Manipulate headers to downstream hosts

[jeroenvheel]

Hi is was playing with Ocelot and was wondering if it was possible to add information in the headers for the downstream hosts

I'm trying to add the subdomain to the headers so my back end logic can switch things based on a tenant domain.

I found this in the closed issues #1011

        var configuration = new OcelotPipelineConfiguration()
        {
            PreQueryStringBuilderMiddleware = async (context, next) =>
            {
                var host = $"{context.HttpContext.Request.Host.Value}";
                context.DownstreamRequest.Headers.Add("OriginalHost", host);
                await next.Invoke();
            }
        };

but the solution gives a error on the HttpContext and the DownstreamRequest
when i try to fix the code i can't find the DownstreamRequest

Ocelot version: 16.0.1

[jeroenvheel]

I reverted back to 15.0.6 and found out the above code is working.
Sinds version 15.0.7 the solution is broken.

[rh101]

@jeroenvheel This may be an alternative solution for you:

public class HostInjectorDelegatingHandler : DelegatingHandler
{
    private readonly IHttpContextAccessor _httpContextAccessor;

    public HostInjectorDelegatingHandler(IHttpContextAccessor httpContextAccessor)
    {
        _httpContextAccessor = httpContextAccessor;
    }

    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var host = $"{_httpContextAccessor.HttpContext.Request.Host.Value}";
        request.Headers.Add("OriginalHost",  host);
        return base.SendAsync(request, cancellationToken);
    }
}

In Startup.cs, add the handler like this:

services.AddHttpContextAccessor(); // This is required to enable access to the HttpContext

services.AddOcelot()
    .AddDelegatingHandler<HostInjectorDelegatingHandler>();

Then in your ocelot config, you set the delegating handler as follows:

{
    "DownstreamPathTemplate": ...
    "UpstreamPathTemplate": ...
    "DelegatingHandlers": [
        "HostInjectorDelegatingHandler"
    ]
}

Note: There may be an issue with the above implementation for version 15.0.7+, as described in #1252

[jeroenvheel]

@rh101 Thanks ! this is working perfect.