Hi Cyrus, The proposed changes for the two major issues look good to me:
[1] I'm pleased that the concern about adding elements turned out to be a wording issue. [2] Your proposed new text is fine - it provides adequate notice/warning about possible collection inconsistency, so I'm ok with not providing pseudo-code. I'll leave the Downref issue ([3]) for you and Peter to work out with the IESG, and I'm fine with continued use of your name in the examples if that's common practice. Thanks, --David > -----Original Message----- > From: Cyrus Daboo [mailto:cy...@daboo.name] > Sent: Monday, January 02, 2012 2:44 PM > To: Black, David; arnaud.quill...@oracle.com; gen-...@ietf.org; ietf@ietf.org > Cc: stpe...@stpeter.im > Subject: Re: Gen-ART review of draft-daboo-webdav-sync-06 > > Hi David, > Thank you for your review. Comments inline: > > --On December 27, 2011 11:07:49 PM -0500 david.bl...@emc.com wrote: > > > [1] -Major- Section 3.5 does not appear to cover the case reporting added > > elements on a subsequent synchronization. The problem may be that the > > word "changed" as used in Section 3.5.1 is assumed to cover adding an > > element - if so, that's not a good assumption, and the addition case > > should be explicitly called out in the title and body of Section 3.5.1. > > The first sentence of 3.5.1 is: > > A member URL MUST be reported as changed if it has been mapped as a > member of the target collection since the request sync-token was > generated. > > The term "mapped" implies creation/addition of a new resource in this case. > That may not be obvious to anyone who is not intimately familiar with > WebDAV terminology here, so I propose changing that to: > > A member URL MUST be reported as changed if it has been newly mapped as > a member of the target collection since the request sync-token was > generated (e.g., when a new resource has been created as a child of the > collection). > > > [2] -Major- The operations to retrieve changed members of a collection > > are not atomic wrt the operation that obtains a report on what has > > changed; collection changes can occur between retrieving the report and > > retrieving the changed elements or while retrieving the changed elements. > > For this reason, simply obtaining a change report and then retrieving the > > elements that have changed according to the report may not result in a > > consistent (e.g., as of a point in time) copy of a collection. I believe > > that this absence of atomicity is a WebDAV "feature", as opposed to a > > "bug", but I believe that this behavior and what to do about it should be > > discussed in the draft. I suggest the following, possibly to the end of > > section 3.1 > > > > i) Add a sentence or two to warn that obtaining a change report and then > > retrieving the changed elements may not result in a consistent local > > version of the collection if nothing else is done because changes may > > have occurred in the interim. > > > > ii Add a discussion of how to ensure that a local copy of the collection > > is consistent. The basic idea is to re-presented the sync token for that > > copy to the server after the changed elements have been retrieved; the > > local copy is consistent if the server reports that there have been no > > changes. Some pseudo-code may help, e.g.: > > > > GetSyncCollectionReport(in token, out newtoken, out report); > > while (ReportHasChangedItems(report) { > > GetChangedItems(report) > > token = newtoken; > > GetSyncCollectionReport(in token, out newtoken, out report); > > } > > > > Actual code should include a counter that counts the number of iterations > > of the while loop and exits with an error if the number of iterations > > exceeds some limit; that error exit implies that the collection is > > (currently) changing too rapidly to obtain a consistent local version. > > Good point. I agree that this deserves some additional text to clarify this > situation. However, I would rather not go into too much detail of how > clients "re-sync" in cases like this as there are a bunch of different ways > that could happen each of which depends on exactly what the client is > trying to do (e.g., in a lot of cases clients will be doing two-way syncs > so will need to reconcile server and local changes within the loop you > propose above - the details of that are not in scope for this > specification). What I propose is the addition of the following paragraph > to the end of Section 3.1: > > Typically, a client will use the synchronization report to retrieve the > list of changes, and will follow that with requests to retrieve the > content of changed resources. It is possible that additional changes to > the collection could occur between the time of the synchronization > report and resource content retrieval, which could result in an > inconsistent view of the collection. When clients use this method of > synchronization, they need to be aware that such additional changes > could occur, and track them through normal means (e.g., differences > between the ETag values returned in the synchronization report and > those returned when actually fetching resource content), conditional > requests as described in Section 5, or repeating the synchronization > process until no changes are returned. > > > [3] -Minor- idnits 2.12.12 reports a Downref to RFC 5842. Please > > consult your Area Director (Peter Saint-Andre) to determine what to do > > about this Downref (it requires attention, but may not require changes to > > the draft). > > Working with IESG on this one. > > > Nit: I suggest not using the author's own name (cyrusdaboo) in the > > examples. Someone may copy the code from the resulting RFC. > > This has been common practice in most of the other CalDAV/CardDAV RFCs I > have worked on and has not been the source of any problems, so I would > rather leave this unchanged. If there is an official IETF policy on using > "real names" in examples, then I would be happy to change to follow that, > but I am not aware of anything like that. > > > Nit: idnits 2.12.12 reports that draft-ietf-vcarddav-carddav has been > > published as RFC 6352; the RFC Editor will correct this if a new version > > of the draft is not required for other reasons. > > Fixed in my working copy. > > > -- > Cyrus Daboo > _______________________________________________ Ietf mailing list Ietf@ietf.org https://www.ietf.org/mailman/listinfo/ietf
