Blazor Server Memory Leak

Describe the bug

Old data isn’t cleared from memory, regardless of time passage and CircutOptions configuration.

To Reproduce

Project

Repository Link

I’ve experienced this in a production app, but I have recreated the behavior using the default blazor server template. I made the following changes:

Startup.cs - reduce retained connections.

services.AddServerSideBlazor(o => {
    o.DisconnectedCircuitMaxRetained = 1;
    o.DisconnectedCircuitRetentionPeriod = TimeSpan.FromSeconds(10);
});

Data/WeatherForcastService.cs - Add variable forecast length.

public class WeatherForecastService
{
    // ...

    public Task<WeatherForecast[]> GetForecastAsync(DateTime startDate, int count) // added `count` parameter
    {
        var rng = new Random();
        return Task.FromResult(Enumerable.Range(1, count).Select(index => new WeatherForecast
        { // ...

Pages/FetchData.razor - add controls for appending x amount of forecast rows.

else
{
    <span>Load</span>
    <input type="number" @bind="Count"/>
    <span>Items</span>
    <button @onclick="LoadMore">Go</button>

@* ... *@

@code {
    private List<WeatherForecast> Forecasts { get; set; } = new();
    private int Count { get; set; } = 5;
    private async Task LoadMore() => Forecasts
        .AddRange(await ForecastService.GetForecastAsync(DateTime.Now, Count));

    // ...
}

Steps

1. Navigate to /fetchdata
2. Load a large number of rows (e.g. 10,000)
3. Navigate away from the page
4. Repeat 1-3 until memory grows substantially (should jump ~ 25 MB / 10,000 rows).

Memory is never released at this point, regardless of time passed or page closed/reloaded. Even if it was, why does memory grow this way? I would expect it to release memory when I navigate away because that data is never accessed after that point.

Exceptions (if any)

n/a

Further technical details

ASP.NET Core version: net5.0

Include the output of dotnet --info:

.NET SDK (reflecting any global.json):
 Version:   6.0.100-preview.3.21202.5
 Commit:    aee38a6dd4

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19043
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-preview.3.21202.5\

Host (useful for support):
  Version: 6.0.0-preview.3.21201.4
  Commit:  236cb21e3c

.NET SDKs installed:
  5.0.100 [C:\Program Files\dotnet\sdk]
  5.0.102 [C:\Program Files\dotnet\sdk]
  5.0.202 [C:\Program Files\dotnet\sdk]
  5.0.300-preview.21180.15 [C:\Program Files\dotnet\sdk]
  6.0.100-preview.3.21202.5 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0-preview.3.21201.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.26 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0-preview.3.21201.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.13 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.0-preview.3.21201.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

The IDE (VS / VS Code/ VS4Mac) you’re running on, and its version: Microsoft Visual Studio Community 2019, Version 16.9.4

[SteveSandersonMS]

Also as per another comment in #30210:

Blazor keeps a limited number of circuits in memory for up to 3 minutes (by default) to enable applications to reconnect to the same session in the event that there is an intermittent network connection.

… you would need to wait 3 minutes before triggering the collection in order for an abandoned circuit’s data to be released. Please see DisconnectedCircuitRetentionPeriod if you want to change the config for this.

[davidfowl]

Is client GC the same thing as Workstation GC?

Yes

Yes, our application has a fair amount of concurrency.

What’s fair amount? 1000, 10000 concurrent users?

What does your hardware look like? RAM?