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

[George Shuklin <george.shuklin@xxxxxxxxx>]

Wow, cool news. I've all time have troubles with xapi been 'low-level domain manager' as high-level same time (f.e. if xapi have issues with space in dom0 due excessive logging, all operations stops, including domain reboot).

If you did not already implement everything, would you like to add some way to get those notifications to be available to external subscriptors? I know about xapi events subscription, but xapi requirer master to be online and sometimes getting information directly is much more preferable. I know it all about hacking around xapi, but why not?


On 27.04.2012 18:07, Dave Scott wrote:

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: 黃獻輝
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, 黃獻輝 <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!!




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Todd Deshane
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http://blog.xen.org/
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