kolla-ansible/doc/source/reference/high-availability/haproxy-guide.rst

HAProxy Guide

Kolla Ansible supports a Highly Available (HA) deployment of Openstack and other services. High-availability in Kolla is implented as via Keepalived and HAProxy. Keepalived manages virtual IP addresses, while HAProxy load-balances traffic to service backends. These two components must be installed on the same hosts and they are deployed to hosts in the loadbalancer group.

Preparation and deployment

HAProxy and Keepalived are enabled by default. They may be disabled by setting the following in /etc/kolla/globals.yml:

enable_haproxy: "no"
enable_keepalived: "no"

Single external frontend for services

Single external frontend for particular service can be enabled by adding the following in /etc/kolla/globals.yml (feature and example services):

haproxy_single_external_frontend: true

nova_external_fqdn: "nova.example.com"
neutron_external_fqdn: "neutron.example.com"
horizon_external_fqdn: "horizon.example.com"
opensearch_external_fqdn: "opensearch.example.com"
grafana_external_fqdn: "grafana.example.com"

The abovementioned functionality allows for exposing of services on separate fqdns on commonly used port i.e. 443 instead of the usual high ports.

Configuration

Failover tuning

When a VIP fails over from one host to another, hosts may take some time to detect that the connection has been dropped. This can lead to service downtime.

To reduce the time by the kernel to close dead connections to VIP address, modify the net.ipv4.tcp_retries2 kernel option by setting the following in /etc/kolla/globals.yml:

haproxy_host_ipv4_tcp_retries2: 6

This is especially helpful for connections to MariaDB. See here, here and here for further information about this kernel option.

Backend weights

When different baremetal are used in infrastructure as haproxy backends or they are overloaded for some reason, kolla-ansible is able to change weight of backend per sevice. Weight can be any integer value from 1 to 256.

To set weight of backend per service, modify inventory file as below:

[control]
server1 haproxy_nova_api_weight=10
server2 haproxy_nova_api_weight=2 haproxy_keystone_internal_weight=10
server3 haproxy_keystone_admin_weight=50

HTTP/2 Support

HAProxy with HTTP/2 frontend support is enabled by default. It may be disabled by setting the following in /etc/kolla/globals.yml:

haproxy_enable_http2: "no"