mod_h2: mod_proxy_http2: gRPC bi-directional messages stuck

Hi,

maybe you can help me out, I am using gRPC bi-directional messaging with grpc-dotnet. When I directly connect client and server, the messages from the client are streamed to the server without any problems. Once I change the client configuration to connect over the mod_proxy_http2 port, the messages are stuck. It seems like they are buffered because once I start sending messages from the server to the client, sometimes the client messages are delivered, too (depending on the timing) and when I shut down the gRPC server, messages also get delivered sometimes.

Here is my apache configuration:

Protocols h2
SSLProxyEngine On

<Location /tunnel.TunnelMessaging>
    Require all granted
    
    ProxyPass h2://localhost:5001/tunnel.TunnelMessaging retry=0
    ProxyPassReverse https://localhost:5001/tunnel.TunnelMessaging
</Location>

And the debug log output:

• Sending the message which is not received: apache.log
• Logs when shutting down gRPC server: shutting_down_grpc_server.log

Any help would be appreciated!