title: ClickHouse replica out of sync
body: <p>I have a cluster of 3 ClickHouse servers with a table using ReplicatedMergeTree. Two of the servers are out of sync and the count of queue in 'system.replication_queue' keeps increasing. I can see this error in logs.</p>
  <pre><code>Not executing log entry for part e87a3a2d13950a90846a513f435c2560_2428139_2436934_22 because source parts size (470.12 MiB) is greater than the current maximum (4.45 MiB).
  </code></pre>
  <p>How do I increase the source parts size? I could not find it in settings.</p>
  <p><strong>Update:</strong></p>
  <p>I read the source code, it is auto calculated based on the available resources. I am also getting this message</p>
  <pre><code>Not executing log entry for part de77ce6a2937ce543cd003eb289fdb7e_8097652_8107495_1904 because another log entry for the same part is being processed. This shouldn't happen often.
  </code></pre>
  <p>The servers which are getting the above message in log have high CPU usage and latency in inserts.</p>
  <p>Replication Queue gets cleared once I stop insertion.</p>