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

2 files changed, 164 insertions, 1 deletions

diff --git a/test/etap/210-os-proc-pool.t b/test/etap/210-os-proc-pool.t
new file mode 100644
index 00000000..b68d66be
--- /dev/null
+++ b/test/etap/210-os-proc-pool.t
@@ -0,0 +1,161 @@
+#!/usr/bin/env escript
+%% -*- erlang -*-
+% 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.
+
+main(_) ->
+    test_util:init_code_path(),
+
+    etap:plan(19),
+    case (catch test()) of
+        ok ->
+            etap:end_tests();
+        Other ->
+            etap:diag(io_lib:format("Test died abnormally: ~p", [Other])),
+            etap:bail(Other)
+    end,
+    ok.
+
+
+test() ->
+    couch_server_sup:start_link(test_util:config_files()),
+    couch_config:set("query_server_config", "os_process_limit", "3", false),
+
+    test_pool_full(),
+    test_client_unexpected_exit(),
+
+    couch_server_sup:stop(),
+    ok.
+
+
+test_pool_full() ->
+    Client1 = spawn_client(),
+    Client2 = spawn_client(),
+    Client3 = spawn_client(),
+
+    etap:diag("Check that we can spawn the max number of processes."),
+    etap:is(ping_client(Client1), ok, "Client 1 started ok."),
+    etap:is(ping_client(Client2), ok, "Client 2 started ok."),
+    etap:is(ping_client(Client3), ok, "Client 3 started ok."),
+
+    Proc1 = get_client_proc(Client1, "1"),
+    Proc2 = get_client_proc(Client2, "2"),
+    Proc3 = get_client_proc(Client3, "3"),
+    etap:isnt(Proc1, Proc2, "Clients 1 and 2 got different procs."),
+    etap:isnt(Proc2, Proc3, "Clients 2 and 3 got different procs."),
+
+    etap:diag("Check that client 4 blocks waiting for a process."),
+    Client4 = spawn_client(),
+    etap:is(ping_client(Client4), timeout, "Client 4 blocked while waiting."),
+
+    etap:diag("Check that stopping a client gives up its process."),
+    etap:is(stop_client(Client1), ok, "First client stopped."),
+
+    etap:diag("And check that our blocked process has been unblocked."),
+    etap:is(ping_client(Client4), ok, "Client was unblocked."),
+
+    Proc4 = get_client_proc(Client4, "4"),
+    etap:is(Proc4, Proc1, "Client 4 got proc that client 1 got before."),
+
+    lists:map(fun(C) -> ok = stop_client(C) end, [Client2, Client3, Client4]).
+
+
+test_client_unexpected_exit() ->
+    Client1 = spawn_client(),
+    Client2 = spawn_client(),
+    Client3 = spawn_client(),
+
+    etap:diag("Check that up to os_process_limit clients started."),
+    etap:is(ping_client(Client1), ok, "Client 1 started ok."),
+    etap:is(ping_client(Client2), ok, "Client 2 started ok."),
+    etap:is(ping_client(Client3), ok, "Client 3 started ok."),
+
+    Proc1 = get_client_proc(Client1, "1"),
+    Proc2 = get_client_proc(Client2, "2"),
+    Proc3 = get_client_proc(Client3, "3"),
+    etap:isnt(Proc1, Proc2, "Clients 1 and 2 got different procs."),
+    etap:isnt(Proc2, Proc3, "Clients 2 and 3 got different procs."),
+
+    etap:diag("Check that killing a client frees an os_process."),
+    etap:is(kill_client(Client1), ok, "Client 1 died all right."),
+
+    etap:diag("Check that a new client is not blocked on boot."),
+    Client4 = spawn_client(),
+    etap:is(ping_client(Client4), ok, "New client booted without blocking."),
+
+    Proc4 = get_client_proc(Client4, "4"),
+    etap:isnt(Proc4, Proc1,
+        "Client 4 got a proc different from the one client 1 got before."),
+    etap:isnt(Proc4, Proc2, "Client 4's proc different from client 2's proc."),
+    etap:isnt(Proc4, Proc3, "Client 4's proc different from client 3's proc."),
+
+    lists:map(fun(C) -> ok = stop_client(C) end, [Client2, Client3, Client4]).
+
+
+spawn_client() ->
+    Parent = self(),
+    Ref = make_ref(),
+    Pid = spawn(fun() ->
+        Proc = couch_query_servers:get_os_process(<<"javascript">>),
+        loop(Parent, Ref, Proc)
+    end),
+    {Pid, Ref}.
+
+
+ping_client({Pid, Ref}) ->
+    Pid ! ping,
+    receive
+        {pong, Ref} -> ok
+        after 3000 -> timeout
+    end.
+
+
+get_client_proc({Pid, Ref}, ClientName) ->
+    Pid ! get_proc,
+    receive
+        {proc, Ref, Proc} -> Proc
+    after 3000 ->
+        etap:bail("Timeout getting client " ++ ClientName ++ " proc.")
+    end.
+
+
+stop_client({Pid, Ref}) ->
+    Pid ! stop,
+    receive
+        {stop, Ref} -> ok
+        after 3000 -> timeout
+    end.
+
+
+kill_client({Pid, Ref}) ->
+    Pid ! die,
+    receive
+        {die, Ref} -> ok
+        after 3000 -> timeout
+    end.
+
+
+loop(Parent, Ref, Proc) ->
+    receive
+        ping ->
+            Parent ! {pong, Ref},
+            loop(Parent, Ref, Proc);
+        get_proc  ->
+            Parent ! {proc, Ref, Proc},
+            loop(Parent, Ref, Proc);
+        stop ->
+            couch_query_servers:ret_os_process(Proc),
+            Parent ! {stop, Ref};
+        die ->
+            Parent ! {die, Ref},
+            exit(some_error)
+    end.
diff --git a/test/etap/Makefile.am b/test/etap/Makefile.am
index ecbc3a93..c3a4ddab 100644
--- a/test/etap/Makefile.am
+++ b/test/etap/Makefile.am
@@ -87,4 +87,6 @@ EXTRA_DIST = \
 	180-http-proxy.ini \
 	180-http-proxy.t \
   190-oauth.t \
-	200-view-group-no-db-leaks.t
+	200-view-group-no-db-leaks.t \
+	210-os-proc-pool.t
+