Elasticsearch : Connection refused while connecting to upstream - nginx

Question

I've set up an Elasticsearch server with Kibana to gather some logs.
Elasticsearch is behind a reverse proxy by Nginx, here is the conf :
server {
listen 8080;
server_name myserver.com;
error_log /var/log/nginx/elasticsearch.proxy.error.log;
access_log off;
location / {
# Deny Nodes Shutdown API
if ($request_filename ~ "_shutdown") {
return 403;
break;
}
# Pass requests to ElasticSearch
proxy_pass http://localhost:9200;
proxy_redirect off;
proxy_http_version 1.1;
proxy_set_header Connection "";
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
# For CORS Ajax
proxy_pass_header Access-Control-Allow-Origin;
proxy_pass_header Access-Control-Allow-Methods;
proxy_hide_header Access-Control-Allow-Headers;
add_header Access-Control-Allow-Headers 'X-Requested-With, Content-Type';
add_header Access-Control-Allow-Credentials true;
}
}
Everything works well, I can curl -XGET "myserver.com:8080" to check, and my logs come in.
But every minute or so, in the nginx error logs, I get that :
2014/05/28 12:55:45 [error] 27007#0: *396 connect() failed (111: Connection refused) while connecting to upstream, client: [REDACTED_IP], server: myserver.com, request: "POST /_bulk?replication=sync HTTP/1.1", upstream: "http://[::1]:9200/_bulk?replication=sync", host: "myserver.com"
I can't figure out what it is, is there any problem in the conf that would prevent some _bulk requests to come through ?

Answer 1

Seems like upstream and a different keepalive is necessary for the ES backend to work properly, I finally had it working using the following configuration :
upstream elasticsearch {
server 127.0.0.1:9200;
keepalive 64;
}
server {
listen 8080;
server_name myserver.com;
error_log /var/log/nginx/elasticsearch.proxy.error.log;
access_log off;
location / {
# Deny Nodes Shutdown API
if ($request_filename ~ "_shutdown") {
return 403;
break;
}
# Pass requests to ElasticSearch
proxy_pass http://elasticsearch;
proxy_redirect off;
proxy_http_version 1.1;
proxy_set_header Connection "";
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
# For CORS Ajax
proxy_pass_header Access-Control-Allow-Origin;
proxy_pass_header Access-Control-Allow-Methods;
proxy_hide_header Access-Control-Allow-Headers;
add_header Access-Control-Allow-Headers 'X-Requested-With, Content-Type';
add_header Access-Control-Allow-Credentials true;
}
}