Best Practices for Configuring /etc/hosts

Products

• VMware Tanzu Greenplum

Issue/Introduction

This article explains setting up of /etc/hosts to prevent INTERCONNECT and NETWORK errors when running GPDB scripts that involve the communication between the Master and Segments and sometimes the Standby Master too.

 

Environment

Cause

The objective is to avoid the interconnect and networking errors when running scripts like gpcheckcat, segments trying to grab a sequence, which uses entries in /etc/hosts. 

 

Resolution

While setting up a GPDB multinode cluster follow the best practices as shown below to create /etc/hosts

Find out the right interface that is open for communication. For example, if eth1 is the network interface configured, find out the IP on all of the hosts (master, segments, and standby-master) by running /sbin/ifconfig eth1. Find out the hostname of the server using "hostname"

vi /etc/hosts on master host, every host needs to know who "mdw" is, so the alias in GPDB for master should always be mdw.

All segment hosts and standby master hosts and entries are mentioned below:

<eth1-ip-from-master> full-hostname mdw
<eth1-ip-from-segment1> full-hostname short-hostname
<eth1-ip-from-segment2> full-hostname short-hostname
<eth1-ip-from-segmentn> full-hostname short-hostname
<eth1-ip-from-standby-master> full-hostname short-hostname 

To find out if a port is open, use the below command:

telnet <ip-address> <port-used-for-communication>

Additional Information

Below are typical errors seen when /etc/hosts are not configured properly

• Query Fails with "Interconnect Error- Could not connect to seqserver, Connection timed out" when the Sequence Cache is Very Big
• Interconnect Error Writing an Outgoing Packet: Network is unreachable" seen during gpcheckcat Execution