Object(s3ObjectName: String, s3Client: AmazonS3, evtClient: EventHubClient): String = {
        retry(2,s3ObjectName) {
          val inputS3Stream = s3Client.getObject("my_s3_bucket", s3ObjectName).getObjectContent
          val inputS3String = IOUtils.toString(inputS3Stream, "UTF-8")
          return inputS3String
        }
      }

I get the below compilation failed message:-

error: type mismatch
found : Option[Nothing]
required: String
retry2(2,s3ObjectName)

How to declare the return types of the retry and main functions so that they match?

CodePudding user response:

In terms of types retry look's okay. You need to adapt your other method.

Either make it return a Option[String] or use getOrElse(..) if you want to fallback to some other value.

 def getS3Object(s3ObjectName: String, s3Client: AmazonS3, evtClient: EventHubClient): Option[String] = {
        retry(2,s3ObjectName) {
          val inputS3Stream = s3Client.getObject("my_s3_bucket", s3ObjectName).getObjectContent
          val inputS3String = IOUtils.toString(inputS3Stream, "UTF-8")
          inputS3String
        }
      }

Notice the removal of return keyword which is useless and doesn't do what you think it does (I'll let you search on this topic by yourself).

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