diff --git a/lib/resty/healthcheck.lua b/lib/resty/healthcheck.lua
index 64a0979..4a5fcf3 100644
--- a/lib/resty/healthcheck.lua
+++ b/lib/resty/healthcheck.lua
@@ -1668,7 +1668,7 @@ function _M.new(opts)
   self.TARGET_LIST      = SHM_PREFIX .. self.name .. ":target_list"
   self.TARGET_LIST_LOCK = SHM_PREFIX .. self.name .. ":target_list_lock"
   self.TARGET_LOCK      = SHM_PREFIX .. self.name .. ":target_lock"
-  self.PERIODIC_LOCK    = SHM_PREFIX .. ":period_lock:"
+  self.PERIODIC_LOCK    = SHM_PREFIX .. self.name .. ":period_lock"
   -- prepare constants
   self.EVENT_SOURCE     = EVENT_SOURCE_PREFIX .. " [" .. self.name .. "]"
   self.LOG_PREFIX       = LOG_PREFIX .. "(" .. self.name .. ") "
@@ -1723,7 +1723,6 @@ function _M.new(opts)
 
     self:log(DEBUG, "worker ", ngx_worker_id(), " (pid: ", ngx_worker_pid(), ") ",
       "starting active check timer")
-    local shm, key = self.shm, self.PERIODIC_LOCK
     last_cleanup_check = ngx_now()
     active_check_timer, err = resty_timer({
       recurring = true,
@@ -1732,64 +1731,60 @@ function _M.new(opts)
       detached = false,
       expire = function()
 
-        if get_periodic_lock(shm, key) then
-          active_check_timer.interval = CHECK_INTERVAL
-          renew_periodic_lock(shm, key)
-        else
-          active_check_timer.interval = CHECK_INTERVAL * 10
-          return
-        end
-
         local cur_time = ngx_now()
         for _, checker_obj in pairs(hcs) do
-
-          if (last_cleanup_check + CLEANUP_INTERVAL) < cur_time then
-            -- clear targets marked for delayed removal
-            locking_target_list(checker_obj, function(target_list)
-              local removed_targets = {}
-              local index = 1
-              while index <= #target_list do
-                local target = target_list[index]
-                if target.purge_time and target.purge_time <= cur_time then
-                  table_insert(removed_targets, target)
-                  table_remove(target_list, index)
-                else
-                  index = index + 1
+          local shm, key = checker_obj.shm, checker_obj.PERIODIC_LOCK
+          if get_periodic_lock(shm, key) then
+            renew_periodic_lock(shm, key)
+
+            if (last_cleanup_check + CLEANUP_INTERVAL) < cur_time then
+              -- clear targets marked for delayed removal
+              locking_target_list(checker_obj, function(target_list)
+                local removed_targets = {}
+                local index = 1
+                while index <= #target_list do
+                  local target = target_list[index]
+                  if target.purge_time and target.purge_time <= cur_time then
+                    table_insert(removed_targets, target)
+                    table_remove(target_list, index)
+                  else
+                    index = index + 1
+                  end
                 end
-              end
 
-              if #removed_targets > 0 then
-                target_list = serialize(target_list)
+                if #removed_targets > 0 then
+                  target_list = serialize(target_list)
 
-                local ok, err = shm:set(checker_obj.TARGET_LIST, target_list)
-                if not ok then
-                  return nil, "failed to store target_list in shm: " .. err
-                end
+                  local ok, err = shm:set(checker_obj.TARGET_LIST, target_list)
+                  if not ok then
+                    return nil, "failed to store target_list in shm: " .. err
+                  end
 
-                for _, target in ipairs(removed_targets) do
-                  clear_target_data_from_shm(checker_obj, target.ip, target.port, target.hostname)
-                  checker_obj:raise_event(checker_obj.events.remove, target.ip, target.port, target.hostname)
+                  for _, target in ipairs(removed_targets) do
+                    clear_target_data_from_shm(checker_obj, target.ip, target.port, target.hostname)
+                    checker_obj:raise_event(checker_obj.events.remove, target.ip, target.port, target.hostname)
+                  end
                 end
-              end
-            end)
+              end)
 
-            last_cleanup_check = cur_time
-          end
+              last_cleanup_check = cur_time
+            end
 
-          if checker_obj.checks.active.healthy.active and
-            (checker_obj.checks.active.healthy.last_run +
-              checker_obj.checks.active.healthy.interval <= cur_time)
-          then
-            checker_obj.checks.active.healthy.last_run = cur_time
-            checker_callback(checker_obj, "healthy")
-          end
+            if checker_obj.checks.active.healthy.active and
+              (checker_obj.checks.active.healthy.last_run +
+                checker_obj.checks.active.healthy.interval <= cur_time)
+            then
+              checker_obj.checks.active.healthy.last_run = cur_time
+              checker_callback(checker_obj, "healthy")
+            end
 
-          if checker_obj.checks.active.unhealthy.active and
-            (checker_obj.checks.active.unhealthy.last_run +
-              checker_obj.checks.active.unhealthy.interval <= cur_time)
-          then
-            checker_obj.checks.active.unhealthy.last_run = cur_time
-            checker_callback(checker_obj, "unhealthy")
+            if checker_obj.checks.active.unhealthy.active and
+              (checker_obj.checks.active.unhealthy.last_run +
+                checker_obj.checks.active.unhealthy.interval <= cur_time)
+            then
+              checker_obj.checks.active.unhealthy.last_run = cur_time
+              checker_callback(checker_obj, "unhealthy")
+            end
           end
         end
       end,