perf(http_proxy): small optimization to avoid unnecessary allocation

Author: tkan145

gateway/src/apicast/http_proxy.lua

@@ -1,7 +1,9 @@
 local format = string.format
 local tostring = tostring
+local ngx = ngx
 local ngx_get_method = ngx.req.get_method
 local ngx_http_version = ngx.req.http_version
+local ngx_req_get_headers = ngx.req.get_headers
 
 local resty_url = require "resty.url"
 local url_helper = require('resty.url_helper')
@@ -49,9 +51,10 @@ local function forward_https_request(proxy_uri, uri, proxy_opts)
     local sock
     local opts = proxy_opts or {}
     local req_method = ngx_get_method()
-    local encoding = ngx.req.get_headers()["Transfer-Encoding"]
+    local headers = ngx_req_get_headers(0, true)
+    local encoding = headers["Transfer-Encoding"]
     local is_chunked = encoding and encoding:lower() == "chunked"
-    local content_type = ngx.req.get_headers()["Content-Type"]
+    local content_type = headers["Content-Type"]
     local content_type_is_urlencoded = content_type and content_type:lower() == "application/x-www-form-urlencoded"
     local raw = false
 
@@ -123,6 +126,7 @@ local function forward_https_request(proxy_uri, uri, proxy_opts)
                 end
 
                 ngx.req.set_header("Content-Length", tostring(contentLength))
+                headers["Content-Length"] = tostring(contentLength)
               end
             end
         end
@@ -131,16 +135,16 @@ local function forward_https_request(proxy_uri, uri, proxy_opts)
         -- header, otherwise the upstream won't be able to read the body as it expected chunk encoded
         -- body
         if is_chunked then
-            ngx.req.set_header("Transfer-Encoding", nil)
+            headers["Content-Length"] = nil
         end
       end
     end
 
     local request = {
         uri = uri,
-        method = ngx.req.get_method(),
-        headers = ngx.req.get_headers(0, true),
-        path = format('%s%s%s', ngx.var.uri, ngx.var.is_args, ngx.var.query_string or ''),
+        method = req_method,
+        headers = headers,
+        path = (ngx.var.uri or '') .. (ngx.var.is_args or '') .. (ngx.var.query_string or ''),
         body = body,
         proxy_uri = proxy_uri,
         proxy_options = opts
@@ -194,7 +198,7 @@ function _M.request(upstream, proxy_uri)
     local proxy_auth
 
     if proxy_uri.user or proxy_uri.password then
-        proxy_auth = "Basic " .. ngx.encode_base64(concat({ proxy_uri.user or '', proxy_uri.password or '' }, ':'))
+        proxy_auth = "Basic " .. ngx.encode_base64((proxy_uri.user or '') .. ":" .. (proxy_uri.password or ''))
     end
 
     if uri.scheme == 'http' then -- rewrite the request to use http_proxy