code: public StreamExecutionEnvironment enableCheckpointing(long interval, CheckpointingMode mode) {
  		checkpointCfg.setCheckpointingMode(mode);
  		checkpointCfg.setCheckpointInterval(interval);
  		return this;
  	}
docs: Enables checkpointing for the streaming job. The distributed state of the streaming
  dataflow will be periodically snapshotted. In case of a failure, the streaming
  dataflow will be restarted from the latest completed checkpoint.
  
  <p>The job draws checkpoints periodically, in the given interval. The system uses the
  given {@link CheckpointingMode} for the checkpointing ("exactly once" vs "at least once").
  The state will be stored in the configured state backend.
  
  <p>NOTE: Checkpointing iterative streaming dataflows in not properly supported at
  the moment. For that reason, iterative jobs will not be started if used
  with enabled checkpointing. To override this mechanism, use the
  {@link #enableCheckpointing(long, CheckpointingMode, boolean)} method.
  
  @param interval
  Time interval between state checkpoints in milliseconds.
  @param mode
  The checkpointing mode, selecting between "exactly once" and "at least once" guaranteed.