High RAM usage on idle with prometheus 7.0

After upgrading to prometheus-net.AspNetCore “7.0.0” i’m noticing high usage of RAM on my web api projects even on idle but only if you open metrics page at least once. Same behavior with Sample.Web project in this repo. At start RAM usage is not high, but it’s continues to grow with time, so with “7.0.0” version it’s begins to slowly grow after launch from 20 mb up to 70-100mb after 30-60min in my case. Problem disappear if you downgrade to “6.0.0”

Steps to reproduce:

1. Create project with code below.
2. Open metrics page “*/metrics” couple of times.

Code:

using Prometheus;

var builder = WebApplication.CreateBuilder(args);

var app = builder.Build();

app.UseMetricServer();
app.UseHttpMetrics();

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

app.Run();

csproj:

<Project Sdk="Microsoft.NET.Sdk.Web">

    <PropertyGroup>
        <TargetFramework>net6.0</TargetFramework>
        <Nullable>enable</Nullable>
        <ImplicitUsings>enable</ImplicitUsings>
    </PropertyGroup>

    <ItemGroup>
        <PackageReference Include="prometheus-net.AspNetCore" Version="7.0.0" />
    </ItemGroup>

</Project>

Update So i finded advice from @sandersaares in issue #392 to disable event counter integration and it’s also does the trick and abnormal RAM usage stops.

workaround:

Metrics.SuppressDefaultMetrics(new SuppressDefaultMetricOptions
{
    SuppressEventCounters = true
});

[sandersaares]

I confirm that I can reproduce this. Interesting find!

It seems to be native memory that is accumulating for some reason. Specifically, the process appears to be accumulating EventCounter event payload values (memory contents closely resemble EventWrittenEventArgs.Payload[n].Values):

I have filed a bug with the .NET runtime, as this seems to be some deep internal wiring: https://github.com/dotnet/runtime/issues/80684

Meanwhile, the workaround you referenced should indeed help you out (assuming you do not need this functionality that is being suppressed). I will continue to explore a permanent solution and will see what the runtime folks say.

[Jakimar]

After a week of observations i can’t see any problem with version “8.0.0-pre-230127154206-9ec9e9b” both memory and CPU looks totally fine.