feat(balancer) recreate request to update Host header

Author: locao

lualib/resty/kong/balancer.lua

@@ -0,0 +1,54 @@
+local _M = {}
+
+
+local ffi = require("ffi")
+
+
+ffi.cdef([[
+    int ngx_http_lua_kong_ffi_recreate_request(ngx_http_request_t *r);
+]])
+
+
+local get_phase = ngx.get_phase
+local C = ffi.C
+
+
+local get_request
+do
+    local ok, exdata = pcall(require, "thread.exdata")
+    if ok and exdata then
+        function get_request()
+            local r = exdata()
+            if r ~= nil then
+                return r
+            end
+        end
+
+    else
+        local getfenv = getfenv
+
+        function get_request()
+            return getfenv(0).__ngx_req
+        end
+    end
+end
+
+
+function _M.update_host_header()
+    if get_phase() ~= "balancer" then
+        error("API disabled in the current context", 2)
+    end
+
+    local r = get_request()
+
+    local ret = C.ngx_http_lua_kong_ffi_recreate_request(r)
+    if ret == ngx.NGX_OK then
+        return true
+    end
+
+    return nil, "could not recreate request"
+
+end
+
+
+return _M