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Nagios plugin to monitor AWS/EC2 Elastic Load Balancers for healthy hosts
#!/usr/bin/env python
"""
A nagios plugin for ensuring that load balancers have at least a certain
number of healthy nodes.
Usage:
Nagios Command:
define command {
command_name check_elb_healthy_hosts
command_line /path/to/virtualenv/bin/python /path/to/nagios-plugins/check_elb_healthy_hosts.py -k $USER3$ -s $USER4$ -n $HOSTALIAS$ -w $ARG1$ -c $ARG2$
}
Nagios Service:
define service {
check_command check_elb_healthy_hosts!2:!1:
notification_interval 0
use generic-service
service_description elb-healthy-hosts
hostgroup_name elb
}
Example Host (we use virtual hosts for ELBs; the alias (LB name) is important):
define host {
check_command check_http
address brooklynbeta-ssl-12345.us-east-1.elb.amazonaws.com
host_name lb_brooklynbeta-ssl-12345
alias brooklynbeta-ssl
use generic-host
hostgroups elb,http,https,elb-https
}
And finally, you'll need the credentials in Nagios's resources.cfg:
# AWS credentials (here so they can be embedded without revealing content)
# USER3 is the AWS key ID
# USER4 is the AWS secret access key
$USER3$=AAABLEEPBLOOP
$USER4$=blEeP+bloopity+rob0T+N01SE5
Boto and NagiosPlugin are available via PyPI/pip: https://pypi.python.org/pypi
"""
import os
from boto.ec2.elb import ELBConnection
import nagiosplugin
import argparse
class HealthyHosts(nagiosplugin.Resource):
"""Nagios Plugin Resource to check load balancers for the number of healthy hosts"""
def __init__(self, elb_conn, lb_name):
"""Set up instance variables"""
self.elb_conn = elb_conn
self.lb_name = lb_name
def probe(self):
"""Actually check AWS/EC2 via boto"""
health = self.elb_conn.describe_instance_health(self.lb_name)
healthy_count = 0
for instance in health:
if instance.state == 'InService':
healthy_count += 1
# truncates to a max of 20 characters
return [nagiosplugin.Metric(self.lb_name[:20], healthy_count, context="hosts")]
class HealthySummary(nagiosplugin.Summary):
"""Summary class for Nagios Plugin"""
def ok(self, results):
"""Human-readable status line"""
return 'healthy hosts for %s' % str(results[0])
@nagiosplugin.guarded
def main():
"""Main check"""
# Parse arguments
argp = argparse.ArgumentParser(description="Nagios plugin to check ELB instance health")
# outside of 2 to infinity
argp.add_argument('-w', '--warning', metavar='RANGE', default='2:',
help='return warning if healthy instances is outside RANGE')
# outside of 1 to infinity
argp.add_argument('-c', '--critical', metavar='RANGE', default='1:',
help='return critical if healthy_instances is outside RANGE')
argp.add_argument('-n', '--name', required=True, help="Load Balancer name")
argp.add_argument('-k', '--key', required=True, help="AWS Access Key ID")
argp.add_argument('-s', '--secret', required=True, help="AWS Secret Access Key")
argp.add_argument('-v', '--verbose', default=False, action="store_true", help="Verbose")
args = argp.parse_args()
# establish EC2/ELB connection (Boto)
elb_conn = ELBConnection(
aws_access_key_id = args.key,
aws_secret_access_key = args.secret
)
# Hook the actual nagios plugin
check = nagiosplugin.Check(
HealthyHosts(elb_conn, args.name),
nagiosplugin.ScalarContext('hosts', args.warning, args.critical),
HealthySummary())
check.main(verbose=args.verbose)
if __name__ == '__main__':
main()
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