[sheepdog] [PATCH v2 3/4] sheep: handle block/unblock/notify error

[Liu Yuan]

On Tue, Jul 09, 2013 at 10:15:50AM +0800, Kai Zhang wrote:
> 
> On Jul 9, 2013, at 8:43 AM, MORITA Kazutaka <morita.kazutaka at gmail.com> wrote:
> 
> > I think block/unblock/notify should return SD_RES_xxx since they know
> > the error reason rather than the callers.  Currently, all the
> > callbacks only can return SD_RES_CLUSTER_ERROR or SD_RES_SUCCESS,
> > though.
> 
> 
> Here is my personal opinion.
> 
> I think SD_RES_xxx is used as return code to external module (other sheep and client)
> to indicate the error of a request.

No, we don't have this assumption. Mostly we recommend return SD_RES_XXX between
functions and modules, return -1, 0 only if it is hard to do so.

> However, block/unblock/notify are internal functions who don't know they are serving for
> external requests.
> I think, we can indicate internal error by logging and only use return code '-1' when fail.
> It is the caller's responsible (here the caller is queue_cluster_request) to mark the result
> as SD_RES_xxx.
> 
> The drawback is that we cannot know the specific error from return code.
> However, as an internal function, I think only use 0 and -1 as return code is enough.

You already said the benefit, even though currently return 0 and -1 equal SD_RES_XXX
because we only have binary ret state, but in the long run, we might add more
ret state in the future.

Thanks,
Yuan