cloudstack-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Prasanna Santhanam <...@apache.org>
Subject Re: [DISCUSS] getting rid of KVM patchdisk
Date Mon, 11 Mar 2013 05:29:55 GMT
On Tue, Mar 05, 2013 at 11:58:55PM +0530, Edison Su wrote:
> 
> 
> > -----Original Message-----
> > From: Marcus Sorensen [mailto:shadowsor@gmail.com]
> > Sent: Monday, March 04, 2013 10:26 PM
> > To: cloudstack-dev@incubator.apache.org
> > Subject: Re: [DISCUSS] getting rid of KVM patchdisk
> > 
> > I've been thinking about how to tackle this, written a little concept code, and
> > it seems fairly straightforward to include our own little python daemon that
> > speaks JSON via this local character device in the system vm. I'm assuming
> > we'd start it up at the beginning of cloud-early-config.
> > 
> > What I'm not certain of is how to get the 'cmdline' bits into the system before
> > cloud-early-config needs them. Do we block in cloud-early-config, waiting on
> > getting the cmdline file before continuing, and push it via StartCommand?
> 
> We put a lot of logic into init scripts inside system vm, which is unnecessary complicated
the system vm programming:
> 1. init script is not portable, if people want to use other Linux
> distribution as system vm OS, then he has to write his own init
> scripts.
> 2. init script is not easy to hack, it has its own dialect(how to
> log message, how to write dependence etc)
> 3. init script is running in a limited environment(some system wide
> services are not available), put the limitation on what you can do
> in a init script.
> 
> Maybe we need to start working on new system vm programming model
> now? Better to just put a python daemon inside system vm, and
> provide restful API through link local ip address(or private ip if
> it's vmware), then mgt server or hypervisor agent code can just send
> commands to the python daemon through http, instead of ssh.
> 

+1 to this approach. Agent services in puppet nodes are implemented
this way too. It also makes testing the systemVM in isolation without
the existence of cloudstack easier if it's an API.

