Playwright/Browsers hang when having more than 3 (sometimes 2) instances running at the same time when testing a Blazor Server App

Context:

• Playwright Version: 1.23.0
• Operating System: Windows 11
• Node.js version: 16.13.0
• Browser: Chromium, Firefox

Code Snippet

using var playwright = await Playwright.CreateAsync();
await using var browser = await playwright.Firefox.LaunchAsync(
    new BrowserTypeLaunchOptions
    {
        Headless = false
    }
);

await Parallel.ForEachAsync(
    Enumerable.Range(1, options.Iterations),
    new ParallelOptions { MaxDegreeOfParallelism = options.Iterations },
    async (iteration, cancellationToken) =>
    {
        await using var browserContext = await browser.NewContextAsync();
        var page = await browserContext.NewPageAsync();

        page.GotoAsync("https://localhost/");
        page.ClickAsync("body > header > nav > button");

        await Task.Delay(10000); // This is just for debugging purposes
    }
);

Description

I have a Blazor Server App that is hosted in IIS. In this App, I have a Button (HTML) that has a Click handler () => NavigationManager.NavigateTo(url, true);. All the handler does is navigate to a Login Page.

I wanted to test my Application with Playwright and it works OK when I start only 1-2 instances. When I try with more than 3 instances then it hangs as soon as the click page.ClickAsync("body > header > nav > button"); is executed. if I close some instances then other instances continue working as they should.

What I have noticed is that if the second parameter in NavigationManager.NavigateTo(url, true); is set to false then it works.

This can be reproduced with the default Blazor Server Template.

P.S.

If I just run the App with dotnet run then it works!

[dardanlibrary]

I’ve been experimenting with this since my last comment. It seems the issue is on the IIS side. I was using IIS on Windows Home and not on Windows Server and based on some online documentation, IIS on Windows Home has a limit on the number of concurrent connections.

I have created a virtual machine with Windows Server and I am not facing the same issue - I was able to execute 100 parallel tests.

Sorry if I bothered you and thanks a lot for your time.

[mxschmitt]

Sorry for the late reply. I’m unfortunately not familiar with Blazor either but, happy to accept any PRs/research in that direction.