From 53c167da84ab83242373eeb7a575fe8dba7d80f6 Mon Sep 17 00:00:00 2001
From: Chrono <chronolaw@gmail.com>
Date: Tue, 3 Dec 2024 16:36:05 +0800
Subject: [PATCH] Revert "refactor(clustering/sync): clean the logic of
 sync_once (#13956)"

This reverts commit 127d0a237cefb77dff64d5fc6b3424cd79ac9a0f.
---
 kong/clustering/services/sync/rpc.lua | 48 +++++++++++++++++----------
 1 file changed, 31 insertions(+), 17 deletions(-)

diff --git a/kong/clustering/services/sync/rpc.lua b/kong/clustering/services/sync/rpc.lua
index fdd3d0cb6f02..4100afbb9675 100644
--- a/kong/clustering/services/sync/rpc.lua
+++ b/kong/clustering/services/sync/rpc.lua
@@ -17,7 +17,7 @@ local CLUSTERING_DATA_PLANES_LATEST_VERSION_KEY = constants.CLUSTERING_DATA_PLAN
 local DECLARATIVE_DEFAULT_WORKSPACE_KEY = constants.DECLARATIVE_DEFAULT_WORKSPACE_KEY
 local CLUSTERING_SYNC_STATUS = constants.CLUSTERING_SYNC_STATUS
 local SYNC_MUTEX_OPTS = { name = "get_delta", timeout = 0, }
-local SYNC_MAX_RETRY = 5
+local MAX_RETRY = 5
 
 
 local assert = assert
@@ -392,8 +392,7 @@ local function do_sync()
 end
 
 
-local sync_handler
-sync_handler = function(premature, try_counter)
+local function sync_handler(premature)
   if premature then
     return
   end
@@ -402,37 +401,52 @@ sync_handler = function(premature, try_counter)
   if not res and err ~= "timeout" then
     ngx_log(ngx_ERR, "unable to create worker mutex and sync: ", err)
   end
+end
 
-  -- try_counter is not set, only run once
-  if not try_counter then
-    return
-  end
 
-  if try_counter <= 0 then
-    ngx_log(ngx_ERR, "sync_once try count exceeded.")
-    return
+local sync_once_impl
+
+
+local function start_sync_once_timer(retry_count)
+  local ok, err = ngx.timer.at(0, sync_once_impl, retry_count or 0)
+  if not ok then
+    return nil, err
   end
 
-  assert(try_counter >= 1)
+  return true
+end
 
-  local latest_notified_version = ngx.shared.kong:get(CLUSTERING_DATA_PLANES_LATEST_VERSION_KEY)
-  if not latest_notified_version then
-    ngx_log(ngx_DEBUG, "no version notified yet")
+
+function sync_once_impl(premature, retry_count)
+  if premature then
     return
   end
 
+  sync_handler()  
+  
+  local latest_notified_version = ngx.shared.kong:get(CLUSTERING_DATA_PLANES_LATEST_VERSION_KEY)
   local current_version = tonumber(declarative.get_current_hash()) or 0
-  if current_version >= latest_notified_version then
+
+  if not latest_notified_version then
+    ngx_log(ngx_DEBUG, "no version notified yet")
     return
   end
 
   -- retry if the version is not updated
-  return ngx.timer.at(0, sync_handler, try_counter - 1)
+  if current_version < latest_notified_version then
+    retry_count = retry_count or 0
+    if retry_count > MAX_RETRY then
+      ngx_log(ngx_ERR, "sync_once retry count exceeded. retry_count: ", retry_count)
+      return
+    end
+
+    return start_sync_once_timer(retry_count + 1)
+  end
 end
 
 
 function _M:sync_once(delay)
-  return ngx.timer.at(delay or 0, sync_handler, SYNC_MAX_RETRY)
+  return ngx.timer.at(delay or 0, sync_once_impl, 0)
 end