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Re: [Qemu-devel] [RFC] Fixing the error failure
From: |
Luiz Capitulino |
Subject: |
Re: [Qemu-devel] [RFC] Fixing the error failure |
Date: |
Mon, 2 Jul 2012 10:47:39 -0300 |
On Mon, 02 Jul 2012 07:47:56 -0500
Anthony Liguori <address@hidden> wrote:
> > So far, there haven't been any calls for a change of the wire protocol.
>
> Changing all existing errors and repurposing 'desc' is effectively changing
> the
> wire protocol.
We're not going to change existing errors and I disagree that making 'desc'
a "free" string is an incompatible change, as we note in the spec that it
shouldn't be parsed.
> > There has been an agreement of sorts that the current "rich errors" have
> > been "a failure" (your words). Doesn't mean we all agree on the nature
> > of the failure.
> >
> > Several people pointed out that:
> >
> > * our "rich" errors are so cumbersome to emit that adoption has been
> > slow,
> >
> > * our "rich" errors' human-readable descriptions lead to piss-poor
> > human-readable error messages[*] (pardon my french), and
> >
> > * the "richness" has no known uses after 2+ years.
>
> Do you know of *any* QMP user beyond libvirt?
Apart from casual people scripting around QMP, no I don't. But that doesn't
imply they don't exist.
> Let's face it, QMP is a protocol
> for libvirt. What it looks like shouldn't be dictated by anything other than
> what libvirt wants/needs.
>
> If libvirt isn't going to do more than look at an error type, then there's no
> point in providing more than that.
They have asked us to turn 'desc' into a free string and I believe this is
a good change.
> The real problem we need to solve is not the quality of error messages.
> Honestly, we have all of the tools today to improve error messages.
>
> The problem we need to solve is error propagation because without it, we
> cannot
> have asynchronous commands. We keep ending up with extremely
> complex/cumbersome
> management interfaces that we need to support forever because we still have
> out-of-band errors that cannot be associated with a specific QMP command.
>
> So I don't want to see us focus a bunch of effort on rewriting existing error
> users. Is that a hard and fast rule? Of course not. If it makes sense to
> tweak an error here and there, that's fine.
>
> But the problem to solve is killing off error_report.
I agree this is an important problem too.