Make LUA redirect hosts

custom_redirects.lua

access_by_lua '
  proto = "http://"
  proto1 = "https://"
  temporary = 302
  permanent = 301

  if ngx.var.host == "example.com" then
    new_host = "new_example.com"
    return ngx.redirect(proto ..new_host .. ngx.var.request_uri, temporary)
  end
';

custom_redirects_by_table.lua

access_by_lua '
-- openresty sample config, see https://openresty.org/en/linux-packages.html
-- lua_package_path "/usr/local/openresty/nginx/lua.d/?.lua";
-- lua_code_cache on;
-- 
-- server {
--     listen       80;
--     server_name  localhost;
--     location / {
--         default_type text/html;
--         include /usr/local/openresty/nginx/lua.d/custom_redirects.lua;
--         proxy_pass http://upstream;
--     }

  default_scheme = "http://"
  permanent = 301

  -- Can load table below as seperate file mappings.lua by calling require(".mappings")
  map = {
        -- customer example.com
        -- ticket OPS-3929
	-- date 05/02/2001
        ["example.com"] = "new_example.com",
        ["old.com"]     = "new.com",
        ["bad.com"]     = "good.com",

  }

  -- fastest method BUT UNTESTED!!!!!
  if map[tostring(ngx.var.host)] then
    return ngx.redirect(default_scheme .. map[tostring(ngx.var.host)] .. ngx.var.request_uri, permanent)
  end

  -- tested but slow
  --for source, destination in pairs(map) do
  --  if tostring(ngx.var.host) == source then
  --    return ngx.redirect(default_scheme .. destination .. ngx.var.request_uri, permanent)
  --  end
  --end
';

nginx.conf

--- snippet ---
    lua_package_path "/usr/local/openresty/nginx/lua.d/?.lua";

    server {
        listen       80;
        server_name  localhost;

        location / {
            default_type text/html;
            include /usr/local/openresty/nginx/lua.d/custom_redirects.lua;
            proxy_pass http://aol.com;

        }
  
--- snippet --

redirects_from_file.lua

access_by_lua '
-- this is probably the least inefficient although coolest method

-- python like split function
-- https://stackoverflow.com/questions/1891473/how-to-load-text-file-into-sort-of-table-like-variable-in-lua

function string:split(sSeparator, nMax, bRegexp)
   local aRecord = {}

   if self:len() > 0 then
      local bPlain = not bRegexp
      nMax = nMax or -1

      local nField, nStart = 1, 1
      local nFirst,nLast = self:find(sSeparator, nStart, bPlain)
      while nFirst and nMax ~= 0 do
         aRecord[nField] = self:sub(nStart, nFirst-1)
         nField = nField+1
         nStart = nLast+1
         nFirst,nLast = self:find(sSeparator, nStart, bPlain)
         nMax = nMax-1
      end
      aRecord[nField] = self:sub(nStart)
   end

   return aRecord
end


  default_scheme = "http://"
  temporary = 307
  local file = io.open("/mnt/redirects_ramdisk/redirect_map.txt", "r")
  if file then
    for line in file:lines() do
        local source, dest = unpack(line:split(" "))
        if tostring(ngx.var.host) == source then
            return ngx.redirect(default_scheme .. dest .. ngx.var.request_uri, temporary)
        end
    end
  else
    local file = io.open("/opt/redirect_map.txt", "r")
    ngx.log(ngx.ERR, "RAMdisk has failed for domain mappings!")
    for line in file:lines() do
        local source, dest = unpack(line:split(" "))
        if tostring(ngx.var.host) == source then
            return ngx.redirect(default_scheme .. dest .. ngx.var.request_uri, temporary)
        end
    end
  end
';