diff --git a/src/crawler/crawler_app.erl b/src/crawler/crawler_app.erl
index f6f5d1c..3f87780 100644
--- a/src/crawler/crawler_app.erl
+++ b/src/crawler/crawler_app.erl
@@ -6,47 +6,28 @@
 -module(crawler_app).
 -behaviour(application).
 -export([start/2, stop/1]).
--export([start/0, startboth/0, stop/0]).
+-export([start/0, stop/0]).
 
+% application behaviour callback
 start(_Type, _StartArgs) ->
-	File = config_file_name(),
-	io:format("load config file ~s ", [File]),
-	case file:consult(File) of
-		{error, _Reason} ->
-			do_default_start(File);
-		{ok, [Cfg]} ->
-			do_start(Cfg)
-	end.
+	config:start_link("dhtcrawler.config", fun() -> config_default() end),
+	do_start().
 
 stop(_State) ->
+	config:stop(),
 	crawler_sup:stop().
 
-config_file_name() ->
-	filename:join([filename:dirname(code:which(?MODULE)), 
-		"..", "priv", "dhtcrawler.config"]).
-
-do_default_start(File) ->
-	List = [{start_port, 6776},
-		{node_count, 50},
-		{hash_max_cache, 10},
-		{loglevel, 3},
-		{dbconn, 15},
-		{dbhost, "localhost"},
-		{dbport, 27017}],
-	filelib:ensure_dir("priv/"),
-	file:write_file(File, io_lib:fwrite("~p.\n",[List])),
-	do_start(List).
-
-do_start(List) ->
-	StartPort = proplists:get_value(start_port, List),
-	Count = proplists:get_value(node_count, List),
-	LogLevel = proplists:get_value(loglevel, List),
-	DBConn = proplists:get_value(dbconn, List),
-	DBHost = proplists:get_value(dbhost, List),
-	DBPort = proplists:get_value(dbport, List),
-	HashMaxCache = proplists:get_value(hash_max_cache, List),
+do_start() ->
+	StartPort = config:get(start_port),
+	Count = config:get(node_count),
+	LogLevel = config:get(loglevel),
+	DBConn = config:get(dbconn),
+	DBHost = config:get(dbhost),
+	DBPort = config:get(dbport),
+	CacheMaxCount = config:get(hash_max_cache),
+	CacheMaxTime = config:get(cache_max_time),
 	io:format("dhtcrawler startup ~p, ~p, ~p:~p~n", [StartPort, Count, DBHost, DBPort]),
-	crawler_sup:start_link({StartPort, Count, DBHost, DBPort, LogLevel, DBConn, HashMaxCache}).
+	crawler_sup:start_link({StartPort, Count, DBHost, DBPort, LogLevel, DBConn, CacheMaxTime, CacheMaxCount}).
 
 start() ->
 	error_logger:logfile({open, "crash.log"}),
@@ -60,7 +41,13 @@ start() ->
 stop() ->
 	application:stop(dhtcrawler).
 
-startboth() ->
-    start(),
-    crawler_http:start().
+config_default() ->
+	[{start_port, 6776},
+	 {node_count, 50},
+	 {hash_max_cache, 300},
+	 {cache_max_time, 2*60}, % seconds
+	 {loglevel, 3},
+	 {dbconn, 5},
+	 {dbhost, "localhost"},
+	 {dbport, 27017}].
 
diff --git a/src/crawler/crawler_sup.erl b/src/crawler/crawler_sup.erl
index 2495285..a4477dd 100644
--- a/src/crawler/crawler_sup.erl
+++ b/src/crawler/crawler_sup.erl
@@ -21,20 +21,15 @@ stop() ->
 srv_name() ->
 	dht_crawler_sup.
 
