Filter:drop performance varies by 200x

TL;DR: for no apparent reason, logstash will take as low as 0.24ms to drop events, or up to 56ms (a 200x difference!).

I've been trying to track down a performance issue with our logstash setup. We're getting huge backlogs, and it may have to do with the amount of data we're putting into it. We're filtering out a lot of events but still getting poor performance, so last night I started to look at the pipeline performance and see the following for a drop filter:

To play around with the setup and test out locally on my development box, I duplicated a similar pipeline, injecting randomly generated events (some of which get filtered) and got the following:


Not great performance but similar to what I'm seeing in prod.

After slight changes to the filter (using else if instead of if one after the other), suddenly I got a drastic performance increase:

Then, to verify that this was the cause of the change, I reverted to the original structure, but the performance increase stayed (verification failed):

At this point I left it for the night.

This morning, I decided to, without restarting anything, re-run the exact same test I did last night. And got a 200x performance difference, with the pipeline viewer reporting it was now taking 50ms/event to DROP messages:


This doesn't make any sense to me and makes me feel that something wrong is happening inside of logstash. Help!


  • logstash 6.0.1
  • es 6.0.0
  • kibana 6.0.0
  • ubuntu 16.04.3
  • docker 17.12.0-ce

logstash filter:

filter {
  mutate {
    convert => [
      "status", "integer",
      "intensity", "integer"
  # test out the patterns we're using in prod
  if [type] == "rails" {
    if [status] == 200 {
      if [path] =~ /^(\/[^\/]+)?\/magic\/string/ {
        drop { }
      if [path] =~ /^(\/[^\/]+)?\/secret\/sauce/ {
        drop { }

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