diff --git a/lualib/resty/events/broker.lua b/lualib/resty/events/broker.lua
index 537beb43..39abde02 100644
--- a/lualib/resty/events/broker.lua
+++ b/lualib/resty/events/broker.lua
@@ -30,7 +30,7 @@ local cjson_encode = cjson.encode
 local MAX_UNIQUE_EVENTS = 1024
 
 local function is_closed(err)
-    return err and
+    return type(err) == "string" and
            (str_sub(err, -6) == "closed" or
             str_sub(err, -11) == "broken pipe")
 end
diff --git a/lualib/resty/events/callback.lua b/lualib/resty/events/callback.lua
index 1da6a8b0..10d1cb2d 100644
--- a/lualib/resty/events/callback.lua
+++ b/lualib/resty/events/callback.lua
@@ -110,9 +110,19 @@ function _M:do_event(d)
     local event  = d.event
     local data   = d.data
     local wid    = d.wid
+    local time   = d.time
+
+    ngx.update_time()
+    local now = ngx.now()
+
+    if time then
+      log(DEBUG, "worker-events [receive]: source=", source,
+          ", event=", event, ", wid=", wid, ", time=", now - time,
+          ", data=", encode(data))
+    end
 
     log(DEBUG, "worker-events: handling event; source=", source,
-        ", event=", event, ", wid=", wid)
+        ", event=", event, ", wid=", wid, ", data=", encode(data))
 
     local funcs = self._funcs
     local list
@@ -128,6 +138,12 @@ function _M:do_event(d)
     -- source+event callback
     list = get_callback_list(self, source, event)
     do_handlerlist(funcs, list, source, event, data, wid)
+
+    ngx.update_time()
+    log(DEBUG, "worker-events [done] : source=", source,
+        ", event=", event, ", wid=", wid, ", time=", ngx.now() - now,
+        ", data=", encode(data))
+
 end
 
 return _M
diff --git a/lualib/resty/events/codec.lua b/lualib/resty/events/codec.lua
index eba7ec01..42a7ef02 100644
--- a/lualib/resty/events/codec.lua
+++ b/lualib/resty/events/codec.lua
@@ -9,6 +9,7 @@ end
 local options = {
   dict = { "spec", "data",
            "source", "event", "wid", "unique",
+           "time",
          },
 }
 
diff --git a/lualib/resty/events/queue.lua b/lualib/resty/events/queue.lua
index 5260afc7..177b286c 100644
--- a/lualib/resty/events/queue.lua
+++ b/lualib/resty/events/queue.lua
@@ -1,3 +1,5 @@
+local cjson = require "cjson.safe"
+local codec = require "resty.events.codec"
 local semaphore = require "ngx.semaphore"
 
 local table_new = require "table.new"
@@ -6,6 +8,8 @@ local assert = assert
 local setmetatable = setmetatable
 local math_min = math.min
 
+local decode = codec.decode
+local cjson_encode = cjson.encode
 
 local _M = {}
 local _MT = { __index = _M, }
@@ -20,8 +24,14 @@ function _M.new(max_len)
         elts = table_new(math_min(max_len, DEFAULT_QUEUE_LEN), 0),
         first = 0,
         last = -1,
+
+        -- debug
+        outcome = 0,
+        income = 0,
     }
 
+    ngx.log(ngx.DEBUG, "worker-events [queue]: init, max_len=", self.max_len)
+
     return setmetatable(self, _MT)
 end
 
@@ -29,7 +39,12 @@ end
 function _M:push(item)
     local last = self.last
 
-    if last - self.first + 1 >= self.max then
+    local count = last - self.first + 1
+
+    ngx.log(ngx.DEBUG, "worker-events [queue]: push , len=", count,
+            ", income=", self.income, ", outcome=", self.outcome)
+
+    if count >= self.max then
         return nil, "queue overflow"
     end
 
@@ -37,6 +52,8 @@ function _M:push(item)
     self.last = last
     self.elts[last] = item
 
+    self.income = self.income + 1
+
     self.semaphore:post()
 
     return true
@@ -59,6 +76,13 @@ function _M:pop()
     self.elts[first] = nil
     self.first = first + 1
 
+    self.outcome = self.outcome + 1
+
+    local count = self.last - self.first + 1
+
+    ngx.log(ngx.DEBUG, "worker-events [queue]: pop , len=", count,
+            ", income=", self.income, ", outcome=", self.outcome)
+
     return item
 end
 
diff --git a/lualib/resty/events/worker.lua b/lualib/resty/events/worker.lua
index 40b6f1f9..d9ef7931 100644
--- a/lualib/resty/events/worker.lua
+++ b/lualib/resty/events/worker.lua
@@ -40,6 +40,7 @@ local EVENT_T = {
     event = '',
     data = '',
     wid = '',
+    time = '',
 }
 
 local SPEC_T = {
@@ -172,6 +173,8 @@ function _M:communicate(premature)
                 return nil, "failed to decode event data: " .. err
             end
 
+            ngx.log(ngx.DEBUG, "worker-events [queue]: push sub_queue, data=", cjson_encode(d))
+
             -- got an event data, push to queue, callback in events_thread
             local ok, err = self._sub_queue:push(d)
             if not ok then
@@ -198,6 +201,9 @@ function _M:communicate(premature)
                 goto continue
             end
 
+            local obj = decode(decode(payload).data)
+            ngx.log(ngx.DEBUG, "worker-events [queue]: pop pub_queue, data=", cjson_encode(obj))
+
             if exiting() then
                 return
             end
@@ -232,6 +238,8 @@ function _M:communicate(premature)
                 goto continue
             end
 
+            ngx.log(ngx.DEBUG, "worker-events [queue]: pop sub_queue, data=", cjson_encode(data))
+
             if exiting() then
                 return
             end
@@ -286,6 +294,11 @@ local function post_event(self, source, event, data, spec)
     EVENT_T.data = data
     EVENT_T.wid = _worker_id
 
+    ngx.update_time()
+    EVENT_T.time = ngx.now()
+
+    ngx.log(ngx.DEBUG, "worker-events [queue]: push pub_queue, data=", cjson_encode(EVENT_T))
+
     -- encode event info
     str, err = encode(EVENT_T)
 
@@ -331,6 +344,8 @@ function _M:publish(target, source, event, data)
     assert(type(source) == "string" and source ~= "", "source is required")
     assert(type(event) == "string" and event ~= "", "event is required")
 
+    log(DEBUG, "[publish] source=", source, ", event=", event, ", data=", cjson_encode(data))
+
     -- fall back to local events
     if self._opts.testing == true then
         log(DEBUG, "event published to 1 workers")
@@ -345,6 +360,10 @@ function _M:publish(target, source, event, data)
     end
 
     if target == "current" then
+        log(DEBUG, "event published to local worker")
+
+        ngx.log(ngx.DEBUG, "worker-events [queue]: push sub_queue, data=", cjson_encode(data))
+
         ok, err = self._sub_queue:push({
             source = source,
             event = event,