title: Diagnosing failed Cloud Dataflow pipeline
body: <p>I had a Cloud Dataflow pipeline fail after about 14 worker-hours with the following cryptic log message:</p>
  
  <blockquote>
    <p>Mar 29, 2016, 8:18:16 PM
    (3253bcfbb8c9c2a7): Workflow failed. Causes: (2bfe8449fe3ba464): S745 (STAGE REDACTED) Causes: (1a6d5387c382ba3a): A work item was attempted 4 times without success. Each time the worker eventually lost contact with the service. The work item was attempted on: (WORKERS REDACTED)</p>
  </blockquote>
  
  <p>I glanced quickly at worker logs and it wasn't immediately obvious what was happening either. Is there supposed to be something to those cause codes?</p>
  
  <p>The <a href="https://cloud.google.com/dataflow/pipelines/troubleshooting-your-pipeline#Causes" rel="noreferrer">troubleshooting guide</a> wasn't particular elucidating here, either. My best guess was that it fell under the "shuffle-bound" category (the job is very shuffle intensive), but none of the errors listed are present in the logs.</p>
  
  <p>Thanks!</p>