[GitHub] iilyak commented on a change in pull request #484: Apply random jitter during initial _replicator shard discovery

[gi...@git.apache.org]

iilyak commented on a change in pull request #484: Apply random jitter during initial _replicator shard discovery
URL: https://github.com/apache/couchdb/pull/484#discussion_r115071025
 
 

 ##########
 File path: src/couch/src/couch_multidb_changes.erl
 ##########
 @@ -257,40 +257,54 @@ scan_all_dbs(Server, DbSuffix) when is_pid(Server) ->
     {ok, Db} = mem3_util:ensure_exists(
         config:get("mem3", "shards_db", "_dbs")),
     ChangesFun = couch_changes:handle_changes(#changes_args{}, nil, Db, nil),
-    ChangesFun(fun({change, {Change}, _}, _) ->
-        DbName = couch_util:get_value(<<"id">>, Change),
-        case DbName of
-            <<"_design/", _/binary>> ->
-                ok;
-            _Else ->
-                case couch_replicator_utils:is_deleted(Change) of
-                    true ->
-                        ok;
-                    false ->
-                        [gen_server:cast(Server, {resume_scan, ShardName})
-                         || ShardName <- filter_shards(DbName, DbSuffix)],
-                        ok
-                end
-        end;
-        (_, _) -> ok
-    end),
+    ChangesFun({fun scan_changes_cb/3, {Server, DbSuffix, 1}}),
     couch_db:close(Db).
 
 
-filter_shards(DbName, DbSuffix) ->
-    case DbSuffix =:= couch_db:dbname_suffix(DbName) of
-    false ->
-        [];
-    true ->
-        try
-            [ShardName || #shard{name = ShardName} <- mem3:local_shards(DbName)]
-        catch
-            error:database_does_not_exist ->
-                []
+scan_changes_cb({change, {Change}, _}, _, {_Server, DbSuffix, _Count} = Acc) ->
+    DbName = couch_util:get_value(<<"id">>, Change),
+    case DbName of <<"_design/", _/binary>> -> Acc; _Else ->
+        NameMatch = DbSuffix =:= couch_db:dbname_suffix(DbName),
+        case {NameMatch, couch_replicator_utils:is_deleted(Change)} of
+            {false, _} ->
+                Acc;
+            {true, true} ->
+                Acc;
+            {true, false} ->
+                Shards = local_shards(DbName),
+                lists:foldl(fun notify_fold/2, Acc, Shards)
         end
+    end;
+scan_changes_cb(_, _, Acc) ->
+    Acc.
+
+
+local_shards(DbName) ->
+    try
+        [ShardName || #shard{name = ShardName} <- mem3:local_shards(DbName)]
+    catch
+        error:database_does_not_exist ->
+            []
     end.
 
 
+notify_fold(DbName, {Server, DbSuffix, Count}) ->
+    Jitter = jitter(Count),
+    spawn_link(fun() ->
 
 Review comment:
   We might want to seed random somehow. 
 
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on GitHub and use the
URL above to go to the specific comment.
 
For queries about this service, please contact Infrastructure at:
users@infra.apache.org


With regards,
Apache Git Services