diff --git a/src/hash_reader/db_hash_reader.erl b/src/hash_reader/db_hash_reader.erl
index c575173..ef6454d 100644
--- a/src/hash_reader/db_hash_reader.erl
+++ b/src/hash_reader/db_hash_reader.erl
@@ -45,11 +45,14 @@ handle_info({got_torrent, failed, _Hash}, State) ->
 	#state{downloading = D} = State,
 	Conn = db_conn(State),
 	try_next_download(Conn),
+	?T(?FMT("got torrent failed ~s", [_Hash])),
 	{noreply, State#state{downloading = D - 1}};
 
 handle_info({got_torrent, ok, Hash, Content}, State) ->
 	Conn = db_conn(State),
+	true = is_binary(Content),
 	% save the torrent file
+	?T(?FMT("got torrent ok ~s size ~p", [Hash, byte_size(Content)])),
 	SaveTor = config:get(save_torrent, true),
 	if SaveTor -> loc_torrent_cache:save(Conn, Hash, Content); true -> ok end,
 	NewState = got_torrent_content(Conn, State, Hash, Content),
@@ -62,21 +65,21 @@ handle_info({got_torrent_from_cache, Hash, Content}, State) ->
 
 handle_info(timeout, State) ->
 	Conn = db_conn(State),
+	?T("handle timeout, try next"),
 	try_next(Conn),
 	{noreply, State};
 
-handle_info(_, State) ->
-	{noreply, State}.
-
 % when there's no hash to process
-handle_cast(process_download_hash, State) ->
+handle_info(process_download_hash, State) ->
 	#state{downloading = D} = State,
 	NewD = case D >= ?MAX_DOWNLOAD of
 		true ->
 			% the only thing we can do is just wait
 			timer:send_after(?WAIT_TIME, timeout),
+			?T(?FMT("reach the max download ~p", [D])),
 			D;
 		false ->
+			?T(?FMT("start a new download ~p", [D])),
 			% launch downloader
 			Conn = db_conn(State),
 			try_next_download(Conn),
@@ -86,10 +89,15 @@ handle_cast(process_download_hash, State) ->
 	end,
 	{noreply, State#state{downloading = NewD}};
 
+handle_info(M, State) ->
+	?W(?FMT("unhandled message ~p", [M])),
+	{noreply, State}.
+
 handle_cast({process_hash, Doc,  DownloadDoc}, State) ->
 	Conn = db_conn(State),
 	{Hash} = bson:lookup(hash, Doc),
 	ListHash = binary_to_list(Hash),
+	?T(?FMT("process a hash ~s download-doc ~p", [ListHash, DownloadDoc])),
 	% to avoid register many timers when the hash is empty but download hash is not
 	% it also can avoid increase the message queue size, everytime this function get called,
 	% it remove this message and append only another 1.
@@ -115,6 +123,7 @@ try_download(State, Hash, Doc) ->
 	#state{downloading = D} = State,
 	NewDownloading = case D >= ?MAX_DOWNLOAD of
 		true -> % put it into the download queue
+			?T(?FMT("reach the max download, insert it to wait queue ~s", [Hash])),
 			Conn = db_conn(State),
 			insert_to_download_wait(Conn, Doc),
 			D;
@@ -130,8 +139,10 @@ do_download(State, Hash) ->
 	Conn = db_conn(State),
 	case loc_torrent_cache:load(Conn, Hash) of
 		not_found -> % not in the local cache, download it now
+			?T(?FMT("push a request to tor_download ~s", [Hash])),
 			tor_download:download(Pid, Hash);
 		Content -> % process later
+			?T(?FMT("load a torrent from cache ~s", [Hash])),
 			on_used_cache(),
 			self() ! {got_torrent_from_cache, Hash, Content}
 	end.
@@ -167,6 +178,7 @@ got_torrent_content(Conn, State, MagHash, Content) ->
 	try_next_download(Conn),
 	case catch(torrent_file:parse(Content)) of
 		{'EXIT', _} ->
+			?W(?FMT("parse a torrent failed ~s", [MagHash])),
 			skip;
 		{Type, Info} -> 
 			got_torrent(State, MagHash, Type, Info)
@@ -217,7 +229,8 @@ schedule_next({}, true) ->
 	ok;
 
 schedule_next({}, false) ->
-	gen_server:cast(self(), process_download_hash);
+	?T("hash is empty, try to startup downloader"),
+	self() ! process_download_hash;
 
 schedule_next({Doc}, DownloadDoc) ->
 	gen_server:cast(self(), {process_hash, Doc, DownloadDoc}).