• Microsoft.ApplicationInsights.WorkerService 2.21
• .NET 6
• AKS - Linux

Describe the bug

It seams that the heartbeat isn't working for applications that run shorter than 30 seconds, even when FlushAsync is called.

To Reproduce

1. Create a console application that writes to the application insight traces
2. Using this configuration:

        services.ConfigureTelemetryModule<DiagnosticsTelemetryModule>((module, _) =>
        {
            module.HeartbeatInterval = TimeSpan.FromSeconds(30);
            module.IsHeartbeatEnabled = true;
        });
        services.AddApplicationInsightsTelemetry(config);

3. Flush for 30 seconds. In the finally

       await _myTelemetryClient.FlushAsync(CancellationToken.None);
       await Task.Delay(TimeSpan.FromSeconds(30));

Sometimes it's too late.
The traces are sent really earlier (29 sec)

I tried lowering the HeartbeatInterval, but 30 seconds is the lowest possible value?

So the FlushAsync doesn't seem to send the heartbeat, that's the bug.

Is there a way to send the heartbeat manually?

Work around: await Task.Delay(TimeSpan.FromSeconds(45)); - we don't really like this. The job needs 5 seconds, and now 50 (10 times!)

Related: #1689, #407