Strange behaviour - Logstash forwarder read logs fine however the logfile is 0 byte

Elastic Stack Logstash
1

We are using Logstash-forwarder to send Nginx access logs to remote Logstash server, but there is something strange, that the access.log file size is 0 byte and nginx is writing to access.log.1 ( I know this is not the right place to ask Why).

Here is Logstash-forwarder configuration:

{
  "files": [
    {
      "paths": [
        "/var/log/nginx/access.log"
      ],
      "fields": { "type": "nginx-access" }
    },
  ]
}

And Here is the ls for nginx folder

root@eg-lb:~# ls -alh /var/log/nginx
total 355M
drwxr-x---  2 www-data adm  4.0K Jun  2 06:16 .
drwxr-xr-x 14 root     root 4.0K Jun  5 06:16 ..
-rw-r-----  1 www-data adm     0 Jun  2 06:16 access.log
-rw-r-----  1 www-data adm  355M Jun  5 19:59 access.log.1

But everything I can see in access.log.1 when I tail, I find it also in our ELK stack!

So, can anyone tell me what's wrong?