From 82a10d77d0c206c89e640ca7097d8e12e95eb8be Mon Sep 17 00:00:00 2001
From: Filipe David Borba Manana <fdmanana@apache.org>
Date: Thu, 18 Aug 2011 05:50:42 +0000
Subject: Merge revision 1159045 from trunk

    Fix dead lock case in the os process pool

    Part of this patch was done by Paul Davis.
    The patch also introduces a test case to validate that
    the os process pool (couch_query_servers) operates as it
    should.
    Closes COUCHDB-1246.



git-svn-id: https://svn.apache.org/repos/asf/couchdb/branches/1.1.x@1159049 13f79535-47bb-0310-9956-ffa450edef68
---
 src/couchdb/couch_os_process.erl    |  6 +-----
 src/couchdb/couch_query_servers.erl | 22 +++++++++++++++-------
 2 files changed, 16 insertions(+), 12 deletions(-)

(limited to 'src')

diff --git a/src/couchdb/couch_os_process.erl b/src/couchdb/couch_os_process.erl
index 5776776b..3ee52865 100644
--- a/src/couchdb/couch_os_process.erl
+++ b/src/couchdb/couch_os_process.erl
@@ -104,7 +104,6 @@ readjson(OsProc) when is_record(OsProc, os_proc) ->
 
 % gen_server API
 init([Command, Options, PortOptions]) ->
-    process_flag(trap_exit, true),
     PrivDir = couch_util:priv_dir(),
     Spawnkiller = filename:join(PrivDir, "couchspawnkillable"),
     BaseProc = #os_proc{
@@ -175,10 +174,7 @@ handle_info({Port, {exit_status, 0}}, #os_proc{port=Port}=OsProc) ->
     {stop, normal, OsProc};
 handle_info({Port, {exit_status, Status}}, #os_proc{port=Port}=OsProc) ->
     ?LOG_ERROR("OS Process died with status: ~p", [Status]),
-    {stop, {exit_status, Status}, OsProc};
-handle_info(Msg, OsProc) ->
-    ?LOG_DEBUG("OS Proc: Unknown info: ~p", [Msg]),
-    {noreply, OsProc}.
+    {stop, {exit_status, Status}, OsProc}.
 
 code_change(_OldVsn, State, _Extra) ->
     {ok, State}.
diff --git a/src/couchdb/couch_query_servers.erl b/src/couchdb/couch_query_servers.erl
index b0e46937..f8bbcaed 100644
--- a/src/couchdb/couch_query_servers.erl
+++ b/src/couchdb/couch_query_servers.erl
@@ -22,7 +22,8 @@
 
 -export([with_ddoc_proc/2, proc_prompt/2, ddoc_prompt/3, ddoc_proc_prompt/3, json_doc/1]).
 
-% -export([test/0]).
+% For 210-os-proc-pool.t
+-export([get_os_process/1, ret_os_process/1]).
 
 -include("couch_db.hrl").
 
@@ -343,8 +344,7 @@ handle_call({get_proc, Lang}, From, Server) ->
     Error ->
         {reply, Error, Server}
     end;
-handle_call({unlink_proc, Pid}, _From, #qserver{pid_procs=PidProcs}=Server) ->
-    rem_value(PidProcs, Pid),
+handle_call({unlink_proc, Pid}, _From, Server) ->
     unlink(Pid),
     {reply, ok, Server};
 handle_call({ret_proc, Proc}, _From, #qserver{
@@ -352,15 +352,22 @@ handle_call({ret_proc, Proc}, _From, #qserver{
         lang_procs=LangProcs}=Server) ->
     % Along with max process limit, here we should check
     % if we're over the limit and discard when we are.
-    add_value(PidProcs, Proc#proc.pid, Proc),
-    add_to_list(LangProcs, Proc#proc.lang, Proc),
-    link(Proc#proc.pid),
+    case is_process_alive(Proc#proc.pid) of
+        true ->
+            add_value(PidProcs, Proc#proc.pid, Proc),
+            add_to_list(LangProcs, Proc#proc.lang, Proc),
+            link(Proc#proc.pid);
+        false ->
+            ok
+    end,
     {reply, true, service_waitlist(Server)}.
 
 handle_cast(_Whatever, Server) ->
     {noreply, Server}.
 
-handle_info({'EXIT', Pid, Status}, #qserver{
+handle_info({'EXIT', _, _}, Server) ->
+    {noreply, Server};
+handle_info({'DOWN', _, process, Pid, Status}, #qserver{
         pid_procs=PidProcs,
         lang_procs=LangProcs,
         lang_limits=LangLimits}=Server) ->
@@ -461,6 +468,7 @@ new_process(Langs, LangLimits, Lang) ->
         case ets:lookup(Langs, Lang) of
         [{Lang, Mod, Func, Arg}] ->
             {ok, Pid} = apply(Mod, Func, Arg),
+            erlang:monitor(process, Pid),
             true = ets:insert(LangLimits, {Lang, Lim, Current+1}),
             {ok, #proc{lang=Lang,
                        pid=Pid,
-- 
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