From 4aac0f7c6dcd3f3a29cfe5e1bf2bee84b9bae9d5 Mon Sep 17 00:00:00 2001
From: "Damien F. Katz" <damien@apache.org>
Date: Sun, 24 May 2009 00:04:36 +0000
Subject: Added stats tracking for active _changes clients.

git-svn-id: https://svn.apache.org/repos/asf/couchdb/trunk@778072 13f79535-47bb-0310-9956-ffa450edef68
---
 src/couchdb/couch_httpd_db.erl         | 7 +++++--
 src/couchdb/couch_stats_aggregator.erl | 1 +
 src/couchdb/couch_stats_collector.erl  | 9 +++++----
 3 files changed, 11 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/couchdb/couch_httpd_db.erl b/src/couchdb/couch_httpd_db.erl
index 04f178d5..03cba11e 100644
--- a/src/couchdb/couch_httpd_db.erl
+++ b/src/couchdb/couch_httpd_db.erl
@@ -51,18 +51,21 @@ handle_changes_req(#httpd{method='GET',path_parts=[DbName|_]}=Req, Db) ->
     case couch_httpd:qs_value(Req, "continuous", "false") of
     "true" ->
         Self = self(),
-        Notify = couch_db_update_notifier:start_link(
+        {ok, Notify} = couch_db_update_notifier:start_link(
             fun({_, DbName0}) when DbName0 == DbName ->
                 Self ! db_updated;
             (_) ->
                 ok
             end),
+        couch_stats_collector:track_process_count(Self,
+                            {httpd, clients_requesting_changes}),
         try
             keep_sending_changes(Req, Resp, Db, StartSeq, <<"">>)
         after
-            catch couch_db_update_notifier:stop(Notify),
+            couch_db_update_notifier:stop(Notify),
             wait_db_updated(0) % clean out any remaining update messages
         end;
+        
     "false" ->
         {ok, {LastSeq, _Prepend}} = 
                 send_changes(Req, Resp, Db, StartSeq, <<"">>),
diff --git a/src/couchdb/couch_stats_aggregator.erl b/src/couchdb/couch_stats_aggregator.erl
index bc37ab96..9aa3e468 100644
--- a/src/couchdb/couch_stats_aggregator.erl
+++ b/src/couchdb/couch_stats_aggregator.erl
@@ -309,6 +309,7 @@ init_descriptions() ->
     ets:insert(?MODULE, {{httpd, requests}, <<"number of HTTP requests">>}),
     ets:insert(?MODULE, {{httpd, temporary_view_reads}, <<"number of temporary view reads">>}),
     ets:insert(?MODULE, {{httpd, view_reads}, <<"number of view reads">>}),
+    ets:insert(?MODULE, {{httpd, clients_requesting_changes}, <<"Number of clients currently requesting continuous _changes">>}),
     
     ets:insert(?MODULE, {{httpd_request_methods, 'COPY'}, <<"number of HTTP COPY requests">>}),
     ets:insert(?MODULE, {{httpd_request_methods, 'DELETE'}, <<"number of HTTP DELETE requests">>}),
diff --git a/src/couchdb/couch_stats_collector.erl b/src/couchdb/couch_stats_collector.erl
index ad5e9e9a..9139f6cb 100644
--- a/src/couchdb/couch_stats_collector.erl
+++ b/src/couchdb/couch_stats_collector.erl
@@ -24,7 +24,7 @@
 
 -export([start/0, stop/0, get/1, 
         increment/1, decrement/1,
-        track_process_count/1,
+        track_process_count/1, track_process_count/2,
         record/2, clear/1,
         all/0, all/1]).
 
@@ -87,14 +87,15 @@ all(Type) ->
         absolute -> ets:tab2list(?ABSOLUTE_VALUE_COUNTER_TABLE)
     end.
 
-
 track_process_count(Stat) ->
+    track_process_count(self(), Stat).
+
+track_process_count(Pid, Stat) ->
     case (catch couch_stats_collector:increment(Stat)) of
     ok ->
-        Self = self(),
         spawn(
             fun() ->
-                erlang:monitor(process, Self),
+                erlang:monitor(process, Pid),
                 receive {'DOWN', _, _, _, _} -> ok end,
                 couch_stats_collector:decrement(Stat)
             end);
-- 
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