Integrate DNS peer discovery backend, more logging

 * Returned value must be a list of atoms
 * Support more tuple types in normalize/1
 * Update tests

4 files changed, 66 insertions, 26 deletions

diff --git a/src/rabbit_mnesia.erl b/src/rabbit_mnesia.erl
index 1ec9a46880..51deed8597 100644
--- a/src/rabbit_mnesia.erl
+++ b/src/rabbit_mnesia.erl
@@ -98,11 +98,10 @@ init() ->
     ensure_mnesia_dir(),
     case is_virgin_node() of
         true  ->
-            rabbit_log:info("Database directory at ~s is empty. "
+            rabbit_log:info("Node database directory at ~s is empty. "
                             "Assuming we need to join an existing cluster or initialise from scratch...~n",
                             [dir()]),
-            rabbit_log:info("Using ~p as peer discovery backend~n",
-                            [rabbit_peer_discovery:backend()]),
+             rabbit_peer_discovery:log_configured_backend(),
             init_from_config();
         false ->
             NodeType = node_type(),
@@ -141,7 +140,9 @@ init_from_config() ->
                 e(invalid_cluster_nodes_conf)
         end,
     case DiscoveredNodes of
-        [] -> init_db_and_upgrade([node()], disc, false, _Retry = true);
+        [] ->
+            rabbit_log:info("Discovered no peer nodes to cluster with"),
+            init_db_and_upgrade([node()], disc, false, _Retry = true);
         _  ->
             rabbit_log:info("Discovered peer nodes: ~s~n",
                 [rabbit_peer_discovery:format_discovered_nodes(DiscoveredNodes)]),
@@ -158,8 +159,9 @@ auto_cluster(TryNodes, NodeType) ->
             rabbit_node_monitor:notify_joined_cluster();
         none ->
             rabbit_log:warning(
-              "Could not find any node for auto-clustering from: ~p~n"
-              "Starting blank node...~n", [TryNodes]),
+              "Could not successfully contact any node of: ~s (as in Erlang distribution). "
+               "Starting as a blank standalone node...~n",
+                [string:join(lists:map(fun atom_to_list/1, TryNodes), ",")]),
             init_db_and_upgrade([node()], disc, false, _Retry = true)
     end.
 
diff --git a/src/rabbit_peer_discovery.erl b/src/rabbit_peer_discovery.erl
index e04df6a02d..c0b554e3b3 100644
--- a/src/rabbit_peer_discovery.erl
+++ b/src/rabbit_peer_discovery.erl
@@ -16,21 +16,53 @@
 
 -module(rabbit_peer_discovery).
 
+%%
 %% API
--export([discover_cluster_nodes/0, backend/0,
-         normalize/1, format_discovered_nodes/1]).
+%%
+
+-export([discover_cluster_nodes/0, backend/0, node_type/0,
+         normalize/1, format_discovered_nodes/1, log_configured_backend/0]).
 -export([append_node_prefix/1, node_prefix/0]).
 
+-define(DEFAULT_BACKEND,   rabbit_peer_discovery_classic_config).
+%% what node type is used by default for this node when joining
+%% a new cluster as a virgin node
+-define(DEFAULT_NODE_TYPE, disc).
+%% default node prefix to attach to discovered hostnames
+-define(DEFAULT_PREFIX, "rabbit").
+-define(NODENAME_PART_SEPARATOR, "@").
+
 
 -spec backend() -> atom().
 
 backend() ->
-  case application:get_env(rabbit, peer_discovery_backend) of
-    {ok, Backend} when is_atom(Backend) -> Backend;
-    undefined                           -> rabbit_peer_discovery_classic_config
+  case application:get_env(rabbit, autocluster) of
+    {ok, Proplist} ->
+      proplists:get_value(peer_discovery_backend, Proplist, ?DEFAULT_BACKEND);
+    undefined      ->
+      ?DEFAULT_BACKEND
+  end.
+
+
+
+-spec node_type() -> rabbit_types:node_type().
+
+node_type() ->
+  case application:get_env(rabbit, autocluster) of
+    {ok, Proplist} ->
+      proplists:get_value(node_type, Proplist, ?DEFAULT_NODE_TYPE);
+    undefined      ->
+      ?DEFAULT_NODE_TYPE
   end.
 
 
+
+-spec log_configured_backend() -> ok.
+
+log_configured_backend() ->
+  rabbit_log:info("Configured peer discovery backend: ~s~n", [backend()]).
+
+
 -spec discover_cluster_nodes() -> {ok, Nodes :: list()} |
                                   {ok, {Nodes :: list(), NodeType :: rabbit_types:node_type()}} |
                                   {error, Reason :: string()}.
@@ -40,11 +72,17 @@ discover_cluster_nodes() ->
     normalize(Backend:list_nodes()).
 
