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-module(fabric_view_changes).
-export([go/5, start_update_notifier/1]).
-include("fabric.hrl").
-include_lib("mem3/include/mem3.hrl").
-include_lib("couch/include/couch_db.hrl").
go(DbName, Feed, Options, Callback, Acc0) when Feed == "continuous" orelse
Feed == "longpoll" ->
Args = make_changes_args(Options),
{ok, Acc} = Callback(start, Acc0),
Notifiers = start_update_notifiers(DbName),
{Timeout, TimeoutFun} = couch_changes:get_changes_timeout(Args, Callback),
try
keep_sending_changes(
DbName,
Args,
Callback,
get_start_seq(DbName, Args),
Acc,
Timeout,
TimeoutFun
)
after
stop_update_notifiers(Notifiers),
couch_changes:get_rest_db_updated()
end;
go(DbName, "normal", Options, Callback, Acc0) ->
Args = make_changes_args(Options),
{ok, Acc} = Callback(start, Acc0),
{ok, #collector{counters=Seqs, user_acc=AccOut}} = send_changes(
DbName,
Args,
Callback,
get_start_seq(DbName, Args),
Acc
),
Callback({stop, pack_seqs(Seqs)}, AccOut).
keep_sending_changes(DbName, Args, Callback, Seqs, AccIn, Timeout, TFun) ->
#changes_args{limit=Limit, feed=Feed} = Args,
{ok, Collector} = send_changes(DbName, Args, Callback, Seqs, AccIn),
#collector{limit=Limit2, counters=NewSeqs, user_acc=AccOut} = Collector,
LastSeq = pack_seqs(NewSeqs),
if Limit > Limit2, Feed == "longpoll" ->
Callback({stop, LastSeq}, AccOut);
true ->
case couch_changes:wait_db_updated(Timeout, TFun) of
updated ->
keep_sending_changes(
DbName,
Args#changes_args{limit=Limit2},
Callback,
LastSeq,
AccIn,
Timeout,
TFun
);
stop ->
Callback({stop, LastSeq}, AccOut)
end
end.
send_changes(DbName, ChangesArgs, Callback, PackedSeqs, AccIn) ->
AllShards = mem3:shards(DbName),
Seqs = lists:flatmap(fun({#shard{name=Name, node=N} = Shard, Seq}) ->
case lists:member(Shard, AllShards) of
true ->
Ref = rexi:cast(N, {fabric_rpc, changes, [Name,ChangesArgs,Seq]}),
[{Shard#shard{ref = Ref}, Seq}];
false ->
% Find some replacement shards to cover the missing range
% TODO It's possible in rare cases of shard merging to end up
% with overlapping shard ranges from this technique
lists:map(fun(#shard{name=Name2, node=N2} = NewShard) ->
Ref = rexi:cast(N2, {fabric_rpc, changes, [Name2,ChangesArgs,0]}),
{NewShard#shard{ref = Ref}, 0}
end, find_replacement_shards(Shard, AllShards))
end
end, unpack_seqs(PackedSeqs, DbName)),
{Workers, _} = lists:unzip(Seqs),
State = #collector{
query_args = ChangesArgs,
callback = Callback,
counters = fabric_dict:init(Workers, 0),
user_acc = AccIn,
limit = ChangesArgs#changes_args.limit,
rows = Seqs % store sequence positions instead
},
try fabric_util:receive_loop(Workers, #shard.ref, fun handle_message/3,
State, infinity, 5000)
after
fabric_util:cleanup(Workers)
end.
handle_message({rexi_DOWN, _, _, _}, nil, State) ->
% TODO see if progress can be made here, possibly by removing all shards
% from that node and checking is_progress_possible
{ok, State};
handle_message({rexi_EXIT, Reason}, Worker, State) ->
?LOG_ERROR("~p rexi_EXIT ~p", [?MODULE, Reason]),
#collector{
callback=Callback,
counters=Counters0,
rows = Seqs0,
user_acc=Acc
} = State,
Counters = fabric_dict:erase(Worker, Counters0),
Seqs = fabric_dict:erase(Worker, Seqs0),
case fabric_view:is_progress_possible(Counters) of
true ->
{ok, State#collector{counters = Counters, rows=Seqs}};
false ->
Callback({error, dead_shards}, Acc),
{error, dead_shards}
end;
handle_message(_, _, #collector{limit=0} = State) ->
{stop, State};
handle_message(#view_row{key=Seq} = Row0, {Worker, From}, St) ->
#collector{
query_args = #changes_args{include_docs=IncludeDocs},
callback = Callback,
counters = S0,
limit = Limit,
user_acc = AccIn
} = St,
case fabric_dict:lookup_element(Worker, S0) of
undefined ->
% this worker lost the race with other partition copies, terminate it
gen_server:reply(From, stop),
{ok, St};
_ ->
S1 = fabric_dict:store(Worker, Seq, S0),
S2 = fabric_view:remove_overlapping_shards(Worker, S1),
Row = Row0#view_row{key = pack_seqs(S2)},
{Go, Acc} = Callback(changes_row(Row, IncludeDocs), AccIn),
gen_server:reply(From, Go),
{Go, St#collector{counters=S2, limit=Limit-1, user_acc=Acc}}
end;
handle_message({complete, EndSeq}, Worker, State) ->
#collector{
counters = S0,
total_rows = Completed % override
} = State,
case fabric_dict:lookup_element(Worker, S0) of
undefined ->
{ok, State};
_ ->
S1 = fabric_dict:store(Worker, EndSeq, S0),
% unlikely to have overlaps here, but possible w/ filters
S2 = fabric_view:remove_overlapping_shards(Worker, S1),
NewState = State#collector{counters=S2, total_rows=Completed+1},
case fabric_dict:size(S2) =:= (Completed+1) of
true ->
{stop, NewState};
false ->
{ok, NewState}
end
end.
