Xen Summit 2008 Tokyo - Operating Xen domains through LL(Perl/Python) with libvirt

Xen Summit 2008 Tokyo 2008/11/21 paperboy&co. Gosuke Miyashita

Agenda
About me
Purpose of this talk
What is libvirt
libvirt Xen driver architecture
libvirt sample codes with Perl/Python
Related tools (Avahi and Func)

About me
Gosuke Miyashita
http://mizzy.org/
Technical manager at paperboy&co.
Web hosting, blog, ec hosting and so on for indivisuals
Thinking introduce virtualization technologies to our services

Purpose of this talk
I seek how to manage Xen domains on many host machines
I need a simple and customizable tool
It may be fast to develop my own tool
libvirt is the one for developing my own Xen management tool
Why python and perl?
These languages may be used widly in system administration

What is libvirt?
The virtualization API
A library intracts with virtualization systems
Xen, QEMU, KVM, LXC and OpenVZ
Language bindings
C, Python, Perl, OCaml, Ruby, Java and C#
Support multiple authentication methods
SSH, TLS and X.509, SASL and Kerberos
Avahi multicast DNS support

What can you do with libvirt?
Get Dom0 info
CPU model/threads/cores, memory size and so on
List domains
Get domain info
id, uuid, name, xml description, os type and state
Various domain operations
create, shutdown, reboot, suspend, resume
set/get max memory/memory size, get max vcpus
Network, Storage operations (excluded in this talk)
See http://libvirt.org/html/libvirt-libvirt.html

libvirt Xen driver(local) xend xenstored xen hypervisor libvirt Perl Python OCaml Ruby Java C# C

libvirt Xen driver(remote) xend xenstored xen hypervisor libvirtd Perl Python OCaml Ruby Java C# C libvirt Over a network

Perl code example
use Sys::Virt ;
# connect to the remote host
my $vmm =
Sys::Virt->new( uri => "xen://remote_host/“ );
# get domains
my @doms = $vmm->list_domains;
# print state of each domains
for my $dom ( @doms ) {
printf " %s: %s " ,
$dom->get_name, $dom->get_info->{ state };
}

Python code example
import libvirt
# connect to the remote host
conn = libvirt.open(‘ xen://remote_host/’ )
# get domain ids
ids = conn.listDomainsID()
# print state of each domains
for id in ids:
vm = conn.lookupByID(id)
print "%s: %s" % ( vm.name(), vm.info()[0] )

Avahi support
libvirt is integrated with Avahi
Ahahi is a one of mDNS implementation
You can discover hosts with libvirtd running by mDNS client automatically

Perl example with libvirt and avahi
use Net::Bonjour ;
use Sys::Virt ;
# discover hosts with libvirtd running
my $res =
Net::Bonjour->new( 'libvirt' );
$res->discover;
# access libvirtd on each host
for my $host ( $res->entries ) {
my $vmm =
Sys::Virt->new( uri => ‘xen://’ . $host->address );
....
}

Func
Fedora Unified Network Controller
https://fedorahosted.org/func/
Sysadmin application framework made of Python
A programming framework for “Exec some operations for multiple hosts”
Many modules
yum, user, service, command, smart, virt ...
Virt module uses libvirt

Func virt module sample code
import func.overlord.client as fc
# call state method of virt module on all hosts
results = fc.Client( "*" ).virt.state()
# create domain if domain state is ‘shutdown’
for ( host, vms ) in results.iteritems():
if vms[0] == 'REMOTE_ERROR':
continue
for vm in vms:
( domain, state ) = vm.split( ' ' )
if state == 'shutdown' :
fc.Client(host).virt.create(domain)

Xen Summit 2008 Tokyo - Operating Xen domains through LL(Perl/Python) with libvirt

by Gosuke Miyashita on Nov 19, 2008

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