HP BL680c XenServer Software Development Kit Guide 4.1.0 - Page 23

Using the API

17

Events also contain a monotonically increasing ID, the name of the class of object and a snapshot of the

object state equivalent to the result of a

get_record()

.

Clients register for events by calling

event.register()

with a list of class names or the special string "*".

Clients receive events by executing

event.next()

which blocks until events are available and returns the

new events.

Note

Since the queue of generated events on the server is of finite length a very slow client might fail to

read the events fast enough; if this happens an

EVENTS_LOST

error is returned. Clients should be

prepared to handle this by re-registering for events and checking that the condition they are waiting

for hasn't become true while they were unregistered.

The following python code fragment demonstrates how to print a summary of every event generated by a

system: (similar code exists in

/SDK/client-examples/python/watch-all-events.py

)

fmt = "%8s

%20s

%5s

%s"

session.xenapi.event.register(["*"])

while True:

try:

for event in session.xenapi.event.next():

name = "(unknown)"

if "snapshot" in event.keys():

snapshot = event["snapshot"]

if "name_label" in snapshot.keys():

name = snapshot["name_label"]

print fmt % (event['id'], event['class'], event['operation'], name)

except XenAPI.Failure, e:

if e.details == [ "EVENTS_LOST" ]:

print "Caught EVENTS_LOST; should reregister"

4.2. Language bindings

Although it is possible to write applications which use the XenServer Management API directly through raw

XML-RPC calls, the task of developing third-party applications is greatly simplified through the use of a

language binding

which exposes the individual API calls as first-class functions in the target language. The

SDK includes language bindings and example code for the C, C# and python programming languages and

for both Linux and Windows clients.

4.2.1. C

The SDK includes the source to the C language binding in the directory

/SDK/client-examples/c

to-

gether with a Makefile which compiles the binding into a library. Every API object is associated with a head-

er file which contains declarations for all that object's API functions; for example the type definitions and

functions required to invoke VM operations are all contained with

xen_vm.h

.

C binding dependencies

Platform

supported:

Linux

Library:

The language binding is generated as a "libxen.a" that is linked by C programs.

Section	Page
XenServer Software Development Kit Guide	1
Table of Contents	4
Chapter 1. Introduction	7
Chapter 2. Getting Started	8
2.1. System Requirements and Preparation	8
2.2. Downloading	8
2.3. Installation	8
2.4. What's new	8
2.5. Content Map	8
2.6. Building Samples for the Linux Platform	9
2.7. Building Samples for the Windows Platform	9
2.8. Running the CLI	9
2.8.1. Tab Completion	9
2.9. Accessing SDK reference	9
Chapter 3. Overview of the XenServer API	11
3.1. Getting Started with the API	11
3.1.1. Authentication: acquiring a session reference	11
3.1.2. Acquiring a list of templates to base a new VM installation on	11
3.1.3. Installing the VM based on a template	12
3.1.4. Taking the VM through a start/suspend/resume/stop cycle	12
3.1.5. Logging out	12
3.1.6. \	13
3.2. Object Model Overview	13
3.3. Working with VIFs and VBDs	15
3.3.1. Creating disks and attaching them to VMs	15
3.3.1.1. Creating a new blank disk image	16
3.3.1.2. Attaching the disk image to a VM	16
3.3.1.3. Hotplugging the VBD	17
3.3.2. Creating and attaching Network Devices to VMs	17
3.3.3. Host configuration for networking and storage	17
3.3.3.1. Host storage configuration: PBDs	18
3.3.3.2. Host networking configuration: PIFs	18
3.4. Exporting and Importing VMs	18
3.5. Where to look next	19
Chapter 4. Using the API	20
4.1. Anatomy of a typical application	20
4.1.1. Choosing a low-level transport	20
4.1.2. Authentication and session handling	20
4.1.3. Finding references to useful objects	21
4.1.4. Invoking synchronous operations on objects	21
4.1.5. Using Tasks to manage asynchronous operations	22
4.1.6. Subscribing to and listening for events	22
4.2. Language bindings	23
4.2.1. C	23
4.2.2. C#	24
4.2.3. Python	24
4.2.4. Command Line Interface (CLI)	25
4.3. Complete application examples	25
4.3.1. Simultaneously migrating VMs using XenMotion	25
4.3.2. Cloning a VM via the XE CLI	28
Chapter 5. XenServer API extensions	30
5.1. VM console forwarding	30
5.1.1. Retrieving VNC consoles via the API	30
5.1.2. Disabling VNC forwarding for Linux VM	31
5.2. Paravirtual Linux installation	32
5.2.1. Red Hat Enterprise Linux 4.1/4.4	32
5.2.2. Red Hat Enterprise Linux 4.5/5.0	32
5.2.3. SUSE Enterprise Linux 10 SP1	33
5.2.4. CentOS 4.5/5.0	33
5.3. Adding Xenstore entries to VMs	33
5.4. Security enhancements	33
5.5. Advanced settings for network interfaces	34
5.5.1. ethtool settings	34
5.5.2. Miscellaneous settings	35
5.6. Internationalization for SR names	35
5.7. Hiding objects from XenCenter	36

HP BL680c XenServer Software Development Kit Guide 4.1.0 - Page 23

Language bindings, 4.2.1. C

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