This library simplifies the requirements for building high availabilty coordination using https://www.consul.io/. It will manage the key and state, while allowing you to define functions for promotion, demotion, and health checks.
This package is intended to run as a process along side each consul server. Therefore, you should have a 1-1 ratio of consul server to process running this.
First, define your state handler for your monitored application or database:
class DatabaseHandler:
def __init__(self):
self
def is_leader(self):
# determine if process is the leader
# returns boolean
def passes_health_requirements(self, members_array):
# determine if this member is healthy enough to become primary
# returns boolean
def promote(self):
# actions taken, which promotes this member to leadership
def demote(self, leader):
# actions taken to demote this member from leadership
def follow_the_leader(self, leader):
# actions taken to ensure secondary member is following proper leaderThen, supply your initialized class to the a ConsulHa class:
from consulHa import ConsulHa
service_name = "my-database" # must match service name in Consul
demotion_delay_in_seconds = 60 # between 0 and 60 seconds
consul_ha = ConsulHa(service_name, demotion_delay_in_seconds)
consul_ha.state_handler = DatabaseHandler()
consul_ha.run()