perf(proxy/upstream_connection): setup configuration in init phase

Previously, the configuration for these two policies was set up in the
export() phase. This phase only runs once, when the PolicyChain is built
at configuration load time.

In PR #1485, we moved those parts to the rewrite phase and caused a small
allocation per request. This PR eliminates that by moving the configuration
construction to the init phase.

Author: tkan145

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Routing Policy: eliminate unnecessary TemplateString allocation per request [PR #1585](https://github.com/3scale/APIcast/pull/1585)
 - Headers Policy: don't render template string when delete header [PR #1586](https://github.com/3scale/APIcast/pull/1586)
 - 3scale Batcher Policy: replace regex with string operations [PR #1583](https://github.com/3scale/APIcast/pull/1583)
+- Proxy/Upstream Connection: setup configuration in init phase - [PR #1602](https://github.com/3scale/APIcast/pull/1602)
 
 ### Fixed
 - Correct FAPI header to `x-fapi-interaction-id` [PR #1557](https://github.com/3scale/APIcast/pull/1557) [THREESCALE-11957](https://issues.redhat.com/browse/THREESCALE-11957)

gateway/src/apicast/policy/http_proxy/proxy.lua

@@ -8,6 +8,10 @@ local new = _M.new
 
 local proxies = {"http", "https"}
 
+local function find_proxy(self, scheme)
+  return self.proxies[scheme]
+end
+
 function _M.new(config)
   local self = new(config)
   self.proxies = {}
@@ -27,22 +31,21 @@ function _M.new(config)
     end
     self.proxies[proto] = val or self.all_proxy
   end
-  return self
-end
-
-local function find_proxy(self, scheme)
-  return self.proxies[scheme]
-end
 
-function _M:rewrite(context)
-  -- APIcast reads this flag in the access phase, that's why we need to set it
-  -- in rewrite phase.
-  context.get_http_proxy = function(uri)
+  self.get_http_proxy = function(uri)
     if not uri.scheme then
       return nil
     end
     return find_proxy(self, uri.scheme)
   end
+
+  return self
+end
+
+function _M:rewrite(context)
+  -- APIcast reads this flag in the access phase, that's why we need to set it
+  -- in rewrite phase.
+  context.get_http_proxy = self.get_http_proxy
 end
 
 return _M

gateway/src/apicast/policy/upstream_connection/upstream_connection.lua

@@ -15,15 +15,17 @@ function _M.new(config)
   self.send_timeout = tonumber(config.send_timeout)
   self.read_timeout = tonumber(config.read_timeout)
 
-  return self
-end
-
-function _M:rewrite(context)
-  context.upstream_connection_opts = {
+  self.upstream_connection_opts = {
     connect_timeout = self.connect_timeout,
     send_timeout = self.send_timeout,
     read_timeout = self.read_timeout
   }
+
+  return self
+end
+
+function _M:rewrite(context)
+  context.upstream_connection_opts = self.upstream_connection_opts
 end
 
 return _M

spec/policy/http_proxy/http_proxy_spec.lua

@@ -46,6 +46,17 @@ describe('HTTP proxy  policy', function()
     assert.is_nil(context.get_http_proxy(http_uri))
   end)
 
+  it("reuses the same get_http_proxy function across requests instead of allocating a new one", function()
+    local proxy = proxy_policy.new({ all_proxy = all_proxy_val })
+
+    local context_a = {}
+    local context_b = {}
+    proxy:rewrite(context_a)
+    proxy:rewrite(context_b)
+
+    assert.equal(context_a.get_http_proxy, context_b.get_http_proxy)
+  end)
+
   describe("get_http_proxy callback", function()
     local proxy = proxy_policy.new({
       all_proxy = all_proxy_val,

spec/policy/upstream_connection/upstream_connection_spec.lua

@@ -23,5 +23,16 @@ describe('Upstream connection policy', function()
 
       assert.same(config_timeouts, context.upstream_connection_opts)
     end)
+
+    it('reuses the same table across requests instead of allocating a new one', function()
+      local policy = UpstreamConnectionPolicy.new({ connect_timeout = 1, send_timeout = 2, read_timeout = 3 })
+
+      local context_a = {}
+      local context_b = {}
+      policy:rewrite(context_a)
+      policy:rewrite(context_b)
+
+      assert.equal(context_a.upstream_connection_opts, context_b.upstream_connection_opts)
+    end)
   end)
 end)