title: NiFi MergeContent not doing processing flowfiles
body: <p>I have several Nifi flows consuming data from Kafka then writing it on HDFS. Before writing on HDFS, we use <code>MergeContent</code> to merge flowfiles and write bigger messages (sort of like a batch).</p>
  <p>For 2 of those flows however, <code>MergeContent</code> doesn't seem to process flowfiles : flowfiles stay stuck in the queue before <code>MergeContent</code> processor. I've tried modifying the <code>Max Bin Age</code> parameter, as well as the Maximum  and Minimum Number of Entries, it doesn't change anything. Flowfiles stay in the queue far beyond the <code>max bin age</code> period.</p>
  <p>Here are screenshots of the <code>MergeContent</code> properties :</p>
  <p><a href="https://i.stack.imgur.com/fURqu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/fURqu.png" alt="Merge Content Properties" /></a></p>
  <p><a href="https://i.stack.imgur.com/vyHK6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vyHK6.png" alt="Merge Content Scheduling Properties" /></a></p>
  <p>Here is also a screenshot of the queue. You can see nothing has been processed for at least the last 5 minutes. You can also see that some flowfiles did get merged, the flow was working fine when I first started it, the problem appeared after 10 minutes or so.</p>
  <p><a href="https://i.stack.imgur.com/JO25k.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/JO25k.png" alt="Nifi queue" /></a></p>
  <p>Any idea what the problem might be?</p>