| Interface | Description | 
|---|---|
| DataStreams.OutputChunkConsumer<T> | A callback which is invoked whenever the  DataStreams.outbound(org.apache.beam.sdk.fn.stream.DataStreams.OutputChunkConsumer<org.apache.beam.vendor.grpc.v1p60p1.com.google.protobuf.ByteString>)OutputStreambecomes full. | 
| OutboundObserverFactory.BasicFactory<ReqT,RespT> | Creates an outbound observer for the given inbound observer. | 
| PrefetchableIterable<T> | An  Iterablethat returnsPrefetchableIterators. | 
| PrefetchableIterator<T> | Iteratorthat supports prefetching the next set of records. | 
| Class | Description | 
|---|---|
| AdvancingPhaser | A  Phaserwhich never terminates. | 
| BufferingStreamObserver<T> | A thread safe  StreamObserverwhich uses a bounded queue to pass elements to a processing
 thread responsible for interacting with the underlyingCallStreamObserver. | 
| DataStreams | DataStreams.DataStreamDecodertreats multipleByteStrings as a single input stream decoding
 values with the supplied iterator. | 
| DataStreams.DataStreamDecoder<T> | An adapter which converts an  InputStreamto aPrefetchableIteratorofTvalues using the specifiedCoder. | 
| DataStreams.ElementDelimitedOutputStream | An adapter which wraps an  DataStreams.OutputChunkConsumeras anOutputStream. | 
| DirectStreamObserver<T> | A  StreamObserverwhich uses synchronization on the underlyingCallStreamObserverto provide thread safety. | 
| ForwardingClientResponseObserver<ReqT,RespT> | A  ClientResponseObserverwhich delegates allStreamObservercalls. | 
| OutboundObserverFactory | Creates factories which determine an underlying  StreamObserverimplementation to use in
 to interact with fn execution APIs. | 
| PrefetchableIterables | This class contains static utility functions that operate on or return objects of type  PrefetchableIterable. | 
| PrefetchableIterables.Default<T> | A default implementation that caches an iterator to be returned when  PrefetchableIterables.Default.prefetch()is
 invoked. | 
| PrefetchableIterators | |
| SynchronizedStreamObserver<V> | A  StreamObserverwhich provides synchronous access access to an underlyingStreamObserver. |