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Diffstat (limited to 'apps/couch/src/couch_db_update_notifier.erl')
-rw-r--r-- | apps/couch/src/couch_db_update_notifier.erl | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/apps/couch/src/couch_db_update_notifier.erl b/apps/couch/src/couch_db_update_notifier.erl new file mode 100644 index 00000000..150eb31b --- /dev/null +++ b/apps/couch/src/couch_db_update_notifier.erl @@ -0,0 +1,73 @@ +% 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. + +% +% This causes an OS process to spawned and it is notified every time a database +% is updated. +% +% The notifications are in the form of a the database name sent as a line of +% text to the OS processes stdout. +% + +-module(couch_db_update_notifier). + +-behaviour(gen_event). + +-export([start_link/1, notify/1]). +-export([init/1, terminate/2, handle_event/2, handle_call/2, handle_info/2, code_change/3,stop/1]). + +-include("couch_db.hrl"). + +start_link(Exec) -> + couch_event_sup:start_link(couch_db_update, {couch_db_update_notifier, make_ref()}, Exec). + +notify(Event) -> + gen_event:notify(couch_db_update, Event). + +stop(Pid) -> + couch_event_sup:stop(Pid). + +init(Exec) when is_list(Exec) -> % an exe + couch_os_process:start_link(Exec, []); +init(Else) -> + {ok, Else}. + +terminate(_Reason, Pid) when is_pid(Pid) -> + couch_os_process:stop(Pid), + ok; +terminate(_Reason, _State) -> + ok. + +handle_event(Event, Fun) when is_function(Fun, 1) -> + Fun(Event), + {ok, Fun}; +handle_event(Event, {Fun, FunAcc}) -> + FunAcc2 = Fun(Event, FunAcc), + {ok, {Fun, FunAcc2}}; +handle_event({EventAtom, DbName}, Pid) -> + Obj = {[{type, list_to_binary(atom_to_list(EventAtom))}, {db, DbName}]}, + ok = couch_os_process:send(Pid, Obj), + {ok, Pid}. + +handle_call(_Request, State) -> + {reply, ok, State}. + +handle_info({'EXIT', Pid, Reason}, Pid) -> + ?LOG_ERROR("Update notification process ~p died: ~p", [Pid, Reason]), + remove_handler; +handle_info({'EXIT', _, _}, Pid) -> + %% the db_update event manager traps exits and forwards this message to all + %% its handlers. Just ignore as it wasn't our os_process that exited. + {ok, Pid}. + +code_change(_OldVsn, State, _Extra) -> + {ok, State}. |