blazor wasm --hosted + gRCP web (stream)

Question

Is it possible to do cleint-server streaming responses over gRCP web (http/1.1)?

I've got a working client/server + db solution, but it seems like I have to wait for the full server response (see //await Task.Delay(2000); in server)

What I would like to happen is that the client should render on every "server-tick" it sends back to the client, instead of waiting for the stream to close and render the full response.

Any ides?

Proto

syntax = "proto3";
option csharp_namespace = "GrpcReports";
package reports;

service Reports {
  rpc AllReports (ReportRequest) returns (stream ReportReply);
}

message ReportRequest {}
message ReportReply {
   string name = 1;
}

Server

// server
public class ReportsService : Reports.ReportsBase
{
        private readonly IReportRepository _repository;
        private readonly IMapper _mapper;

        public ReportsService(IReportRepository repository, IMapper mapper)
        {
            _repository = repository ?? throw new ArgumentNullException(nameof(IReportRepository));
            _mapper = mapper ?? throw new ArgumentNullException(nameof(IMapper));
        }

        public override async Task AllReports(ReportRequest request, IServerStreamWriter<ReportReply> responseStream, ServerCallContext context)
        {
            foreach (var item in _mapper.Map<List<ReportReply>>(await _repository.GetAllReportsAsync()))
            {
                Log.Information("{@ReportReply}", item);
                await responseStream.WriteAsync(item);
                //await Task.Delay(2000);
            }
        }
}

Client

@page "/"
@using Grpc.Core
@using GrpcReports
@using AutoMapper
@inject Reports.ReportsClient _reportsClient
@inject IMapper _mapper

<h1>Invoke gRPC service</h1>

<button @onclick="AllReports" class="btn btn-primary">Call gRPC service</button>
<p>Server report response from database:</p>

<ul>
    @foreach (var item in reportReplys)
    {
        <li>@item.Name</li>
    }
</ul>

@code {
    List<ReportReply> reportReplys = new List<ReportReply>();

    async Task AllReports()
    {
        using (var call = _reportsClient.AllReports(new ReportRequest()))
        {
            while (await call.ResponseStream.MoveNext())
            {
                reportReplys.Add(call?.ResponseStream?.Current);
            }
        }
    }
}

Henkolicious Henkolicious · Accepted Answer · 2020-08-14T07:08:01

So gRPC web stream does work, the only thing I needed to add was to re-render the UI on every server tick.

The only thing you need to add to the code is StateHasChanged();.

Client side update:

while (await call?.ResponseStream?.MoveNext())
{
    reportReplys.Add(call?.ResponseStream?.Current);
    StateHasChanged();
}

Ref: https://docs.microsoft.com/en-us/aspnet/core/blazor/components/lifecycle?view=aspnetcore-3.1#state-changes

blazor wasm --hosted + gRCP web (stream)

1 Answers