Version 0.4.20150414

• Initial Beta release of the Dataflow SDK for Java.
• Improved execution performance in many areas of the system.
• Added support for progress estimation and dynamic work rebalancing for user-defined sources.
• Added support for user-defined sources to provide the timestamp of the values read via Reader.getCurrentTimestamp().
• Added support for user-defined sinks.
• Added support for custom types in PubsubIO.
• Added support for reading and writing XML files. See XmlSource and XmlSink.
• Renamed DatastoreIO.Write.to to DatastoreIO.writeTo. In addition, entities written to Cloud Datastore must have complete keys.
• Renamed ReadSource transform into Read.
• Replaced Source.createBasicReader with Source.createReader.
• Added support for triggers, which allows getting early or partial results for a window, and specifying when to process late data. See Window.into.triggering.
• Reduced visibility of PTransform's getInput(), getOutput(), getPipeline(), and getCoderRegistry(). These methods will soon be deleted.
• Renamed DoFn.ProcessContext#windows to DoFn.ProcessContext#window. In order for a DoFn to call DoFn.ProcessContext#window, it must implement RequiresWindowAccess.
• Added DoFn.ProcessContext#windowingInternals to enable windowing on third-party runners.
• Added support for side inputs when running streaming pipelines on the [Blocking]DataflowPipelineRunner.
• Changed [Keyed]CombineFn.addInput() to return the new accumulator value. Renamed Combine.perElement().withHotKeys() to Combine.perElement().withHotKeyFanout().
• Renamed First.of to Sample.any and RateLimiting to IntraBundleParallelization to better represent its functionality.