-init([{StartPort, Count, DBHost, DBPort, LogLevel, DBConn, HashCacheMax}]) ->
+init([{StartPort, Count, DBHost, DBPort, LogLevel, DBConn, CacheTime, HashCacheMax}]) ->
 	Spec = {one_for_one, 1, 600},
 	Instances = create_dht_instance(StartPort, Count),
 	Logger = [{dht_logger, {vlog, start_link, ["dht_crawler.txt", LogLevel]},
 					permanent, 2000, worker, dynamic}],
-	%Downloader = [{torrent_downloader, {torrent_download, start_link, []},
-	%				permanent, 2000, worker, dynamic}],
-	%DBStorer = [{torrent_index, {torrent_index, start_link, [DBHost, DBPort, crawler_stats, DBConn]},
-	%				permanent, 2000, worker, dynamic}],
-	HashInserter = [{db_hash, {db_hash, start_link, [DBHost, DBPort, DBConn, HashCacheMax]},
+	HashInserter = [{hash_cache_writer, {hash_cache_writer, start_link, [DBHost, DBPort, DBConn, CacheTime, HashCacheMax]},
 					permanent, 2000, worker, dynamic}],
 	Stats = [{crawler_stats, {crawler_stats, start_link, []},
 					permanent, 2000, worker, dynamic}],
-	%Children = Logger ++ Downloader ++ DBStorer ++ Instances,
 	Children = Logger ++ HashInserter ++ Stats ++ Instances,
     {ok, {Spec, Children}}.
 
diff --git a/src/crawler/dht_monitor.erl b/src/crawler/dht_monitor.erl
index 6c0f7b7..3572ae1 100644
--- a/src/crawler/dht_monitor.erl
+++ b/src/crawler/dht_monitor.erl
@@ -23,7 +23,8 @@ handle_event(get_peers, {InfoHash, _IP, _Port}) ->
 	crawler_stats:get_peers(),
 	%spawn(?MODULE, process_infohash_event, [InfoHash]);
 	MagHash = dht_id:tohex(InfoHash),
-	db_hash:insert(MagHash);
+	%db_hash:insert(MagHash);
+	hash_cache_writer:insert(MagHash);
 
