Logstash output from filebeat. What is 'index' configuration option?

Elastic Stack Beats
1

This is an excerpt taken from filebeat config for logstash output here

image
I'm wondering what does index have to do with logstash. In my logstash configuration itslef, if I redirect logs to ElasticSearch I believe my logs will be indexed under "logstash-%{+YYYY.MM.dd}" as the documentation says here.

So why is there an option to set index for filebeat's logstash output?

2

Yes, there is an index parameter. From the doc, if filebeat 7.5.0 send the data to logstash, the index would be filebeat-7.5.0.

output {
  elasticsearch {
    hosts => ["http://localhost:9200"]
    index => "%{[@metadata][beat]}-%{[@metadata][version]}" 
  }
}