Add rabbit_quorum_queue:grow/4 function

To allow operators to grow quorum queue clusters with some degree of
selection.

[#162782801]

1 files changed, 51 insertions, 3 deletions

diff --git a/src/rabbit_quorum_queue.erl b/src/rabbit_quorum_queue.erl
index 63b182ef20..08b4eaf5b3 100644
--- a/src/rabbit_quorum_queue.erl
+++ b/src/rabbit_quorum_queue.erl
@@ -37,7 +37,8 @@
 -export([requeue/3]).
 -export([policy_changed/2]).
 -export([cleanup_data_dir/0]).
--export([shrink_all/1]).
+-export([shrink_all/1,
+         grow/4]).
 
 %%-include_lib("rabbit_common/include/rabbit.hrl").
 -include_lib("rabbit.hrl").
@@ -664,7 +665,7 @@ add_member(Q, Node) when ?amqqueue_is_quorum(Q) ->
     %% TODO parallel calls might crash this, or add a duplicate in quorum_nodes
     ServerId = {RaName, Node},
     case ra:start_server(RaName, ServerId, ra_machine(Q),
-                       [{RaName, N} || N <- QNodes]) of
+                         [{RaName, N} || N <- QNodes]) of
         ok ->
             case ra:add_member(ServerRef, ServerId) of
                 {ok, _, Leader} ->
@@ -677,11 +678,15 @@ add_member(Q, Node) when ?amqqueue_is_quorum(Q) ->
                     rabbit_misc:execute_mnesia_transaction(
                       fun() -> rabbit_amqqueue:update(QName, Fun) end),
                     ok;
+                timeout ->
+                    {error, timeout};
                 E ->
                     %% TODO should we stop the ra process here?
                     E
             end;
-        {error, _} = E ->
+        timeout ->
+            {error, timeout};
+        E ->
             E
     end.
 
@@ -734,6 +739,9 @@ delete_member(Q, Node) when ?amqqueue_is_quorum(Q) ->
             end
     end.
 
+-spec shrink_all(node()) ->
+    [{rabbit_amqqueue:name(),
+      {ok, pos_integer()} | {error, pos_integer(), term()}}].
 shrink_all(Node) ->
     [begin
          QName = amqqueue:get_name(Q),
@@ -752,6 +760,46 @@ shrink_all(Node) ->
             amqqueue:get_type(Q) == quorum,
             lists:member(Node, amqqueue:get_quorum_nodes(Q))].
 
+-spec grow(node(), binary(), binary(),
+           all | even) ->
+    [{rabbit_amqqueue:name(),
+      {ok, pos_integer()} | {error, pos_integer(), term()}}].
+grow(Node, VhostSpec, QueueSpec, Strategy) ->
+    ConnectedNodes = [node() | nodes()],
+    [begin
+         QName = amqqueue:get_name(Q),
+         rabbit_log:info("~s: Adding member ~w",
+                         [rabbit_misc:rs(QName), Node]),
+         Size = length(amqqueue:get_quorum_nodes(Q)),
+         case add_member(Q, Node) of
+             ok ->
+                 {QName, {ok, Size + 1}};
+             {error, Err} ->
+                 rabbit_log:warning("~s: Failed to add member ~w, Error ~w",
+                                    [rabbit_misc:rs(QName), Node, Err]),
+                 {QName, {error, Size, Err}}
+         end
+     end
+     || Q <- rabbit_amqqueue:list(),
+        amqqueue:get_type(Q) == quorum,
+        %% don't add a member if there is already one on the node
+        not lists:member(Node, amqqueue:get_quorum_nodes(Q)),
+        %% if the node isn't connected, best not to add it
+        lists:member(Node, ConnectedNodes),
+        matches_strategy(Strategy, amqqueue:get_quorum_nodes(Q)),
+        is_match(amqqueue:get_vhost(Q), VhostSpec) andalso
+        is_match(get_resource_name(amqqueue:get_name(Q)), QueueSpec) ].
+
+get_resource_name(#resource{name  = Name}) ->
+    Name.
+
+matches_strategy(all, _) -> true;
+matches_strategy(even, Members) ->
+    length(Members) rem 2 == 0.
+
+is_match(Subj, E) ->
+   nomatch /= re:run(Subj, E).
+
 
 %%----------------------------------------------------------------------------
 dlx_mfa(Q) ->