fix(core): fix an issue where Kong do not handle properly when Python…

… and Javascript plugin server crashes

The bug was introduced when refactoring/cherry-picking.

Fix #12364

Co-authored-by: Guilherme Salazar <gsz@acm.org>

changelog/unreleased/kong/plugin_server_restart.yml

@@ -0,0 +1,3 @@
+message: "**Plugin Server**: fix an issue where Kong fails to properly restart MessagePack-based pluginservers (used in Python and Javascript plugins, for example)"
+type: bugfix
+scope: Core

kong/runloop/plugin_servers/mp_rpc.lua

@@ -1,5 +1,7 @@
 local kong_global = require "kong.global"
 local cjson = require "cjson.safe"
+local _
+
 local msgpack do
   msgpack = require "MessagePack"
   local nil_pack = msgpack.packers["nil"]
@@ -326,20 +328,20 @@ end
 
 
 function Rpc:handle_event(plugin_name, conf, phase)
-  local instance_id = self.get_instance_id(plugin_name, conf)
-  local _, err = bridge_loop(self, instance_id, phase)
+  local instance_id, err = self.get_instance_id(plugin_name, conf)
+  if not err then
+    _, err = bridge_loop(self, instance_id, phase)
+  end
 
   if err then
-    local ok, err2 = kong.worker_events.post("plugin_server", "reset_instances",
-    { plugin_name = plugin_name, conf = conf })
-    if not ok then
-      kong.log.err("failed to post plugin_server reset_instances event: ", err2)
-    end
+    local err_lowered = err:lower()
 
-    if str_find(err:lower(), "no plugin instance") then
+    if str_find(err_lowered, "no plugin instance") then
+      self.reset_instance(plugin_name, conf)
       kong.log.warn(err)
       return self:handle_event(plugin_name, conf, phase)
     end
+
     kong.log.err(err)
   end
 end

kong/runloop/plugin_servers/pb_rpc.lua

@@ -392,8 +392,8 @@ end
 
 
 function Rpc:handle_event(plugin_name, conf, phase)
-  local instance_id, res, err
-  instance_id, err = self.get_instance_id(plugin_name, conf)
+  local instance_id, err = self.get_instance_id(plugin_name, conf)
+  local res
   if not err then
     res, err = self:call("cmd_handle_event", {
       instance_id = instance_id,
@@ -402,20 +402,16 @@ function Rpc:handle_event(plugin_name, conf, phase)
   end
 
   if not res or res == "" then
-    if err then
-      local err_lowered = err and err:lower() or ""
-
-      kong.log.err(err_lowered)
+    local err_lowered = err and err:lower() or "unknown error"
 
-      if err_lowered == "not ready" then
-        self.reset_instance(plugin_name, conf)
-      end
-      if str_find(err_lowered, "no plugin instance")
-        or str_find(err_lowered, "closed")  then
-        self.reset_instance(plugin_name, conf)
-        return self:handle_event(plugin_name, conf, phase)
-      end
+    if str_find(err_lowered, "no plugin instance", nil, true)
+      or str_find(err_lowered, "closed", nil, true) then
+      self.reset_instance(plugin_name, conf)
+      kong.log.warn(err)
+      return self:handle_event(plugin_name, conf, phase)
     end
+
+    kong.log.err(err)
   end
 end