On Thu, Feb 09, 2012 at 03:23:19PM -0500, Ayal Baron wrote:
> ----- Original Message -----
> > -1
> > 
> > I agree that for messaging environment having a Message ID is a must
> > because you sometimes don't have a particular target so when you get
> > a response you need to know what this node is actually responding
> > to.
> > 
> > The message ID could be composed with <FLOWID><MSGID> so you can
> > reuse the field.
> > 
> > But that is all besides the point.
> > 
> > I understand that someone might find it fun to go on following the
> > entire flow in the Engine and in VDSM. But I would like to hear an
> > actual use case where someone would have actually benefited from
> > this.
> > As I see it having VSDM return the task ID with every response (and
> > not just for async tasks) is a lot more useful and correct.
> > 
> > A generic debugging scenario as I see it.
> > 
> > 1. Something went wrong
> > 2. You go looking in the ENGINE log trying to figure out what
> > happend.
> > 3. You see that ENGINE got SomeError.
> > 4. Check to see if this error makes sense imagining that VDSM is
> > always right and is a black box.
> > 5. You did your digging and now you think that VDSM is as fault.
> > 6. Go look for the call that failed. (If we returned the taskID it's
> > pretty simple to find that call).
> > 7. Look around the call to check VDSM state.
> > 8. Profit.
> > 
> > There is never a point where you want to follow a whole flow call by
> > call going back and forth, and even if you did having the VDSM
> > taskID is a better anchor then flowID.
> > 
> > VDSM is built in a way that every call takes in to account the
> > current state only. Debugging it with an engine flow mindset is just
> > wrong and distracting. I see it doing more harm the good by
> > reinforcing bad debugging practices.
> I don't know about harm, but, today the engine logs every call and return 
> value to and from vdsm.  This means that all the info that is needed to 
> follow a flow is already present in the engine log (which was not the case 
> previously) so I believe that the flow id is redundant.
> In addition, instead of focusing on how to track a flow between components, 
> we should focus on how to improve the engine log so that the users don't need 
> to go to the hosts in the first place.

> My biggest problem with it is that it changes each and every verb in the API 
> and makes the log itself also more verbose and less readable.

The good thing about the currently suggested implementation


is that it (ab)uses an http header for carrying FlowID, thus keeping the
formal API intact. FlowID is logged only on API entry point, so it would
not clutter the logs too much.

Keith, Dan, I will need your support in Gerrit for the patch.

vdsm-devel mailing list

Reply via email to