make_changes_args(Options) ->
Options.
get_start_seq(_DbName, #changes_args{dir=fwd, since=Since}) ->
Since;
get_start_seq(DbName, #changes_args{dir=rev}) ->
Shards = mem3:shards(DbName),
Workers = fabric_util:submit_jobs(Shards, get_update_seq, []),
{ok, Since} = fabric_util:recv(Workers, #shard.ref,
fun collect_update_seqs/3, fabric_dict:init(Workers, -1)),
Since.
collect_update_seqs(Seq, Shard, Counters) when is_integer(Seq) ->
case fabric_dict:lookup_element(Shard, Counters) of
undefined ->
% already heard from someone else in this range
{ok, Counters};
-1 ->
C1 = fabric_dict:store(Shard, Seq, Counters),
C2 = fabric_view:remove_overlapping_shards(Shard, C1),
case fabric_dict:any(-1, C2) of
true ->
{ok, C2};
false ->
{stop, pack_seqs(C2)}
end
end.
pack_seqs(Workers) ->
SeqList = [{N,R,S} || {#shard{node=N, range=R}, S} <- Workers],
couch_util:encodeBase64Url(term_to_binary(SeqList, [compressed])).
unpack_seqs(0, DbName) ->
fabric_dict:init(mem3:shards(DbName), 0);
unpack_seqs("0", DbName) ->
fabric_dict:init(mem3:shards(DbName), 0);
unpack_seqs(Packed, DbName) ->
% TODO relies on internal structure of fabric_dict as keylist
lists:map(fun({Node, [A,B], Seq}) ->
Shard = #shard{node=Node, range=[A,B], dbname=DbName},
{mem3_util:name_shard(Shard), Seq}
end, binary_to_term(couch_util:decodeBase64Url(Packed))).
start_update_notifiers(DbName) ->
lists:map(fun(#shard{node=Node, name=Name}) ->
{Node, rexi:cast(Node, {?MODULE, start_update_notifier, [Name]})}
end, mem3:shards(DbName)).
% rexi endpoint
start_update_notifier(DbName) ->
{Caller, _} = get(rexi_from),
Fun = fun({_, X}) when X == DbName -> Caller ! db_updated; (_) -> ok end,
Id = {couch_db_update_notifier, make_ref()},
ok = gen_event:add_sup_handler(couch_db_update, Id, Fun),
receive {gen_event_EXIT, Id, Reason} ->
rexi:reply({gen_event_EXIT, DbName, Reason})
end.
stop_update_notifiers(Notifiers) ->
[rexi:kill(Node, Ref) || {Node, Ref} <- Notifiers].
changes_row(#view_row{key=Seq, id=Id, value=Value, doc=deleted}, true) ->
{change, {[{seq,Seq}, {id,Id}, {changes,Value}, {deleted, true}, {doc, null}]}};
changes_row(#view_row{key=Seq, id=Id, value=Value, doc=deleted}, false) ->
{change, {[{seq,Seq}, {id,Id}, {changes,Value}, {deleted, true}]}};
changes_row(#view_row{key=Seq, id=Id, value=Value, doc={error,Reason}}, true) ->
{change, {[{seq,Seq}, {id,Id}, {changes,Value}, {error,Reason}]}};
changes_row(#view_row{key=Seq, id=Id, value=Value, doc=Doc}, true) ->
{change, {[{seq,Seq}, {id,Id}, {changes,Value}, {doc,Doc}]}};
changes_row(#view_row{key=Seq, id=Id, value=Value}, false) ->
{change, {[{seq,Seq}, {id,Id}, {changes,Value}]}}.
find_replacement_shards(#shard{range=Range}, AllShards) ->
% TODO make this moar betta -- we might have split or merged the partition
[Shard || Shard <- AllShards, Shard#shard.range =:= Range].
|
