# Client.transport.sniff when connecting localhost to an EC2 node **URL:** \ **Category:** Elasticsearch\ **Created:** [October 8, 2012, 3:30pm UTC](https://discuss.elastic.co/t/client-transport-sniff-when-connecting-localhost-to-an-ec2-node/9273 "2012-10-08T15:30:20Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Jon\_Riegel](https://avatars.discourse-cdn.com/v4/letter/j/9de0a6/32.png) [@Jon\_Riegel](https://discuss.elastic.co/u/Jon_Riegel)\ **Post date:** [October 8, 2012, 3:30pm UTC](https://discuss.elastic.co/t/client-transport-sniff-when-connecting-localhost-to-an-ec2-node/9273/1 "2012-10-08T15:30:20Z")
I'm inexperienced with ES and EC2 so forgive me if this is a novice question. I'm attempting to run a local java/tomcat application, using the TransportClient to connect to ES running on EC2. I have the following configuration on the server (note: some items not included for the sake of brevity): discovery: type: ec2 ec2: tag: host\_type: public\_dns network: publish\_host: _ec2:publicDns_ On the client side: [host=ec2-23-XX-XX-XX.compute-1.amazonaws.com](http://host=ec2-23-XX-XX-XX.compute-1.amazonaws.com) port=9300 cloud.aws.access\_key= cloud.aws.secret\_key= cloud.aws.region=us-east-1b discovery.type=ec2 discovery.ec2.tag.stuff= discovery.ec2.host\_type=public\_dns So my initial connection is to the public domain, and I have the ports open to My initial connection appears to succeed, and the client also works fine when I set client.transport.sniff to false. I have set the log level to TRACE for org.elasticsearch.client.transport, so I can see this in my logs on the initial connection: 2012-10-08 08:38:21 DEBUG main org.elasticsearch.client.transport - [Gatecrasher] adding address [[#transport#-1][inet[[ec2-23-XX-XX-XX.compute-1.amazonaws.com/23.XX.XX.XX:9300](http://ec2-23-XX-XX-XX.compute-1.amazonaws.com/23.XX.XX.XX:9300)]]] From here we can see that, since localhost is outside of EC2, that domain name resolves to the external EC2 ip, 23.XX.XX.XX, and the client is able to connect. When I set client.transport.sniff to false, my client connects, the above is all I see in the logs, and searching/indexing works, so I don't believe I have any issues with firewalls, open ports or security groups. However, if I set sniff to true, the client "discovers" the node it has already connected to - except it attempts to reconnect using the internal IP, 10.YY.YY.YY: 2012-10-08 08:38:26 DEBUG main org.elasticsearch.client.transport - [Gatecrasher] failed to connect to discovered node [[Kleinstocks][yyexVITpQ-W8GPnl77LkJg][inet[/10.YY.YY.YY:9300]]] org.elasticsearch.transport.ConnectTransportException: [Kleinstocks][inet[/10.YY.YY.YY:9300]] connect\_timeout[5s] at org.elasticsearch.transport.netty.NettyTransport.connectToChannels(NettyTransport.java:612) at org.elasticsearch.transport.netty.NettyTransport.connectToNode(NettyTransport.java:554) My theory is that even though the server is publishing on public\_dns, it resolves the domain locally (to the internal ip) and then keeps the result, and then when nodes sniff it out, they attempt to connect to that cached result rather than resolving the domain. I have played with various settings trying to get around this - for example, if set network.publish\_host to _ec2:publicIp_ and restart, my local client connects, rediscovers the node and connects again, but I see this in the server logs, presumably because the server can't resolve the external IP: [2012-10-08 15:04:44,338][WARN][cluster.service] [Abraham Cornelius] failed to reconnect to node [Abraham Cornelius][zTWY25A5RzS31vLHzBak8A][inet[/23.XX.XX.XX:9300]] org.elasticsearch.transport.ConnectTransportException: [Abraham Cornelius][inet[/23.XX.XX.XX:9300]] connect\_timeout[30s] at org.elasticsearch.transport.netty.NettyTransport.connectToChannels(NettyTransport.java:640) at org.elasticsearch.transport.netty.NettyTransport.connectToNode(NettyTransport.java:579) at org.elasticsearch.transport.netty.NettyTransport.connectToNode(NettyTransport.java:549) I've also messed with ec2.discovery.host\_type and network.tcp.reuse\_address on the server and client sides, and network.publish\_host on the client side to no effect. So the questions: -Is my theory correct or am I missing something? -Is there a way to configure my client or server such that during the sniff/discovery process, internal nodes use the internal IP and external nodes (i.e. transport clients on webservers) use the external IP? -What exactly is the difference between the settings "network.publish\_host" and "ec2.discovery.host\_type"? I can work around this for now by disabling client.transport.sniff, but I'm posting the question because I feel like I'm missing some critical aspect of configuration that I will need down the line, and this feels like something that ought to work. Thanks for your attention. -- ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 3:09am UTC](https://discuss.elastic.co/t/client-transport-sniff-when-connecting-localhost-to-an-ec2-node/9273/2 "2017-07-06T03:09:44Z")