Lua Filter

In this example, we show how a Lua filter can be used with the Envoy proxy. The Envoy proxy configuration includes a Lua filter that contains two functions namely envoy_on_request(request_handle) and envoy_on_response(response_handle) as documented here.

Running the Sandboxes

The following documentation runs through the setup of both services.

Step 1: Install Docker

Ensure that you have a recent versions of docker and docker-compose.

A simple way to achieve this is via the Docker Desktop.

Step 2: Clone the Envoy repo and start all of our containers

If you have not cloned the Envoy repo, clone it with git clone git@github.com:envoyproxy/envoy or git clone https://github.com/envoyproxy/envoy.git

Terminal 1

  1. $ pwd
  2. envoy/examples/lua
  3. $ docker-compose pull
  4. $ docker-compose up --build -d
  5. $ docker-compose ps
  7.     Name                     Command               State                            Ports
  8. --------------------------------------------------------------------------------------------------------------------
  9. lua_proxy_1         /docker-entrypoint.sh /bin       Up      10000/tcp, 0.0.0.0:8000->80/tcp, 0.0.0.0:8001->8001/tcp
  10. lua_web_service_1   node ./index.js                  Up      0.0.0.0:8080->80/tcp

Step 3: Send a request to the service

The output from the curl command below should include the headers foo.

Terminal 1

  1. $ curl -v localhost:8000
  3.    Trying ::1...
  4. * TCP_NODELAY set
  5. * Connected to localhost (::1) port 8000 (#0)
  6. > GET / HTTP/1.1
  7. > Host: localhost:8000
  8. > User-Agent: curl/7.64.1
  9. > Accept: */*
  10. >
  11. < HTTP/1.1 200 OK
  12. < x-powered-by: Express
  13. < content-type: application/json; charset=utf-8
  14. < content-length: 544
  15. < etag: W/"220-IhsqVTh4HjcpuJQ3C+rEL1Cw1jA"
  16. < date: Thu, 31 Oct 2019 03:13:24 GMT
  17. < x-envoy-upstream-service-time: 1
  18. < response-body-size: 544                      <-- This is added to the response header by our Lua script. --<
  19. < server: envoy
  20. <
  21. {
  22.   "path": "/",
  23.   "headers": {
  24.     "host": "localhost:8000",
  25.     "user-agent": "curl/7.64.1",
  26.     "accept": "*/*",
  27.     "x-forwarded-proto": "http",
  28.     "x-request-id": "a78fcce7-2d67-4eeb-890a-73eebb942a17",
  29.     "foo": "bar",                              <-- This is added to the request header by our Lua script. --<
  30.     "x-envoy-expected-rq-timeout-ms": "15000",
  31.     "content-length": "0"
  32.   },
  33.   "method": "GET",
  34.   "body": "",
  35.   "fresh": false,
  36.   "hostname": "localhost",
  37.   "ip": "::ffff:172.20.0.2",
  38.   "ips": [],
  39.   "protocol": "http",
  40.   "query": {},
  41.   "subdomains": [],
  42.   "xhr": false,
  43.   "os": {
  44.     "hostname": "7ca39ead805a"
  45.   }
  46. * Connection #0 to host localhost left intact
  47. }* Closing connection 0