nickva commented on a change in pull request #1658: Enable cluster 
auto-assembly through a seedlist
URL: https://github.com/apache/couchdb/pull/1658#discussion_r228279345
 
 

 ##########
 File path: src/mem3/src/mem3_seeds.erl
 ##########
 @@ -0,0 +1,163 @@
+% Licensed under the Apache License, Version 2.0 (the "License"); you may not
+% use this file except in compliance with the License. You may obtain a copy of
+% the License at
+%
+%   http://www.apache.org/licenses/LICENSE-2.0
+%
+% Unless required by applicable law or agreed to in writing, software
+% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+% License for the specific language governing permissions and limitations under
+% the License.
+
+-module(mem3_seeds).
+-behaviour(gen_server).
+
+-export([
+    init/1,
+    handle_call/3,
+    handle_cast/2,
+    handle_info/2,
+    code_change/3,
+    terminate/2
+]).
+
+-export([
+    start_link/0,
+    get_seeds/0,
+    get_status/0
+]).
+
+-record(st, {
+    ready = false,
+    seeds = [],
+    jobref = nil,
+    status = [] % nested proplist keyed on node name
+}).
+
+-define(REPLICATION_INTERVAL, 60000).
+
+start_link() ->
+    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+get_seeds() ->
+    case config:get("cluster", "seedlist") of
+        undefined ->
+            [];
+        List ->
+            Nodes = string:tokens(List, ","),
+            Seeds = [list_to_atom(Node) || Node <- Nodes] -- [node()],
+            mem3_util:rotate_list(node(), Seeds)
+    end.
+
+get_status() ->
+    gen_server:call(?MODULE, get_status).
+
+init([]) ->
+    Seeds = get_seeds(),
+    timer:send_interval(?REPLICATION_INTERVAL, start_replication),
 
 Review comment:
   This will send `start_replication` forever every minute. What is the idea 
behind it? Something like, "once we have a seed list, we'll try to continuously 
replicate dbs from the seed list to our this node". Once we do it one time, 
wouldn't mem3_sync take care of this afterwards. Or this is just to handle 
retries if there are failures?

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