How can I configure Ocelot programmatically?

[cizu64]

I get this error message when trying to configure ocelot programmatically

Ocelot.Responder.Middleware.ResponderMiddleware[0]
      requestId: 0HN8B1C7OOUES:00000001, previousRequestId: No PreviousRequestId,
message: 'Error Code: UnableToFindDownstreamRouteError 
Message: Failed to match Route configuration for upstream path: /banks, verb: GET.
errors found in ResponderMiddleware. Setting error response for request path:/banks, request method: GET'

This is my code

using System.Security.Claims;
using Microsoft.AspNetCore.Mvc.Filters;
using Ocelot.Configuration.File;
using Ocelot.Configuration.Repository;

public class Middleware : IMiddleware
{
    private readonly IFileConfigurationRepository _fileConfigurationRepository;
    public Middleware(IFileConfigurationRepository fileConfigurationRepository)
    {
        _fileConfigurationRepository = fileConfigurationRepository;
    }
    private List<FileRoute> Configuration(string downStreamPathTemplate)
    {
       
    }
    public async Task InvokeAsync(HttpContext context, RequestDelegate next)
    {
       
        var fileConfig = new FileConfiguration
        {
            Routes = new List<FileRoute>
            {
                new FileRoute
                {
                    DownstreamPathTemplate = "/api/bank/banks",
                    DownstreamScheme = "https",
                    DownstreamHostAndPorts = new List<FileHostAndPort>
                    {
                        new FileHostAndPort { Host = "https://gateway.mybankapp123.com", Port = 443 }
                    },
                    DownstreamHttpMethod = "GET",
                    UpstreamPathTemplate = "/banks",
                    UpstreamHttpMethod = new List<string> { "GET" }
                }
            },
            GlobalConfiguration = new FileGlobalConfiguration
            {
                BaseUrl = "https://localhost:7174"
            }
        };


        await _fileConfigurationRepository.Set(fileConfig);
        
        await next.Invoke(context);
    }
}

This is my program.cs

builder.Services.AddOcelot();
builder.Services.AddScoped<Middleware>();
var app = builder.Build();

app.UseHttpsRedirection();
app.UseAuthentication();
app.UseAuthorization();
//await app.UseOcelot().ContinueWith(a => app.UseMiddleware<Middleware>());
await app.UseOcelot();
app.UseMiddleware<Middleware>();
app.Run();

[raman-m]

😄 🐯

Yes, you can! And everybody can! Yahoo!
My final answer → #2217 (reply in thread)

[cizu64]

Should i mark this as answer?

[cizu64]

I get it! I changed the host to google because i don't want to give the real host.

[raman-m]

Final answer → #2217 (reply in thread)

[raman-m]

OK Let's start professional discussion...

    private readonly IFileConfigurationRepository _fileConfigurationRepository;
    public Middleware(IFileConfigurationRepository fileConfigurationRepository)
    {
        _fileConfigurationRepository = fileConfigurationRepository;
    }

The proposed middleware solution is based on the IFileConfigurationRepository interface, which is implemented by the FileConfigurationRepository class →

Ocelot/src/Ocelot/DependencyInjection/OcelotBuilder.cs

Line 79 in a79ae8a

Services.TryAddSingleton<IFileConfigurationRepository, DiskFileConfigurationRepository>();

This service within the DI-container is solely responsible for file operations. This is the correct direction; however, the configuration logic in Ocelot is rather complex. First, you must conduct some research on the Ocelot code by examining all references to IFileConfigurationRepository! The appropriate solution should be grounded in the functionality of FileConfigurationController:

Ocelot/src/Ocelot/Configuration/FileConfigurationController.cs

Lines 38 to 55 in a79ae8a

	public async Task<IActionResult> Post([FromBody] FileConfiguration fileConfiguration)
	{
	try
	{
	var response = await _setter.Set(fileConfiguration);
	if (response.IsError)
	{
	return new BadRequestObjectResult(response.Errors);
	}
	return new OkObjectResult(fileConfiguration);
	}
	catch (Exception e)
	{
	return new BadRequestObjectResult($"{e.Message}:{e.StackTrace}");
	}
	}

To change the configuration dynamically after the Ocelot application starts, it is necessary to utilize both the IFileConfigurationRepository and IFileConfigurationSetter services.

[raman-m]

The second,

Ocelot has no any fluent syntax to build configuration on the fly as it allowed by YARP for example.
But injecting FileConfiguration object is possible during app start in the ConfigurationBuilderExtensions class methods:

Ocelot/src/Ocelot/DependencyInjection/ConfigurationBuilderExtensions.cs

Lines 165 to 170 in a79ae8a

	public static IConfigurationBuilder AddOcelot(this IConfigurationBuilder builder, FileConfiguration fileConfiguration,
	string primaryConfigFile = null, bool? optional = null, bool? reloadOnChange = null) // optional injections
	{
	var json = JsonConvert.SerializeObject(fileConfiguration, Formatting.Indented);
	return AddOcelotJsonFile(builder, json, primaryConfigFile, optional, reloadOnChange);
	}

This method will deserialize the object to disk.
If you want to keep configuration in memory then this method has MergeOcelotJson option:

Ocelot/src/Ocelot/DependencyInjection/ConfigurationBuilderExtensions.cs

Lines 185 to 190 in a79ae8a

	public static IConfigurationBuilder AddOcelot(this IConfigurationBuilder builder, FileConfiguration fileConfiguration, IWebHostEnvironment env, MergeOcelotJson mergeTo,
	string primaryConfigFile = null, string globalConfigFile = null, string environmentConfigFile = null, bool? optional = null, bool? reloadOnChange = null) // optional injections
	{
	var json = GetMergedOcelotJson(".", env, fileConfiguration, primaryConfigFile, globalConfigFile, environmentConfigFile);
	return ApplyMergeOcelotJsonOption(builder, mergeTo, json, primaryConfigFile, optional, reloadOnChange);
	}

So, final solution based on .NET 8

Program.cs (implicit usings)

using Ocelot.Configuration.File;
using Ocelot.DependencyInjection;
using Ocelot.Middleware;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddOcelot();

// Build Ocelot's configuration object on the fly: add routes, global config, etc.
var ocelotConfig = new FileConfiguration(); // ... initialize props: add routes, global config, etc.

builder.Configuration
    .SetBasePath(builder.Environment.ContentRootPath)
    .AddJsonFile($"appsettings.json", true, true)
    .AddEnvironmentVariables()

    // !!! Solution
    .AddOcelot(ocelotConfig) // MergeOcelotJson.ToFile : writing config JSON back to disk
    .AddOcelot(ocelotConfig, builder.Environment, MergeOcelotJson.ToMemory); // merging to memory

var app = builder.Build();
app.UseHttpsRedirection();
app.UseAuthentication();
app.UseAuthorization();
await app.UseOcelot();
app.Run();

Hope it helps!

[cizu64]

Thanks a lot!

[raman-m]

Just additional links to our official docs where injection of FileConfiguration is explained:

• Dependency Injection → IConfigurationBuilder extensions → AddOcelot methods → Signatures with FileConfiguration parameter explained, and read Note 2

However, developers typically do not read documentation regularly 😄 and it appears that we need to add brief subsection after this section:

• Configuration → Merging Configuration Files → Merging files to memory

...something named as "Write dynamic configurations on the fly" or "Injecting FileConfiguration objects"

[raman-m]

Answer in updated docs for Configuration feature → cf8daf7