Difference between revisions of "Nova Compute Load Averages"

Revision as of 10:46, 18 February 2014

Introduction

The system load averages for a compute could be used to define policies during the scheduler of an instance. Unix based system provides a text file '/proc/loadavg' that allow to get information of the system load averages for the last 1, 5, and 15 minutes.

Overview

Currently the base class `virt.driver.ComputeDriver` defines a method "get_host_uptime". The method asks the driver to call the command 'uptime'. This command provides the system load averages and some other information, the problem is that, this method does not define a correct output format and a reflexion is necessary about the really necessity to keep the API.

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 define a new API 'loadavg' that return a tuple for the last 1, 5 and 15 minutes of the system load averages.

   {
       "hypervisor": {
           "hypervisor_hostname": "fake-mini",
           "id": %(hypervisor_id)s,
           "loadavg": [0.20, 0.12, 0.14]
       }
   }

Implementation

A new method will be added to 'nova.virt.driver' called 'get_host_loadavg'
A new API will be added to 'nova.api.openstack.hypervisors' called 'loadavg'

Usage

V2 REST API: not implemented.
V3 REST API: /v3/os-hypervisors/{ID}/loadavg

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

@@ Line 1: / Line 1: @@
 == 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.
+The system load averages for a compute could be used to define policies during the scheduler of an instance. Unix based system provides a text file '/proc/loadavg' that allow to get information of the system load averages for the last 1, 5, and 15 minutes.
 == 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.
+Currently the base class `virt.driver.ComputeDriver` defines a method "get_host_uptime". The method asks the driver to call the command 'uptime'. This command provides the system load averages and some other information, the problem is that, this method does not define a correct output format and a reflexion is necessary about the really necessity to keep the API.
 === libvirt ===
@@ Line 12: / Line 13: @@
 == Proposal ==
-The proposal is to have the drivers returns the following information in a dictionary. The load average will be in a tuple for the last 1, 5 and 15 minutes. The uptime is the number of seconds the system is up.
+The proposal is to define a new API 'loadavg' that return a tuple for the last 1, 5 and 15 minutes of the system load averages.
      {
-       "time": "15:57:03",
+        "hypervisor": {
-       "uptime": 634423.26,
+            "hypervisor_hostname": "fake-mini",
-       "users": 3,
+            "id": %(hypervisor_id)s,
-       "loadavg": [0.31, 0.17, 0.14],
+            "loadavg": [0.20, 0.12, 0.14]
+        }
      }
+=== Implementation ===
+* A new method will be added to 'nova.virt.driver' called 'get_host_loadavg'
+* A new API will be added to 'nova.api.openstack.hypervisors' called 'loadavg'
 === 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.
+* V2 REST API: not implemented.
-* V3 REST API- the data defined above will be returned
+* V3 REST API: /v3/os-hypervisors/{ID}/loadavg
 The blueprint can be seen at: https://blueprints.launchpad.net/nova/+spec/compute-loadavg