Difference between revisions of "Nova Compute Load Averages"

Revision as of 14:04, 17 February 2014

Introduction

The system load averages for the past 1, 5 and 15 minutes are returns by the command "uptime" on linux based system. The load averages are not normalized for the number of CPUs in a system, so a load average of 1 means a single CPU system is loaded all the time while on a 4 CPU system it means it was idle 75% of the time.

Overview

Currently the base classe `virt.driver.ComputeDriver` defines a method "get_host_uptime". The method asks the driver to call the command uptime but does not define a correct output format.

libvirt

get_host_uptime: 13:37:30 up 7 days,  4:29, 19 users,  load average: 0.04, 0.04, 0.0

vmware

get_host_uptime: Please refer to {HOST_IP} for the uptime

xenapi

get_host_uptime: 13:37:30 up 7 days,  4:29, 19 users,  load average: 0.04, 0.04, 0.0

Proposal

The proposal is to have the drivers returns the following information in a dictionary. The load average will be in a tuple of the 1, 5 and 15 minutes based system load averages normalized by the number of CPUs in the system. So a load average of 1 means the system is loaded all the time even if there is 1 or n CPUs .

   {
      "time": 15:57:03, 
      "up": 5:22,
      "users": 3,
      "loadavg": (0.2, 0.55, 0.01)
   }

Usage

V2 REST API - no changes. This will ensure that the code is backward compatible and users that have applications written against the V2 API will continue to work. In this case only the raw data will be returned.
V3 REST API- the data defined above will be returned

The blueprint can be seen at: https://blueprints.launchpad.net/nova/+spec/compute-loadavg

@@ Line 20: / Line 20: @@
      }
-=== Implementation Details ===
+=== Usage ===
-An additional method `get_host_loadavg` will be added to `virt.driver.ComputeDriver`. This method will returns a tuple of the last 1, 5, and 15minutes of the system load average normalized by the number of CPUs by invoking the standard command `uptime`
+* V2 REST API - no changes. This will ensure that the code is backward compatible and users that have applications written against the V2 API will continue to work. In this case only the raw data will be returned.
+* V3 REST API- the data defined above will be returned
+The blueprint can be seen at: https://blueprints.launchpad.net/nova/+spec/compute-loadavg