@Override
    public void fetchAndParseServerSideStreaming(FetchAndParseRequest request,
                                                 StreamObserver<FetchAndParseReply> responseObserver) {
        fetchAndParseImpl(request, responseObserver);
    }
FetcherID is key, The pair is the Fetcher object and the Metadata
tika-grpc/src/main/java/org/apache/tika/pipes/grpc/TikaGrpcServerImpl.java