rnewson commented on code in PR #5558:
URL: https://github.com/apache/couchdb/pull/5558#discussion_r2161288682
##########
src/fabric/src/fabric_drop_seq.erl:
##########
@@ -0,0 +1,1020 @@
+-module(fabric_drop_seq).
+
+-include_lib("mem3/include/mem3.hrl").
+-include_lib("couch/include/couch_db.hrl").
+-include_lib("couch_mrview/include/couch_mrview.hrl").
+-include_lib("stdlib/include/assert.hrl").
+
+-export([go/1]).
+
+-export([
+ create_peer_checkpoint_doc_if_missing/5,
+ update_peer_checkpoint_doc/5,
+ cleanup_peer_checkpoint_docs/3,
+ peer_checkpoint_doc/4,
+ peer_id_from_sig/2
+]).
+
+%% rpc
+-export([gather_drop_seq_info_rpc/1]).
+
+-type range() :: [non_neg_integer()].
+
+-type uuid() :: binary().
+
+-type seq() :: non_neg_integer().
+
+-type uuid_map() :: #{{Range :: range(), Node :: node()} => uuid()}.
+
+-type peer_checkpoints() :: #{{range(), Node :: node()} => {Uuid :: uuid(),
Seq :: seq()}}.
+
+-type history_item() :: {
+ SourceUuid :: uuid(), SourceSeq :: seq(), TargetUuid :: uuid(), TargetSeq
:: seq()
+}.
+
+-type shard_sync_history() :: #{
+ {Range :: range(), SourceNode :: node(), TargetNode :: node()} =>
[history_item()]
+}.
+
+-define(START_KEY(SubType), <<?LOCAL_DOC_PREFIX, "peer-checkpoint-",
SubType/binary, "-">>).
+-define(END_KEY(SubType), <<?LOCAL_DOC_PREFIX, "peer-checkpoint-",
SubType/binary, ".">>).
+
+go(DbName) ->
+ Shards0 = mem3:shards(DbName),
+ case gather_drop_seq_info(Shards0) of
+ {error, Reason} ->
+ {error, Reason};
+ {ok, #{
+ uuid_map := UuidMap,
+ peer_checkpoints := PeerCheckpoints,
+ shard_sync_history := ShardSyncHistory
+ }} ->
+ Shards1 = fully_replicated_shards_only(Shards0, ShardSyncHistory),
+ DropSeqs = calculate_drop_seqs(
+ Shards0, UuidMap, PeerCheckpoints, ShardSyncHistory
+ ),
+ Workers = lists:filtermap(
+ fun(Shard) ->
+ #shard{range = Range, node = Node, name = ShardName} =
Shard,
+ case maps:find({Range, Node}, DropSeqs) of
+ {ok, {_UuidPrefix, 0}} ->
+ false;
+ {ok, {UuidPrefix, DropSeq}} ->
+ Ref = rexi:cast(
+ Node,
+ {fabric_rpc, set_drop_seq, [
+ ShardName, UuidPrefix, DropSeq,
[?ADMIN_CTX]
+ ]}
+ ),
+ {true, Shard#shard{ref = Ref, opts = [{drop_seq,
DropSeq}]}};
+ error ->
+ false
+ end
+ end,
+ Shards1
+ ),
+ if
+ Workers == [] ->
+ %% nothing to do
+ {ok, #{}};
+ true ->
+ RexiMon = fabric_util:create_monitors(Shards1),
+ Acc0 = {#{}, length(Workers) - 1},
+ try
+ case
+ fabric_util:recv(
+ Workers, #shard.ref, fun
handle_set_drop_seq_reply/3, Acc0
+ )
+ of
+ {ok, Results} ->
+ {ok, Results};
+ {timeout, {WorkersDict, _}} ->
+ DefunctWorkers =
fabric_util:remove_done_workers(
+ WorkersDict,
+ nil
+ ),
+ fabric_util:log_timeout(
+ DefunctWorkers,
+ "set_drop_seq"
+ ),
+ {error, timeout};
+ {error, Reason} ->
+ {error, Reason}
+ end
+ after
+ rexi_monitor:stop(RexiMon)
+ end
+ end
+ end.
+
+-spec calculate_drop_seqs([#shard{}], uuid_map(), peer_checkpoints(),
shard_sync_history()) ->
+ peer_checkpoints().
+calculate_drop_seqs(Shards, UuidMap, PeerCheckpoints0, ShardSyncHistory) ->
+ PeerCheckpoints1 = substitute_splits(Shards, UuidMap, PeerCheckpoints0),
+ PeerCheckpoints2 = crossref(PeerCheckpoints1, ShardSyncHistory),
+ ShardSyncCheckpoints = latest_shard_sync_checkpoints(ShardSyncHistory),
+ maps:merge_with(fun merge_peers/3, PeerCheckpoints2, ShardSyncCheckpoints).
+
+handle_set_drop_seq_reply(ok, Worker, {Results0, Waiting}) ->
+ DropSeq = proplists:get_value(drop_seq, Worker#shard.opts),
+ [B, E] = Worker#shard.range,
+ BHex = couch_util:to_hex_bin(<<B:32/integer>>),
+ EHex = couch_util:to_hex_bin(<<E:32/integer>>),
+ Range = <<BHex/binary, "-", EHex/binary>>,
+ Results1 = maps:merge_with(
+ fun(_Key, Val1, Val2) ->
+ maps:merge(Val1, Val2)
+ end,
+ Results0,
+ #{Range => #{Worker#shard.node => DropSeq}}
+ ),
+ if
+ Waiting == 0 ->
+ {stop, Results1};
+ true ->
+ {ok, {Results1, Waiting - 1}}
+ end;
+handle_set_drop_seq_reply(Error, _, _Acc) ->
+ {error, Error}.
+
+crossref(PeerCheckpoints0, ShardSyncHistory) ->
+ PeerCheckpoints1 = maps:fold(
+ fun({Range, Node}, {Uuid, Seq}, Acc1) ->
+ Others = maps:filter(
+ fun({R, S, _T}, _History) -> R == Range andalso S == Node end,
ShardSyncHistory
+ ),
+ if
+ Seq == 0 ->
+ %% propogate any 0 checkpoint as they would not be
+ %% matched in shard sync history.
+ maps:fold(
+ fun({R, _S, T}, _History, Acc2) ->
+ maps:merge_with(fun merge_peers/3, #{{R, T} =>
{<<>>, 0}}, Acc2)
+ end,
+ Acc1,
+ Others
+ );
+ true ->
+ maps:fold(
+ fun({R, _S, T}, History, Acc2) ->
+ case
+ lists:search(
+ fun({SU, SS, _TU, _TS}) ->
+ uuids_match([Uuid, SU]) andalso SS =<
Seq
Review Comment:
that's a good idea. it's the `SS =< Seq` condition that matters ("find the
most recent checkpoint that includes the seq I care about"), the uuid check is
a safeguard.
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