 handle_event(startup, {MyID}) ->
 	spawn(?MODULE, tell_more_nodes, [MyID]).
diff --git a/src/crawler/hash_cache_writer.erl b/src/crawler/hash_cache_writer.erl
new file mode 100644
index 0000000..1999256
--- /dev/null
+++ b/src/crawler/hash_cache_writer.erl
@@ -0,0 +1,122 @@
+%%
+%% hash_cache_writer.erl
+%% Kevin Lynx
+%% 07.17.2013
+%% cache received hashes and pre-process theses hashes before inserted into database
+%%
+-module(hash_cache_writer).
+-include("db_common.hrl").
+-include("vlog.hrl").
+-behaviour(gen_server).
+-export([init/1,
+         handle_call/3,
+         handle_cast/2,
+         handle_info/2,
+         terminate/2,
+         code_change/3]).
+-export([start_link/5, stop/0, insert/1]).
+-record(state, {cache_time, cache_max}).
+-define(TBLNAME, hash_table).
+-define(DBPOOL, hash_write_db).
+
+start_link(IP, Port, DBConn, MaxTime, MaxCnt) ->
+	gen_server:start_link({local, srv_name()}, ?MODULE, [IP, Port, DBConn, MaxTime, MaxCnt], []).
+
+stop() ->
+	gen_server:cast(srv_name(), stop).
+
+insert(Hash) when is_list(Hash) ->
+	gen_server:cast(srv_name(), {insert, Hash}).
+
+srv_name() ->
+	?MODULE.
+
+init([IP, Port, DBConn, MaxTime, Max]) ->
+	mongo_sup:start_pool(?DBPOOL, DBConn, {IP, Port}),
+	ets:new(?TBLNAME, [set, named_table]),
+	{ok, #state{cache_time = 1000 * MaxTime, cache_max = Max}, 0}.
+
+terminate(_, State) ->
+	mongo_sup:stop_pool(?DBPOOL),
+    {ok, State}.
+
+code_change(_, _, State) ->
+    {ok, State}.
+
+handle_cast({insert, Hash}, State) ->
+	do_insert(Hash),
+	try_save(State),
+	{noreply, State};
+
+handle_cast(stop, State) ->
+	{stop, normal, State}.
+
+handle_call(_, _From, State) ->
+	{noreply, State}.
+
+handle_info(do_save_cache, #state{cache_time = Time} = State) ->
+	?T("timeout to save cache hashes"),
+	do_save(table_size(?TBLNAME)),
+	schedule_save(Time),
+	{noreply, State};
+
+handle_info(timeout, #state{cache_time = Time} = State) ->
+	schedule_save(Time),
+	{noreply, State}.
+
+schedule_save(Time) ->
+	timer:send_after(Time, do_save_cache).
+
+%%
+do_insert(Hash) when is_list(Hash) ->
+	NewVal = 1 + get_req_cnt(Hash),
+	ets:insert(?TBLNAME, {Hash, NewVal}).
+
+table_size(Tbl) ->
+	Infos = ets:info(Tbl),
+	proplists:get_value(size, Infos).
+
+try_save(#state{cache_max = Max}) ->
+	TSize = table_size(?TBLNAME),
+	try_save(TSize, Max).
+
+try_save(Size, Max) when Size >= Max ->
+	?T(?FMT("try save all cache hashes ~p", [Size])),
+	do_save(Size);
+try_save(_, _) ->
+	ok.
+
+do_save(0) ->
+	ok;
+do_save(_) ->
+	Conn = mongo_pool:get(?DBPOOL),
+	First = ets:first(?TBLNAME),
+	ReqAt = time_util:now_seconds(),
+	{ReqSum, Docs} = to_docs(First, ReqAt),
+	ets:delete_all_objects(?TBLNAME),
+	do_save(Conn, Docs, ReqSum).
+
+to_docs('$end_of_table', _) ->
+	{0, []};
+to_docs(Key, ReqAt) ->
+	ReqCnt = get_req_cnt(Key),
+	Doc = {hash, list_to_binary(Key), req_at, ReqAt, req_cnt, ReqCnt},
+	Next = ets:next(?TBLNAME, Key),
+	{ReqSum, Docs} = to_docs(Next, ReqAt),
+	{ReqSum + ReqCnt, [Doc|Docs]}.
+
+do_save(Conn, Docs, ReqSum) ->
+	?T(?FMT("send ~p hashes req-count ~p to db", [length(Docs), ReqSum])),
+	% `safe' may cause this process message queue increasing, but `unsafe' may cause the 
+	% database crashes.
+	mongo:do(safe, master, Conn, ?HASH_DBNAME, fun() ->
+		mongo:insert(?HASH_COLLNAME, Docs)
+	end),
+	db_system:stats_cache_query_inserted(Conn, length(Docs)),
+	db_system:stats_query_inserted(Conn, ReqSum).
+
+get_req_cnt(Hash) ->
+	case ets:lookup(?TBLNAME, Hash) of
+		[{Hash, ReqCnt}] -> ReqCnt;
+		[] -> 0
+	end.
diff --git a/src/db_daterange.erl b/src/db_daterange.erl
index 897ddac..828d952 100644
--- a/src/db_daterange.erl
+++ b/src/db_daterange.erl
@@ -5,7 +5,7 @@
 %% To track the most recently hashes
 %%
 -module(db_daterange).
--export([insert/2,
+-export([insert/3,
 		 lookup/3]).
 -export([start_link/1,
 		 stop/0]).
@@ -31,11 +31,11 @@ ensure_date_index(Conn) ->
 	end).
 
