From 4fc7bef5c4a44c971852f8c9251faef48779f4d1 Mon Sep 17 00:00:00 2001
From: "Damien F. Katz" <damien@apache.org>
Date: Mon, 22 Dec 2008 20:41:05 +0000
Subject: Checking in new erlang source file, used for tracking file stats.

git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@728767 13f79535-47bb-0310-9956-ffa450edef68
---
 src/couchdb/Makefile.am          |  2 ++
 src/couchdb/couch_file_stats.erl | 68 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 src/couchdb/couch_file_stats.erl

diff --git a/src/couchdb/Makefile.am b/src/couchdb/Makefile.am
index aaa6c67c..ae7a06e1 100644
--- a/src/couchdb/Makefile.am
+++ b/src/couchdb/Makefile.am
@@ -51,6 +51,7 @@ source_files = \
     couch_external_manager.erl \
     couch_external_server.erl \
     couch_file.erl \
+    couch_file_stats.erl \
     couch_httpd.erl \
     couch_httpd_db.erl \
     couch_httpd_external.erl \
@@ -85,6 +86,7 @@ compiled_files = \
     couch_external_manager.beam \
     couch_external_server.beam \
     couch_file.beam \
+    couch_file_stats.beam \
     couch_httpd.beam \
     couch_httpd_db.beam \
     couch_httpd_external.beam \
diff --git a/src/couchdb/couch_file_stats.erl b/src/couchdb/couch_file_stats.erl
new file mode 100644
index 00000000..90ed973e
--- /dev/null
+++ b/src/couchdb/couch_file_stats.erl
@@ -0,0 +1,68 @@
+% 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_file_stats).
+-behaviour(gen_server).
+
+-export([init/1, terminate/2, handle_call/3, handle_cast/2, code_change/3,
+        handle_info/2]).
+
+-export([start_link/0,track_file/1,get_stats/0]).
+
+-record(stats,{
+    opened=0,
+    closed=0
+    }).
+
+
+track_file(Fd) ->
+    catch gen_server:cast(couch_file_stats, {track, Fd}).
+
+
+get_stats() ->
+    #stats{opened=Opened,closed=Closed}=gen_server:call(couch_file_stats,get),
+    {ok, [{opened,Opened}, {closed,Closed}]}.
+
+
+start_link() ->
+    gen_server:start_link({local, couch_file_stats}, couch_file_stats, [], []).
+
+
+init([]) ->
+    {ok, #stats{}}.
+
+
+terminate(_Reason, _Fd) ->
+    ok.
+
+
+handle_call(get, _From, Stats) ->
+    {reply, Stats, Stats}.
+
+
+handle_cast({track, Fd}, #stats{opened=Opened,closed=Closed}=Stats) ->
+    try erlang:monitor(process, Fd) of
+    _Ref ->
+        {noreply, Stats#stats{opened=Opened+1}}
+    catch
+    _Error ->
+        {noreply, Stats#stats{opened=Opened+1, closed=Closed+1}}
+    end.
+
+
+handle_info({'DOWN',_MonRef,_Type,_Pid,_Info}, #stats{closed=Closed}=Stats) ->
+    {noreply, Stats#stats{closed=Closed+1}}.
+
+
+code_change(_OldVsn, State, _Extra) ->
+    {ok, State}.
+
-- 
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