Re: [Xen-devel] [RFC V8 2/3] libxl domain snapshot API design

[Wei Liu <wei.liu2@xxxxxxxxxx>]

I have to admit I'm confused by the back and forth discussion. It's hard
to justify the design of new API without knowing what the constraints
and requirements are from your PoV.

Here are my two cents, not about details, but about general constraints.

There are two layers, one is user of libxl (clients -- xl, libvirt etc)
and libxl (the library itself).

1. it's better to *not* have storage management in libxl.

It's likely that clients can have their own management functionality
already.  I'm told that libvirt has that as well as XAPI. Having this
functionality in libxl is a bit redundant and requires lots of work
(enlighten libxl on what a disk looks like and call out to various
utilities).

2. it's *not* a requirement for xl to have the capability to manage
snapshots.

It's the same arguement that xl has no idea on how to manage snapshots
created by "xl save".  This should ease your concern on having to
duplicate code for libvirt and xl.  IMHO the xl only needs to have the
capability to create a snapshot and create a domain from a snapshot. The
downside is that now xl and libvirt are disconnected, but I think it's
fine. The arguement is that you're not allowed to run two toolstack on
the same host (think about xl and xend in previous releases).

Do these two constraints make your work easier (or harder)?

Regarding JSON API, as Ian said, feel free to hook it up to libxlu.

Wei.

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