Logstash to Logstash Flow, Where to filter the logs

Elastic Stack Logstash
1

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

2

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.