MLSQLRest returns more informative response for different types of errors

[chncaesar]

What changes were proposed in this pull request?

1. Fixed RestUtils.executeWithRetrying executes one more time than expected.
2. MLSQLRest load function refactoring and 4 new test cases.
3. More informative response

RestUtils.executeWithRetrying executes one more time than expected.

In the old implementation, function executes at least two times. It's fixed now, and is covered by test case in RestUtilsTest

 def executeWithRetrying[T](maxTries: Int)(function: => T, checker: T => Boolean, failed: T => Unit): T = {
   // Run the function for the first time
    var result: T = function
    if (checker(result)) {
      return result
    }

    breakable {
      for (i <- 0 until maxTries) {
       // Run again even if maxTries == 1
        result = function
        if (checker(result)) {
          break
        }
        if (i == maxTries - 1) {
          failed(result)
        }
      }
    }
    result
  }

MLSQLRest load function refactoring

The logic to call http endpoints with retrying is repated 3 times with small differences. Now , we encapsulate it in
_httpWithRetrying. For pagnation, use do while loop to avoid reapted code.

Since it's a big change, 4 new caes are added. And unit test covers

• Single page http rest
• Three pagination strategies: auto-increment, default and offset st.
• Stop strategy : bad status-code, config.page.limit, sizeZero, equals

More informative response

Now, MLSQLRest returns

• 405 for unsupported http method
• 415 for unsupported content-type
• 0 for Exception such as UnknownHost.
• 4xx for client side errors
• 5xx for server side errors

How was this patch tested?

MLSQLRest test result

RestUtils test result

Are there and DOC need to update?

• Changes does not impact current documents.

Spark Core Compatibility

[chncaesar]

Issue #1738