 
--spec normalize({ok, Nodes :: list()} |
+-spec normalize(Nodes :: list() |
+                {Nodes :: list(), NodeType :: rabbit_types:node_type()} |
+                {ok, Nodes :: list()} |
                 {ok, {Nodes :: list(), NodeType :: rabbit_types:node_type()}} |
                 {error, Reason :: string()}) -> {ok, {Nodes :: list(), NodeType :: rabbit_types:node_type()}} |
                                                 {error, Reason :: string()}.
 
+normalize(Nodes) when is_list(Nodes) ->
+  {ok, {Nodes, disc}};
+normalize({Nodes, NodeType}) when is_list(Nodes) andalso is_atom(NodeType) ->
+  {ok, {Nodes, NodeType}};
 normalize({ok, Nodes}) when is_list(Nodes) ->
   {ok, {Nodes, disc}};
 normalize({ok, {Nodes, NodeType}}) when is_list(Nodes) andalso is_atom(NodeType) ->
@@ -59,9 +97,6 @@ format_discovered_nodes(Nodes) ->
   string:join(lists:map(fun (Val) -> hd(io_lib:format("~s", [Val])) end, Nodes), ", ").
 
 
--define(DEFAULT_PREFIX, "rabbit").
--define(NODENAME_PART_SEPARATOR, "@").
-
 
 -spec node_prefix() -> string().
 
diff --git a/src/rabbit_peer_discovery_dns.erl b/src/rabbit_peer_discovery_dns.erl
index 8656a9523f..53a10333b0 100644
--- a/src/rabbit_peer_discovery_dns.erl
+++ b/src/rabbit_peer_discovery_dns.erl
@@ -37,9 +37,8 @@ list_nodes() ->
             undefined -> io:format("rabbit.autocluster.peer_discovery_dns~n", []), {[], disc};
             Proplist  ->
                 Hostname = rabbit_data_coercion:to_list(proplists:get_value(hostname, Proplist)),
-                NodeType = proplists:get_value(node_type, Autocluster, disc),
 
-                {discover_nodes(Hostname, net_kernel:longnames()), NodeType}
+                {discover_nodes(Hostname, net_kernel:longnames()), rabbit_peer_discovery:node_type()}
         end
     end.
 
@@ -59,21 +58,25 @@ unregister() ->
 %%
 
 discover_nodes(SeedHostname, LongNamesUsed) ->
-    [rabbit_peer_discovery:append_node_prefix(H) ||
+    [list_to_atom(rabbit_peer_discovery:append_node_prefix(H)) ||
         H <- discover_hostnames(SeedHostname, LongNamesUsed)].
 
 discover_hostnames(SeedHostname, LongNamesUsed) ->
     %% TODO: IPv6 support
-    Hosts = [extract_host(inet_res:gethostbyaddr(A), LongNamesUsed) ||
-                A <- inet_res:lookup(SeedHostname, in, a)],
+    IPs   = inet_res:lookup(SeedHostname, in, a),
+    rabbit_log:info("Addresses discovered via A records of ~s: ~s",
+      [SeedHostname, string:join([inet_parse:ntoa(IP) || IP <- IPs], ", ")]),
+    Hosts = [extract_host(inet_res:gethostbyaddr(A), LongNamesUsed, A) ||
+                A <- IPs],
     lists:filter(fun(E) -> E =/= error end, Hosts).
 
 %% long node names are used
-extract_host({ok, {hostent, FQDN, _, _, _, _}}, true) ->
+extract_host({ok, {hostent, FQDN, _, _, _, _}}, true, _Address) ->
   FQDN;
 %% short node names are used
-extract_host({ok, {hostent, FQDN, _, _, _, _}}, false) ->
+extract_host({ok, {hostent, FQDN, _, _, _, _}}, false, _Address) ->
   lists:nth(1, string:tokens(FQDN, "."));
-extract_host(Error, _) ->
-  rabbit_log:error("DNS peer discovery failed: ~p", [Error]),
+extract_host({error, Error}, _, Address) ->
+  rabbit_log:error("Reverse DNS lookup for address ~s failed: ~p",
+                   [inet_parse:ntoa(Address), Error]),
   error.
diff --git a/test/peer_discovery_dns_SUITE.erl b/test/peer_discovery_dns_SUITE.erl
index 80bb2f8de6..da01aeebdd 100644
--- a/test/peer_discovery_dns_SUITE.erl
+++ b/test/peer_discovery_dns_SUITE.erl
@@ -95,8 +95,8 @@ hostname_discovery_with_short_node_names(_) ->
 
 node_discovery_with_long_node_names(_) ->
     Result = rabbit_peer_discovery_dns:discover_nodes(?DISCOVERY_ENDPOINT, true),
-    ?assertEqual(["ct_rabbit@www.rabbitmq.com"], Result).
+    ?assertEqual(['ct_rabbit@www.rabbitmq.com'], Result).
 
 node_discovery_with_short_node_names(_) ->
     Result = rabbit_peer_discovery_dns:discover_nodes(?DISCOVERY_ENDPOINT, false),
-    ?assertEqual(["ct_rabbit@www"], Result).
+    ?assertEqual([ct_rabbit@www], Result).