display helpful diagnostics on badrpc error in rabbitmqctlbug21662

3 files changed, 45 insertions, 6 deletions

diff --git a/src/rabbit.erl b/src/rabbit.erl
index 27f085c2..b098fd5a 100644
--- a/src/rabbit.erl
+++ b/src/rabbit.erl
@@ -219,6 +219,12 @@ app_location() ->
     {ok, Application} = application:get_application(),
     filename:absname(code:where_is_file(atom_to_list(Application) ++ ".app")).
 
+home_dir() ->
+    case init:get_argument(home) of
+        {ok, [[Home]]} -> Home;
+        Other          -> Other
+    end.
+
 %---------------------------------------------------------------------------
 
 print_banner() ->
@@ -243,6 +249,8 @@ print_banner() ->
                ?COPYRIGHT_MESSAGE, ?INFORMATION_MESSAGE]),
     Settings = [{"node",           node()},
                 {"app descriptor", app_location()},
+                {"home dir",       home_dir()},
+                {"cookie hash",    rabbit_misc:cookie_hash()},
                 {"log",            log_location(kernel)},
                 {"sasl log",       log_location(sasl)},
                 {"database dir",   rabbit_mnesia:dir()}],
diff --git a/src/rabbit_control.erl b/src/rabbit_control.erl
index f701c4aa..a15c7fd8 100644
--- a/src/rabbit_control.erl
+++ b/src/rabbit_control.erl
@@ -80,13 +80,38 @@ start() ->
         {error, Reason} ->
             error("~p", [Reason]),
             halt(2);
+        {badrpc, Reason} ->
+            error("unable to connect to node ~w: ~w", [Node, Reason]),
+            print_badrpc_diagnostics(Node),
+            halt(2);
         Other ->
             error("~p", [Other]),
             halt(2)
     end.
 
-error(Format, Args) ->
-    rabbit_misc:format_stderr("Error: " ++ Format ++ "~n", Args).
+fmt_stderr(Format, Args) -> rabbit_misc:format_stderr(Format ++ "~n", Args).
+
+error(Format, Args) -> fmt_stderr("Error: " ++ Format, Args).
+
+print_badrpc_diagnostics(Node) ->
+    fmt_stderr("diagnostics:", []),
+    NodeHost = rabbit_misc:nodehost(Node),
+    case net_adm:names(NodeHost) of
+        {error, EpmdReason} ->
+            fmt_stderr("- unable to connect to epmd on ~s: ~w",
+                       [NodeHost, EpmdReason]);
+                {ok, NamePorts} ->
+            fmt_stderr("- nodes and their ports on ~s: ~p",
+                       [NodeHost, [{list_to_atom(Name), Port} ||
+                                      {Name, Port} <- NamePorts]])
+            end,
+    fmt_stderr("- current node: ~w", [node()]),
+    case init:get_argument(home) of
+        {ok, [[Home]]} -> fmt_stderr("- current node home dir: ~s", [Home]);
+        Other          -> fmt_stderr("- no current node home dir: ~p", [Other])
+    end,
+    fmt_stderr("- current node cookie hash: ~s", [rabbit_misc:cookie_hash()]),
+    ok.
 
 parse_args(["-n", NodeS | Args], Params) ->
     Node = case lists:member($@, NodeS) of
diff --git a/src/rabbit_misc.erl b/src/rabbit_misc.erl
index 58431438..b20e9a86 100644
--- a/src/rabbit_misc.erl
+++ b/src/rabbit_misc.erl
@@ -47,7 +47,7 @@
 -export([with_user/2, with_vhost/2, with_user_and_vhost/3]).
 -export([execute_mnesia_transaction/1]).
 -export([ensure_ok/2]).
--export([localnode/1, tcp_name/3]).
+-export([localnode/1, nodehost/1, cookie_hash/0, tcp_name/3]).
 -export([intersperse/2, upmap/2, map_in_order/2]).
 -export([table_foreach/2]).
 -export([dirty_read_all/1, dirty_foreach_key/2, dirty_dump_log/1]).
@@ -106,6 +106,8 @@
 -spec(execute_mnesia_transaction/1 :: (thunk(A)) -> A).
 -spec(ensure_ok/2 :: (ok_or_error(), atom()) -> 'ok').
 -spec(localnode/1 :: (atom()) -> erlang_node()).
+-spec(nodehost/1 :: (erlang_node()) -> string()).
+-spec(cookie_hash/0 :: () -> string()).
 -spec(tcp_name/3 :: (atom(), ip_address(), ip_port()) -> atom()).
 -spec(intersperse/2 :: (A, [A]) -> [A]).
 -spec(upmap/2 :: (fun ((A) -> B), [A]) -> [B]).
@@ -307,11 +309,15 @@ ensure_ok(ok, _) -> ok;
 ensure_ok({error, Reason}, ErrorTag) -> throw({error, {ErrorTag, Reason}}).
 
 localnode(Name) ->
+    list_to_atom(lists:append([atom_to_list(Name), "@", nodehost(node())])).
+
+nodehost(Node) ->
     %% This is horrible, but there doesn't seem to be a way to split a
     %% nodename into its constituent parts.
-    list_to_atom(lists:append(atom_to_list(Name),
-                              lists:dropwhile(fun (E) -> E =/= $@ end,
-                                              atom_to_list(node())))).
+    tl(lists:dropwhile(fun (E) -> E =/= $@ end, atom_to_list(Node))).
+
+cookie_hash() ->
+    ssl_base64:encode(erlang:md5(atom_to_list(erlang:get_cookie()))).
 
 tcp_name(Prefix, IPAddress, Port)
   when is_atom(Prefix) andalso is_number(Port) ->