code: public boolean triggerCheckpoint(long timestamp, boolean isPeriodic) {
  		try {
  			triggerCheckpoint(timestamp, checkpointProperties, null, isPeriodic, false);
  			return true;
  		} catch (CheckpointException e) {
  			return false;
  		}
  	}
docs: Triggers a new standard checkpoint and uses the given timestamp as the checkpoint
  timestamp.
  
  @param timestamp The timestamp for the checkpoint.
  @param isPeriodic Flag indicating whether this triggered checkpoint is
  periodic. If this flag is true, but the periodic scheduler is disabled,
  the checkpoint will be declined.
  @return <code>true</code> if triggering the checkpoint succeeded.