How to create a simple side car proxy

Implementation

• Side car proxy container will intercept the request and re-route the request to intented app container.
• Side car proxy container sits between the interface and app container.

• We will reroute the incoming requests to interface to proxy using the iptables cmds. See
  • we are running these cmds in an init container.
  • this will put proxy in between interface and app container.
• When our proxy receives a request at port 8000. See
  • it will forward the request to our app at port 80
  • if request was successful, our proxy will return the response
• We will create docker image with dockerfile present inside each folder.
• We are testing our approach by launching a pod. See

Testing

1. Get the IP of Pod

   •   $ kubectl get pods -o wide
       NAME          READY   STATUS    RESTARTS   AGE   IP          NODE             NOMINATED NODE   READINESS GATES
       httpbin-pod   2/2     Running   0          65s   10.1.0.16   docker-desktop   <none>           <none>

2. Send a Get request

   •  $ kubectl run -i --rm --restart=Never busybox --image=odise/busybox-curl \
        -- sh -c "curl -i 10.1.0.16:80/get?query=param"
      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                      Dload  Upload   Total   Spent    Left  Speed
      HTTP/1.1 200 OK
      Access-Control-Allow-Credentials: true
      Access-Control-Allow-Origin: *
      Connection: keep-alive
      Content-Length: 237
      Content-Type: application/json
      Date: Mon, 08 Aug 2022 08:44:55 GMT
      Server: amazing-proxy
     
      {
      "args": {
          "query": "param"
      }, 
      "headers": {
          "Accept-Encoding": "gzip", 
          "Host": "127.0.0.1:80", 
          "User-Agent": "Go-http-client/1.1"
      }, 
      "origin": "127.0.0.1", 
      "url": "http://127.0.0.1:80/get?query=param"
      }
      100   237  100   237    0     0  28413      0 --:--:-- --:--:-- --:--:-- 29625
      pod "busybox" deleted

3. Send a Post request

   •   $ kubectl run -i --rm --restart=Never busybox --image=odise/busybox-curl \
         -- sh -c "curl -i -X POST -d 'body=parameters' 10.1.0.16:80/post"
       % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                       Dload  Upload   Total   Spent    Left  Speed
       HTTP/1.1 200 OK
       Access-Control-Allow-Credentials: true
       Access-Control-Allow-Origin: *
       Connection: keep-alive
       Content-Length: 317
       Content-Type: application/json
       Date: Mon, 08 Aug 2022 08:45:29 GMT
       Server: amazing-proxy
     
       {
       "args": {}, 
       "data": "body=parameters", 
       "files": {}, 
       "form": {}, 
       "headers": {
           "Accept-Encoding": "gzip", 
           "Host": "127.0.0.1:80", 
           "Transfer-Encoding": "chunked", 
           "User-Agent": "Go-http-client/1.1"
       }, 
       "json": null, 
       "origin": "127.0.0.1", 
       "url": "http://127.0.0.1:80/post"
       }
       100   332  100   317  100    15   130k   6339 --:--:-- --:--:-- --:--:--  154k
       pod "busybox" deleted

4. Send a request to /status endpoint.

   •   $ kubectl run -i --rm --restart=Never busybox --image=odise/busybox-curl \
         -- sh -c "curl -i http://10.1.0.16:80/status/429"
       % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                       Dload  Upload   Total   Spent    Left  Speed
       0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
       HTTP/1.1 429 Too Many Requests
       Access-Control-Allow-Credentials: true
       Access-Control-Allow-Origin: *
       Connection: keep-alive
       Content-Length: 0
       Content-Type: text/html; charset=utf-8
       Date: Mon, 08 Aug 2022 08:46:55 GMT
       Server: amazing-proxy
     
       pod "busybox" deleted

5. Now check the logs of proxy.

   •   $ kubectl logs httpbin-pod --container="proxy"
       Original URL: http://10.1.0.16:80/get?query=param
       Proxy URL: http://127.0.0.1:80/get?query=param
       Request Duration: 6.360182ms
       Request Size: 0
       Response Size: 237
       Response Status: 200
     
       Original URL: http://10.1.0.16:80/post
       Proxy URL: http://127.0.0.1:80/post
       Request Duration: 1.67244ms
       Request Size: 15
       Response Size: 317
       Response Status: 200
     
       Original URL: http://10.1.0.16:80/status/429
       Proxy URL: http://127.0.0.1:80/status/429
       Request Duration: 2.356356ms
       Request Size: 0
       Response Size: 0
       Response Status: 429

We have now implemented the HTTP traffic side car proxy. See original post at https://venilnoronha.io/hand-crafting-a-sidecar-proxy-and-demystifying-istio