On 11/15/2011 11:24 AM, Barak Azulay wrote:
Hi,
One of the breakout sessions during the ovirt workshop [1] was about the guest tools, and focused mainly on the ovirt-guest-agent [2].
One of the issues discussed there, was the various existing guest agents out there, and the need to converge the efforts to a single agent that will serve all.
while 4 agents were mentioned (Matahari, vdagent, qemu-ga& ovirt-guest-agent) during that discussion, we narrowed it down to 2 candidates:
qemu-ga (aka virt-agent):
- Qemu specific - it was aimed for specific qemu needs (mainly quiesce guest
I/O)
- Communicates directly with qemu (not implemented yet)
Won't be implemented until we finish the QMP conversion to QAPI since that's a prereq to implementing a QMP server with proper async support (needed for communication with a potentially non-responsive guest agent). But once it's in guest extensions are completely transparent to QMP/libvirt, which is highly desirable from a management perspective since you're coding against a single API/transport.
- Supports ?
Documented in qemu.git/qapi-schema.json:
mdroth@illuin:~/w/qemu.git$ grep command qapi-schema-guest.json # Such clients should also preceed this command { 'command': 'guest-sync' { 'command': 'guest-ping' } { 'command': 'guest-info', { 'command': 'guest-shutdown', 'data': { '*mode': 'str' } } { 'command': 'guest-file-open', { 'command': 'guest-file-close', { 'command': 'guest-file-read', { 'command': 'guest-file-write', { 'command': 'guest-file-seek', { 'command': 'guest-file-flush', { 'command': 'guest-fsfreeze-status', { 'command': 'guest-fsfreeze-freeze', { 'command': 'guest-fsfreeze-thaw',
There's a wiki page with additional details:
- So far linux only
Windows port is *almost* there. I have patches to build/run it on windows but there are some remaining bugs, and guest-fsfreeze* and guest-shutdown* are gonna need windows-specific command implementations.
- written in C
Ovirt-guest-agent:
- Has been around for a long time (~5 years) - considered stable
- Started as rhevm specific but evolved a lot since then
- Currently the only fully functional guest agent available for ovirt
- Written in python
- Some VDI related sub components are written in C& C++
- Supports a well defined list of message types / protocol [3]
- Supports the folowing guest OSs Linux: RHEL5, RHEL6 F15, F16(soon) Windows: xp, 2k3 (32/64), w7 (32/64), 2k8 (32/64/R2)
In terms of completeness/support for ovirt (and node/cluster-level management frameworks in general), the ovirt-guest-agent certainly seems like a win. The main problem with convergence within the qemu space is that we can't have guest extensions to qemu-driven guest events like, say, hotplug or shutdown be managed by an external agent: the functionality, specificity, and assurances required are not things that are necessarily suited for ovirt-guest-agent; the scope is very different.
And the same holds true in the other direction: I don't, personally at least, foresee qemu-ga ever doing things like providing a list of logged in users on a system or handling SSO, though if there are those who'd like to take qemu-ga in that direction I think that's fine.
But practically-speaking, it's unavoidable that qemu-specific management tooling will need to communicate with qemu (via QMP/libqmp/HMP/etc, or by proxy via libvirt). It's through those same channels that the qemu-ga interfaces will ultimately be exposed, so the problem of qemu-ga vs. ovirt-guest-agent isn't really any different than the problem of QMP's system_powerdown/info_balloon/etc vs. ovirt-guest-agent's Shutdown/Available_Ram/etc: it's a policy decision rather than argument for choosing one project over another.
The need to converge is obvious, and now that ovirt-guest-agent is opensourced under the ovirt stack, and since it already produces value for enterprise installations, and is cross platform, I offer to join hands around ovirt- guest-agent and formalize a single code base that will serve us all.
git @ git://gerrit.ovirt.org/ovirt-guest-agent
Thoughts ?
Thanks Barak Azulay
[1] http://www.ovirt.org/news-and-events/workshop [2] http://www.ovirt.org/wiki/File:Ovirt-guest-agent.odp [3] http://www.ovirt.org/wiki/Ovirt_guest_agent