KB-1687 Unable to connect to other servers in HA environment

Symptoms

• During start-up servers are not able to find Kafka broker on other servers.  
• Unable to telnet to other servers on the Kafka port. 
• The engines fail to start up.
• Following errors are observed in service_manager.log located in <APPIAN-HOME>/logs/:

WARN [ReplicaFetcherThread-0-2], Error in fetch kafka.server.ReplicaFetcherThread$FetchRequest@3905d112 (kafka.server.ReplicaFetcherThread)
java.io.IOException: Connection to <server's IP address>:9092 (id: 2 rack: null) failed
...
Waiting for <number of servers> brokers to be available. 
...
Unable to connect to Kafka broker <server's IP address>

Cause

Improper network connectivity can lead to this issue. Active firewalls on one or more of the servers running Appian can prevent the servers from communicating with each other.

Action

Check for active firewall rules or other network configuration which is preventing the servers from communicating with each other. 

Affected Versions

This article applies to all versions of Appian.

Last Reviewed: August 2018