> In your case, the python daemon, needs to wait on the well-defined
> serial port(e.g
> /dev/virtio-ports/org.apache.cloudstack.guest.agent), get cmdline,
> then programming system vm itself, and reboot.
> 
> 
>  
> > 
> > On Mon, Mar 4, 2013 at 5:27 PM, Marcus Sorensen <shadowsor@gmail.com>
> > wrote:
> > > I tested this with Rohit's systemvm from master. It works fine,
> > > provided you install the qemu-guest-agent software and modify the
> > > libvirt xml definition of the system vm to include something like:
> > >
> > >    <channel type='unix'>
> > >       <source mode='bind' path='/var/lib/libvirt/qemu/v-2-VM.agent'/>
> > >       <target type='virtio' name='org.qemu.guest_agent.0'/>
> > >       <alias name='channel0'/>
> > >       <address type='virtio-serial' controller='0' bus='0' port='1'/>
> > >     </channel>
> > >
> > > Then on the host you can connect to the
> > > /var/lib/libvirt/qemu/v-2-VM.agent unix socket and send QMP JSON to do
> > > things like write files. We can't execute the various scripts through
> > > it, but we also don't have to use qemu-ga; we could have our own thing
> > > listening on the unix socket.
> > >
> > >
> > >
> > > On Mon, Mar 4, 2013 at 3:24 PM, Marcus Sorensen
> > <shadowsor@gmail.com> wrote:
> > >> I think this just requires an updated system vm (the virtio-serial
> > >> portion). I've played a bit with the old debian 2.6.32-5-686-bigmem
> > >> one and can't get the device nodes to show up, even though the
> > >> /boot/config shows that it has CONFIG_VIRTIO_CONSOLE=y. However, if I
> > >> try this with a CentOS 6.3 VM, on a CentOS 6.3 or Ubuntu 12.04 KVM
> > >> host it works. So I'm not sure what's being used for the ipv6 update,
> > >> but we can probably make one that works. We'll need to install
> > >> qemu-ga and start it within the systemvm as well.
> > >>
> > >> On Mon, Mar 4, 2013 at 12:41 PM, Edison Su <Edison.su@citrix.com>
> > wrote:
> > >>>
> > >>>
> > >>>> -----Original Message-----
> > >>>> From: Marcus Sorensen [mailto:shadowsor@gmail.com]
> > >>>> Sent: Sunday, March 03, 2013 12:13 PM
> > >>>> To: cloudstack-dev@incubator.apache.org
> > >>>> Subject: [DISCUSS] getting rid of KVM patchdisk
> > >>>>
> > >>>> For those who don't know (this probably doesn't matter, but...),
> > >>>> when KVM brings up a system VM, it creates a 'patchdisk' on primary
> > >>>> storage. This patchdisk is used to pass along 1) the authorized_keys
file
> > and 2) a 'cmdline'
> > >>>> file that describes to the systemvm startup services all of the
> > >>>> various properties of the system vm.
> > >>>>
> > >>>> Example cmdline file:
> > >>>>
> > >>>>  template=domP type=secstorage host=172.17.10.10 port=8250
> > >>>> name=s-1- VM
> > >>>> zone=1 pod=1 guid=s-1-VM
> > >>>> resource=com.cloud.storage.resource.NfsSecondaryStorageResource
> > >>>> instance=SecStorage sslcopy=true role=templateProcessor mtu=1500
> > >>>> eth2ip=192.168.100.170 eth2mask=255.255.255.0
> > gateway=192.168.100.1
> > >>>> public.network.device=eth2 eth0ip=169.254.1.46
> > eth0mask=255.255.0.0
> > >>>> eth1ip=172.17.10.150 eth1mask=255.255.255.0
> > mgmtcidr=172.17.10.0/24
> > >>>> localgw=172.17.10.1 private.network.device=eth1
> > >>>> eth3ip=172.17.10.192
> > >>>> eth3mask=255.255.255.0 storageip=172.17.10.192
> > >>>> storagenetmask=255.255.255.0 storagegateway=172.17.10.1
> > >>>> internaldns1=8.8.4.4 dns1=8.8.8.8
> > >>>>
> > >>>> This patch disk has been bugging me for awhile, as it creates a
> > >>>> volume that isn't really tracked anywhere or known about in
> > >>>> cloudstack's database. Up until recently these would just litter
> > >>>> the KVM primary storages, but there's been some triage done to
> > >>>> attempt to clean them up when the system vms go away. It's not
> > >>>> perfect. It also can be inefficient for certain primary storage
> > >>>> types, for example if you end up creating a bunch of 10MB luns
on a
> > SAN for these.
> > >>>>
> > >>>> So my question goes to those who have been working on the system
> > vm.
> > >>>> My first preference (aside from a full system vm redesign, perhaps
> > >>>> something that is controlled via an API) would be to copy these
up
> > >>>> to the system vm via SCP or something. But the cloud services start
> > >>>> so early on that this isn't possible. Next would be to inject them
> > >>>> into the system vm's root disk before starting the server, but
if
> > >>>> we're allowing people to make their own system vms, can we count
on
> > >>>> the partitions being what we expect? Also I don't think this will
> > >>>> work for RBD, which qemu directly connects to, with the host OS
> > unaware of any disk.
> > >>>>
> > >>>> Options?
> > >>>
> > >>> Could you take a look at the status of this projects in KVM?
> > >>> http://wiki.qemu.org/Features/QAPI/GuestAgent
> > >>> https://fedoraproject.org/wiki/Features/VirtioSerial
> > >>>
> > >>> Basically, we need a way to talk to guest VM(sending parameters to
> > KVM guest) after VM is booted up. Both VMware/Xenserver has its own way
> > to send parameters to guest VM through PV driver, but there is no such thing
> > for KVM few years ago.

-- 
Prasanna.,

Mime
View raw message