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%%%-------------------------------------------------------------------
%%% File : ejabberd_cluster.erl
%%% Author : Evgeniy Khramtsov <ekhramtsov@process-one.net>
%%% Description :
%%%
%%% Created : 2 Apr 2010 by Evgeniy Khramtsov <ekhramtsov@process-one.net>
%%%-------------------------------------------------------------------
-module(ejabberd_cluster).
-behaviour(gen_server).
%% API
-export([start_link/0, get_node/1, get_node_new/1, announce/0,
node_id/0, get_node_by_id/1, get_nodes/0, rehash_timeout/0]).
%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
-include("ejabberd.hrl").
-define(HASHTBL, nodes_hash).
-define(HASHTBL_NEW, nodes_hash_new).
-define(POINTS, 16).
-define(REHASH_TIMEOUT, 5000).
-record(state, {}).
%%====================================================================
%% API
%%====================================================================
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
get_node(Key) ->
Hash = erlang:phash2(Key),
get_node_by_hash(?HASHTBL, Hash).
get_node_new(Key) ->
Hash = erlang:phash2(Key),
get_node_by_hash(?HASHTBL_NEW, Hash).
get_nodes() ->
%% TODO
mnesia:system_info(running_db_nodes).
announce() ->
gen_server:call(?MODULE, announce, infinity).
node_id() ->
integer_to_list(erlang:phash2(node())).
rehash_timeout() ->
?REHASH_TIMEOUT.
get_node_by_id(NodeID) when is_list(NodeID) ->
case catch list_to_existing_atom(NodeID) of
{'EXIT', _} ->
node();
Res ->
get_node_by_id(Res)
end;
get_node_by_id(NodeID) ->
case global:whereis_name(NodeID) of
Pid when is_pid(Pid) ->
node(Pid);
_ ->
node()
end.
%%====================================================================
%% gen_server callbacks
%%====================================================================
init([]) ->
net_kernel:monitor_nodes(true, [{node_type, visible}]),
ets:new(?HASHTBL, [named_table, public, ordered_set]),
ets:new(?HASHTBL_NEW, [named_table, public, ordered_set]),
register_node(),
AllNodes = mnesia:system_info(running_db_nodes),
OtherNodes = case AllNodes of
[_] ->
AllNodes;
_ ->
AllNodes -- [node()]
end,
append_nodes(?HASHTBL, OtherNodes),
append_nodes(?HASHTBL_NEW, AllNodes),
{ok, #state{}}.
handle_call(announce, _From, State) ->
case mnesia:system_info(running_db_nodes) of
[_MyNode] ->
ok;
Nodes ->
OtherNodes = Nodes -- [node()],
lists:foreach(
fun(Node) ->
{?MODULE, Node} ! {node_ready, node()}
end, OtherNodes),
?INFO_MSG("waiting for migration from nodes: ~w",
[OtherNodes]),
timer:sleep(?REHASH_TIMEOUT),
append_node(?HASHTBL, node())
end,
{reply, ok, State};
handle_call(_Request, _From, State) ->
Reply = ok,
{reply, Reply, State}.
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info({node_ready, Node}, State) ->
?INFO_MSG("node ~p is ready, starting migration", [Node]),
append_node(?HASHTBL_NEW, Node),
ejabberd_hooks:run(node_hash_update, [?REHASH_TIMEOUT]),
timer:sleep(?REHASH_TIMEOUT),
?INFO_MSG("adding node ~p to hash", [Node]),
append_node(?HASHTBL, Node),
{noreply, State};
handle_info({nodedown, Node, _}, State) ->
?INFO_MSG("node ~p goes down", [Node]),
delete_node(?HASHTBL, Node),
delete_node(?HASHTBL_NEW, Node),
{noreply, State};
handle_info(_Info, State) ->
{noreply, State}.
terminate(_Reason, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%%--------------------------------------------------------------------
%% Internal functions
%%--------------------------------------------------------------------
append_nodes(Tab, Nodes) ->
lists:foreach(
fun(Node) ->
append_node(Tab, Node)
end, Nodes).
append_node(Tab, Node) ->
lists:foreach(
fun(I) ->
Hash = erlang:phash2({I, Node}),
ets:insert(Tab, {Hash, Node})
end, lists:seq(1, ?POINTS)).
delete_node(Tab, Node) ->
lists:foreach(
fun(I) ->
Hash = erlang:phash2({I, Node}),
ets:delete(Tab, Hash)
end, lists:seq(1, ?POINTS)).
get_node_by_hash(Tab, Hash) ->
NodeHash = case ets:next(Tab, Hash) of
'$end_of_table' ->
ets:first(Tab);
NH ->
NH
end,
if NodeHash == '$end_of_table' ->
erlang:error(no_running_nodes);
true ->
case ets:lookup(Tab, NodeHash) of
[] ->
get_node_by_hash(Tab, Hash);
[{_, Node}] ->
Node
end
end.
register_node() ->
global:register_name(list_to_atom(node_id()), self()).
|
