[couchdb] 26/26: FIXUP: Process processes in the process of dying

[da...@apache.org]

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davisp pushed a commit to branch optimize-ddoc-cache
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit e87bbe72351a6050ccc49a00174f2efa2b2271db
Author: Paul J. Davis <pa...@gmail.com>
AuthorDate: Thu Jul 20 14:02:57 2017 -0500

    FIXUP: Process processes in the process of dying
    
    Turns out we could go to evict an entry just after it had decided to
    leave the cache (i.e., its ddoc was just deleted). When that happens
    ddoc_cache_lru would die trying to shut the process down becuase the
    process died normal earlier than expected.
---
 src/ddoc_cache/src/ddoc_cache_entry.erl | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/ddoc_cache/src/ddoc_cache_entry.erl b/src/ddoc_cache/src/ddoc_cache_entry.erl
index 63a2efa..77539eb 100644
--- a/src/ddoc_cache/src/ddoc_cache_entry.erl
+++ b/src/ddoc_cache/src/ddoc_cache_entry.erl
@@ -77,7 +77,17 @@ start_link(Key, Default) ->
 
 
 shutdown(Pid) ->
-    ok = gen_server:call(Pid, shutdown).
+    Ref = erlang:monitor(process, Pid),
+    ok = gen_server:cast(Pid, shutdown),
+    receive
+        {'DOWN', Ref, process, Pid, normal} ->
+            ok;
+        {'DOWN', Ref, process, Pid, Reason} ->
+            erlang:exit(Reason)
+    after ?SHUTDOWN_TIMEOUT ->
+        erlang:demonitor(Ref, [flush]),
+        erlang:exit({timeout, {entry_shutdown, Pid}})
+    end.
 
 
 open(Pid, Key) ->
@@ -170,10 +180,6 @@ handle_call(open, From, #st{opener = Pid} = St) when is_pid(Pid) ->
 handle_call(open, _From, St) ->
     {reply, St#st.val, St};
 
-handle_call(shutdown, _From, St) ->
-    remove_from_cache(St),
-    {stop, normal, ok, St};
-
 handle_call(Msg, _From, St) ->
     {stop, {bad_call, Msg}, {bad_call, Msg}, St}.
 
@@ -227,6 +233,10 @@ handle_cast(refresh, #st{opener = Pid} = St) when is_pid(Pid) ->
     },
     {noreply, NewSt};
 
+handle_cast(shutdown, St) ->
+    remove_from_cache(St),
+    {stop, normal, St};
+
 handle_cast(Msg, St) ->
     {stop, {bad_cast, Msg}, St}.
 

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