private void setFileReferencesToDownload(Request req) {
        req.detach();
        rpcAuthorizer.authorizeFileRequest(req)
                .thenRun(() -> { // okay to do in authorizer thread as downloadFromSource is async
                    String[] fileReferenceStrings = req.parameters().get(0).asStringArray();

                    // Download directly from the source that has the file reference, which
                    // is the client that sent the request
                    var client = req.target();
                    var peerSpec = client.peerSpec();
                    Stream.of(fileReferenceStrings)
                            .map(FileReference::new)
                            .forEach(fileReference -> downloadFromSource(fileReference, client.toString(), peerSpec));
                    req.returnValues().add(new Int32Value(0));
                });
        req.returnValues().add(new Int32Value(0));
        req.returnRequest();
    }
Returns true if empty sentinel config can be returned when a request from a host that is
not part of an application asks for sentinel config
configserver/src/main/java/com/yahoo/vespa/config/server/rpc/RpcServer.java