Initial DNS backend config schema support; decouple autocluster node type key

Since node type won't vary from backend to backend we should pull it up
to `autocluster.node_type`.

3 files changed, 78 insertions, 14 deletions

diff --git a/docs/rabbitmq.conf.example b/docs/rabbitmq.conf.example
index f03145b447..9de81548b6 100644
--- a/docs/rabbitmq.conf.example
+++ b/docs/rabbitmq.conf.example
@@ -312,9 +312,14 @@
 # autocluster.classic_config.nodes.node3 = rabbit3@hostname
 # autocluster.classic_config.nodes.node4 = rabbit4@hostname
 
+## DNS-based peer discovery. This backend will list A records
+## of the configured hostname and perform reverse lookups for
+## the addresses returned.
+# autocluster.dns.hostname = "rabbitmq.discovery.mycompany.local"
+
 ## This node's type can be configured. If you are not sure
 ## what node type to use, always use 'disc'.
-# autocluster.classic_config.node_type = disc
+# autocluster.node_type = disc
 
 ## Interval (in milliseconds) at which we send keepalive messages
 ## to other cluster members. Note that this is not the same thing
diff --git a/priv/schema/rabbitmq.schema b/priv/schema/rabbitmq.schema
index 687101dd74..1e2fd6473a 100644
--- a/priv/schema/rabbitmq.schema
+++ b/priv/schema/rabbitmq.schema
@@ -757,6 +757,27 @@ end}.
 {mapping, "mirroring_sync_batch_size", "rabbit.mirroring_sync_batch_size",
     [{datatype, bytesize}, {validators, ["size_less_than_2G"]}]}.
 
+%% Own node type used by autoclustering.
+%%
+
+{mapping, "autocluster.node_type", "rabbit.autocluster.node_type", [
+    {datatype, {enum, [disc, disk, ram]}}
+]}.
+
+{translation, "rabbit.autocluster.node_type",
+fun(Conf) ->
+    case cuttlefish:conf_get("autocluster.node_type", Conf) of
+        undefined ->cuttlefish:unset(); 
+        disc      -> disc;
+        %% Always cast to `disc`
+        disk      -> disc;
+        ram       -> ram;
+        _Other    -> disc
+    end
+end}.
+
+%% Classic config-driven autocluster backend.
+%%
 %% Make clustering happen *automatically* at startup - only applied
 %% to nodes that have just been reset or started for the first time.
 %% See http://www.rabbitmq.com/clustering.html#auto-config for
@@ -767,11 +788,6 @@ end}.
 {mapping, "autocluster.classic_config.nodes.$node", "rabbit.cluster_nodes",
     [{datatype, atom}]}.
 
-{mapping, "autocluster.classic_config.node_type", "rabbit.cluster_nodes", [
-    {datatype, {enum, [disc, disk, ram]}},
-    {default,  disc}
-]}.
-
 {translation, "rabbit.cluster_nodes",
 fun(Conf) ->
     Nodes = [V || {_, V} <- cuttlefish_variable:filter_by_prefix("autocluster.classic_config.nodes", Conf)],
@@ -779,15 +795,29 @@ fun(Conf) ->
     case Nodes of
         []    -> cuttlefish:unset();
         Other ->
-            case cuttlefish:conf_get("autocluster.classic_config.node_type", Conf, disc) of
+            case cuttlefish:conf_get("autocluster.node_type", Conf, disc) of
                 disc -> {Other, disc};
-                % Always cast to `disc`
+                %% Always cast to `disc`
                 disk -> {Other, disc};
                 ram  -> {Other, ram}
             end
     end
 end}.
 
