title: Best way to trigger and window python beam process that read from google storage on dataflow
body: <p>I never used beam before, and the whole trigger and window stuff kind of confuse me.</p>
  <p>I need to write a program that would run on dataflow, and reads from google storage from a path like this: <code>node-&lt;num&gt;/&lt;table_name&gt;/&lt;timestamp&gt;/file</code> (I have multiple from nodes, the tables name are the same per node and I have one file per timestamp) also files are being uploaded there continually. (I would love to avoid using pubsub since I work for a small company and its more money...)</p>
  <p>Now since there are multiple nodes there could be some duplicates in the files so I do want to group them by timestamp and from what I've read I need to take that in account to the windowing.</p>
  <p>So how should I trigger and window it so that it would run &quot;forever&quot; and with a way for me to group the files by timestamp and remove duplicates?</p>
  <p>Thanks a lot!</p>