Getting HttpClient for downstream path

[mbendtsen]

Is there anyway for me to get and HttpClient based on a path?
I want to build an aggregator (the builtin functionality is not enough) where one POST is calling 3 services, like Facade pattern.
I tried using a custom controller, but couldn't get it to map to the controller. Ocelot kept saying there was no route for the request.

So I digged into DelegateHandlers which could work. I'm using ServiceDiscovery with Kubernetes and I thought why not let Ocelot give me an HttpClient based on the path I want to call.

This is what I got so far, which is probably a big hack. Any ideas? This doesn't work. It doesn't find the right route, and the HttpClientBuilder does not set the base url.

builder.Services.AddTransient<Ocelot.Requester.IHttpClientBuilder, Ocelot.Requester.HttpClientBuilder>();
builder.Services.AddTransient<IOcelotLogger>(c =>
{
    var loggerFactory = c.GetService<IOcelotLoggerFactory>();
    return loggerFactory.CreateLogger<HttpClientHttpRequester>();
});


public class GetDeviceHandler : DelegatingHandler
{
    private readonly IHttpContextAccessor httpContext;
    private readonly Ocelot.Requester.IHttpClientBuilder httpClientBuilder;
    private readonly IDownstreamRouteProvider downstreamRouteProvider;

    public GetDeviceHandler(IHttpContextAccessor httpContext, Ocelot.Requester.IHttpClientBuilder httpClientBuilder, IDownstreamRouteProvider downstreamRouteProvider)
    {
        this.httpContext = httpContext;
        this.httpClientBuilder = httpClientBuilder;
        this.downstreamRouteProvider = downstreamRouteProvider;
    }

    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var configuration = httpContext.HttpContext.Items.IInternalConfiguration();
        var downstreamRouteHolder = httpContext.HttpContext.Items.DownstreamRouteHolder();
        var downstreamRoute = downstreamRouteHolder.Route.DownstreamRoute.FirstOrDefault();
        var client = httpClientBuilder.Create(downstreamRoute);

        var devEui = downstreamRouteHolder.TemplatePlaceholderNameAndValues.First().Value;

        var response = downstreamRouteProvider.Get($"api/devices/{devEui}/endpoints", null, "Get", configuration, null).Data;
        var endpoiintsHttpClient = httpClientBuilder.Create(response.Route.DownstreamRoute.FirstOrDefault());
        
        //do stuff and optionally call the base handler..
        return await base.SendAsync(request, cancellationToken);
    }
}

[raman-m]

Hi Michael!
Cool research! 😄
It is hard to say something right now. 😑

Do you have an intention to discuss your code further?