Imported trunk.

git-svn-id: https://svn.apache.org/repos/asf/incubator/couchdb/trunk@642432 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 66 insertions, 0 deletions

diff --git a/src/couchdb/couch_db_update_notifier.erl b/src/couchdb/couch_db_update_notifier.erl
new file mode 100644
index 00000000..96354620
--- /dev/null
+++ b/src/couchdb/couch_db_update_notifier.erl
@@ -0,0 +1,66 @@
+% 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]).
+
+-define(ERR_HANDLE, {Port, {exit_status, Status}} -> {stop, {unknown_error, Status}, {unknown_error, Status}, Port}).
+
+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
+    Port = open_port({spawn, Exec}, [stream, exit_status, hide]),
+    {ok, Port};
+init(Else) ->
+    {ok, Else}.
+
+terminate(_Reason, _Port) ->
+    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}, Port) ->
+    Obj = {obj, [{type, atom_to_list(EventAtom)}, {db, DbName}]},
+    true = port_command(Port, cjson:encode(Obj) ++ "\n"),
+    {ok, Port}.
+
+handle_call(_Request, State) ->
+    {ok, ok, State}.
+
+handle_info({'EXIT', _, _Reason}, _Port) ->
+    remove_handler.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.