how to fix the cannot be shared between threads safely error in client Streaming proxy?

[HaoYang670]

Hi, I am writing a proxy server using tonic and met the cannot be shared between threads safely error when implementing a client streaming handle. Could you help on that?

    async fn add_artifacts(
        &self,
        request: Request<tonic::Streaming<AddArtifactsRequest>>,
    ) -> Result<Response<AddArtifactsResponse>, Status> {
        let mut client = Self::connect_to_spark(&request).await?;
        let mut stream = request.into_inner();
        let mut items = Vec::new();
        while let Some(req) = stream.next().await {
            items.push(req?);
        }
        let out_stream = futures::stream::iter(items);
        client.add_artifacts(out_stream).await
    }

The error message is complicated to understand:

error[E0277]: `(dyn tonic::transport::Body<Data = prost::bytes::Bytes, Error = Status> + std::marker::Send + 'static)` cannot be shared between threads safely
    --> rucat_engine_proxy_server/src/spark_proxy_server.rs:65:57
     |
65   |       ) -> Result<Response<AddArtifactsResponse>, Status> {
     |  _________________________________________________________^
66   | |         let mut client = Self::connect_to_spark(&request).await?;
67   | |         let mut stream = request.into_inner();
68   | |         let mut items = Vec::new();
...    |
81   | |         client.add_artifacts(out_stream).await
82   | |     }
     | |_____^ `(dyn tonic::transport::Body<Data = prost::bytes::Bytes, Error = Status> + std::marker::Send + 'static)` cannot be shared between threads safely
     |
     = help: the trait `Sync` is not implemented for `(dyn tonic::transport::Body<Data = prost::bytes::Bytes, Error = Status> + std::marker::Send + 'static)`
     = note: required for `Unique<dyn Body<Data = Bytes, Error = Status> + Send>` to implement `Sync`

[HaoYang670]

seems related to #241, but could anyone point me out how to fix that?

[HaoYang670]

I fixed it by using futures::executor::block_on