# Logstash ConcurrentModificationException: null **URL:** \ **Category:** Logstash\ **Created:** [July 15, 2021, 9:36am UTC](https://discuss.elastic.co/t/logstash-concurrentmodificationexception-null/278759 "2021-07-15T09:36:40Z")\ **Posts on this page:** 1\ **Showing post:** 6
**Author:** ![Janko](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/janko/32/26896_2.png) [@Janko](https://discuss.elastic.co/u/Janko)\ **Post date:** [July 17, 2021, 12:31am UTC](https://discuss.elastic.co/t/logstash-concurrentmodificationexception-null/278759/6 "2021-07-17T00:31:25Z")
Thanks for the details @rojin Funnily enough this sounds exactly like [Logstash execption in pipeline worker](https://discuss.elastic.co/t/logstash-execption-in-pipeline-worker/259965) where @badger also responded and pointed to [ConcurrentModificationException · Issue #19 · ip2location/logstash-filter-ip2location · GitHub](https://github.com/ip2location/logstash-filter-ip2location/issues/19#issuecomment-660755521) where it was suggested to try `version 2.1.2.` of `ip2location`. You seem to be using a previous version here so I'd give updating a try. Not hearing back on that previous issue could well mean that this resolved the problem back then. I had seen this issue initially and now that you also use `ip2location`, and on the same Elastic stack version, it seems that this might indeed be fitting. It can be hard at times to select the correct parts of a message to search for related issues and, as I mentioned on Slack, more information upfront is always helpful. Had you initially mentioned that this plugin was used and on what version, I would have directly suggested to look in that direction. Have a great weekend, all! --- _[View the full topic](https://discuss.elastic.co/t/logstash-concurrentmodificationexception-null/278759)._