feat(core) ensure required shms are declared

Signed-off-by: Thibault Charbonnier <thibaultcha@me.com>

Applied with stronger test (more reliable in case of failure), style
changes and error message changes for readability.

From #2466

CHANGELOG.md

@@ -37,8 +37,8 @@
 - Serf commands executed by a running Kong node are now logged in the Nginx
   error logs with a `DEBUG` level.
   [#2410](https://github.com/Mashape/kong/pull/2410)
-- Logging retries and failure information.
-  [#2429](https://github.com/Mashape/kong/pull/2429).
+- Checking that core Lua shared dictionaries are declared in the configuration.
+  [#2466](https://github.com/Mashape/kong/pull/2466)
 - Plugins:
   - :fireworks: **New Request termination plugin**. This plugin allows to
     temporarily disable an API and return a pre-configured response status and

kong/constants.lua

@@ -69,5 +69,6 @@ return {
   },
   CACHE = {
     CLUSTER = "cluster"
-  }
+  },
+  DICTS = { "kong", "cache", "cache_locks", "process_events", "cassandra"},
 }

kong/kong.lua

@@ -121,6 +121,17 @@ end
 local Kong = {}
 
 function Kong.init()
+  -- let's ensure the required shared dictionaries are
+  -- declared via lua_shared_dict in the Nginx conf
+  for _, dict in ipairs(constants.DICTS) do
+    if not ngx.shared[dict] then
+      return error("missing shared dict '" .. dict .. "' in Nginx "          ..
+                   "configuration, are you using a custom template? "        ..
+                   "Make sure the 'lua_shared_dict " .. dict .. " [SIZE];' " ..
+                   "directive is defined.")
+    end
+  end
+
   local pl_path = require "pl.path"
   local conf_loader = require "kong.conf_loader"
 

spec/02-integration/01-cmd/02-start_stop_spec.lua

@@ -199,5 +199,31 @@ describe("kong start/stop", function()
 
       assert(kill.is_running(helpers.test_conf.nginx_pid))
     end)
+    it("ensures the required shared dictionaries are defined", function()
+      local constants = require "kong.constants"
+      local pl_file   = require "pl.file"
+      local fmt       = string.format
+
+      local templ_fixture     = "spec/fixtures/custom_nginx.template"
+      local new_templ_fixture = "spec/fixtures/custom_nginx.template.tmp"
+
+      finally(function()
+        pl_file.delete(new_templ_fixture)
+        helpers.stop_kong()
+      end)
+
+      for _, dict in ipairs(constants.DICTS) do
+        -- remove shared dictionary entry
+        assert(os.execute(fmt("sed '/lua_shared_dict %s .*;/d' %s > %s",
+                              dict, templ_fixture, new_templ_fixture)))
+
+        local ok, err = helpers.start_kong({ nginx_conf = new_templ_fixture })
+        assert.falsy(ok)
+        assert.matches(
+          "missing shared dict '" .. dict .. "' in Nginx configuration, "    ..
+          "are you using a custom template? Make sure the 'lua_shared_dict " ..
+          dict .. " [SIZE];' directive is defined.", err, nil, true)
+      end
+    end)
   end)
 end)