HP BL680c XenEnterprise Management API - Page 5

Chapter 1

Introduction

This document defines the XenEnterprise Management API—an API for remotely configuring and

controlling virtualised guests running on a Xen-enabled cluster.

The API is presented here as a set of Remote Procedure Calls, with a wire format based upon

XML-RPC. No specific language bindings are prescribed, although examples will be given in the

python programming language.

Although we adopt some terminology from object-oriented programming, future client language

bindings may or may not be object oriented. The API reference uses the terminology

classes

and

objects

. For our purposes a

class

is simply a hierarchical namespace; an

object

is an instance of

a class with its fields set to specific values. Objects are persistent and exist on the server-side.

Clients may obtain opaque references to these server-side objects and then access their fields via

get/set RPCs.

For each class we specify a list of fields along with their

types

and

qualifiers

. A qualifier is one of:

•

RO

run

: the field is Read Only. Furthermore, its value is automatically computed at runtime.

For example: current CPU load and disk IO throughput.

•

RO

ins

: the field must be manually set when a new object is created, but is then Read Only

for the duration of the object’s life. For example, the maximum memory addressable by a

guest is set before the guest boots.

•

RW

: the field is Read/Write. For example, the name of a VM.

A full list of types is given in Chapter 2.

However, there are three types that require explicit

mention:

•

t

Ref

: signifies a reference to an object of type

t

.

•

t

Set

: signifies a set containing values of type

t

.

•

(

t

1

,t

2

)

Map

: signifies a mapping from values of type

t

1

to values of type

t

2

.

Note that there are a number of cases where

Ref

s are

doubly linked

—e.g. a VM has a field called

VIFs

of type (

VIF Ref

)

Set

; this field lists the network interfaces attached to a particular VM.

Similarly, the VIF class has a field called

VM

of type (

VM R

ef

) which references the VM to which

the interface is connected. These two fields are

bound together

, in the sense that creating a new

VIF causes the

VIFs

field of the corresponding VM object to be updated automatically.

The API reference explicitly lists the fields that are bound together in this way. It also contains a

diagram that shows relationships between classes. In this diagram an edge signifies the existance

of a pair of fields that are bound together, using standard crows-foot notation to signify the type

of relationship (e.g. one-many, many-many).

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HP BL680c XenEnterprise Management API - Page 5

Introduction

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