Table of Contents
Primary and backup configuration
How to setup Trisul Hub and Probe in a High Availability configuration. This guide describes how a backup probe and hub can be setup to take over in case of a primary failure.
Setup
You need an identically sized backup installation of Trisul that can takeover the load in the event of a primary failure.
- Download the replication scripts sync.sh and host_alive.sh
Configure SSH between the primary and backup nodes
On both the primary and backup node use ssh_copy_id to allow login without an interactive password.
Data replication
The primary hub and probe nodes contains the database and configuration. We use a script based on RSYNC to replicate this database incrementally over to the backup node.
- Download the script sync.sh
- Edit the script to enter the IP Address of the Backup script
- In a SCREEN session run the backup script
On the primary node
screen ./rsync.sh
Heartbeat check
The backup node needs to keep checking the liveness of the primary node using a heartbeat.
On the backup node
screen ./host_alive.sh
Takeover
The keepalive uses a PING to check the reachability of the primary node. When a configured number of PINGs (default 6 PING failures) fail, the backup starts the Trisul HUB ad PROBE processes and this takes over the primary function.
Recovery
The recovery process is not automatic. After the primary node is restored, you stop the Trisul processes on the backup and start the process on the primary node.