 % '_id': Hash, date: DaySecs, reqs: RequestCount
-insert(Conn, Hash) when is_list(Hash) ->
+insert(Conn, Hash, ReqCnt) when is_list(Hash) ->
 	DaySecs = time_util:now_day_seconds(),
 	BHash = list_to_binary(Hash),
 	Cmd = {findAndModify, ?COLLNAME, query, {'_id', BHash}, upsert, true,
-		update, {'$inc', {reqs, 1}, '$set', {?DATE_COL, DaySecs}}, fields, {'_id', 1}},
+		update, {'$inc', {reqs, ReqCnt}, '$set', {?DATE_COL, DaySecs}}, fields, {'_id', 1}},
 	IRet = mongo:do(safe, master, Conn, ?DBNAME, fun() ->
 		mongo:command(Cmd)
 	end),
diff --git a/src/db_store_mongo.erl b/src/db_store_mongo.erl
index fb0c611..48f7e54 100644
--- a/src/db_store_mongo.erl
+++ b/src/db_store_mongo.erl
@@ -11,6 +11,7 @@
 		 unsafe_insert/2,
 		 count/1,
 		 inc_announce/2,
+		 inc_announce/3,
 		 exist/2,
 		 index/2,
 		 search_newest_top_by_date/3,
@@ -114,7 +115,8 @@ index(Conn, Hash) when is_list(Hash) ->
 
 insert(Conn, Hash, Name, Length, Files) when is_list(Hash) ->
 	NewDoc = create_torrent_desc(Conn, Hash, Name, Length, 1, Files),
-	db_daterange:insert(Conn, Hash),
+	% TODO: because of the hash_cache_writer, the new inserted torrent lost the req_cnt value
+	db_daterange:insert(Conn, Hash, 1),
 	mongo_do(Conn, fun() ->
 		% the doc may already exist because the other process has inserted before
 		Sel = {'_id', list_to_binary(Hash)},
@@ -129,13 +131,14 @@ unsafe_insert(Conn, Tors) when is_list(Tors) ->
 	end).
 
 inc_announce(Conn, Hash) when is_list(Hash) ->
-	inc_announce(Conn, list_to_binary(Hash));
-	
-inc_announce(Conn, Hash) when is_binary(Hash) ->
+	inc_announce(Conn, Hash, 1).
+
+inc_announce(Conn, Hash, Inc) when is_list(Hash) ->
 	% damn, mongodb-erlang doesnot support update a field for an object,
 	% `findAndModify` works but it will change `announce' datatype to double
-	Cmd = {findAndModify, ?COLLNAME, query, {'_id', Hash}, 
-		update, {'$inc', {announce, 1}}, fields, {'_id', 1}, % not specifed or {} will return whole object
+	BHash = list_to_binary(Hash),
+	Cmd = {findAndModify, ?COLLNAME, query, {'_id', BHash}, 
+		update, {'$inc', {announce, Inc}}, fields, {'_id', 1}, % not specifed or {} will return whole object
 		new, false},
 	Ret = mongo_do(Conn, fun() ->
 		mongo:command(Cmd)
@@ -143,7 +146,7 @@ inc_announce(Conn, Hash) when is_binary(Hash) ->
 	case Ret of
 		{value, undefined, ok, 1.0} -> false;
 		{value, _Obj, lastErrorObject, {updatedExisting, true, n, 1}, ok, 1.0} -> 
-			db_daterange:insert(Conn, binary_to_list(Hash)),
+			db_daterange:insert(Conn, Hash, Inc),
 			true;
 		_ -> false
 	end.
diff --git a/src/db_system.erl b/src/db_system.erl
index 1f73937..9b430a4 100644
--- a/src/db_system.erl
+++ b/src/db_system.erl
@@ -89,7 +89,10 @@ stats_get_peers(Conn) ->
 % all queries, not processed
 stats_query_inserted(Conn, Count) ->
 	stats_inc_field(Conn, get_peers_query, Count).
-	
+
+stats_cache_query_inserted(Conn, Count) ->
+	stats_inc_field(Conn, inserted_query, Count).
+
 stats_inc_field(Conn, Filed) ->
 	stats_inc_field(Conn, Filed, 1).
 
