title: When will LogStash exceed the queue capacity and drop messages?
body: <p>I am using LogStash to collect the logs from my service. The volume of the data is so large (20GB/day) that I am afraid that some of the data will be dropped at peak time.</p>
  
  <p>So I asked <a href="https://stackoverflow.com/questions/25397148/how-to-monitor-if-logstash-is-fully-loaded/25397505#25397505">question</a> here and decided to add a Redis as a buffer between ELB and LogStash to prevent data loss.</p>
  
  <p>However, I am curious about <strong>when will LogStash exceed the queue capacity and drop messages?</strong> </p>
  
  <p>Because I've done some experiments and the result shows that LogStash can completely process all the data without any loss, e.g., local file --> LogStash --> local file, netcat --> LogStash --> local file.</p>
  
  <p>Can someone give me a solid example when LogStash eventually drop messages? So I can have a better understanding about why we need a buffer in front of it.</p>