Send concurrent SignalR messages with one connection

Question

How can I send multple SignalR messages in parallel with only one connection?

I have the following hub method:

public async Task Test()  
{  
    Console.WriteLine($"Start: {DateTime.Now}");  
    await Task.Run(() => Task.Delay(1000));  
    Console.WriteLine($"Stop: {DateTime.Now}");  
}

In my client I have the following connection:

private connection: HubConnection = new HubConnectionBuilder()
  .withUrl(this.url)
  .configureLogging(LogLevel.Information)
  .withAutomaticReconnect([1000, 2000, 3000, 4000, 5000])
  .build();

I'm calling the hub method like this:

async test(): Promise<void> {
  try {
    console.log('start: ' + new Date().toString());
    await this.connection.invoke('Test');
    console.log('stop: ' + new Date().toString());
  } catch (err) {
    console.error(err);
  }
}

When I call the test method in my client multiple times, the hub is receiving the messages one after the other instead of all at once.

Client log:

start: Mon Nov 29 2021 17:27:35 GMT+0100 (3)
stop: Mon Nov 29 2021 17:27:36 GMT+0100
stop: Mon Nov 29 2021 17:27:37 GMT+0100
stop: Mon Nov 29 2021 17:27:38 GMT+0100

Server log:

Start: 29.11.2021 17:27:35
Stop: 29.11.2021 17:27:36
Start: 29.11.2021 17:27:36
Stop: 29.11.2021 17:27:37
Start: 29.11.2021 17:27:37
Stop: 29.11.2021 17:27:38

Did you try multiple simultaneous clients or is this trace from just a single client? — Caius Jard
– Caius Jard, Commented Nov 29, 2021 at 16:53
Which version of Asp.net core SignalR you are using? If you are using the Asp.net core 5.0 or 6.0, you could try to configure the server MaximumParallelInvocationsPerClient option. Besides, if you are using the previous version, Hub methods from the same connection are invoked sequentially. If you want to support parallel processing, you could have your Hub method start a background process that calls a client method when it completes (using HubContext). — Zhi Lv
– Zhi Lv, Commented Nov 30, 2021 at 3:12
@Caius Jard: The log above is from a single client. When using multiple clients, the server is processing the calls in parallel. — gartenriese
– gartenriese, Commented Nov 30, 2021 at 7:18
@Zhi Lv: Thank you! Using MaximumParallelInvocationsPerClient worked. — gartenriese
– gartenriese, Commented Nov 30, 2021 at 7:38

gartenriese · Accepted Answer · 2021-11-30 07:43:43Z

3

In order to allow multiple parallel invocations per client, you need to set the MaximumParallelInvocationsPerClient property, like this:

builder.Services.AddSignalR(options => options.MaximumParallelInvocationsPerClient = 10);

answered Nov 30, 2021 at 7:43

gartenriese

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