Websocket Example

Upgrading to websockets

NOTE In marathon-lb 1.12.x it is necessary to also override HAPROXY_0_HTTP_BACKEND_REVPROXY_GLUE as follows:

"HAPROXY_0_HTTP_BACKEND_REVPROXY_GLUE": "  acl hdr_location res.hdr(Location) -m found\n  rspirep \"^Location: (https?://{hostname}(:[0-9]+)?)?(/.*)\" \"Location:\\ {rootpath}\\3\" if hdr_location\n"

This has been fixed in 96b045f0 and will be included in the next release.

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In order to upgrade the connection to a websocket, modify the HAPROXY_0_HTTP_FRONTEND_ACL label adding and acl and having it use that backend (\\n acl is_websocket hdr(Upgrade) -i WebSocket\\n use_backend {backend} if is_websocket):

"HAPROXY_0_HTTP_FRONTEND_ACL": "  acl host_{cleanedUpHostname} hdr(host) -i {hostname}\\n  use_backend {backend} if host_{cleanedUpHostname}\\n  acl is_websocket hdr(Upgrade) -i WebSocket\\n  use_backend {backend} if is_websocket",

Make sure to include the default portion of HAPROXY_0_HTTP_FRONTEND_ACL.

A full example of a deployment that just echos on the websocket is as follows:

{
  "id": "/websocket",
  "user":"root",
  "cmd": "/bin/sh -c \"wget https://github.com/vi/websocat/releases/download/v1.2.0/websocat_amd64-linux-static -O /websocat && chmod +x /websocat && /websocat --text --exit-on-eof ws-l:0.0.0.0:1234 mirror:\"",
  "container": {
    "portMappings": [
      {
        "containerPort": 1234,
        "hostPort": 0,
        "protocol": "tcp"
      }
    ],
    "type": "DOCKER",
    "volumes": [],
    "docker": {
      "image": "alpine"
    }
  },
  "cpus": 0.1,
  "instances": 4,
  "labels": {
    "HAPROXY_GROUP": "external",
    "HAPROXY_0_HTTP_FRONTEND_ACL": "  acl host_{cleanedUpHostname} hdr(host) -i {hostname}\\n  use_backend {backend} if host_{cleanedUpHostname}\\n  acl is_websocket hdr(Upgrade) -i WebSocket\\n  use_backend {backend} if is_websocket",
    "HAPROXY_0_HTTP_BACKEND_PROXYPASS_PATH": "/websocket",
    "HAPROXY_0_HTTP_BACKEND_REVPROXY_PATH": "/",
    "HAPROXY_0_PATH": "/websocket",
    "HAPROXY_0_VHOST": "vhost.example.com",
    "HAPROXY_0_ENABLED": "true"
  },
  "mem": 32,
  "networks": [
    {
      "mode": "container/bridge"
    }
  ],
  "requirePorts": false
}