feat(proxy) implement delayed response with stream module

### Summary

Implements delayed responses with stream module that is used to
short-circuit streams.

kong/init.lua

@@ -264,18 +264,21 @@ local function execute_init_worker_plugins_iterator(plugins_iterator, ctx)
 end
 
 
-local function execute_access_plugins_iterator(plugins_iterator, ctx)
+local function execute_collecting_plugins_iterator(plugins_iterator, phase, ctx)
   local old_ws = ctx.workspace
 
   ctx.delay_response = true
 
-  for plugin, configuration in plugins_iterator:iterate("access", ctx) do
+  for plugin, configuration in plugins_iterator:iterate(phase, ctx) do
     if not ctx.delayed_response then
-      local span = instrumentation.plugin_access(plugin)
+      local span
+      if phase == "access" then
+        span = instrumentation.plugin_access(plugin)
+      end
 
       setup_plugin_context(ctx, plugin)
 
-      local co = coroutine.create(plugin.handler.access)
+      local co = coroutine.create(plugin.handler[phase])
       local cok, cerr = coroutine.resume(co, plugin.handler, configuration)
       if not cok then
         -- set tracing error
@@ -795,7 +798,17 @@ function Kong.preread()
   end
 
   local plugins_iterator = runloop.get_updated_plugins_iterator()
-  execute_plugins_iterator(plugins_iterator, "preread", ctx)
+  execute_collecting_plugins_iterator(plugins_iterator, "preread", ctx)
+
+  if ctx.delayed_response then
+    ctx.KONG_PREREAD_ENDED_AT = get_updated_now_ms()
+    ctx.KONG_PREREAD_TIME = ctx.KONG_PREREAD_ENDED_AT - ctx.KONG_PREREAD_START
+    ctx.KONG_RESPONSE_LATENCY = ctx.KONG_PREREAD_ENDED_AT - ctx.KONG_PROCESSING_START
+
+    return flush_delayed_response(ctx)
+  end
+
+  ctx.delay_response = nil
 
   if not ctx.service then
     ctx.KONG_PREREAD_ENDED_AT = get_updated_now_ms()
@@ -893,7 +906,7 @@ function Kong.access()
 
   local plugins_iterator = runloop.get_plugins_iterator()
 
-  execute_access_plugins_iterator(plugins_iterator, ctx)
+  execute_collecting_plugins_iterator(plugins_iterator, "access", ctx)
 
   if ctx.delayed_response then
     ctx.KONG_ACCESS_ENDED_AT = get_updated_now_ms()

kong/pdk/response.lua

@@ -26,7 +26,9 @@ local find = string.find
 local lower = string.lower
 local error = error
 local pairs = pairs
+local ipairs = ipairs
 local concat = table.concat
+local tonumber = tonumber
 local coroutine = coroutine
 local normalize_header = checks.normalize_header
 local normalize_multi_header = checks.normalize_multi_header
@@ -812,6 +814,33 @@ local function new(self, major_version)
     return send(response.status_code, response.content, response.headers)
   end
 
+
+  local function send_stream(status, body, headers)
+    if body then
+      if status < 400 then
+        -- only sends body to the client for < 400 status code
+        local res, err = ngx.print(body)
+        if not res then
+          error("unable to send body to client: " .. err, 2)
+        end
+
+      else
+        self.log.err("unable to proxy stream connection, " ..
+                     "status: " .. status .. ", err: ", body)
+      end
+    end
+
+    return ngx.exit(status)
+  end
+
+
+  local function flush_stream(ctx)
+    ctx = ctx or ngx.ctx
+    local response = ctx.delayed_response
+    return send_stream(response.status_code, response.content, response.headers)
+  end
+
+
   if ngx and ngx.config.subsystem == 'http' then
     ---
     -- This function interrupts the current processing and produces a response.
@@ -994,21 +1023,22 @@ local function new(self, major_version)
         end
       end
 
-      if body then
-        if status < 400 then
-          -- only sends body to the client for 200 status code
-          local res, err = ngx.print(body)
-          if not res then
-            error("unable to send body to client: " .. err, 2)
-          end
+      local ctx = ngx.ctx
+      ctx.KONG_EXITED = true
 
-        else
-          self.log.err("unable to proxy stream connection, " ..
-                       "status: " .. status .. ", err: ", body)
-        end
-      end
+      if ctx.delay_response and not ctx.delayed_response then
+        ctx.delayed_response = {
+          status_code = status,
+          content     = body,
+          headers     = headers,
+        }
+
+        ctx.delayed_response_callback = flush_stream
+        coroutine.yield()
 
-      return ngx.exit(status)
+      else
+        return send_stream(status, body, headers)
+      end
     end
   end
 
@@ -1127,7 +1157,6 @@ local function new(self, major_version)
       if type(message) ~= "string" then
         error("message must be a nil, a string or a table", 2)
       end
-
     end
 
     if headers ~= nil and type(headers) ~= "table" then

spec/02-integration/05-proxy/28-stream_plugins_triggering_spec.lua

@@ -1,5 +1,6 @@
 local helpers = require "spec.helpers"
 local pl_file = require "pl.file"
+local cjson = require "cjson"
 
 
 local TEST_CONF = helpers.test_conf
@@ -42,21 +43,33 @@ local phases = {
   ["%[logger%] log phase"] = 1,
 }
 
+local phases_2 = {
+  ["%[logger%] init_worker phase"] = 1,
+  ["%[logger%] preread phase"] = 0,
+  ["%[logger%] log phase"] = 1,
+}
+
 local phases_tls = {
   ["%[logger%] init_worker phase"] = 1,
   ["%[logger%] certificate phase"] = 1,
   ["%[logger%] preread phase"] = 1,
   ["%[logger%] log phase"] = 1,
 }
 
