Optimistic Concurrency & Data Services

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Microsoft news and tips » Optimistic Concurrency & Data Services — Wed, 23 Apr 2008 01:36:08 GMT

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re: Optimistic Concurrency & Data Services

John Spurlock — Wed, 23 Apr 2008 02:54:50 GMT

If you're going to implement etags - it would also be helpful to also support the if-none-match request header for GETs. This allows efficient conditional GETs for cache updates.

Also, many systems already use a timestamp for simplistic optimistic concurrency (timestamp meaning date and time, not mssql timestamp). This has the advantage of being human-parseable.

It would seem that these timestamp concurrency tokens would map well to the http last-modified header and allow the use of conditional if-(un)modified-since request-headers.

re: Optimistic Concurrency & Data Services

John Spurlock — Wed, 23 Apr 2008 02:57:50 GMT

Also just thought I'd point out that all of this behavior would impossible to utilize in the current Silverlight2 beta (with a direct client-side call) - due to the limitations in the current http stack re: headers and response status codes. Are you working with the SL team on this?

re: Optimistic Concurrency & Data Services

pabloc — Wed, 23 Apr 2008 04:12:43 GMT

John: we actually do support if-none-match for GETs already. It's not that cheap on the server (we still need to ask the data source for the resource), but the resouce does not have to be sent over the wire to the client. We don't plan to do timestamps right now, but we may in the future. Note that the primary goal with implementing ETags in Astoria is for concurrency support and not so much for optimization.

Thanks for pointing out the Silverlight thing. We know about it and we're working with the Silverlight team to make sure the experience is there once all the pieces are done.

-pablo

REST and Concurrency Control

Pablo Castro's blog — Wed, 23 Apr 2008 04:17:55 GMT

As part of the Astoria design process we scanned through many topics, some of them are straightforward,

re: Optimistic Concurrency & Data Services

Mark Baker — Thu, 24 Apr 2008 21:14:11 GMT

Hey Pablo. FYI, the issue you describe wrt weak etags and PUT requests is not quite as clear cut as you make it out to be. There's been a bunch of discussion about similar issues in the HTTPBIS WG (which you guys should be participating in IMO!!).

Some people believe that weak etags should be able to be used on a PUT with If-None-Match. I think they could be used anywhere a strong etag could be used: the meaning of the message will change, that's all. e.g. PUT with If-Match with a weak etag means "set the state to that represented in the provided representation so long as the current state is semantically equivalent to the state identified by the etag I'm providing". With a strong etag, that meaning would change to "... so long as the current state is bit-wise equivalent to the state identified by the etag I'm providing".

While this has been discussed in the WG, it's on the periphery and may require its own issue. Do you want to handle that or will I?

re: Optimistic Concurrency & Data Services

pabloc — Fri, 25 Apr 2008 03:20:15 GMT

Hi Mark, thanks for the feedback. It's really interesting to hear this, as we struggled with it quite a bit.

I completely agree with you that weak ETags should be applicable anywhere. In fact, given that actual resources and their actual representation(s) are different constructs, I found it surprising that the ETag checks were based on bit-wise comparison and not on semantics alone.

I would be interesting to bring up this issue with the WG if there is enough momentum. I wrote to the AtomPub group because this seemed to be an application-level issue. That said, now that I know we're not alone I'd be happy to bring it up in other forums as well. Is the HTTPBIS WG mailing-list still active and a good place to send this?

-pablo

New and Notable 234

Sam Gentile — Fri, 25 Apr 2008 16:11:44 GMT

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re: Optimistic Concurrency & Data Services

Steve — Fri, 25 Apr 2008 19:35:42 GMT

Is it possible to use data services with Silverlight2 beta 1 or future releases? and how easy is it to use with non microsoft ajax frameworks/javascript libraries, such as JQuery?

If so, can you supply some code/articles?

Astoria Data Services and Optimistic Concurrency

Hot Topics — Sat, 26 Apr 2008 18:51:20 GMT

Pablo Castro explains the new ETags attributes that will be available for ADO.NET Data Services classes

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Project Astoria Team Blog — Mon, 12 May 2008 19:21:03 GMT

We are very excited to announce that .NET 3.5 SP1 Beta 1 and Visual Studio 2008 SP1 Beta 1 are now available!

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Sam Gentile's Blog — Wed, 03 Dec 2008 01:20:35 GMT

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Optimistic Concurrency &amp; Data Services

Microsoft news and tips » Optimistic Concurrency & Data Services

re: Optimistic Concurrency & Data Services

re: Optimistic Concurrency & Data Services

re: Optimistic Concurrency & Data Services

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re: Optimistic Concurrency & Data Services

re: Optimistic Concurrency & Data Services

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re: Optimistic Concurrency & Data Services

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Optimistic Concurrency & Data Services