title: Graylog: Bad GELF UDP performance
body: <p>I have a Graylog installation that can handle well over 25.000 msg/sec.</p>
  
  <p>I am now experimenting with setting up a dedicated Logstash cluster. So something like this:
  Filebeat (n hosts) -> Logstash Cluster -> Graylog</p>
  
  <p>The biggest issue now is that I can not send more than ~2.500 msg/sec <strong>from one host</strong> to Graylog. No matter how big the host is (4, 8, 16, … CPUs), no matter how small the messages are, there is always this 2.500 msg/sec limit.</p>
  
  <p>I’ve even created messages with only 1 Byte payload, the limit here is ~2.800 msg/sec.</p>
  
  <p>I can send messages from, for example, 4 different hosts. Resulting in 10.000 msg/sec (4 x 2.500). Graylog can handle this easily.</p>
  
  <p>So my question is: Why can <strong>one host</strong> send no more than ~2.500 msg/sec via GELF UDP?</p>