@@ -116,6 +119,7 @@ stats_ensure_today(TodaySecs) ->
 	case mongo:find_one(?STATS_COLLNAME, {'_id', TodaySecs}) of
 		{} ->
 			NewDoc = {'_id', TodaySecs, get_peers, 0, get_peers_query, 0,
+				inserted_query, 0, % because has_cache_writer will merge some queries
 				updated, 0, new_saved, 0},
 			mongo:insert(?STATS_COLLNAME, NewDoc),
 			NewDoc;
@@ -128,5 +132,3 @@ test_torrent_id() ->
 	{ok, Conn} = mongo_connection:start_link({localhost, 27017}),
 	ID = get_torrent_id(Conn),
 	ID.
-
-
diff --git a/src/hash_reader/hash_reader.erl b/src/hash_reader/hash_reader.erl
index 86504d3..fc68f4f 100644
--- a/src/hash_reader/hash_reader.erl
+++ b/src/hash_reader/hash_reader.erl
@@ -107,13 +107,14 @@ handle_info(M, State) ->
 handle_cast({process_hash, Doc,  DownloadDoc}, State) ->
 	Conn = db_conn(State),
 	{Hash} = bson:lookup(hash, Doc),
+	ReqCnt = get_req_cnt(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.
 	if DownloadDoc -> do_nothing; true -> try_next(Conn) end,
-	NewState = case db_store_mongo:inc_announce(Conn, ListHash) of
+	NewState = case db_store_mongo:inc_announce(Conn, ListHash, ReqCnt) of
 		true -> 
 			?T(?FMT("inc_announce success ~s", [ListHash])),
 			on_updated(Conn),
@@ -131,6 +132,12 @@ handle_cast(stop, State) ->
 handle_call(_, _From, State) ->
 	{noreply, State}.
 
+get_req_cnt(Doc) ->
+	case bson:lookup(req_cnt, Doc) of
+		{} -> 0;
+		{R} -> R
+	end.
+
 try_download(State, Hash, Doc) ->
 	#state{downloading = D} = State,
 	NewDownloading = case D >= ?MAX_DOWNLOAD of
diff --git a/src/transfer.erl b/src/transfer.erl
deleted file mode 100644
index 8c95731..0000000
--- a/src/transfer.erl
+++ /dev/null
@@ -1,43 +0,0 @@
--module(transfer).
--compile(export_all).
--export([start/0]).
--define(DBNAME, torrents).
--define(COLLNAME, hash).
--define(ONE_DAY, 24*60*60).
--define(READ_POOL, read_pool).
--define(WRITE_POOL, write_pool).
--export([start/2]).
-
-start() ->
-	mongo_sup:start_pool(?READ_POOL, 5, {localhost, 10000}),
-	mongo_sup:start_pool(?WRITE_POOL, 5, {localhost, 27010}),
-	[spawn(?MODULE, start, [DayStart, DayEnd]) ||
-		{DayStart, DayEnd} <- gen_day_ranges()],
-	ok.
-
-gen_day_ranges() ->
-	Today = time_util:now_day_seconds(),
-	[day_secs_at(Today, Before) || Before <- lists:seq(0, 15)].
-
-day_secs_at(Today, Before) ->
-	{Today - Before * ?ONE_DAY, Today - Before * ?ONE_DAY + ?ONE_DAY}.
-
-start(DaySecs, DaySecsMax) ->
-	RConn = mongo_pool:get(?READ_POOL),
-	WConn = mongo_pool:get(?WRITE_POOL),
-	Docs = mongo:do(safe, master, RConn, ?DBNAME, fun() ->
-		Cursor = mongo:find(?COLLNAME, {created_at, {'$gt', DaySecs, '$lt', DaySecsMax}}),
-		mongo_cursor:rest(Cursor)
-	end),
-	case Docs of 
-		[] ->
-			ok;
-		_ ->	
-			mongo:do(safe, master, WConn, ?DBNAME, fun() ->
-				mongo:insert(?COLLNAME, Docs)
-			end)
-	end,
-	io:format("done at ~p size ~p~n", [DaySecs, length(Docs)]).
-
-
-