The PSU CLI and SNMP support - Staphylo/SONiC GitHub Wiki

The PSU CLI and SNMP support

High Level Design Document

Rev 0.3

List of Tables
Revision
About this Manual
Scope
Definitions/Abbreviation
1 Overview
- 1.1 PSU Chart
- 1.2 Modules description
  - 1.2.1 SNMP agent
  - 1.2.2 SONiC-utilities
2 Requirements
3 Modules Design
- 3.1 Modules that need to be updated
  - 3.1.1 SNMP agent
  - 3.1.2 SONiC-utilities
4 Flows
- 4.1 Get the PSU status by CLI
- 4.2 Get the PSU status by SNMP
5 Open Questions

List of Tables

Table 1: Revision
Table 2: Abbreviations

Revision

Rev	Date	Author	Change Description
0.1		Andrii Savka	Initial version
0.2		Andrii Savka	Added presence status to API and CLI

About this Manual

This document provides general information about the PSU CLI and SNMP support feature.

Scope

This document describes the high level design of the PSU CLI and SNMP support feature.

Definitions/Abbreviation

Table 2: Abbreviations

Definitions/Abbreviation	Description
SNMP	Simple Network Management Protocol
PSU	Power supply unit
API	Application Programmable Interface
CLI	Command-line utility

1 Overview

1.1 PSU Chart

Following diagram describes a top level overview of the SONiC PSU architecture:

1.2 Modules description

1.2.1 SNMP agent

The agent handles the SNMP requests and takes the PSU status from PSU API.

1.2.2 SONiC-utilities

The command-line utilities for SONiC

1.2.3 PSU daemon

The daemon is to collect the PSU information and write to state DB.

2 Requirements

2.1 Platform PSU API

Microsoft will develop a simple plugin-style API in the vein of sfputil.py and led_control.py. Each vendor needs to implement the PSU module for API which should consist the implementation of each function. The API has the following functions:

API	Return value	Description
get_num_psus()	integer	the number of PSUs which are supported in the platform
get_psu_status(psu_index)	True if PSU has correct functioning, False if not.	Function takes a zero-based PSU index and provides the status. Any platform-specific appropriate voltage/amperage/temperature calculations should be carried out to determine whether the PSU is operating properly or not.
get_psu_presence(psu_index)	True if PSU is plugged, False if not.	Function takes a zero-based PSU index and provides the presence info

2.2 Command-line utility for querying PSU status

Mellanox will implement a simple Python command-line utility which implements the plugin and can output the status of each PSU/all PSUs. The CLI will get the data from state DB to show the PSU status and presence info. The CLI should have the following behavior:

Input parameters	CLI expected result
No Input parameters	Provide the status of all PSUs which are available in the platform
PSU ID	Provide the status for specific PSU

The CLI has a following output:

Module	Status
PSU 1	OK (status == True, presence == True)
PSU 2	NOT OK (status == False, presence == True)
PSU X	NOT PRESENT (presence == False)

2.3 SNMP agent support

Mellanox will add the PSU support to SNMP agent for retrieving PSU statuses. Querying below OID should return the status of PSU/PSUs in the platform. The response has following integer values:

“1” for proper operational status
“0” for faulty

The following OID should be supported:

OID	Description of the SNMP instance
1.3.6.1.4.1.9.9.117.1.1.2	cefcFRUPowerStatusTable
1.3.6.1.4.1.9.9.117.1.1.2.1	cefcFRUPowerStatusEntry
1.3.6.1.4.1.9.9.117.1.1.2.1.2	return the statuses of all PSUs which are available in the platform
1.3.6.1.4.1.9.9.117.1.1.2.1.2.psu_index	return the status of PSU specified by psu_index

3 Modules Design

3.1 Modules that need to be updated

3.1.1 SNMP agent

The support for the new PSU OID should be added.

3.1.2 SONiC-utilities

The following components should be implemented:

The PSU plugin-style API for SONiC that takes a zero-based PSU ID and returns a boolean value indicating the status of the PSU.
The Python command-line utility that provides the PSU(s) status. Also PSU status should be available in general "show platform psustatus" command.
Each vendor needs to provide the PSU module which should consists the implementation of PSU API. The module should be placed under "sonic-buildimage/device/[vendor]/[platform]/plugins/psuutil.py" directory and will be loaded by CLI.

3.1.3 PSU daemon

Supervisord takes charge of this daemon. This daemon will loop every 3 seconds and get the data from PSU API and then write it the state DB.
The num_psus will store in "chassis_info" table. It will just be invoked one time when system boot up or reload. The key is chassis_name, the field is "num_psus" and the value is gotten from PSU API get_num_psus().
The psu_status and psu_presence will store in "psu_info" table. It will be updated every 3 seconds. The key is psu_name, the field is "presence" and "status", the value is from PSU API get_psu_presence() and get_psu_num().