ASP net apps consuming data use a lot more memory than console apps

[q-bertsuit]

I've noticed that ASP net apps that consume MQTT messages also use a lot more memory than console apps that subscribe to the same data.
The memory never seems to be released. Running dotMemory shows that the app uses a lot of unmanaged memory

Which component is your bug related to?

• Client, version 4.3.7.1207

Memory consumption of the Producer console app, Consumer console app and Consumer Asp Net 6 app:

Create a console app that pushes data to the bus:

Program.cs:

using System.Text;
using System.Text.Json;
using MQTTnet;
using MQTTnet.Client;

var factory = new MqttFactory();
var client = factory.CreateMqttClient();

var options = new MqttClientOptionsBuilder()
    .WithClientId("SenderClient")
    .WithTcpServer("localhost", 1883) 
    .Build();

await client.ConnectAsync(options, CancellationToken.None);

var dto = new LargeDto
{
    Id = 1,
    Name = "Sample",
    Data = new byte[1024 * 50]
};

var jsonData = JsonSerializer.Serialize(dto);
var message = new MqttApplicationMessageBuilder()
    .WithTopic("large/dto")
    .WithPayload(Encoding.UTF8.GetBytes(jsonData))
    .WithQualityOfServiceLevel(MQTTnet.Protocol.MqttQualityOfServiceLevel.AtMostOnce)
    .Build();

while (true)
{
    await client.PublishAsync(message, CancellationToken.None);
    await Task.Delay(1); 
}


await client.DisconnectAsync();

public class LargeDto
{
    public int Id { get; set; }
    public string Name { get; set; }
    public byte[] Data { get; set; }
}

Create an ASP Net web API (tested both .Net 6 and .Net 8)

Program.cs:

using WebApplication1;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddHostedService<MqttHostedService>();
var app = builder.Build();

app.MapGet("/", () => "Hello World!");

app.Run();

MqttHostedService.cs

using MQTTnet;
using MQTTnet.Client;

namespace WebApplication1;

public class MqttHostedService : IHostedService
{
    private readonly IMqttClient _client;
    private readonly MqttClientOptions _options;

    public MqttHostedService()
    {
        var factory = new MqttFactory();
        _client = factory.CreateMqttClient();

        _options = new MqttClientOptionsBuilder()
            .WithClientId("ListenerClientAsp6")
            .WithTcpServer("localhost", 1883) 
            .Build();

        _client.ApplicationMessageReceivedAsync += e =>
        {
            return Task.CompletedTask;
        };
    }

    public async Task StartAsync(CancellationToken cancellationToken)
    {
        await _client.ConnectAsync(_options, cancellationToken);
        await _client.SubscribeAsync(new MqttTopicFilterBuilder()
            .WithTopic("large/dto")
            .Build());
    }

    public async Task StopAsync(CancellationToken cancellationToken)
    {
        var disconnectOptions = new MqttClientDisconnectOptions
        {
            Reason = MqttClientDisconnectOptionsReason.NormalDisconnection,
            ReasonString = "Service stopping"
        };

        await _client.DisconnectAsync(disconnectOptions, cancellationToken);
    }
}

[xljiulang]

This is not a bug, it's a different GC mode.
https://learn.microsoft.com/en-us/dotnet/core/runtime-config/garbage-collector#workstation-vs-server

[q-bertsuit]

@xljiulang Thanks for your reply. When forcing the ASP net app to use workstation GC, i see very similar memory usage to the console app, like you said.

When using Server GC though, even when disconnecting to the MQTT server and disposing the client, the memory never seems to be released, even when i force a GC. Not sure if this is related to MQTTNet or if it's just how .Net works in this mode.