# Logstash to Logstash Flow, Where to filter the logs **URL:** \ **Category:** Logstash\ **Created:** [March 29, 2019, 1:46pm UTC](https://discuss.elastic.co/t/logstash-to-logstash-flow-where-to-filter-the-logs/174546 "2019-03-29T13:46:25Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Kris.devops](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@Kris.devops](https://discuss.elastic.co/u/Kris.devops)\ **Post date:** [March 29, 2019, 1:46pm UTC](https://discuss.elastic.co/t/logstash-to-logstash-flow-where-to-filter-the-logs/174546/1 "2019-03-29T13:46:25Z")
Hello Team, I am trying to send logs from LOgstash A to Logstash B , and from logstash B to elasticsearch . My question is where do I have to filter the logs and add additional fields to the messages. In logstash A or Logsatsh B . Also Is there any good Grok constructor that you would advise. I am a new to the elk environment. Thanks ---
**Author:** ![kharvey](https://avatars.discourse-cdn.com/v4/letter/k/d07c76/32.png) [@kharvey](https://discuss.elastic.co/u/kharvey)\ **Post date:** [April 1, 2019, 5:07pm UTC](https://discuss.elastic.co/t/logstash-to-logstash-flow-where-to-filter-the-logs/174546/2 "2019-04-01T17:07:39Z")
[https://www.elastic.co/guide/en/logstash/current/ls-to-ls.html](https://www.elastic.co/guide/en/logstash/current/ls-to-ls.html) It depends on where you want to process the logs at. There is no spot where you HAVE to process your logs. I currently am processing all of my logs on Logstash B, but I could easily process them at Logstash A if I wanted. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [April 29, 2019, 5:07pm UTC](https://discuss.elastic.co/t/logstash-to-logstash-flow-where-to-filter-the-logs/174546/3 "2019-04-29T17:07:48Z")
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