Lua filter

Requirements

Sandbox environment

Setup your sandbox environment with Docker and Docker Compose, and clone the Envoy repository with Git.

curl

Used to make HTTP requests.

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:

  • envoy_on_request(request_handle)

  • envoy_on_response(response_handle)

See here for an overview of Envoy’s Lua filter and documentation regarding these functions.

Step 1: Build the sandbox

Change to the examples/lua directory.

  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->8000/tcp
  10. lua_web_service_1   node ./index.js                Up      0.0.0.0:8080->80/tcp

Step 2: 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

See also

Envoy Lua filter

Learn more about the Envoy Lua filter.

Lua

The Lua programming language.