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:

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.

$ pwd
envoy/examples/lua
$ docker-compose pull
$ docker-compose up --build -d
$ docker-compose ps

    Name                     Command               State             Ports
--------------------------------------------------------------------------------------------
lua_proxy_1         /docker-entrypoint.sh /bin ... Up      10000/tcp, 0.0.0.0:8000->8000/tcp
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

$ curl -v localhost:8000

   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8000 (#0)
> GET / HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/7.64.1
> Accept: */*
>
< HTTP/1.1 200 OK
< x-powered-by: Express
< content-type: application/json; charset=utf-8
< content-length: 544
< etag: W/"220-IhsqVTh4HjcpuJQ3C+rEL1Cw1jA"
< date: Thu, 31 Oct 2019 03:13:24 GMT
< x-envoy-upstream-service-time: 1
< response-body-size: 544                      <-- This is added to the response header by our Lua script. --<
< server: envoy
<
{
  "path": "/",
  "headers": {
    "host": "localhost:8000",
    "user-agent": "curl/7.64.1",
    "accept": "*/*",
    "x-forwarded-proto": "http",
    "x-request-id": "a78fcce7-2d67-4eeb-890a-73eebb942a17",
    "foo": "bar",                              <-- This is added to the request header by our Lua script. --<
    "x-envoy-expected-rq-timeout-ms": "15000",
    "content-length": "0"
  },
  "method": "GET",
  "body": "",
  "fresh": false,
  "hostname": "localhost",
  "ip": "::ffff:172.20.0.2",
  "ips": [],
  "protocol": "http",
  "query": {},
  "subdomains": [],
  "xhr": false,
  "os": {
    "hostname": "7ca39ead805a"
  }
* Connection #0 to host localhost left intact
}* Closing connection 0