[libvirt] [PATCH] qemu: Refactor parsing of block device IO tuning parameters.
Daniel P. Berrange
berrange at redhat.com
Thu Aug 9 09:48:43 UTC 2012
On Thu, Aug 09, 2012 at 11:39:57AM +0200, Jiri Denemark wrote:
> On Thu, Aug 09, 2012 at 10:48:42 +0200, Peter Krempa wrote:
> > This patch refactors the JSON parsing function that extracts the block
> > IO tuning parameters from qemu's output. The most impacting change
> > concerns the error message that is returned if the reply from qemu does
> > not contain the needed data. The data for IO parameter tuning were added
> > in qemu 1.1 and the previous error message was confusing.
> >
> > This patch also breaks long lines and extracts a multiple time used code
> > pattern to a macro.
> > ---
> > Old error message looks like:
> > # virsh blkdeviotune asdf hda
> > error: Unable to get block I/O throttle parameters
> > error: internal error cannot read total_bytes_sec
> >
> > and the new:
> > # virsh blkdeviotune asdf hda
> > error: Unable to get block I/O throttle parameters
> > error: internal error block_io_throttle field 'total_bytes_sec' missing in qemu's output
>
> I think the old/new error messages can be included directly in the commit
> message. Anyway, I wonder if we should take this as an opportunity to fix the
> "internal error", however I'm not sure what is the best code to use. It seems
> we use OPERATION_INVALID in such cases, which could be good enough.
No, OPERATION_INVALID is for scenarios where the API request cannot
be performed because the object is in the wrong state.
eg when you request to pause a VM that is shutoff.
This is a case where the data we receive back from QEMU is incorrect.
I don't think we have a current error code that is suitable for this
kind of scenario, so we ought to invent a new one.
Some ideas
MISSING_DATA
DATA_INVALID
UNEXPECTED_DATA
...insert others...
my favour is probably DATA_INVALID
Daniel
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