Windowsn, Watermarks Triggers

What are the types of windows that you can use with Beam?

• It depends on the runner, because each runner has different types of windows.

• Open and closed windows.

• Fixed, sliding, and session windows.

How does Apache Beam decide that a message is late?

• A message is late if its timestamp is after the watermark.

• A message is late if its timestamp is before the clock of the worker where it is processed.

• 
  

  This is a runner-specific value. It depends on the runner.

Answer explanation

This is one of the main advantages of using a watermark.

How many triggers can a window have?

• 
  

  Exactly one.

• As many as we set.

• One or none.

Answer explanation

The same window may be triggered an indefinite number of times.

What can you do if two messages arrive at your pipeline out of order?

• You cannot do anything to recover the order of the messages.

• You can recover the order of the messages with a window using event time.

• 
  

  You can recover the order of the messages with a window using processing time.

Answer explanation

This is the main use case for windows with event time.

What is the purpose of a watermark in Apache Beam?

• To mark the end of a window and trigger window computations.

• To mark the beginning of a window and start window computations.

• 
  

  To indicate the progress of event time and handle late data.

How does Apache Beam handle data skew in a pipeline?

• By automatically balancing the data distribution across workers.

• By discarding skewed data to maintain processing efficiency.

• By using key grouping and partitioning to evenly distribute data.

Answer explanation

Apache Beam handles data skew by grouping and partitioning data based on keys, which helps in evenly distributing the data across workers.

Data skew occurs when certain keys are more frequent than others, leading to uneven workload distribution.

Beam's approach to grouping and partitioning ensures that the data is more evenly distributed, reducing the impact of skew and improving overall processing efficiency.

How does Apache Beam handle late data in a pipeline?

• By dropping late data to maintain processing efficiency.

• By reordering late data based on event time.

• 
  

  By using windowing to process late data.

What is the role of a window in Apache Beam processing?

• To define the time boundaries for data processing.

• To filter out irrelevant data from the pipeline.

• 
  

  To control the parallelism of data processing.

How does Apache Beam handle out-of-order data in a streaming pipeline?

• By discarding out-of-order data to prevent processing errors.

• By buffering out-of-order data until it can be correctly ordered.

• 
  

  By using timestamps to reorder out-of-order data.

What is the primary purpose of a watermark in Apache Beam?

• To define when the pipeline should be restarted.

• To measure the completeness of data.

• To filter out irrelevant data.

• To control the parallelism of data processing.