title: Apache Beam / Google dataflow - Error handling
body: <p>I have a pipeline with quite a few steps (just above 15). I want to report failures everytime a <code>DoFn</code> fails. I started implementing it through <code>TupleTags</code> with code such as :</p>
  
  <pre><code>try {
   ... do stuff ...
   c.output(successTag, ...);
  } catch (Exception e) {
   c.output(failureTag, new Failure(...));
  }
  </code></pre>
  
  <p>But since my pipeline contains a lot of steps, this make the pipeline definition code quite hard to read / maintain. </p>
  
  <p>Is there a more global way to achieve it ? Something like raising a custom exception which is handled globally at the pipeline level ?</p>