feat(router) create router in init phase for early error detection

We also remember why the router was not created after an invalidation
event so further failed routings will show the reason in the error logs.

kong/core/handler.lua

@@ -18,7 +18,7 @@ local certificate = require "kong.core.certificate"
 local balancer_execute = require("kong.core.balancer").execute
 
 
-local router
+local router, router_err
 local ngx_now = ngx.now
 local server_header = _KONG._NAME.."/".._KONG._VERSION
 
@@ -28,47 +28,37 @@ local function get_now()
 end
 
 
-local function build_router()
-  local apis, err = singletons.dao.apis:find_all()
-  if err then
-    ngx.log(ngx.CRIT, "[router] could not load APIs: ", err)
-    return
-  end
+-- in the table below the `before` and `after` is to indicate when they run:
+-- before or after the plugins
+return {
+  build_router = function()
+    local apis
 
-  for i = 1, #apis do
-    -- alias since the router expects 'headers'
-    -- as a map
-    if apis[i].hosts then
-      apis[i].headers = { host = apis[i].hosts }
+    apis, router_err = singletons.dao.apis:find_all()
+    if router_err then
+      return nil, "could not load APIs: " .. router_err
     end
-  end
 
-  router, err = Router.new(apis)
-  if not router then
-    ngx.log(ngx.CRIT, "[router] could not create router: ", err)
-    return
-  end
-end
+    for i = 1, #apis do
+      -- alias since the router expects 'headers'
+      -- as a map
+      if apis[i].hosts then
+        apis[i].headers = { host = apis[i].hosts }
+      end
+    end
 
+    router, router_err = Router.new(apis)
+    if not router then
+      return nil, "could not create router: " .. router_err
+    end
+
+    return true
+  end,
 
--- in the table below the `before` and `after` is to indicate when they run; before or after the plugins
-return {
   init_worker = {
     before = function()
       reports.init_worker()
       cluster.init_worker()
-
-      build_router()
-
-      local worker_events = require "resty.worker.events"
-
-      worker_events.register(function(data, event, source, pid)
-        if data and data.collection == "apis" then
-          --local inspect = require "inspect"
-          --print("CHANGE IN APIS DATA: ", source, inspect(event), inspect(source), inspect(data))
-          build_router()
-        end
-      end)
     end
   },
   certificate = {
@@ -78,14 +68,20 @@ return {
   },
   access = {
     before = function()
+      if not router then
+        return responses.send_HTTP_INTERNAL_SERVER_ERROR(
+          "no router to route request (reason: " .. tostring(router_err) .. ")"
+        )
+      end
+
       local ctx = ngx.ctx
       local var = ngx.var
 
       ctx.KONG_ACCESS_START = get_now()
 
       local api, upstream_scheme, upstream_host, upstream_port = router.exec(ngx)
       if not api then
-        return responses.send_HTTP_NOT_FOUND("no API found")
+        return responses.send_HTTP_NOT_FOUND("no API found with those values")
       end
 
       if api.https_only and not utils.check_https(api.http_if_terminated) then

kong/kong.lua

@@ -141,6 +141,8 @@ function Kong.init()
   singletons.configuration = config
 
   attach_hooks(events, require "kong.core.hooks")
+
+  assert(core.build_router())
 end
 
 function Kong.init_worker()
@@ -163,7 +165,10 @@ function Kong.init_worker()
   local worker_events = require "resty.worker.events"
 
   local handler = function(data, event, source, pid)
-    if source and source == constants.CACHE.CLUSTER then
+    if data and data.collection == "apis" then
+      assert(core.build_router())
+
+    elseif source and source == constants.CACHE.CLUSTER then
       singletons.events:publish(event, data)
     end
   end