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.
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