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fix(NODE-4763): tryNext not updating resumeToken for a returned update #4587
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fix(NODE-4763): tryNext not updating resumeToken for a returned update #4587
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Hi @Omnicpie, thanks for the submission. Your right - this fix will need testing. We likely needs tests to confirm that the tryNext() correctly updates the resume token both when there is a document and there is not a document, for both the inital change stream aggregates and subsequent getMores. We have a lot of change stream tests in change_stream.test.ts - if you look at the tests in that file, that should help get you going in the right direction!
Also note that _processChange throws an error if the change is null. So we should only call it if there actually was a change from cursor.tryNext().
Fixed in #4636
Description
This PR attempts to fix an issue noticed when using
tryNextin which it does not correctly update the resumeToken when updates are received, meaning that if the change stream is resumed it can end up resuming in the past, causing issues.What is changing?
The change is small and involves changing the
tryNextfunction to use the internal_processChangefunction which handles updating the resume token before returning the given change. This is used bynextalready, so seems to be a good solution overall.What is the motivation for this change?
To prevent issues where resuming the change-stream using
tryNextcauses the client to go backwards in time, potentially causing issues on systems that use this functionalityNOTE FOR REVIEWERS
I wasn't sure where to add test coverage for this, or what exactly I should call in terms of testing, Happy to add some tests for this functionality if someone can point me in the right direction of the "where and how" to test this.
Double check the following
npm run check:lintscripttype(NODE-xxxx)[!]: descriptionfeat(NODE-1234)!: rewriting everything in coffeescript