Abstract out file locking, and revert to not using the R14-ism exclusive flagbug23547

2 files changed, 16 insertions, 6 deletions

diff --git a/src/rabbit_misc.erl b/src/rabbit_misc.erl
index 0067a410..f549dfe0 100644
--- a/src/rabbit_misc.erl
+++ b/src/rabbit_misc.erl
@@ -66,6 +66,7 @@
 -export([get_options/2]).
 -export([all_module_attributes/1, build_acyclic_graph/3]).
 -export([now_ms/0]).
+-export([lock_file/1]).
 
 -import(mnesia).
 -import(lists).
@@ -200,6 +201,7 @@
                                                {bad_edge, [digraph:vertex()]}),
                                       digraph:vertex(), digraph:vertex()})).
 -spec(now_ms/0 :: () -> non_neg_integer()).
+-spec(lock_file/1 :: (file:filename()) -> rabbit_types:ok_or_error('eexist')).
 
 -endif.
 
@@ -811,3 +813,14 @@ build_acyclic_graph(VertexFun, EdgeFun, Graph) ->
             true = digraph:delete(G),
             {error, Reason}
     end.
+
+%% TODO: When we stop supporting Erlang prior to R14, this should be
+%% replaced with file:open [write, exclusive]
+lock_file(Path) ->
+    case filelib:is_file(Path) of
+        true ->
+            {error, eexist};
+        false ->
+            {ok, Lock} = file:open(Path, [write]),
+            ok = file:close(Lock)
+    end.
diff --git a/src/rabbit_upgrade.erl b/src/rabbit_upgrade.erl
index 64d0c251..97a07514 100644
--- a/src/rabbit_upgrade.erl
+++ b/src/rabbit_upgrade.erl
@@ -127,9 +127,8 @@ heads(G) ->
 
 apply_upgrades(Upgrades) ->
     LockFile = lock_filename(dir()),
-    case file:open(LockFile, [write, exclusive]) of
-        {ok, Lock} ->
-            ok = file:close(Lock),
+    case rabbit_misc:lock_file(LockFile) of
+        ok ->
             BackupDir = dir() ++ "-upgrade-backup",
             info("Upgrades: ~w to apply~n", [length(Upgrades)]),
             case rabbit_mnesia:copy_db(BackupDir) of
@@ -155,9 +154,7 @@ apply_upgrades(Upgrades) ->
                     throw({could_not_back_up_mnesia_dir, E})
             end;
         {error, eexist} ->
-            throw({error, previous_upgrade_failed});
-        {error, _} = Error ->
-            throw(Error)
+            throw({error, previous_upgrade_failed})
     end.
 
 apply_upgrade({M, F}) ->