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HTTP has PATCH method specifically designed for atomic partial updates. It can solve or mitigate the listed issues.
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We will add PATCH method definition into ConnectorsResource, which will call the actual logic in Herder and its child classes StandaloneHerder and DistributedHerder. Due to the way how the herders are implemented now, it's difficult to guarantee 100% race-free partial updates. The implementation will attempt to keep the race window as narrow as possible.
There is a draft pull request: https://github.com/apache/kafka/pull/6934
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