In the past couple of months wrappers[1, 2] have been added to the Beam Java SDK which can execute BoundedSource and UnboundedSource as Splittable DoFns. These have been opt-out for portable pipelines (e.g. Dataflow runner v2, XLang pipelines on Flink/Spark) and opt-in using an experiment for all other pipelines.
I would like to start making the non-portable pipelines starting with the DirectRunner[3] to be opt-out with the plan that eventually all runners will only execute splittable DoFns and the BoundedSource/UnboundedSource specific execution logic from the runners will be removed. Users will be able to opt-in any pipeline using the experiment 'use_sdf_read' and opt-out with the experiment 'use_deprecated_read'. (For portable pipelines these experiments were 'beam_fn_api' and 'beam_fn_api_use_deprecated_read' respectively and I have added these two additional aliases to make the experience less confusing). 1: https://github.com/apache/beam/blob/af1ce643d8fde5352d4519a558de4a2dfd24721d/sdks/java/core/src/main/java/org/apache/beam/sdk/io/Read.java#L275 2: https://github.com/apache/beam/blob/af1ce643d8fde5352d4519a558de4a2dfd24721d/sdks/java/core/src/main/java/org/apache/beam/sdk/io/Read.java#L449 3: https://github.com/apache/beam/pull/12519
