Conflicts with existing wildcard

[thinkingmik]

Version: devopsfaith/krakend:0.10.0-dev

Problem

I'm trying to define the gateway endpoints, this is my krakend.json:

{
  "version": 2,
  "name": "MyLovely API Gateway v1.0.0",
	"port": 8080,
	"timeout": "30s",
	"cache_ttl": "300s",
  "endpoints": [ 
    {
      "method": "POST",
      "endpoint": "/api/exhibitions/{exhibitionCode}",
      "backend": [
        {
          "host": [ "http://localhost:8200" ],
          "url_pattern": "/api/exhibitions/{exhibitionCode}"
        }
      ]
    },
    {
      "method": "POST",
      "endpoint": "/api/exhibitions/{exhibitionCode}/info",
      "backend": [
        {
          "host": [ "http://localhost:8200" ],
          "url_pattern": "/api/exhibitions/{exhibitionCode}/info"
        }
      ]
    },
    {
      "method": "POST",
      "endpoint": "/api/exhibitions/search",
      "backend": [
        {
          "host": [ "http://localhost:8200" ],
          "url_pattern": "/api/exhibitions/search"
        }
      ]
    }
  ]
}

Error

I'm getting this error when I'm running the docker container:

panic: 'search' in new path '/api/exhibitions/search' conflicts with existing wildcard ':exhibitionCode' in existing prefix '/api/exhibitions/:exhibitionCode'

Question

Why I'm getting this error? Is there a way to define a static endpoint like /api/exhibitions/search without have conflicts with wildcard's endpoints?

[kpacha]

hi @thinkingmik ,

the panic you're getting is thrown by the gin router and it's a known limitation of the router package the gin project uses

You can check it with this simple script:

package main

import "github.com/gin-gonic/gin"

func main() {
	r := gin.New()
	r.GET("/ping", handler)
	r.GET("/ping/foo", handler)
	r.GET("/ping/:a", handler)
	r.GET("/ping/:a/bar", handler)
}

func handler(c *gin.Context) {
	c.JSON(200, gin.H{
		"message": "pong",
	})
}

panic: wildcard route ':a' conflicts with existing children in path '/ping/:a'

[thinkingmik]

Ok thank you, but if I want to use another router like gorilla/mux instead of the default gin-gonic/gin router?

I would modify the router_engine.go and rebuild krakend-ce for my own, using gorilla/mux. Is the correct way?

package krakend

import (
	cors "github.com/devopsfaith/krakend-cors/mux"
	httpsecure "github.com/devopsfaith/krakend-httpsecure/mux"
	"github.com/devopsfaith/krakend/config"
	"github.com/devopsfaith/krakend/logging"
	"github.com/gorilla/mux"
)

// NewEngine creates a new mux engine with some default values and a secure middleware
func NewEngine(cfg config.ServiceConfig, logger logging.Logger) *mux.Engine {
	engine := mux.DefaultEngine()

	//engine.RedirectTrailingSlash = true
	//engine.RedirectFixedPath = true
	//engine.HandleMethodNotAllowed = true

	if corsMw := cors.New(cfg.ExtraConfig); corsMw != nil {
		engine.Use(corsMw)
	}

	if err := httpsecure.Register(cfg.ExtraConfig, engine); err != nil {
		logger.Warning(err)
	}

	return engine
}

[kpacha]

you should also modify the handler_factory.go and executor.go because they are injecting router dependent modules and components

[thinkingmik]

Yes of course, thank you.

[tfluehmann]

hi @thinkingmik

I am very interested in the same solution as you asked for in this thread. Do you have published your solution for that topic?

Thanks in advance,
tfluehmann

[thinkingmik]

Hi @tfluehmann

sorry but I haven't implemented this solution... I'm still using the standard krakend-ce with default gin-gonic/gin router.

[novalagung]

hi @thinkingmik

I'm getting the same error as yours. May I know how did you resolve the issue while keep using the standard krakend-ce? or did you just change the endpoint schema to avoid the conflict?

[thinkingmik]

Hi @novalagung,

with krakend-ce, that use by default gin-gonic router framework, there is no way to resolve this issue. You must pay attention when you write the endpoints to avoid conflicts. Sorry.

[cafebabepl]

I have been fascinated by krakend for several days but today I got to the wall. I have no idea how to organize endpoint naming for the existing API with this limitation.

[thinkingmik]

I know @wkozi :( but after days of work writing endpoints with this limitation you will get used to it.

However, if you have existing APIs you will change only the exposed endpoint by krakend, not the backend endpoint of your existing API.

For example:

"method": "GET",
"endpoint": "/exposed/endpoint/ping",
"backend": [
  {
    "host": ["http://localhost:3000"],
    "url_pattern": "/different/ping",
    "sd": "static"
  }
]

[novalagung]

@wkozi I ended up creating my own web service, utilizing the krakend middleware with gorilla mux router.

[cafebabepl]

Of course, I understand the limitations and know the workaround, but now I migrate from Netflix Zuul and decompose our API. I understand api gateway as a product = a set of business methods from different microservices. In my opinion, the fact that I have to change my current endpoints, e.g.

/api/contracts/{contractId}/documents/{documentId}
/api/contracts/{contractId}/documents/{documentId}/attachments
/api/contracts/{contractId}/documents/current

to

/api/contracts/{contractId}/documents/{documentId}
/api/contracts/{contractId}/documents/{documentId}/attachments
/api/contracts/{contractId}/documents#current

is a big limitation ;-(

[cafebabepl]

@novalagung it's very interesting. I understand that this requires modification of krakend sources. Can I see it somewhere?

[github-actions]

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