* src/mod_offline.erl: Started implementation of mod_offline

quota. For now, it require change in code. Will be turn into a
config file parameter soon. (EJAB-314).
* src/p1_mnesia.erl: Added memory efficient record count in
Mnesia.

SVN Revision: 859

3 files changed, 82 insertions, 17 deletions

diff --git a/ChangeLog b/ChangeLog
index cfba33ef8..fe15038c5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2007-08-07  Mickael Remond  <mickael.remond@process-one.net>
+
+	* src/mod_offline.erl: Started implementation of mod_offline
+	quota. For now, it require change in code. Will be turn into a
+	config file parameter soon. (EJAB-314).
+	* src/p1_mnesia.erl: Added memory efficient record count in
+	Mnesia.
+
 2007-08-03  Mickael Remond  <mickael.remond@process-one.net>
 
 	* src/mod_announce.erl: Added support to all the announce features
diff --git a/src/mod_offline.erl b/src/mod_offline.erl
index b9fde8833..96d963fa3 100644
--- a/src/mod_offline.erl
+++ b/src/mod_offline.erl
@@ -1,13 +1,13 @@
 %%%----------------------------------------------------------------------
 %%% File    : mod_offline.erl
-%%% Author  : Alexey Shchepin <alexey@sevcom.net>
-%%% Purpose : 
-%%% Created :  5 Jan 2003 by Alexey Shchepin <alexey@sevcom.net>
+%%% Author  : Alexey Shchepin <alexey@process-one.net>
+%%% Purpose : Store and manage offline messages in Mnesia database.
+%%% Created :  5 Jan 2003 by Alexey Shchepin <alexey@process-one.net>
 %%% Id      : $Id$
 %%%----------------------------------------------------------------------
 
 -module(mod_offline).
--author('alexey@sevcom.net').
+-author('alexey@process-one.net').
 
 -behaviour(gen_mod).
 
@@ -29,6 +29,10 @@
 -define(PROCNAME, ejabberd_offline).
 -define(OFFLINE_TABLE_LOCK_THRESHOLD, 1000).
 
+%% TODO: Move this part as a module config file parameter:
+%% Can be an integer > 0 or infinity:
+-define(MAX_OFFLINE_MSGS, infinity).
+
 start(Host, _Opts) ->
     mnesia:create_table(offline_msg,
 			[{disc_only_copies, [node()]},
@@ -51,19 +55,28 @@ init() ->
 
 loop() ->
     receive
-	#offline_msg{} = Msg ->
-	    Msgs = receive_all([Msg]),
+	#offline_msg{us=US} = Msg ->
+	    Msgs = receive_all(US, [Msg]),
 	    Len = length(Msgs),
 	    F = fun() ->
+			Count = Len + p1_mnesia:count_records(
+					offline_msg, 
+					#offline_msg{us=US, _='_'}),
 			if
-			    Len >= ?OFFLINE_TABLE_LOCK_THRESHOLD ->
-				mnesia:write_lock_table(offline_msg);
+			    Count > ?MAX_OFFLINE_MSGS ->
+				%% TODO: Warn that messages have been discarded
+				ok;
 			    true ->
-				ok
-			end,
-			lists:foreach(fun(M) ->
-					      mnesia:write(M)
-				      end, Msgs)
+				if
+				    Len >= ?OFFLINE_TABLE_LOCK_THRESHOLD ->
+					mnesia:write_lock_table(offline_msg);
+				    true ->
+					ok
+				end,
+				lists:foreach(fun(M) ->
+						      mnesia:write(M)
+					      end, Msgs)
+			end
 		end,
 	    mnesia:transaction(F),
 	    loop();
@@ -71,10 +84,10 @@ loop() ->
 	    loop()
     end.
 
-receive_all(Msgs) ->
+receive_all(US, Msgs) ->
     receive
-	#offline_msg{} = Msg ->
-	    receive_all([Msg | Msgs])
+	#offline_msg{us=US} = Msg ->
+	    receive_all(US, [Msg | Msgs])
     after 0 ->
 	    Msgs
     end.
@@ -387,4 +400,3 @@ update_table() ->
 	    ?INFO_MSG("Recreating offline_msg table", []),
 	    mnesia:transform_table(offline_msg, ignore, Fields)
     end.
-
diff --git a/src/p1_mnesia.erl b/src/p1_mnesia.erl
new file mode 100644
index 000000000..2483a1b3f
--- /dev/null
+++ b/src/p1_mnesia.erl
@@ -0,0 +1,45 @@
+%% ``The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved via the world wide web at http://www.erlang.org/.
+%% 
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%% 
+%% The Initial Developer of the Original Code is Process-one.
+%% Portions created by Process-one are Copyright 2007, Process-one
+%% All Rights Reserved.''
+%% 
+%%     $Id$
+%%
+-module(p1_mnesia).
+-author('mickael.remond@process-one.net').
+
+-export([count_records/2]).
+
+%% Return the number of records matching a given match expression.
+%% This function is intended to be used inside a Mnesia transaction.
+%% The count has been written to use the fewest possible memory by
+%% getting the record by small increment and by using continuation.
+-define(BATCHSIZE, 100).
+count_records(Tab, MatchExpression) ->
+    %% the result contains the atom a for each match: We do not need
+    %% actual values as we only count the data.
+    case mnesia:select(Tab, [{MatchExpression, [], [a]}], ?BATCHSIZE, read) of
+	{Result,Cont} ->
+	    Count = length(Result),
+	    count_records_cont(Cont, Count);
+	'$end_of_table' ->
+	    0
+    end.
+count_records_cont(Cont, Count) ->
+    case mnesia:select(Cont) of
+	{Result,Cont} ->
+	    NewCount = Count + length(Result),
+	    count_records_cont(Cont, NewCount);
+	'$end_of_table' ->
+	    Count
+    end.