@Override
    public void deleteFetcher(DeleteFetcherRequest request,
                              StreamObserver<DeleteFetcherReply> responseObserver) {
        boolean successfulDelete = deleteFetcher(request.getFetcherId());
        if (successfulDelete) {
            try {
                updateTikaConfig();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
        responseObserver.onNext(DeleteFetcherReply.newBuilder().setSuccess(successfulDelete).build());
        responseObserver.onCompleted();
    }
FetcherID is key, The pair is the Fetcher object and the Metadata
tika-grpc/src/main/java/org/apache/tika/pipes/grpc/TikaGrpcServerImpl.java