On Tue, Aug 25, 2009 at 3:54 PM, David Farber <dfarber at numenor.com> wrote:

>
> On Aug 25, 2009, at 2:28 PM, Eliot Miranda wrote:
>
>  One of the things the headless support in VW allows which is quite nice is
>> taking a shapshot which can then be restarted in a headless mode for
>> debugging.
>>
>
> Eliot - Was this VM or image-side support?  Can you describe how it worked?


All image side; no VM support.  I can't describe it in detail as I never
worked on it.  But the basic idea is to have a switchable headless system in
the image so that in deployment it runs headless and when an error occurs
the error handler temporarily throws the switch, saves a snapshot and resets
the switch.  When the snapshot is restarted it will come up headful because
the switch was thrown before the snapshot was taken.  In the resuming
snapshot the error handler then does something like an on: .. do: [:ex| self
shapshotHeadful. ex pass] to allow the GUI to display the debugger.

Download VW non-commercial and play with the headless support if you want
details.


Not quite the same, but very neat:  The other day at Qwaq Craig Latta had a
>> VM crash while running in a Parallels Linux VM under gdb.  He was able to
>> give me a copy of the VM snapshot at the point where gdb stopped the
>> process, giving me the opportunity to debug the live app at my leisure.  A
>> cool idea.
>>
>
> In other words, he was already running the Qwaq VM under gdb, so when the
> Qwaq VM crashed (and left him at a gdb prompt), he simply suspended the
> Parallels Linux VM and sent you a copy of the suspended Parallels Linux VM.
>  Is that right?


Right.  Very nice, as the patient is on the table.


>
> David
>
>
>
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