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Most of them are outdated, but provide historical design context.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

Detailed Host PM Multiple Agents

Host Power Management Multiple Agent Support


Current implementation assumes that a Host that its Power Management is configured has only one fencing agent from a certain type (i.e. rsa, ilo, apc etc.) This document describes what should be done in order to support dual-power Hosts in which each power switch may have its own agent or two agents connected to the same power switch. Agents may be from same or different type We will treat current Power Management agent as Primary Agent and the added one as Secondary Agent.


  • Feature owner: Eli Mesika (emesika)

    • GUI Component owner: Eli Mesika (emesika)

    • REST Component owner: Eli Mesika (emesika)

    • Engine Component owner: Eli Mesika (emesika)

    • QA Owner: Yaniv Kaul (ykaul)

  • Email:

Current status

  • Target Release: 3.2
  • Status: Design
  • Last updated date: Nov 15 2012

Detailed Description

There may be two main configurations for Primary/Secondary Agents: 1) Concurrent, when Host is fenced both agents are used concurrently, for Stop command we need both to succeed and for Start command if one succeeded the Host is considered to be UP. 2) Sequential, when Host is fenced either for Stop or Start commands, Primary Agent is used, if it fails (after all configured retries) then the Secondary Agent is used.


Adding the following columns to vds_static:



 vds (adding all pm_secondary* fields)
      vds_with_tags (adding all pm_secondary* fields)
      dwh_host_configuration_history_view (adding only pm_secondary_ip)
      dwh_host_configuration_full_check_view (adding only pm_secondary_ip)

Stored Procedures:



Adding handling of pm_secondary* fields to



Adding test data for VdsStaticDAOTest and fixtures.xml


Change default configuration FenceStopStatusDelayBetweenRetriesInSec and FenceStartStatusDelayBetweenRetriesInSec to 10 and FenceStopStatusRetries , FenceStartStatusRetries to 18, this will insure we are responding faster to Hosts while it change status.

Business Logic

Add pm_secondary* fields to VdsStatic Add pm_secondary* fields to VDS Changing FenceVdsBaseCommand::executeCommand() to handle all scenarios described in Flow


The REST API will be enhanced to include the multiple Agents definitions as follows Keep in mind that we should preserve the former syntax for backward compatibility and deprecate it in future For any case in which we found old flat PM definitions and other definitions inside the agents block, the setting in the agent block will take presence.

<power_management type="rsa">
  <address>ip or fqdn</address>
  <options><option value="" name="port"/><option value="false" name="secure"/></options>
    <agent type="rsa">
      <address>ip or fqdn</address>
      <username>user</username> order="primary"
      <options><option value="" name="port"/><option value="false" name="secure"/></options>
    <agent type="ipmi">
      <address>ip or fqdn</address>
      <username>user</username> order="primary"
      <options><option value="" name="port"/><option value="false" name="secure"/></options>

concurrent flag will be handled in the Host level Add custom mapping for these new power-management fields in, for both REST–>Backend and Backend–>REST directions)


No Secondary Agent If no Power Management is defined , the Stop/Start scenarios works without a change. For example, the Restart scenario is:

   Send a Stop command
   Wait for status 'off' [1]
   Send a Start command
   Wait for status 'on' [2]

If a secondary agent is defined Sequential: Send a Stop command to Primary agent

   Wait for status 'off' [1]
   If Stop failed
      Send a Stop command to Secondary agent and wait for status 'off'
   Send a Start command to Primary agent
   Wait for status 'on' [2]
   If Start failed
      Send a Start command to Secondary agent and wait for status 'on'


   Send a Stop command to Primary and Secondary agents
   Wait for status 'off' on both Primary and Secondary agents[1]
   Send a Start command to Primary and Secondary agents
   Wait for status 'on' on either  Primary or Secondary agent[2]

[1] Controlled by FenceStopStatusDelayBetweenRetriesInSec,FenceStopStatusRetries configuration values [2] Controlled by FenceStartStatusDelayBetweenRetriesInSec,FenceStartStatusRetries configuration values

User Experience

A new drop-down box will be added to the Power Management screen that enables selection of Primary/Secondary agents in order to insert agent details and test the agent. The Concurrent check box controls if the secondary agent works in the concurrent or sequential mode


Add the new pm_secondary* columns in the upgrade script.

User work-flows


Affected oVirt projects

Host Power Management Proxy Preferences

Documentation / External references


Future Directions

For 3.2 we will handle only Primary/Secondary agents We may add 3rd agent support in future to handle other scenarios