Perf: reduce memory usage when reloading with large configurations.

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - 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)
+- Reduce memory when reloading with large configurations [PR #1608](https://github.com/3scale/APIcast/pull/1608)
 
 ### 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/libexec/boot.lua

@@ -9,4 +9,7 @@ require('apicast.loader')
 local configuration = require 'apicast.configuration_loader'
 local config = configuration.boot()
 
+if type(config) == 'table' then
+  config = require('cjson').encode(config)
+end
 ngx.say(config)

gateway/src/apicast/configuration_loader/oidc.lua

@@ -61,7 +61,11 @@ function _M.call(...)
 
         config.oidc = oidc
 
-        return cjson.encode(config), select(2, ...)
+        -- Return the decoded table instead of re-encoding to JSON.
+        -- configuration_parser.decode() passes tables through untouched, so
+        -- downstream configuration_parser.parse() won't need to re-decode it
+        -- either.
+        return config, select(2, ...)
     else
         return ...
     end

gateway/src/apicast/configuration_loader/remote_v2.lua

@@ -133,7 +133,7 @@ local function parse_proxy_configs(self, proxy_configs)
 
     config.oidc[i] = oidc_copy
   end
-  return cjson.encode(config)
+  return config
 end
 
 local function parse_resp_body(self, resp_body)
@@ -207,7 +207,7 @@ function _M:index_per_service()
     configs[i] = nil
   end
 
-  return cjson.encode(configs)
+  return configs
 end
 
 function _M:index_custom_path(host)

gateway/src/apicast/mapping_rule.lua

@@ -23,10 +23,14 @@ local _M = {
 }
 
 local mt = { __index = _M }
+local empty_table = {}
 
 local function hash_to_array(hash)
-  local array = {}
+  if not hash or next(hash) == nil then
+    return empty_table
+  end
 
+  local array = {}
   for k,v in pairs(hash or {}) do
     insert(array, { k, v })
   end
@@ -86,32 +90,26 @@ local function matches_querystring_params(params, args)
 end
 
 local function matches_uri(rule_pattern, uri)
-  return re_match(uri, format("^%s", rule_pattern), 'oj')
+  return re_match(uri, rule_pattern, 'oj')
 end
 
 local function new(http_method, pattern, params, querystring_params, metric, delta, last, owner_id, owner_type)
-  local self = setmetatable({}, mt)
-
-  local querystring_parameters = hash_to_array(querystring_params)
-
-  self.method = http_method
-  self.pattern = pattern
-  self.regexpified_pattern = regexpify(pattern)
-  self.parameters = params
-  self.system_name = metric or error('missing metric name of rule')
-  self.delta = delta
-  self.last = last or false
+  local self = {
+    querystring_parameters = hash_to_array(querystring_params),
+    method = http_method,
+    pattern = pattern,
+    regexpified_pattern = format("^%s", regexpify(pattern)),
+    parameters = params,
+    system_name = metric or error('missing metric name of rule'),
+    delta = delta,
+    last = last or false
+  }
 
   if owner_type == BackendAPIconst then
     self.owner_id = owner_id
   end
 
-
-  self.querystring_params = function(args)
-    return matches_querystring_params(querystring_parameters, args)
-  end
-
-  return self
+  return setmetatable(self, mt)
 end
 
 --- Initializes a mapping rule from a proxy rule of the service configuration.
@@ -153,7 +151,7 @@ end
 function _M:matches(method, uri, args)
   local match = (self.method == self.any_method or self.method == method) and
       matches_uri(self.regexpified_pattern, uri) and
-      self.querystring_params(args)
+      matches_querystring_params(self.querystring_parameters, args)
 
   -- match can be nil. Convert to boolean.
   return match == true

spec/configuration_loader/oidc_spec.lua

@@ -45,7 +45,9 @@ describe('OIDC Configuration loader', function()
     end)
 
     it('forwards all parameters', function()
-      assert.same({'{"oidc":[]}', 'one', 'two'}, { loader.call('{}', 'one', 'two')})
+      local result = { loader.call('{}', 'one', 'two') }
+      assert.same({ oidc = {} }, result[1])
+      assert.same({ 'one', 'two' }, { result[2], result[3] })
     end)
 
     it('gets openid configuration', function()
@@ -96,7 +98,7 @@ describe('OIDC Configuration loader', function()
           ]
         }
       ]])
-      assert.same(expected_oidc, cjson.decode(oidc))
+      assert.same(expected_oidc, oidc)
     end)
 
     -- This is a regression test. cjson crashed when parsing a config where
@@ -161,7 +163,7 @@ describe('OIDC Configuration loader', function()
           ]
         }
       ]])
-      assert.same(expected_oidc, cjson.decode(oidc))
+      assert.same(expected_oidc, oidc)
     end)
 
     it('handles OIDC discovery failure gracefully without crashing', function()
@@ -201,7 +203,7 @@ describe('OIDC Configuration loader', function()
       local result = loader.call(cjson.encode(config))
       assert.is_not_nil(result)
 
-      local decoded = cjson.decode(result)
+      local decoded = result
       assert.equals(2, #decoded.oidc)
 
       -- First service should have error
@@ -265,7 +267,7 @@ describe('OIDC Configuration loader', function()
       local result = loader.call(cjson.encode(config))
       assert.is_not_nil(result)
 
-      local decoded = cjson.decode(result)
+      local decoded = result
       assert.equals(1, #decoded.oidc)
       assert.equals(99, decoded.oidc[1].service_id)
       -- assert.is_not_nil(decoded.oidc[1].error)