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% Licensed 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.
-module(couch_replicator_db_changes).
-behaviour(gen_server).
-export([
start_link/0
]).
-export([
init/1,
terminate/2,
handle_call/3,
handle_info/2,
handle_cast/2,
code_change/3
]).
-export([
notify_cluster_event/2
]).
-record(state, {
event_listener :: pid(),
mdb_changes :: pid() | nil
}).
-spec notify_cluster_event(pid(), {cluster, any()}) -> ok.
notify_cluster_event(Server, {cluster, _} = Event) ->
gen_server:cast(Server, Event).
-spec start_link() ->
{ok, pid()} | ignore | {error, any()}.
start_link() ->
gen_server:start_link(?MODULE, [], []).
init([]) ->
EvtPid = couch_replicator_clustering:link_cluster_event_listener(?MODULE,
notify_cluster_event, [self()]),
State = #state{event_listener = EvtPid, mdb_changes = nil},
case couch_replicator_clustering:is_stable() of
true ->
{ok, restart_mdb_changes(State)};
false ->
{ok, State}
end.
terminate(_Reason, _State) ->
ok.
handle_call(_Msg, _From, State) ->
{reply, {error, invalid_call}, State}.
handle_cast({cluster, unstable}, State) ->
{noreply, stop_mdb_changes(State)};
handle_cast({cluster, stable}, State) ->
{noreply, restart_mdb_changes(State)}.
handle_info(_Msg, State) ->
{noreply, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
-spec restart_mdb_changes(#state{}) -> #state{}.
restart_mdb_changes(#state{mdb_changes = nil} = State) ->
Suffix = <<"_replicator">>,
CallbackMod = couch_replicator_doc_processor,
Options = [skip_ddocs],
{ok, Pid} = couch_multidb_changes:start_link(Suffix, CallbackMod, nil,
Options),
couch_stats:increment_counter([couch_replicator, db_scans]),
couch_log:notice("Started replicator db changes listener ~p", [Pid]),
State#state{mdb_changes = Pid};
restart_mdb_changes(#state{mdb_changes = _Pid} = State) ->
restart_mdb_changes(stop_mdb_changes(State)).
-spec stop_mdb_changes(#state{}) -> #state{}.
stop_mdb_changes(#state{mdb_changes = nil} = State) ->
State;
stop_mdb_changes(#state{mdb_changes = Pid} = State) ->
couch_log:notice("Stopping replicator db changes listener ~p", [Pid]),
unlink(Pid),
exit(Pid, kill),
State#state{mdb_changes = nil}.
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