Page History

...

Therefore, all existing APIs which don't accept a grace period and apply a default grace period of 24 hours will be removed. These will be replaced with two new APIs: one which ends in `WithNoGrace` and applies a grace period of 0, and one which takes the grace period as a required parameter. In constructing a windowed operation, users must choose between one of these two APIs and make a conscious decision whether to select a grace period or ignore that parameter for the time being.

To elaborate further, the current APIs will continue to have the grace period of 24 hours, however the new APIs will have the option of setting a grace period or having a default grace period of zero milliseconds if none is specified in the method signature. The *NoGrace() counterparts of the API methods will have 0 milliseconds as the grace period and the corresponding *AndGrace() API methods will have the ability to specify the grace period in the calling code.

Semantic Change

For stream-stream left/outer join, we will in addition apply a semantic improvement by enabling 

Jira
server ASF JIRA serverId 5aa69414-a9e9-3523-82ec-879b028fb15b key KAFKA-10847

 if the new `JoinWindows.ofTimeDifferenceWithNoGrace` or `JoinWindows.ofTimeDifferenceAndGrace()` are used. If the existing `JoinsWindows.of()` is used, the old semantics to emit left/outer join results eagerly will be used. This will allow users to opt-into the new feature. The reason why we cannot apply KAFKA-10847 by default is the default grace period of 24h in the existing API (cf. 

Jira
server ASF JIRA serverId 5aa69414-a9e9-3523-82ec-879b028fb15b key KAFKA-12909

) that may lead to emitting left/outer join result very delayed and could break existing applications.

...