Unhandled function clause exception when retrieving queue for nonexistent virtual host

[LoisSotoLopez]

Describe the bug

Retrieving messages on a queue through rabbit_mgmt_wm_queue_get.erl for an invalid virtual host results on an unhandled function_clause exception.

This issue seems to have been introduced by commit 439c2b4 , more precisely by this change .

-    mnesia:async_dirty(
-      fun () ->
-              case VHost of
-                  '_' -> ok;
-                  _   -> rabbit_vhost:assert(VHost)
-              end,
-              Match = #runtime_parameters{key = {VHost, Component, '_'},
-                                          _   = '_'},
-              [p(P) || #runtime_parameters{key = {_VHost, Comp, _Name}} = P <-
-                           mnesia:match_object(?TABLE, Match, read),
-                       Comp =/= <<"policy">> orelse Component =:= <<"policy">>]
-      end).
+    [p(P) || #runtime_parameters{key = {_VHost, Comp, _Name}} = P <-
+             rabbit_db_rtparams:get_all(VHost, Component),
+             Comp =/= <<"policy">> orelse Component =:= <<"policy">>].

While on the previous version of the file the rabbit_vhost:assert/1 was called before searching for the vhost data on the Mnesia table, the current version calls rabbit_db_rtparams:get_all/2. As seen below, that function ends up calling to rabbit_vhost:assert/1 on the vhost too (at get_all_in_mnesia/2) but only if the VHostName parameter passed to get_all/2 is either a binary() or the '_' atom.

+get_all(VHostName, Comp)
+  when (is_binary(VHostName) orelse VHostName =:= '_') andalso
+       (is_binary(Comp) orelse Comp =:= '_') ->
+    rabbit_db:run(
+      #{mnesia => fun() -> get_all_in_mnesia(VHostName, Comp) end}).
+
+get_all_in_mnesia(VHostName, Comp) ->
+    mnesia:async_dirty(
+      fun () ->
+              case VHostName of
+                  '_' -> ok;
+                  _   -> rabbit_vhost:assert(VHostName)
+              end,
+              Match = #runtime_parameters{key = {VHostName, Comp, '_'},
+                                          _   = '_'},
+              mnesia:match_object(?MNESIA_TABLE, Match, read)
+      end).

That new type check is incompatible with a previous step on the data flow, on rabbit_mgmt_wm_queue_get where the parsing of the request leads to the variable for the virtual host having the not_found atom as value if the virtual host does not exist.

The parsing is done by

rabbitmq-server/deps/rabbitmq_management/src/rabbit_mgmt_wm_queue_get.erl

Line 45 in e4da70d

VHost = rabbit_mgmt_util:vhost(ReqData0),

which calls to

rabbitmq-server/deps/rabbitmq_management/src/rabbit_mgmt_util.erl

Line 211 in e4da70d

rabbit_web_dispatch_access_control:vhost(ReqData).

which calls to

rabbitmq-server/deps/rabbitmq_web_dispatch/src/rabbit_web_dispatch_access_control.erl

Line 222 in e4da70d

vhost(ReqData) ->

vhost(ReqData) ->
    Value = case id(vhost, ReqData) of
      none  -> vhost_from_headers(ReqData);
      VHost -> VHost
    end,
    case Value of
      none -> none;
      Name ->
        case rabbit_vhost:exists(Name) of
          true  -> Name;
          false -> not_found % <---------- This propagates and leads to `function_clause`
        end
    end.

Expand this to see the stacktrace associated to the **Reproduction steps** below.

2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>   crasher:
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>     initial call: cowboy_stream_h:request_process/3
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>     pid: <0.1965.0>
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>     registered_name: []
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>     exception error: no case clause matching
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                      {error,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                          {{'EXIT',
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                               {function_clause,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                   [{rabbit_db_rtparams,get_all,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        [not_found,<<"vhost-limits">>],
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        [{file,"rabbit_db_rtparams.erl"},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                         {line,178}]},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                    {rabbit_runtime_parameters,list,2,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        [{file,"rabbit_runtime_parameters.erl"},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                         {line,261}]},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                    {rabbit_vhost_limit,get_limit,2,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        [{file,"rabbit_vhost_limit.erl"},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                         {line,192}]},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                    {rabbit_vhost_limit,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        is_over_connection_limit,1,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        [{file,"rabbit_vhost_limit.erl"},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                         {line,87}]},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                    {rabbit_direct,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        is_over_vhost_connection_limit,3,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        [{file,"rabbit_direct.erl"},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                         {line,173}]},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                    {rabbit_direct,connect,5,
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                        [{file,"rabbit_direct.erl"},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                                         {line,95}]}]}},
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>                           rabbit@34b640576ca8}}
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in function  rabbit_mgmt_util:with_channel/5 (rabbit_mgmt_util.erl, line 868)
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in call from rabbit_mgmt_util:with_decode/5 (rabbit_mgmt_util.erl, line 714)
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in call from rabbit_mgmt_wm_queue_get:accept_content/2 (rabbit_mgmt_wm_queue_get.erl, line 42)
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in call from cowboy_rest:call/3 (src/cowboy_rest.erl, line 1590)
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in call from cowboy_rest:process_content_type/3 (src/cowboy_rest.erl, line 1096)
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in call from cowboy_rest:upgrade/4 (src/cowboy_rest.erl, line 284)
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in call from cowboy_stream_h:execute/3 (src/cowboy_stream_h.erl, line 306)
2024-04-02 06:59:28.296087+00:00 [error] <0.1965.0>       in call from cowboy_stream_h:request_process/3 (src/cowboy_stream_h.erl, line 295)

Reproduction steps

1. docker run --rm -it -p 15673:15672 rabbitmq:3.13.0-management
2. curl -sv -u guest:guest -X POST -H 'Content-Type: application/json' --data '{ "ackmode": "reject_requeue_true", "encoding": "auto", "count": 1 }' http://localhost:15673/api/queues/does-not-exist/foo/get
3. A 500 error returns.

Expected behavior

A 404 HTTP error code specifying the provided virtual host does not exist.

Additional context

We are already working on this.

[michaelklishin]

@LoisSotoLopez I mean, good to see someone working on this but honestly, polling over HTTP API when a virtual host does not exist? This is as low a priority as it gets.

Perhaps CloudAMQP, a company that directly makes money off of RabbitMQ and has been doing that since 2012, should consider more substantial contributions.

[gomoripeti]

For the record Lois just started working with RabbitMQ a few weeks ago. A low priority task is the perfect first step to get familiar with the concepts and notions of RabbitMQ, the code base which is admittedly complex, custom solutions and peculiarities. This is the slow way forward for more substantial contributions. Please expect some more low priority contributions. Thanks for understanding.