How do I serve a single static file from HAProxy?

Help!
11

Hey there,
I came up with the following solution for serving files just like a web-server would do with the help of LUA. The following frontend-config sets the HTTP-header X-LUA-LOADFILE-DOCROOT with a local directory path which serves as the document-root. Furthermore, it defines a lua-service called load-file. See:

lua-load /etc/haproxy/lua/load-file.lua

...

backend lua-load-file
  http-request set-header X-LUA-LOADFILE-DOCROOT /etc/haproxy/docroot
  http-request use-service lua.load-file

As you can see I load a lua-file called load-file.lua. The contents of that file are as follows:

core.register_service("load-file", "http", function(applet)
  local docroot
  local location
  local file
  local retval
  local response
  local extension

  if(applet.path == nil or applet.headers["x-lua-loadfile-docroot"] == nil or applet.headers["x-lua-loadfile-docroot"][0] == "") then
    retval = 500
    response = "Internal Server Error"
  else
    docroot = applet.headers["x-lua-loadfile-docroot"][0]
    location = applet.path
    if(location == "" or location == "/") then
      location = "/index.html"
    end
    file = io.open(docroot .. location, "r")
    if(file == nil) then
      retval = 404
      response = "File Not Found"
    else
      retval = 200
      response = file:read("*all")
      file:close()
    end
  end

  extension = string.match(location, ".(%w+)$")
  if       extension == "css"  then applet:add_header("content-type", "text/css")
    elseif extension == "gif"  then applet:add_header("content-type", "image/gif")
    elseif extension == "htm"  then applet:add_header("content-type", "text/html")
    elseif extension == "html" then applet:add_header("content-type", "text/html")
    elseif extension == "ico"  then applet:add_header("content-type", "image/x-icon")
    elseif extension == "jpg"  then applet:add_header("content-type", "image/jpeg")
    elseif extension == "jpeg" then applet:add_header("content-type", "image/jpeg")
    elseif extension == "js"   then applet:add_header("content-type", "application/javascript; charset=UTF-8")
    elseif extension == "json" then applet:add_header("content-type", "application/json")
    elseif extension == "mpeg" then applet:add_header("content-type", "video/mpeg")
    elseif extension == "png"  then applet:add_header("content-type", "image/png")
    elseif extension == "txt"  then applet:add_header("content-type", "text/plain")
    elseif extension == "xml"  then applet:add_header("content-type", "application/xml")
    elseif extension == "zip"  then applet:add_header("content-type", "application/zip")
  end

  applet:set_status(retval)
  if(response ~= nil and response ~= "") then
    applet:add_header("content-length", string.len(response))
  end
  applet:start_response()
  applet:send(response)
end)

Basically, this code reads files from a specified document-root location in the filesystem based on the query string and generates appropriate HTTP-responses just as a normal webserver would do. That is why the script needs a document-root do be configured via the HTTP-header X-LUA-LOADFILE-DOCROOT . Furthermore, the code also does some very basic mimetype handling - extend the list according your needs. I hope someone finds this useful.

cheers!

3 Likes