https://beam.apache.org/releases/javadoc/2.22.0/org/apache/beam/sdk/transforms/Wait.OnSignal.html
Wait.OnSignal (Apache Beam 2.22.0)
apache beamwait
https://beam.apache.org/releases/javadoc/2.33.0/org/apache/beam/sdk/transforms/Wait.OnSignal.html
Wait.OnSignal (Apache Beam 2.33.0)
apache beamwait