+%% DNS (A records and reverse lookups)-based peer discovery.
+%%
+
+{mapping, "autocluster.dns.hostname", "rabbit.peer_discovery_dns.hostname",
+    [{datatype, string}]}.
+
+{translation, "rabbit.peer_discovery_dns.hostname",
+fun(Conf) ->
+    case cuttlefish:conf_get("autocluster.dns.hostname", Conf) of
+        undefined -> cuttlefish:unset();
+        Value     -> list_to_binary(Value)
+    end
+end}.
+
 
 %% Interval (in milliseconds) at which we send keepalive messages
 %% to other cluster members. Note that this is not the same thing
@@ -799,6 +829,8 @@ end}.
 {mapping, "cluster_keepalive_interval", "rabbit.cluster_keepalive_interval",
     [{datatype, integer}]}.
 
+%% Queue master locator
+%%
 
 {mapping, "queue_master_locator", "rabbit.queue_master_locator",
     [{datatype, string}]}.
diff --git a/test/config_schema_SUITE_data/snippets.config b/test/config_schema_SUITE_data/snippets.config
index 8c4319fa53..114c931622 100644
--- a/test/config_schema_SUITE_data/snippets.config
+++ b/test/config_schema_SUITE_data/snippets.config
@@ -96,22 +96,26 @@ default_permissions.write = .*",
 {13,
 "autocluster.classic_config.nodes.peer1 = rabbit@hostname1
 autocluster.classic_config.nodes.peer2 = rabbit@hostname2
-autocluster.classic_config.node_type = disc",
+autocluster.node_type = disc",
 [{rabbit, [
+    {autocluster,   [{node_type, disc}]},
     {cluster_nodes, {[rabbit@hostname2,rabbit@hostname1], disc}}
 ]}],[]}
 ,
 {13.1,
 "autocluster.classic_config.nodes.peer1 = rabbit@hostname1
 autocluster.classic_config.nodes.peer2 = rabbit@hostname2
-autocluster.classic_config.node_type = disk",
+autocluster.node_type = disk",
 [{rabbit, [
+    {autocluster,   [{node_type, disc}]},
     {cluster_nodes, {[rabbit@hostname2,rabbit@hostname1], disc}}
 ]}],[]}
 ,
 {13.2,
-"autocluster.classic_config.node_type = ram",
-[],[]}
+"autocluster.node_type = ram",
+[{rabbit, [
+    {autocluster, [{node_type,ram}]}
+]}],[]}
 ,
 {14,
 "tcp_listen_options.backlog = 128
@@ -713,7 +717,7 @@ web_stomp.ssl.password   = changeme",
 [{rabbitmq_web_stomp,
     [{sockjs_opts, [{sockjs_url, "https://cdn.jsdelivr.net/sockjs/0.3.4/sockjs.min.js"}]}]}],
 [rabbitmq_web_stomp]},
-{69, 
+{69,
 "auth_backends.1 = http
 rabbitmq_auth_backend_http.user_path     = http://some-server/auth/user
 rabbitmq_auth_backend_http.vhost_path    = http://some-server/auth/vhost
@@ -741,5 +745,28 @@ tcp_listen_options.linger.timeout = 100",
 {74,
 "tcp_listen_options.linger.timeout = 100",
 [{rabbit, [{tcp_listen_options, [{linger, {false, 100}}]}]}],
-[]}
+[]},
+
+{75,
+"autocluster.dns.hostname = 192.168.0.2.xip.io
+autocluster.node_type = disc",
+[{rabbit, [
+    {peer_discovery_dns, [{hostname,  <<"192.168.0.2.xip.io">>}]},
+    {autocluster,        [{node_type, disc}]}
+]}],[]}
+,
+
+{75.1,
+"autocluster.dns.hostname = 192.168.0.2.xip.io
+autocluster.node_type = disk",
+[{rabbit, [
+    {peer_discovery_dns, [{hostname,  <<"192.168.0.2.xip.io">>}]},
+    {autocluster,        [{node_type, disc}]}
+]}],[]}
+,
+{75.2,
+"autocluster.node_type = ram",
+[{rabbit, [
+    {autocluster,        [{node_type, ram}]}
+]}],[]}
 ].