Mirantis Fuel, which is a member of the OpenStack Big Tent, has already made itself one of the leading installers for OpenStack and offers a pluggable architecture that enable you to add new capabilities to your environments. XenServer Fuel Plugin aims to enable use of the XenServer open source hypervisor (versions greater than 6.5 SP1) as a Compute provider with Mirantis OpenStack, in a commercially supportable way.
To be more specific, we want to achieve the following major goals:
- Add customisation to the user interface
- Configuring OpenStack to use XenServer at install time
- Install required plugins and other pre-requisites
- Routing control networks to give access to dom0
- Update the XenServer OpenStack integration
- Replacing the test image
Moreover, Mirantis Fuel even provides a control plane to let you customise the UI. As long as you follow a schema like openstack.yaml, users can define their own OpenStack release. In Mirantis 8.0, users can even define their own resource type with components.yaml. In the screen shot above, a hypervisor type “XenServer” is defined. And if you choose it, the subsequent wizard and setting tabs will be represented based on your choice and the incompatible list described in components.yaml. This feature is useful because OpenStack setup is complicated and there are many restrictions. With the incompatible list, users will be prevented from making the wrong choices.
In addition to providing restrictions, Mirantis also provides a way to add input to the web UI. In environment_config.yaml, we define text fields to ask for XenServer credential information because we need to ssh into XenServer hosts to apply patches later on which will be presented to the user in the web UI.
For now, in Mirantis Fuel, there are only three built-in hypervisor types, which are QEMU, KVM and VMWare; XenServer isn’t included, by default. Our solution will perform the deployment with qemu as the hypervisor and configure to use XenServer when all prerequisites have been settled down. Changing the hypervisor type is quite straightforward; the settings below are added to /etc/nova/nova-compute.conf and the Nova services restarted.
But the timing to do the change might be tricky. Fortunately Mirantis Fuel provides a flexible hook mechanism based on Puppet task dependencies. Once it is done, the new hypervisor type will reflect in Horizon like below.
However, changing the hypervisor type is just the first step. The communication between XAPI and Nova services need to be set up like shown in the below diagram. So, we need to install some plugins.
Usually, the best way to apply patches to XenServer hosts or, more precisely, Dom0, is to pack the changed files into a XenServer supplemental pack and call xe CLI to install it.
Still, it’s important that the different components are installed in the correct order. The major steps can be install-pv-tool, install-dpkg-dependencies and install-sup-pack. So, the task dependencies look like this:
More information about Fuel’s hook mechanism can be found in deployment_tasks.yaml.
In XenServer, Host Internal Management Network (aka. HIMN) is a special internal network which is used for communication between the Compute VM and the Dom0 that it is running on. The HIMN has the following characteristics:
- It is a built-in network isolated from others.
- It is invisible in XenCenter, as it should not normally need to be modified.
- It presents is DHCP service on the network, with a fixed dom0 IP address of 169.254.0.1
The HIMN is ideal for internal use and you don’t have to spend effort on setting up one. More importantly, Dom0 need to have access to OpenStack control networks, as well as Compute nodes do. If we forward control packets via HIMN, that will be easier than setting up additional interfaces for Dom0. And in a sense, Dom0 and Compute node can be regarded as one entity.
In order to make full use of the HIMN, and ensure that dom0 can access the management networks set up by Mirantis Openstack, we need to configure the Compute VM to masquerade packets from dom0 using NAT techniques. Here is the code. We create iptable rules in Compute nodes:
br-storage and br-mgmt refer to OpenStack Storage network and Management networks. They are the OpenStack control networks we talk about. Then we change the default gateway in Dom0 for these two subnets:
This plugin can also be used to deliver bug fixes and new features that are being developed against OpenStack’s trunk, but are of significant importance to a Mirantis 8.0 OpenStack deployment, which is based on a stable branch of OpenStack:
- Neutron plugins : Neutron support for XenServer was introduced into upstream in Mitaka, cannot reflect in Mirantis Fuel 8 which uses Liberty.
- NoVNC proxy configuration : The XenServer VNC server runs on Dom0 but Mirantis Fuel assumes, by default, that it runs in Compute node.
- Guest console logs : Enabling serial consoles from guests requires a script to control disk usage and ensure the logs do not take unbounded space.
- Config drive configuration : Config drive should be set to the default option for file injection rather than libguestfs which is default for other QEMU-based hypervisors.
- Validation for hotfix : XenServer supplemental pack XS65ESP1013 needs to be installed otherwise Virtual Block Device (VBD) connections could be mapped incorrectly.
The default test image “TestVM” is a qemu-specific cirros so need to be replaced with one compatible with XenServer.
Please be noted that Fuel Health check, which will be covered in the next chapter, always picks up the test image “TestVM” as the name is hard-coded.
In the latest XenServer Fuel plugin 3.1 (corresponding to MOS 8.0), the TestVM image has been embedded in the plugin in case the deployment has no internet connection.
Fuel Health Check, or OpenStack Testing Framework (OSTF), is one of greatest advantages of Fuel. Fuel Health Check will go through the following categories of automated tests, and take usually 20-40 minutes to estimate the availability of a deployed environment.
If everything goes right, you will get a result report like below:
XenServer Fuel plugin has been validated since Fuel 6.1 and listed in the Fuel plugin Catalog. This is also where is most recommended to download it.
And the XenCenter HIMN plugin repo can be found under the GitHub account of Citrix OpenStack.