+local phases_tls_2 = {
+  ["%[logger%] init_worker phase"] = 1,
+  ["%[logger%] certificate phase"] = 1,
+  ["%[logger%] preread phase"] = 0,
+  ["%[logger%] log phase"] = 1,
+}
+
 local function assert_phases(phrases)
   for phase, count in pairs(phrases) do
     assert(find_in_file(phase, count))
   end
 end
 
 for _, strategy in helpers.each_strategy() do
-
   describe("#stream Proxying [#" .. strategy .. "]", function()
     local bp
 
@@ -107,9 +120,9 @@ for _, strategy in helpers.each_strategy() do
         service = tls_srv,
       }
 
-      assert(bp.plugins:insert {
+      bp.plugins:insert {
         name = "logger",
-      })
+      }
 
       assert(helpers.start_kong({
         database   = strategy,
@@ -140,7 +153,7 @@ for _, strategy in helpers.each_strategy() do
     it("tls", function()
       local tcp = ngx.socket.tcp()
       assert(tcp:connect(helpers.get_proxy_ip(true), 19443))
-      assert(tcp:sslhandshake(nil, "this-is-needed.test", false))
+      assert(tcp:sslhandshake(nil, nil, false))
       assert(tcp:send(MESSAGE))
       local body = assert(tcp:receive("*a"))
       assert.equal(MESSAGE, body)
@@ -149,4 +162,118 @@ for _, strategy in helpers.each_strategy() do
       assert_phases(phases_tls)
     end)
   end)
+
+  describe("#stream Proxying [#" .. strategy .. "]", function()
+    local bp
+
+    before_each(function()
+      bp = helpers.get_db_utils(strategy, {
+        "routes",
+        "services",
+        "plugins",
+      }, {
+        "logger",
+        "short-circuit",
+      })
+
+      local tcp_srv = bp.services:insert({
+        name = "tcp",
+        host = helpers.mock_upstream_host,
+        port = helpers.mock_upstream_stream_port,
+        protocol = "tcp"
+      })
+
+      bp.routes:insert {
+        destinations = {
+          {
+            port = 19000,
+          },
+        },
+        protocols = {
+          "tcp",
+        },
+        service = tcp_srv,
+      }
+
+      local tls_srv = bp.services:insert({
+        name = "tls",
+        host = helpers.mock_upstream_host,
+        port = helpers.mock_upstream_stream_ssl_port,
+        protocol = "tls"
+      })
+
+      bp.routes:insert {
+        destinations = {
+          {
+            port = 19443,
+          },
+        },
+        protocols = {
+          "tls",
+        },
+        service = tls_srv,
+      }
+
+      bp.plugins:insert {
+        name = "logger",
+      }
+
+      bp.plugins:insert {
+        name = "short-circuit",
+        config = {
+          status = 200,
+          message = "plugin executed"
+        },
+      }
+
+      assert(helpers.start_kong({
+        database   = strategy,
+        nginx_conf = "spec/fixtures/custom_nginx.template",
+        plugins = "logger,short-circuit",
+        proxy_listen = "off",
+        admin_listen = "off",
+        stream_listen = helpers.get_proxy_ip(false) .. ":19000," ..
+                        helpers.get_proxy_ip(false) .. ":19443 ssl"
+      }))
+    end)
+
+    after_each(function()
+      helpers.stop_kong()
+    end)
+
+    it("tcp (short-circuited)", function()
+      local tcp = ngx.socket.tcp()
+      assert(tcp:connect(helpers.get_proxy_ip(false), 19000))
+      local body = assert(tcp:receive("*a"))
+      tcp:close()
+
+      local json = cjson.decode(body)
+      assert.same({
+        init_worker_called = true,
+        message = "plugin executed",
+        status = 200
+      }, json)
+
+      wait()
+      assert_phases(phases_2)
+    end)
+
+    it("tls (short-circuited)", function()
+      local tcp = ngx.socket.tcp()
+      assert(tcp:connect(helpers.get_proxy_ip(true), 19443))
+      assert(tcp:sslhandshake(nil, nil, false))
+      local body = assert(tcp:receive("*a"))
+      tcp:close()
+
+      local json = assert(cjson.decode(body))
+      assert.same({
+        init_worker_called = true,
+        message = "plugin executed",
+        status = 200
+      }, json)
+
+      wait()
+      assert_phases(phases_tls_2)
+    end)
+  end)
 end

spec/fixtures/custom_plugins/kong/plugins/short-circuit/handler.lua

@@ -2,9 +2,6 @@ local cjson = require "cjson"
 
 
 local kong = kong
-local req = ngx.req
-local exit = ngx.exit
-local error = error
 local tostring = tostring
 local init_worker_called = false
 
@@ -23,26 +20,21 @@ end
 function ShortCircuitHandler:access(conf)
   return kong.response.exit(conf.status, {
     status  = conf.status,
-    message = conf.message
+    message = conf.message,
   }, {
     ["Kong-Init-Worker-Called"] = tostring(init_worker_called),
   })
 end
 
 
 function ShortCircuitHandler:preread(conf)
-  local tcpsock, err = req.socket(true)
-  if err then
-    error(err)
-  end
-
-  tcpsock:send(cjson.encode({
-    status  = conf.status,
-    message = conf.message
-  }))
-
-  -- TODO: this should really support delayed short-circuiting!
-  return exit(conf.status)
+  local message = cjson.encode({
+    status             = conf.status,
+    message            = conf.message,
+    init_worker_called = init_worker_called,
+  })
+  return kong.response.exit(conf.status, message)
 end
 
+
 return ShortCircuitHandler