samuelpratt / SwaggerForOcelotBug

Reproduction of Bug https://github.com/Burgyn/MMLib.SwaggerForOcelot/issues/164

Code to reproduce Burgyn/MMLib.SwaggerForOcelot#164

Now fixed!

The author has kindly fixed the issue. This code should now work.

Build and Run

To build and Run the solution

 docker-compose build
 docker-compose up

To reproduce the issue

Getting the aggregte Swagger URL remotely returns a 500 error: -

PS C:\Users\Sam.Pratt> curl http://localhost:8000/swagger/docs/aggregates/aggregates
curl : The remote server returned an error: (500) Internal Server Error.
At line:1 char:1
+ curl http://localhost:8000/swagger/docs/aggregates/aggregates
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-WebRequest], WebExc
   eption
    + FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeWebRequestCommand

Fails with the Exception below

apigateway_1  |       System.Net.Http.HttpRequestException: Cannot assign requested address (localhost:8000)
apigateway_1  |        ---> System.Net.Sockets.SocketException (99): Cannot assign requested address

Connecting to the container and retriving the URL via CURL works: -

PS C:\Users\Sam.Pratt> docker ps
CONTAINER ID   IMAGE                            COMMAND                  CREATED         STATUS         PORTS                    NAMES
d869fc5cff74   swaggerforocelotbug_fooservice   "dotnet FooService.d…"   4 minutes ago   Up 4 minutes                            swaggerforocelotbug_fooservice_1
10926258ab46   swaggerforocelotbug_barservice   "dotnet BarService.d…"   4 minutes ago   Up 4 minutes                            swaggerforocelotbug_barservice_1
d7e2700c5ac2   swaggerforocelotbug_apigateway   "dotnet ApiGateway.d…"   7 minutes ago   Up 4 minutes   0.0.0.0:8000->5000/tcp   swaggerforocelotbug_apigateway_1
PS C:\Users\Sam.Pratt> docker exec -it d7e2700c5ac2 /bin/bash
root@d7e2700c5ac2:/app# curl http://localhost:5000/swagger/docs/aggregates/aggregates
{
  "openapi": "3.0.1",
  "info": {
    "title": "Aggregates",
    "version": "aggregates"
  },
  "paths": {
    "/api/foobar": {
      "get": {
        "tags": [
          "bar-foo"
        ],
        "summary": "Aggregation of routes: bar, foo",
        "description": "",
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "application/json": {
                "schema": {
                  "type": "object",
                  "properties": {
                    "foo": {
                      "type": "string"
                    },
                    "bar": {
                      "type": "string"
                    }
                  },
                  "additionalProperties": false
                }
              }
            }
          }
        }
      }
    }
  },
  "components": { }
}root@d7e2700c5ac2:/app#

Observations

The issue appears to be caused the port translation that we're doing: -

version: "3.9"
services:
  apigateway:
    build: .\ApiGateway\
    ports:
      - "8000:5000"
  fooservice:
    build: .\FooService
  barservice:
    build: .\BarService
    

As you can see we're mapping 5000 in the container to 8000 externally. However inside the container when Kestral tries to generate the swagger it seems is trying to connect to 8000 locally rather than 5000. You can see this in the stack trace: -

apigateway_1  |       Connection id "0HM6TD4HNUVBJ", Request id "0HM6TD4HNUVBJ:00000002": An unhandled exception was thrown by the application.
apigateway_1  |       System.Net.Http.HttpRequestException: Cannot assign requested address (localhost:8000)

Modifying the Docker compose file to remove the port mapping (as below) seems to fix the issue as below: -

version: "3.9"
services:
  apigateway:
    build: .\ApiGateway\
    ports:
      - "5000:5000"
  fooservice:
    build: .\FooService
  barservice:
    build: .\BarService

docker-compose build
docker-compose up

PS C:\Users\Sam.Pratt> curl http://localhost:5000/swagger/docs/aggregates/aggregates


StatusCode        : 200
StatusDescription : OK
Content           : {123, 10, 32, 32...}
RawContent        : HTTP/1.1 200 OK
                    Transfer-Encoding: chunked
                    Date: Tue, 02 Mar 2021 10:59:37 GMT
                    Server: Kestrel

                    {
                      "openapi": "3.0.1",
                      "info": {
                        "title": "Aggregates",
                        "version": "aggregates"
                      },
                      "...
Headers           : {[Transfer-Encoding, chunked], [Date, Tue, 02 Mar 2021 10:59:37 GMT], [Server, Kestrel]}
RawContentLength  : 874