Make rabbit_vhost:add/2 idempotent

Part of rabbitmq/rabbitmq-cli#260

[#160792770]

(cherry picked from commit cab7e58)

Author: michaelklishin

src/rabbit_vhost.erl

@@ -83,15 +83,22 @@ recover(VHost) ->
 
 -define(INFO_KEYS, [name, tracing, cluster_state]).
 
-add(VHostPath, ActingUser) ->
+add(VHost, ActingUser) ->
+    case exists(VHost) of
+        true  -> ok;
+        false -> do_add(VHost, ActingUser)
+    end.
+
+do_add(VHostPath, ActingUser) ->
     rabbit_log:info("Adding vhost '~s'~n", [VHostPath]),
     R = rabbit_misc:execute_mnesia_transaction(
           fun () ->
                   case mnesia:wread({rabbit_vhost, VHostPath}) of
                       []  -> ok = mnesia:write(rabbit_vhost,
                                                #vhost{virtual_host = VHostPath},
                                                write);
-                      [_] -> mnesia:abort({vhost_already_exists, VHostPath})
+                      %% the vhost already exists
+                      [_] -> ok
                   end
           end,
           fun (ok, true) ->

test/vhost_SUITE.erl

@@ -34,7 +34,8 @@ groups() ->
     ClusterSize1Tests = [
         single_node_vhost_deletion_forces_connection_closure,
         vhost_failure_forces_connection_closure,
-        dead_vhost_connection_refused
+        dead_vhost_connection_refused,
+        vhost_creation_idempotency
     ],
     ClusterSize2Tests = [
         cluster_vhost_deletion_forces_connection_closure,
@@ -43,7 +44,8 @@ groups() ->
         vhost_failure_forces_connection_closure_on_failure_node,
         dead_vhost_connection_refused_on_failure_node,
         node_starts_with_dead_vhosts,
-        node_starts_with_dead_vhosts_and_ignore_slaves
+        node_starts_with_dead_vhosts_and_ignore_slaves,
+        vhost_creation_idempotency
     ],
     [
       {cluster_size_1_network, [], ClusterSize1Tests},
@@ -373,6 +375,12 @@ node_starts_with_dead_vhosts_and_ignore_slaves(Config) ->
     true = rabbit_ct_broker_helpers:rpc(Config, 1,
                 rabbit_vhost_sup_sup, is_vhost_alive, [VHost2]).
 
+vhost_creation_idempotency(Config) ->
+    VHost = <<"idempotency-test">>,
+    ?assertEqual(ok, rabbit_ct_broker_helpers:add_vhost(Config, VHost)),
+    ?assertEqual(ok, rabbit_ct_broker_helpers:add_vhost(Config, VHost)),
+    ?assertEqual(ok, rabbit_ct_broker_helpers:add_vhost(Config, VHost)).
+
 %% -------------------------------------------------------------------
 %% Helpers
 %% -------------------------------------------------------------------