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In this article, we'll examine how to deploy a C# application using Puppeteer for web scraping or automated testing within a Docker container on Azure Container Apps. We will also address common issues encountered, especially regarding Chrome installation.

Step 1: Create Dockerfile

Begin with a Dockerfile for your .NET 9 ASP.NET application. The following is an example that installs Chrome and its dependencies:

# Use .NET 9.0 ASP.NET base image
FROM mcr.microsoft.com/dotnet/aspnet:9.0

# Set the working directory to /app
WORKDIR /app

# Expose ports for the application
EXPOSE 8080
EXPOSE 8081

# Install dependencies and Chrome
RUN apt-get update -y && \
    apt-get install -yqq \
    unzip \
    wget \
    curl \
    libgdiplus \
    libc6-dev \
    libx11-dev && \
    wget -q https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb && \
    apt-get install -y ./google-chrome-stable_current_amd64.deb && \
    # Get the latest ChromeDriver version number
    CHROME_DRIVER_VERSION=$(curl -sS https://chromedriver.storage.googleapis.com/LATEST_RELEASE) && \
    wget -q -O /tmp/chromedriver.zip https://chromedriver.storage.googleapis.com/${CHROME_DRIVER_VERSION}/chromedriver_linux64.zip && \
    unzip -q /tmp/chromedriver.zip chromedriver -d /usr/local/bin/ && \
    rm -f /tmp/chromedriver.zip google-chrome-stable_current_amd64.deb && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*

# Set the environment path
ENV PATH="/usr/local/bin/chromedriver:${PATH}"

# Entry point for the .NET application
ENTRYPOINT ["dotnet", "PdfApi.dll"]

Step 2: Implementing Puppeteer in C#

In your C# code, ensure that you can correctly detect Chrome's installation and handle errors if it’s unavailable. Here’s how you can utilize Puppeteer within an ASP.NET controller:

[HttpGet(Name = "GetWeatherForecast")]
public async Task<ActionResult> Get()
{
    byte[] screenshot;
    string chromePath = "/usr/bin/google-chrome-stable";

    bool exists = System.IO.File.Exists(chromePath);
    if (exists)
    {
        _logger.LogInformation("file exists");
    }
    else
    {
        _logger.LogInformation("file does not exist");
    }

    try
    {
        using var browser = await Puppeteer.LaunchAsync(new LaunchOptions
        {
            Headless = true,
            ExecutablePath = Environment.GetEnvironmentVariable("PUPPETEER_EXECUTABLE_PATH") ?? chromePath,
            Args = new[] { "--no-sandbox", "--disable-setuid-sandbox" }
        });

        using var page = await browser.NewPageAsync();
        await page.GoToAsync("https://example.com");
        screenshot = await page.ScreenshotDataAsync();
    }
    catch (Exception ex)
    {
        return BadRequest(ex.Message + ex.StackTrace);
    }

    return File(screenshot, "image/png");
}

Summary

This article covered how to build a Docker container with a .NET 9 ASP.NET application that uses Puppeteer for headless browsing. We addressed a common deployment issue where the Chrome executable could not be found, leading to a failure in launching the browser. By ensuring that Chrome is installed correctly and checking its existence before usage, you can prevent runtime errors in Azure Container Apps.