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%% This file is provided to you under the Apache License,
%% Version 2.0 (the "License"); you may not use this file
%% except in compliance with the License. You may obtain
%% a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing,
%% software distributed under the License is distributed on an
%% "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
%% KIND, either express or implied. See the License for the
%% specific language governing permissions and limitations
%% under the License.
%% Copyright (c) 2007-2010 Basho Technologies, Inc. All Rights Reserved.
-module(riak_core_ring_handler).
-behaviour(gen_event).
%% gen_event callbacks
-export([init/1, handle_event/2, handle_call/2,
handle_info/2, terminate/2, code_change/3]).
-record(state, {}).
%% ===================================================================
%% gen_event callbacks
%% ===================================================================
init([]) ->
%% Pull the initial ring and make sure all vnodes are started
{ok, Ring} = riak_core_ring_manager:get_my_ring(),
ensure_vnodes_started(Ring),
{ok, #state{}}.
handle_event({ring_update, Ring}, State) ->
%% Make sure all vnodes are started...
ensure_vnodes_started(Ring),
{ok, State}.
handle_call(_Event, State) ->
{ok, ok, State}.
handle_info(_Info, State) ->
{ok, State}.
terminate(_Reason, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
%% ===================================================================
%% Internal functions
%% ===================================================================
ensure_vnodes_started(Ring) ->
case riak_core:vnode_modules() of
[] ->
ok;
AppMods ->
case ensure_vnodes_started(AppMods, Ring, []) of
[] -> riak_core_ring_manager:refresh_my_ring();
_ -> ok
end
end.
ensure_vnodes_started([], _Ring, Acc) ->
lists:flatten(Acc);
ensure_vnodes_started([{App, Mod}|T], Ring, Acc) ->
ensure_vnodes_started(T, Ring, [ensure_vnodes_started({App,Mod},Ring)|Acc]).
ensure_vnodes_started({App,Mod}, Ring) ->
Startable = startable_vnodes(Mod, Ring),
%% NOTE: This following is a hack. There's a basic
%% dependency/race between riak_core (want to start vnodes
%% right away to trigger possible handoffs) and riak_kv
%% (needed to support those vnodes). The hack does not fix
%% that dependency: internal techdebt todo list #A7 does.
spawn_link(fun() ->
%% Use a registered name as a lock to prevent the same
%% vnode module from being started twice.
RegName = list_to_atom(
"riak_core_ring_handler_ensure_"
++ atom_to_list(Mod)),
try register(RegName, self())
catch error:badarg ->
exit(normal)
end,
wait_for_app(App, 100, 100),
[Mod:start_vnode(I) || I <- Startable],
exit(normal)
end),
Startable.
startable_vnodes(Mod, Ring) ->
AllMembers = riak_core_ring:all_members(Ring),
case {length(AllMembers), hd(AllMembers) =:= node()} of
{1, true} ->
riak_core_ring:my_indices(Ring);
_ ->
{ok, Excl} = riak_core_handoff_manager:get_exclusions(Mod),
case riak_core_ring:random_other_index(Ring, Excl) of
no_indices ->
case length(Excl) =:= riak_core_ring:num_partitions(Ring) of
true ->
[];
false ->
riak_core_ring:my_indices(Ring)
end;
RO ->
[RO | riak_core_ring:my_indices(Ring)]
end
end.
wait_for_app(_, 0, _) ->
bummer;
wait_for_app(App, Count, Sleep) ->
case lists:keymember(App, 1, application:which_applications()) of
true ->
ok;
false ->
timer:sleep(Sleep),
wait_for_app(App, Count - 1, Sleep)
end.
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