Re: [Xen-API] [Xen-users] What's the different between XAPI and Xenopsd ?

[Dave Scott <Dave.Scott@xxxxxxxxxxxxx>]

Hi,

At the moment xapi is quite monolithic and we wanted to make it easier to 
maintain by splitting it up into several smaller services.

The new xenopsd is the "domain manager" part of xapi. This is now what happens 
when a user starts a VM:

1. client sends the XenAPI VM.start call to xapi
2. xapi decides which host to start the VM on
3. xapi forwards the call to the xapi on the "slave"
4. the slave xapi gives the VM configuration to xenopsd
5. the slave xapi tells xenopsd to start the VM and look after it.

Later if the user reboots the VM:

1. xenopsd notices the domain needs to be restarted
2. xenopsd restarts the VM
3. xapi receives an event from xenopsd telling it that the VM has changed
4. xapi asks xenopsd for the current VM state
5. xapi updates the pool database

So xenopsd is really an internal service.

Apart from being easier to maintain it:

1. will be easier to integrate with libxl because all the low-level xen stuff 
is contained within a "backend" plugin

2. includes a "mock" backend which can be used to simulate a host, useful for 
testing

3. it is aware of driver domains i.e. that backends can be in domains other 
than domain zero

4. is much more cleanly multithreaded (and will hopefully be converted to use 
the "lwt" monadic concurrency library in the future)

HTH,
Dave

> -----Original Message-----
> From: todd.deshane.xen@xxxxxxxxx [mailto:todd.deshane.xen@xxxxxxxxx] On
> Behalf Of Todd Deshane
> Sent: 27 April 2012 13:48
> To: ?S?I?x
> Cc: xen-users@xxxxxxxxxxxxx; xen-api@xxxxxxxxxxxxxxxxxxx; Dave Scott
> Subject: Re: [Xen-users] What's the different between XAPI and Xenopsd ?
> 
> This is a better question for the xen-api mailing list. Adding to the
> CC.
> 
> On Thu, Apr 26, 2012 at 10:58 AM, ?S?I?x <turing@xxxxxxxxxx> wrote:
> > Hi everyone,
> >
> >
> >
> > I have some question about the Xenopsd.
> >
> > I’ve read the wiki document but cannot understand where to use it,
> >
> > Is this different with XAPI ? What’s the main work for?
> >
> >
> >
> > Can anyone describe it more clearly about it?
> >
> > Thanks a lot!!
> >
> >
> >
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-users
> 
> 
> 
> --
> Todd Deshane
> http://www.linkedin.com/in/deshantm
> http://blog.xen.org/
> http://wiki.xen.org/

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