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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/1, shutdown/0,
node_id/0, get_node_by_id/1, get_nodes/0, rehash_timeout/0, start/0,
shutdown_migrate/1, migrate_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, 64).
-define(REHASH_TIMEOUT, timer:seconds(30)).
-define(MIGRATE_TIMEOUT, timer:minutes(2)).
-define(LOCK, {migrate, node()}).
-record(state, {}).
%%====================================================================
%% API
%%====================================================================
start() ->
ChildSpec = {?MODULE,
{?MODULE, start_link, []},
permanent,
brutal_kill,
worker,
[?MODULE]},
supervisor:start_child(ejabberd_sup, ChildSpec).
start_link() ->
gen_server:start_link(?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(Pid) ->
gen_server:call(Pid, announce, infinity).
node_id() ->
integer_to_list(erlang:phash2(node())).
rehash_timeout() ->
case ejabberd_config:get_local_option(rehash_timeout) of
N when is_integer(N), N > 0 ->
timer:seconds(N);
_ ->
?REHASH_TIMEOUT
end.
migrate_timeout() ->
case ejabberd_config:get_local_option(migrate_timeout) of
N when is_integer(N), N > 0 ->
timer:seconds(N);
_ ->
?MIGRATE_TIMEOUT
end.
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.
shutdown() ->
lists:foreach(
fun(Node) when Node /= node() ->
{ejabberd_cluster, Node} ! {node_down, node()};
(_) ->
ok
end, get_nodes()).
shutdown_migrate(WaitTime) ->
delete_node(?HASHTBL_NEW, node()),
ejabberd_hooks:run(node_down, [node()]),
shutdown(),
delete_node(?HASHTBL, node()),
ejabberd_hooks:run(node_hash_update, [node(), down, WaitTime]),
?INFO_MSG("Waiting ~p seconds for the migration to be completed.",
[WaitTime div 1000]),
timer:sleep(WaitTime),
ok.
%%====================================================================
%% gen_server callbacks
%%====================================================================
init([]) ->
{A, B, C} = now(),
random:seed(A, B, C),
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 = get_nodes(),
OtherNodes = case AllNodes of
[_MyNode] ->
AllNodes;
_ ->
AllNodes -- [node()]
end,
append_nodes(?HASHTBL, OtherNodes),
append_nodes(?HASHTBL_NEW, AllNodes),
{ok, #state{}}.
handle_call(announce, _From, State) ->
Migrate_timeout = migrate_timeout(),
case global:set_lock(?LOCK, get_nodes(), 0) of
false ->
?WARNING_MSG("Another node is recently attached to "
"the cluster and is being rebalanced. "
"Waiting for the rebalancing to be completed "
"before starting this node. "
"This will take at least ~p seconds. "
"Please, be patient.", [Migrate_timeout div 1000]),
global:set_lock(?LOCK, get_nodes(), infinity);
true ->
ok
end,
case get_nodes() of
[_MyNode] ->
register(?MODULE, self()),
global:del_lock(?LOCK);
Nodes ->
OtherNodes = Nodes -- [node()],
?INFO_MSG("waiting for migration from nodes: ~w",
[OtherNodes]),
{_Res, BadNodes} = gen_server:multi_call(
OtherNodes, ?MODULE,
{node_ready, node()}, ?REHASH_TIMEOUT),
append_node(?HASHTBL, node()),
register(?MODULE, self()),
case OtherNodes -- BadNodes of
[] ->
global:del_lock(?LOCK);
WorkingNodes ->
gen_server:abcast(WorkingNodes, ?MODULE, {node_ready, node()}),
erlang:send_after(Migrate_timeout, self(), del_lock)
end
end,
{reply, ok, State};
handle_call({node_ready, Node}, _From, State) ->
?INFO_MSG("node ~p is ready, preparing migration", [Node]),
append_node(?HASHTBL_NEW, Node),
ejabberd_hooks:run(node_up, [Node]),
{reply, ok, State};
handle_call(_Request, _From, State) ->
Reply = ok,
{reply, Reply, State}.
handle_cast({node_ready, Node}, State) ->
?INFO_MSG("adding node ~p to hash and starting migration", [Node]),
append_node(?HASHTBL, Node),
ejabberd_hooks:run(node_hash_update, [Node, up, migrate_timeout()]),
{noreply, State};
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info(del_lock, State) ->
global:del_lock(?LOCK),
{noreply, State};
handle_info({node_down, Node}, State) ->
delete_node(?HASHTBL, Node),
delete_node(?HASHTBL_NEW, 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()).
|
