How to enable high availability

Overview

Region and rack controllers manage load balancing and failover automatically. This guide explains how to configure and optimize these features.

Enabling HA

To enable HA, install multiple rack controllers:

sudo snap install maas
sudo maas init rack --maas-url $MAAS_URL --secret $SECRET

For package installs:

sudo apt install maas-rack-controller
sudo maas-rack register --url $MAAS_URL --secret $SECRET

The $SECRET is stored at:

• /var/snap/maas/common/maas/secret (Snap)
• /var/lib/maas/secret (Package)

The UI also provides install instructions under Controllers > Add rack controller.

List racks

maas $PROFILE rack-controllers read | grep hostname | cut -d '"' -f 4

Multiple racks are required for HA. Ensure VM hosts can communicate with new rack controllers.

Delete a rack controller

UI:
Controllers > Select Controller > Delete

CLI:

maas $PROFILE rack-controller delete $SYSTEM_ID

Deleting a DHCP HA rack controller requires disabling DHCP HA first. If software is not removed, a reboot reinstates the rack controller.

Moving a rack controller

Moving a rack controller between MAAS instances or versions is unsupported and may cause data loss. Instead:

1. Delete the rack controller:

   maas $PROFILE rack-controller delete $SYSTEM_ID
   

2. Register a new one:

   sudo maas-rack register --url $NEW_MAAS_URL --secret $NEW_SECRET
   

Rack controller warnings

Avoid these mistakes:

• Rack + VM Host: Resource contention may degrade performance.
• Version Mismatch: A rack controller cannot be moved between MAAS versions.
• Multiple MAAS Connections: One rack controller cannot serve multiple MAAS instances.

Region controllers

Add a region controller

On a secondary host, add the new region controller by installing maas-region-api:

sudo apt install maas-region-api

You will need the /etc/maas/regiond.conf file from the primary API server. Below, we assume it can be copied (scp) from the ‘ubuntu’ account home directory using password authentication (adjust otherwise). The local_config_set command will edit that file by pointing to the host that contains the primary PostgreSQL database. Do not worry: MAAS will rationalise the DNS (bind9) configuration options so that they match those used within MAAS:

sudo systemctl stop maas-regiond
sudo scp ubuntu@$PRIMARY_API_SERVER:regiond.conf /etc/maas/regiond.conf
sudo chown root:maas /etc/maas/regiond.conf
sudo chmod 640 /etc/maas/regiond.conf
sudo maas-region local_config_set --database-host $PRIMARY_PG_SERVER
sudo systemctl restart bind9
sudo systemctl start maas-regiond

Check log files for any errors.

PostgreSQL HA

All region controllers must connect to the same PostgreSQL database.

1. Allow secondary API server:

   echo "host maasdb maas $SECONDARY_API_IP/32 md5" | sudo tee -a /etc/postgresql/9.5/main/pg_hba.conf
   sudo systemctl restart postgresql
   

2. Add a region controller:

   sudo apt install maas-region-api
   

3. Configure it:

   sudo scp ubuntu@$PRIMARY_API:/etc/maas/regiond.conf /etc/maas/
   sudo maas-region local_config_set --database-host $PRIMARY_PG_SERVER
   sudo systemctl restart bind9
   sudo systemctl start maas-regiond
   

Region performance

Increase num_workers in /etc/maas/regiond.conf for better performance:

num_workers: 8

Each worker requires 11 additional PostgreSQL connections. Recommended: 1 worker per CPU, up to 8 total.

HA for BMC and DHCP

BMC HA

Adding a second rack controller enables automatic BMC load balancing.

DHCP HA

Rack controllers replicate DHCP leases, improving failover. DHCP HA setup:

failover peer "failover-partner" {
     primary;
     address dhcp-primary.example.com;
     peer address dhcp-secondary.example.com;
     split 255;
}
failover peer "failover-partner" {
     secondary;
     address dhcp-secondary.example.com;
     peer address dhcp-primary.example.com;
}

Enable DHCP after adding a rack controller:

UI

Subnets > VLAN > Reconfigure DHCP

CLI

vid=$(maas maas subnets read | jq -r '.[] | select(.cidr == "10.0.0.0/24") | .vlan.vid')
fabric_id=$(maas maas fabrics read | jq -r '.[] | select(.name == "fabric-1") | .id')
maas maas vlan update $fabric_id $vid primary_rack=$(hostname) dhcp_on=true

Multiple endpoints

MAAS discovers and connects to available region controllers. You can manually define multiple endpoints in:

• /var/snap/maas/current/rackd.conf (Snap)
• /etc/maas/rackd.conf (Package)

maas_url:
  - http://<ip1>:<port>/MAAS/
  - http://<ip2>:<port>/MAAS/

HA region controllers

Load balancing region controllers is recommended.

PostgreSQL HA

MAAS requires PostgreSQL HA for true region HA. Follow the PostgreSQL HA guide.

Each region controller requires 40 database connections under high load. Increase max_connections accordingly.

API HA with HAProxy

To enable API HA, install and configure HAProxy:

sudo apt install haproxy

Configure /etc/haproxy/haproxy.cfg:

frontend maas
    bind    *:80
    default_backend maas

backend maas
    balance source
    server localhost localhost:5240 check
    server maas-api-1 $PRIMARY_API_SERVER_IP:5240 check
    server maas-api-2 $SECONDARY_API_SERVER_IP:5240 check

Restart HAProxy:

sudo systemctl restart haproxy

Use port 80 instead of 5240 for API/UI access.

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Last updated 3 days ago.