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Ocelot aggregate interceptor

See original GitHub issue

New Feature

Motivation for New Feature

Let say, I have 2 micro services, called as CustomerMicroService and OrderMicroService CustomerMicroService is in charge of managing customer information. OrderMicroService manages orders that a customer has made.

Let me talk about 2 api end-point from Customer micro-service and Order micro service first.

api/customer/search

Request:

{
	"pagination": {
		"page": 1,
		"records": 30
	}
}

-> Get the first 30 customers from Customer micro service.

Response:

{
	"records": [
		.. list of customers
	]
	"total": 30
}

-> Returns a list of customers with total number of customer that match the search condition.

api/order/search

Request:

{
	"customerIds": [1, 2, 3, 4, 5],
	"status": ["pending", "active"]
}

-> Get list of order base on the previous loaded customer from the above api.

Response:

{
	"records": [
		.. list of orders
	]
	"total": 300
}

-> Returns a list of orders that match the search condition.

Steps to Reproduce the Problem

Now, my API Gateway uses Ocelot to aggregate 2 api endpoint api/customer/search and api/order/search into one API for mobile & web to be consumed, let call it api/gateway/load-customer-orders/{customerId}

This is my ocelot.json:

{
  "Aggregates": [
    {
      "ReRouteKeys": [
        "Customer",
        "Order"
      ],
      "UpstreamPathTemplate": "api/gateway/load-customer-orders/{customerId}",
      "Aggregator": "LoadCustomerOrdersAggregator"
    }
  ],
  "ReRoutes": [
    {
      "DownstreamPathTemplate": "/api/customer/search",
      "DownstreamScheme": "http",
      "UpstreamPathTemplate": "/api/customer/search",
      "UpstreamHttpMethod": [ "POST" ],
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 62744
        }
      ],
      "Key": "Customer"
    },
    {
      "DownstreamPathTemplate": "/api/order/search",
      "DownstreamScheme": "http",
      "UpstreamPathTemplate": "/api/order/search",
      "UpstreamHttpMethod": [ "GET" ],
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 62724
        }
      ],
      "Key": "Order"
    }
  ]
}

My LoadCustomerOrdersAggregator.cs:

public class LoadCustomerOrdersAggregator : IDefinedAggregator
    {
        #region Methods

        /// <summary>
        /// Load customer orders.
        /// </summary>
        /// <param name="responses"></param>
        /// <returns></returns>
        public virtual async Task<DownstreamResponse> Aggregate(List<DownstreamResponse> responses)
        {
            throw new NotImplementedException();
        }

        #endregion
    }

As far as I know Ocelot only support GET method. It is Ok for me, for now, since I just pass {customerId} into my aggregate api api/gateway/load-customer-order/{customerId}.

But it would be nice if I can get the information of Dictionary<string, DownStreamRequest> in aggregate class to manually handle the data by my self.

The aggregate class implemenation should be :

  public virtual async Task<DownstreamResponse> Aggregate(Dictionary<string, DownstreamRequest> requests, List<DownstreamResponse> responses)
        {
            // Base on the request dictionary to manually handle HttpClient call.
            throw new NotImplementedException();
        }