OpenStack Charms 19.07 – Percona Cluster Cold Start, DVR SNAT and more

Tytus Kurek

on 14 August 2019

Canonical is proud to announce the availability of OpenStack Charms 19.07. This new release introduces a range of exciting features and several improvements which enhance Charmed OpenStack across various areas. Let’s talk about a few notable ones.

Percona cluster cold start

The percona-cluster charm now contains a new logic and actions to assist with operational tasks surrounding a database shutdown scenario. However, user interaction is still required.

In the event of an unexpected power outage and cold boot, the cluster will be unable to re-establish itself without manual intervention. In such situations, users should determine the node with the highest sequence number, and bootstrap the node by running the following action:

juju run-action –wait percona-cluster/<unit-number> bootstrap-pxc

In order to notify the cluster of the new bootstrap UUID, run the following action:

juju run-action –wait percona-cluster/<unit-number> notify-bootstrapped

The percona-cluster application will then return back to a clustered and healthy state.


The neutron-openvswitch charm now supports deployment of DVR (Distributed Virtual Routing) based routers with combined SNAT (Source Network Address Translation) functionality, removing the need to use the neutron-gateway charm in some types of deployment.

This implicitly requires that ‘external’ networks are routable to all hypervisors within the deployment to allow effective load balancing of SNAT routers and DVR services across the deployment.

In order to turn the feature on, run:

juju config neutron-openvswitch use-dvr-snat=True

Octavia image lifecycle management

This release introduces the octavia-diskimage-retrofit charm which provides a tool for retrofitting cloud images for use as Octavia Amphora.

One of the problems with Octavia was that it needs a method for generating base images to be deployed as load balancing entities. The octavia-diskimage-retrofit charm solves this problem by providing an action which, upon request, downloads the most recent Ubuntu Server or Minimal Cloud image from Glance, applies OpenStack Diskimage-builder elements from OpenStack Octavia and turns it into an image suitable for use by Octavia.

The charm can be deployed as a subordinate application as follows:

juju deploy glance-simplestreams-sync \
  –config source=ppa:simplestreams-dev/trunk

juju deploy octavia-diskimage-retrofit \
  –config amp-image-tag=octavia-amphora

juju add-relation glance-simplestreams-sync keystone
juju add-relation glance-simplestreams-sync rabbitmq-server 
juju add-relation octavia-diskimage-retrofit glance-simplestreams-sync 
juju add-relation octavia-diskimage-retrofit keystone

Once deployed the retrofitting process can be triggered as follows:

juju run-action octavia-diskimage-retrofit/leader retrofit-image

Nova live migration: Streamline SSH host key handling

This release of the nova-cloud-controller charm has improved the host key discovery and distribution algorithm. The net effect being that the addition of a nova-compute unit will be faster than before and the nova-cloud-controller upgrade-charm hook will be significantly improved for large deployments.

The Nova compute service uses direct (machine-to-machine) SSH connections to perform instance migrations. Each compute host must therefore be in possession of every other compute host’s SSH host key via the known hosts file. This release introduces a new boolean configuration option – cache-known-hosts – which allows any given host lookup to be performed just once.

In order to turn the feature on, run:

juju config nova-cloud-controller cache-known-hosts=True

In order to clear the cache, run:

juju run-action nova-cloud-controller clear-unit-knownhost-cache

For more information about OpenStack Charms 19.07, please refer to the official release notes.

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