This library includes two components for communicating with Firebase from Dataflow:
FirebaseSource an UnboundedSource which can watch a Firebase ref for events and attempts (but does not guarantee) to deliver those events in order to the Dataflow pipeline. The source will unmarshal DataSnapshots generated by these events into the paramaterized type specified by your FirebaseSource, which can be any object serializable by Jackson.
Various FirebaseDoFn which can be used to write data to a firebase:
DoFirebasePush will attach unique and time-ordered strings as keys to objects recieved from the pipeline.DoFirebaseSet will overriding data at the key's location with the specified ObjectDoFirebaseUpdate will update the tree at the ref with the given Map<String, Object>These utilities also use various FirebaseEvents to wrap your unmarshalled data in a Jackson Serializable POJO, which retains event type information. So for example you could filter a pipeline on ChildAdded<T> events, where your original DataSnapshot was unmarshalled into a Jackson Serializable POJO of type T.
The library uses the firebase JVM client library and as such takes advantage of Web sockets for data transfer. However this means that writing to Firebase will use one websocket per shard, so if you plan to fan out your writes, make sure to limit the parallelism with PTransform#withMaxParallelism to avoid capping out your available connections.