---
title: Charmhub | Deploy Hacluster using Charmhub - The Open Operator Collection
description: Deploy the latest version of Hacluster on any cloud. Corosync Cluster
  Engine - membership, messaging and quorum
url: https://charmhub.io/hacluster
---

# Hacluster

[OpenStack Charmers](https://charmhub.io/publisher/openstack-charmers "View all packages from OpenStack Charmers")

* [OpenStack Charmers](https://charmhub.io/publisher/openstack-charmers "View all packages from OpenStack Charmers")

Platform:

24.04

23.10

22.10

22.04

21.10

21.04

20.10

20.04

18.04

+4

2.4/stable 173

```
juju deploy hacluster --channel 2.4/stable
```

[Learn to deploy on juju >](https://juju.is/docs/juju/manage-applications)

---

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[Join the discussion](https://discourse.charmhub.io/)

# Overview

The hacluster charm provides high availability for OpenStack applications that lack native (built-in) HA functionality. The clustering solution is based on Corosync and Pacemaker.

It is a subordinate charm that works in conjunction with a principle charm that supports the ‘hacluster’ interface. The current list of such charms can be obtained from the [Charm Store](https://jaas.ai/search?requires=hacluster) (the charms officially supported by the OpenStack Charms project are published by ‘openstack-charmers’).

See [OpenStack high availability](https://docs.openstack.org/charm-guide/latest/admin/ha.html) in the [OpenStack Charms Deployment Guide](https://docs.openstack.org/project-deploy-guide/charm-deployment-guide) for a comprehensive treatment of HA with charmed OpenStack.

> **Note**: The hacluster charm is generally intended to be used with MAAS-based clouds.

**Important:** This documentation supports version `3.x` of the Juju client.
See the [OpenStack Charm
guide](https://docs.openstack.org/charm-guide/latest/project/support-notes.html#breaking-changes-between-juju-2-9-x-and-3-x) if you are using the `2.9.x` client.

# Usage

High availability can be configured in two mutually exclusive ways:

* virtual IP(s)
* DNS

The virtual IP method of implementing HA requires that all units of the clustered OpenStack application are on the same subnet.

The DNS method of implementing HA requires that [MAAS](https://maas.io/) is used as the backing cloud. The clustered nodes must have static or “reserved” IP addresses registered in MAAS. If using a version of MAAS earlier than 2.3 the DNS hostname(s) should be pre-registered in MAAS before use with DNS HA.

## Configuration

This section covers common configuration options. See file `config.yaml` for the full list of options, along with their descriptions and default values.

#### `cluster_count`

The `cluster_count` option sets the number of hacluster units required to form the principle application cluster (the default is 3). It is best practice to provide a value explicitly as doing so ensures that the hacluster charm will wait until all relations are made to the principle application before building the Corosync/Pacemaker cluster, thereby avoiding a race condition.

## Deployment

At deploy time an application name should be set, and be based on the principle charm name (for organisational purposes):

```
juju deploy hacluster <principle-charm-name>-hacluster
```

A relation is then added between the hacluster application and the principle application.

In the below example the VIP approach is taken. These commands will deploy a three-node Keystone HA cluster, with a VIP of 10.246.114.11. Each will reside in a container on existing machines 0, 1, and 2:

```
juju deploy -n 3 --to lxd:0,lxd:1,lxd:2 --config vip=10.246.114.11 keystone
juju deploy --config cluster_count=3 hacluster keystone-hacluster
juju integrate keystone-hacluster:ha keystone:ha
```

## Actions

This section lists Juju [actions](https://juju.is/docs/olm/working-with-actions) supported by the charm. Actions allow specific operations to be performed on a per-unit basis.

* `pause`
* `resume`
* `status`
* `cleanup`
* `update-ring`

To display action descriptions run `juju actions hacluster`. If the charm is not deployed then see file `actions.yaml`.

## Presenting status information

Here are a few examples of how to present useful information with the `status` action and the [jq](https://stedolan.github.io/jq/) utility.

* Querying for `online` and `standby` parameter values:

```
juju run --wait hacluster/leader status \
  --format json | jq '.[] | {(.UnitId):.results.result | fromjson \
  | .nodes | .[] | {unit_name: .name, online: .online, standby: .standby}}'
```

output example

```
{
  "hacluster/0": {
    "unit_name": "juju-a37bc0-3",
    "online": "true",
    "standby": "false"
  }
}
{
  "hacluster/0": {
    "unit_name": "juju-a37bc0-4",
    "online": "true",
    "standby": "false"
  }
}
{
  "hacluster/0": {
    "unit_name": "juju-a37bc0-5",
    "online": "true",
    "standby": "false"
  }
}
```

* Displaying cluster resource information:

```
juju run --wait hacluster/leader status \
  --format json | jq '.[] | {(.UnitId):.results.result | fromjson \
  | .resources.groups}'
```

# Bugs

Please report bugs on [Launchpad](https://bugs.launchpad.net/charm-hacluster/+filebug).

For general charm questions refer to the [OpenStack Charm Guide](https://docs.openstack.org/charm-guide).

---

[Help improve this document in the forum](https://discourse.charmhub.io/t/hacluster-docs-index/11216) ([guidelines](https://discourse.charmhub.io/t/how-to-write-docs-our-documentation-guidelines-for-contributors/1245)). Last updated 3 years ago.