[REEF-1377] Move from C# Tasks to Threads to run user's Task

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.15
• Component/s: REEF.NET Evaluator
• Assignee: Andrew Chung
• Reporter: Andrew Chung
• Created: 02/May/16 18:40
• Updated: 02/May/16 21:36
• Resolved: 02/May/16 21:36

Description

We should use Thread instead of Task to run user's REEF Task to simplify Exception handling. The main motivation to move is the following use-case:

On an unhandled Exception on the REEF system side, we would like to fail the Evaluator and have it relay a message back to the Driver. For this purpose, we will bind a handler for AppDomain.CurrentDomain.UnhandledException. However, this does not work for Tasks. The Task equivalent, TaskScheduler.UnobservedTaskException, only triggers when a Task gets GC'd, which may be a long time after a Task fails unless GC is forced. In addition, Tasks do not crash a process in C# 4.5, so if an Unhandled Exception is not observed on our part, there is a possibility that it remains unobserved for a long time which may cause system state to become corrupted and unstable.

We should thus switch to use Thread to simplify the Exception handling in the REEF.NET Evaluator.

Issue Links

• blocks: REEF-1364 C# Evaluator should attempt to send a failure message back to the Driver on an unhandled Exception
• links to: Link to PR