Loadbalancing with nginx not effective working

[khergner (Korhan Herguner)]

Hi,
I want to use F5 load balance because ı have 2 nodes
ı get the following error at nginx

2019/08/27 09:56:20 [error] 13388#11836: *529 no live upstreams while connecting to upstream, client: 127.0.0.1, server: , request: "POST /_bulk HTTP/1.1", upstream: "http://elasticsearch/_bulk", host: "127.0.0.1:8080"
2019/08/27 10:06:14 [error] 13388#11836: *700 upstream timed out (10060: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond) while reading response header from upstream, client: 127.0.0.1, server: , request: "POST /_bulk HTTP/1.1", upstream: "http://127.0.0.1:9200/_bulk", host: "127.0.0.1:8080"

My arch.
Logstash --> F5* --> Elasticsearh1 || Elasticsearch2 --> Kibana
My nginx conf

events {
    worker_connections  1024;
}
http {
  upstream elasticsearch {
    server 127.0.0.1:9200;
    server 127.0.0.1:9201;
    server 127.0.0.1:9202;
    keepalive 15;
  }
  server {
    listen 8080;
    location / {
      proxy_pass http://elasticsearch;
      proxy_http_version 1.1;
      proxy_set_header Connection "Keep-Alive";
      proxy_set_header Proxy-Connection "Keep-Alive";
    }
  }
}

How can ı solution above error?
Regards