Earthly Powers

Optimistic concurrency

Using PUT with entity tags is a form of optimistic concurrency that can solve the lost update problem, where a resource may be updated concurrently by more than one client and you don't want clients to overwrite each others content.

The lost updated problem can also be solved using another form of optimistic concurrency that uses just URIs. Essentially what would be an entity tag can be part of a URI and when a resource is updated it's URI changes. This form is used to nice effect in Google's GData API for the editing and versioning of Atom entries.

The optimistic concurrency example provided with the RESTful API in R1 of SWDP shows how one can implement such optimistic concurrency and versioning using URIs with the API.

Posted at 04:30PM Mar 26, 2007 by Paul Sandoz in REST  |  Comments[0]