Powerchain support

[aquette]

The idea behind the PowerChain is simple:
There are many links in a powerchain, that supplies power to a device (server, appliance, ...):

• power supply unit,
• UPS,
• PDU.
• STS (static transfer switch),
• bypass module,
• genset,
• ...

Monitoring only UPS is not sufficient to guaranty a smart power protection.
Having a consolidated view on the whole also allows real HA, Green Grid and SmartGrid features.

An example PowerChain for the CLC would be:

PSU1 ==> PDU1:outlet1 ==> UPS1 ==> Main Power
PSU2 ==> PDU2:outlet1 ==> UPS2 ==> Main Power

Other details:

• a parent can have multiple children (UPS, PDU, ...)

• A child can have multiple parents (STS)

  The branch "powerchain" implements this feature: https://github.com/networkupstools/nut/tree/powerchain

Tasks list:

• Create a new power supply unit (PSU) driver,

• Create a new NUT data, 'device.parent', defined in ups.conf and exposed by all NUT drivers.
  This will store the parent reference in NUT canonical form:

  device[:outlet][@hostname[:port]]

  Example:
  ups.conf
  [psu1]
  driver = nut-psu
  port = psu1
  parent = pdu1:outlet1@localhost
  [pdu1]
  driver = snmp-ups
  port =
  parent = ups1@localhost
  [ups1]
  driver = usbhid-ups
  port = auto
  parent = main

  $ upsc psu1 device.parent
  pdu1:outlet1@localhost

• Implement power-chain support in upsc ('-P' option to get a tree list, when using '-l' and '-L')
  Note: only the first version, with coma separators.

  $ upsc -P localhost
  psu1 -> pdu1:outlet1 -> ups1

  $ upsc -Pl localhost
  ups1
  |-> pdu1:outlet1
  |-> pdu1

• Implement a *tree store for upsd, to fix the lack of the current one (powerchain_t, in server/powerchain.ch

• Implement power-chain support in upsmon