From 544a38dd45f6a58d34296c6c768afd086eb2ac70 Mon Sep 17 00:00:00 2001
From: Christopher Lenz <cmlenz@apache.org>
Date: Fri, 28 Mar 2008 23:32:19 +0000
Subject: Imported trunk.

git-svn-id: https://svn.apache.org/repos/asf/incubator/couchdb/trunk@642432 13f79535-47bb-0310-9956-ffa450edef68
---
 src/couchdb/couch_event_sup.erl | 69 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 src/couchdb/couch_event_sup.erl

(limited to 'src/couchdb/couch_event_sup.erl')

diff --git a/src/couchdb/couch_event_sup.erl b/src/couchdb/couch_event_sup.erl
new file mode 100644
index 00000000..72b17e5d
--- /dev/null
+++ b/src/couchdb/couch_event_sup.erl
@@ -0,0 +1,69 @@
+% 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.
+
+%% The purpose of this module is to allow event handlers to particpate in Erlang
+%% supervisor trees. It provide a monitorable process that crashes if the event
+%% handler fails. The process, when shutdown, deregisters the event handler.
+
+-module(couch_event_sup).
+-behaviour(gen_server).
+
+-include("couch_db.hrl").
+
+-export([start_link/3,start_link/4, stop/1]).
+-export([init/1, terminate/2, handle_call/3, handle_cast/2, handle_info/2,code_change/3]).
+
+%
+% Instead calling the
+% ok = gen_event:add_sup_handler(error_logger, my_log, Args)
+%
+% do this:
+% {ok, LinkedPid} = couch_event_sup:start_link(error_logger, my_log, Args)
+%
+% The benefit is the event is now part of the process tree, and can be
+% started, restarted and shutdown consistently like the rest of the server
+% components.
+%
+% And now if the "event" crashes, the supervisor is notified and can restart
+% the event handler.
+%
+% Use this form to named process:
+% {ok, LinkedPid} = couch_event_sup:start_link({local, my_log}, error_logger, my_log, Args)
+%
+
+start_link(EventMgr, EventHandler, Args) ->
+    gen_server:start_link(couch_event_sup, {EventMgr, EventHandler, Args}, []).
+
+start_link(ServerName, EventMgr, EventHandler, Args) ->
+    gen_server:start_link(ServerName, couch_event_sup, {EventMgr, EventHandler, Args}, []).
+
+stop(Pid) ->
+    gen_server:cast(Pid, stop).
+
+init({EventMgr, EventHandler, Args}) ->
+    ok = gen_event:add_sup_handler(EventMgr, EventHandler, Args),
+    {ok, {EventMgr, EventHandler}}.
+
+terminate(_Reason, _State) ->
+    ok.
+
+handle_call(_Whatever, _From, State) ->
+    {ok, State}.
+
+handle_cast(stop, State) ->
+    {stop, normal, State}.
+
+handle_info({gen_event_EXIT, _Handler, Reason}, State) ->
+    {stop, Reason, State}.
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
-- 
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