Dynamic assignment – DynamicUserAssignmentStrategy implementation

The following code shows the implementation of the LeastRecentlyModifiedAssignmentStrategy class. This is a very simple application of the necessary concepts needed to create a working implementation. The class performs a very simple user selection, simply looking for the user that has gone the longest without modification.

Since the selection algorithm needs to inspect the user data to perform the assignment, the class returns the candidate users themselves as the set of entities to lock. This ensures that the assignment code can work without interference from other machines.

package gw.assignment.examples

uses gw.api.assignment.DynamicUserAssignmentStrategy
uses java.util.Set
uses java.util.HashSet

@Export
class LeastRecentlyModifiedAssignmentStrategy implements DynamicUserAssignmentStrategy {

  construct() { }

  override function getCandidateUsers(assignable:Assignable, group:Group, includeSubGroups:boolean ) :
          Set {
     var users = (group.Users as Set<GroupUser>).map( \ groupUser -> groupUser.User )
     var result = new HashSet()
     result.addAll( users )
     return result
  }
  override function findUserToAssign(assignable:Assignable, candidates:Set, locks:Set) : GroupUser {
    var users = candidates as Set<User>
    var oldestModifiedUser = users.iterator().next()
    for (nextUser in users) {
      if (nextUser.UpdateTime < oldestModifiedUser.UpdateTime) {
        oldestModifiedUser = nextUser
      }
    }
    
    return oldestModifiedUser.GroupUsers[0]
  }

  override function getLocksForAssignable(assignable:Assignable, candidates:Set) : Set {
    return candidates
  }
  
  //Must return a unique token
  override function getAssignmentToken(assignable:Assignable) : Object {
    return "LeastRecentlyModifiedAssignmentStrategy_" + assignable
  }
  
  override function rollbackAssignment(assignable:Assignable, assignedEntity:Object) : boolean {
    return false
  }
}