Getting ResponseCompression to work in .NET Core 2.0 Web API

Question

I have followed all the documentation to setup ResponseCompression in my .NET Core 2.0 Web API project but I cannot see a difference in the size of the transfer. Here are the before and after results using Postman:

Before Compression: https://i.stack.imgur.com/jAAuy.jpg

After Compression: https://i.stack.imgur.com/HviP5.jpg

Here is the beginning of my ConfigureServices method in Startup.cs:

public void ConfigureServices(IServiceCollection services)
{
    services.AddResponseCompression(options =>
    {
        options.Providers.Add<GzipCompressionProvider>();
    });
    services.Configure<GzipCompressionProviderOptions>(options =>
    {
        options.Level = CompressionLevel.Optimal;
    });

Here is my Configure method in Startup.cs:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    app.UseResponseCompression();

    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.UseSwagger();
    app.UseSwaggerUI(c =>
    {
        c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
    });

    app.UseMvc();
}

Here is my Get action on my VendorController:

[HttpGet]
public IActionResult Get()
{
    var stuff = new Collection<string>();
    for (int i = 0; i < 100000; i++)
    {
        stuff.Add($"hello{i}");
    }
    return Ok(stuff);
}

I am not using IIS, here is my Program.cs:

public class Program
{
    public static void Main(string[] args)
    {
        BuildWebHost(args).Run();
    }

    public static IWebHost BuildWebHost(string[] args) =>
        WebHost.CreateDefaultBuilder(args)
            .UseStartup<Startup>()
            .Build();
}

Any help would be MUCH appreciated. All the documentation says that this should give me a pretty big difference in the size of my transfer.

CodeFuller CodeFuller · Accepted Answer · 2017-12-03T09:42:06

Compression works OK in your case, you just check it not quite right.

Postman shows you the size of non-compressed data actually. It makes sense because Postman is an application that operates with HTTP protocol, and it does not care too much about the size of underlying transfer protocol (like TCP).

The easiest way for you to to see the actual response size is to use Fiddler. You could add ResponseSize column that is under Miscellaneous collection because it's not actually a part of HTTP response. Then you will see that for such synthetic data the size of compressed packet is indeed more than 10 times smaller that for non-compressed:

Getting ResponseCompression to work in .NET Core 2.0 Web API

1 Answers