Feature pages are design documents that developers have created while collaborating on oVirt.

Most of them are outdated , but provide historical design context.

They are not user documentation and should not be treated as such.

Documentation is available here.

overview

In 4.0 onward adding more hosts to the hosted engine cluster is supported only via the engine. This has various advantages:

  1. It's one place, that takes advantage of SDK, REST, UI. validations etc.
  2. The hosts are now part of the cluster and datacenter with regards to host_id - there will be no collision/distinction between hosted engine or other host that try to monitor domains.

High level

To deploy hosted engine we extended the host-deploy subsystem API to support an action - deploy/remove and default none.

The engine, when it invokes host-deploy that installs vdsm RPMs, will now also install the hosted engine RPMs. In addition, it will take the hosted-engine.conf as an argument and will place it under /etc. This is enough to get a host into the HA cluster.

To un-deploy or remove the hosted engine role of a host the engine passes action=remove and then host-deploy empties the configuration files so the HA agent is practically non-functional.

Detailed flow

Supply detailed into on how to get the info from the disk, and what is the host-deploy enums we use

UI side dialog tab

The UI of 'Add' and 'Reinstall' host has a new side panel named 'Hosted-Engine'. It supplies 3 options for the deployment of a host:

  • 'None' meaning don't touch the hosted-engine components
  • 'Deploy' meaning install the ovirt-hosted-engine-ha rpms, place a custom hosted-engine.conf under /etc and start the service
  • 'Undeploy' Remove the hosted-engine.conf and rpms. That action decomissions a host from the HA cluster of hosted engine.

REST request parameters

The API exposes those URLs to implement the 3 proposed actions as the UI:

  • Add Host
  • None - done pass any argument
  • Deploy
    • POST …/hosts?deploy_hosted_engine
    • POST …/hosts?deploy_hosted_engine=true
  • Undeploy
    • POST …/hosts?undeploy_hosted_engine
    • POST …/hosts?undeploy_hosted_engine=true
  • Install Host
  • None - done pass any argument
  • Deploy
    • POST …/hosts/xxx/install?deploy_hosted_engine
    • POST …/hosts/xxx/install?deploy_hosted_engine=true
  • Undeploy
    • POST …/hosts/xxx/install?undeploy_hosted_engine
    • POST …/hosts/xxx/install?undeploy_hosted_engine=true