CP-2418, WADO-RS can no longer return 206
Adam Nygard
Per CP-2418, the use of HTTP 206 in PS3.18 for WADO-RS has been removed.
I'm building a middleware service that forwards and translates WADO-RS requests to downstream systems (e.g. via DIMSE). In some situations, such as a study or series level request where communication with the downstream system fails partway through, the middleware may only have a partial set of the available instances. Previously I planned to return HTTP 206 to indicate an incomplete result, but that's not permitted anymore.
I'm looking for guidance on what would be most interoperable fix across existing clients. One option is returning a 500 with whatever partial Instances were retrieved in the body of the response. Clients not expecting partial responses will already treat 500s as a failure, while more robust clients could still extract the available content.
Another option is returning 200 with a status indicator describing the error, though it risks “failing open” if clients ignore the non-DICOM portion and assume the result set is complete. The existing DICOM standard already mentions that a 200 indicates all resources were returned, which also makes this option less promising.
CP-2418 mentions 413, but in these scenarios, the failure is entirely server-side. Using a client-error code seems inappropriate, and 413 appears intended for oversized requests rather than incomplete responses.
Given these constraints, I'd appreciate advice from implementers on what patterns they are adopting post-CP-2418. Are there expectations for how servers should convey partial results now that 206 is no longer available?
