NewDopplerServer creates a new DopplerServer.

NewRouter is the constructor for Router.

DopplerServer is the GRPC server component that accepts requests for firehose streams, application streams, and recent logs.

Router routes envelopes to particular buffers (called DataSetter here).

DataSetter accepts writes of marshalled data.

EnvelopeStore returns Envelopes recent logs requests.

MetricClient creates new CounterMetrics to be emitted periodically.

Registrar registers stream and firehose DataSetters to accept reads.