leveled/src/leveled_pmem.erl

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%% -------- PENCILLER MEMORY ---------
%%
%% Module that provides functions for maintaining the L0 memory of the
%% Penciller.
%%
%% It is desirable that the L0Mem can efficiently handle the push of new trees
%% whilst maintaining the capability to quickly snapshot the memory for clones
%% of the Penciller.
%%
%% ETS tables are not used due to complications with managing their mutability,
%% as the database is snapshotted.
%%
%% An attempt was made to merge all trees into a single tree on push (in a
%% spawned process), but this proved to have an expensive impact as the tree
%% got larger.
%%
%% This approach is to keep a list of trees which have been received in the
%% order which they were received. There is then a fixed-size array of hashes
%% used to either point lookups at the right tree in the list, or inform the
%% requestor it is not present avoiding any lookups.
%%
%% Tests show this takes one third of the time at push (when compared to
%% merging to a single tree), and is an order of magnitude more efficient as
%% the tree reaches peak size. It is also an order of magnitude more
%% efficient to use the hash index when compared to looking through all the
%% trees.
%%
%% Total time for single_tree 217000 microseconds
%% Total time for array_tree 209000 microseconds
%% Total time for array_list 142000 microseconds
%% Total time for array_filter 69000 microseconds
%% List of 2000 checked without array - success count of 90 in 36000 microsecs
%% List of 2000 checked with array - success count of 90 in 1000 microsecs
%%
%% The trade-off taken with the approach is that the size of the L0Cache is
%% uncertain. The Size count is incremented if the hash is not already
%% present, so the size may be lower than the actual size due to hash
%% collisions
-module(leveled_pmem).
-include("include/leveled.hrl").
-export([
add_to_index/5,
to_list/2,
new_index/0,
check_levelzero/3,
merge_trees/4
]).
-include_lib("eunit/include/eunit.hrl").
-define(SLOT_WIDTH, {2048, 11}).
-define(SKIP_WIDTH, 32).
-define(INFINITE_KEY, {null, null, null, null, null}).
-define(EMPTY_SKIPLIST, [{?INFINITE_KEY, []}]).
%%%============================================================================
%%% API
%%%============================================================================
add_to_index(L0Index, L0Size, LevelMinus1, LedgerSQN, TreeList) ->
SW = os:timestamp(),
SlotInTreeList = length(TreeList) + 1,
FoldFun = fun({K, V}, {AccMinSQN, AccMaxSQN, AccCount, HashIndex}) ->
SQN = leveled_codec:strip_to_seqonly({K, V}),
{Hash, Slot} = hash_to_slot(K),
L = array:get(Slot, HashIndex),
Count0 = case lists:keymember(Hash, 1, L) of
true ->
AccCount;
false ->
AccCount + 1
end,
{min(SQN, AccMinSQN),
max(SQN, AccMaxSQN),
Count0,
array:set(Slot, [{Hash, SlotInTreeList}|L], HashIndex)}
end,
LM1List = gb_trees:to_list(LevelMinus1),
StartingT = {infinity, 0, L0Size, L0Index},
{MinSQN, MaxSQN, NewL0Size, UpdL0Index} = lists:foldl(FoldFun,
StartingT,
LM1List),
leveled_log:log_timer("PM001", [NewL0Size], SW),
if
MinSQN > LedgerSQN ->
{MaxSQN,
NewL0Size,
UpdL0Index,
lists:append(TreeList, [LevelMinus1])}
end.
to_list(Slots, FetchFun) ->
SW = os:timestamp(),
SlotList = lists:reverse(lists:seq(1, Slots)),
FullList = lists:foldl(fun(Slot, Acc) ->
Tree = FetchFun(Slot),
L = gb_trees:to_list(Tree),
lists:ukeymerge(1, Acc, L)
end,
[],
SlotList),
leveled_log:log_timer("PM002", [length(FullList)], SW),
FullList.
new_index() ->
array:new(element(1, ?SLOT_WIDTH), [{default, []}, fixed]).
check_levelzero(Key, L0Index, TreeList) ->
{Hash, Slot} = hash_to_slot(Key),
CheckList = array:get(Slot, L0Index),
SlotList = lists:foldl(fun({H0, S0}, SL) ->
case H0 of
Hash ->
[S0|SL];
_ ->
SL
end
end,
[],
CheckList),
lists:foldl(fun(SlotToCheck, {Found, KV}) ->
case Found of
true ->
{Found, KV};
false ->
CheckTree = lists:nth(SlotToCheck, TreeList),
case gb_trees:lookup(Key, CheckTree) of
none ->
{Found, KV};
{value, Value} ->
{true, {Key, Value}}
end
end
end,
{false, not_found},
lists:reverse(lists:usort(SlotList))).
merge_trees(StartKey, EndKey, TreeList, LevelMinus1) ->
lists:foldl(fun(Tree, TreeAcc) ->
merge_nexttree(Tree, TreeAcc, StartKey, EndKey) end,
gb_trees:empty(),
lists:append(TreeList, [LevelMinus1])).
%%%============================================================================
%%% SkipList
%%%============================================================================
addhash_to_index(HashIndex, Hash, Slot, Count) ->
L = array:get(Slot, HashIndex),
case lists:member(Hash, L) of
true ->
{HashIndex, Count};
false ->
{array:set(Slot, [Hash|L], HashIndex), Count + 1}
end.
merge_indexes(HashIndex, MergedIndex, Count, L0Slot) ->
lists:foldl(fun(Slot, {MHI, AccCount}) ->
HashList = array:get(Slot, HashIndex),
case length(HashList) > 0 of
true ->
merge_indexes_singleslot(HashList,
Slot,
MHI,
L0Slot,
AccCount);
false ->
{MHI, AccCount}
end end,
{MergedIndex, Count},
lists:seq(0, element(1, ?SLOT_WIDTH) - 1)).
merge_indexes_singleslot(HashList, IndexSlot, MergedIndex, L0Slot, Count) ->
L = array:get(IndexSlot, MergedIndex),
{UpdHL, UpdCount} = lists:foldl(fun(H, {HL, C}) ->
case lists:keymember(H, 1, L) of
true ->
{[{H, L0Slot}|HL], C + 1};
false ->
{[{H, L0Slot}|HL], C}
end end,
{L, Count},
HashList),
{array:set(IndexSlot, UpdHL, MergedIndex), UpdCount}.
skiplist_put(SkipList, Key, Value, Hash) ->
{MarkerKey, SubList} = lists:foldl(fun({Marker, SL}, Acc) ->
case Acc of
false ->
case Marker >= Key of
true ->
{Marker, SL};
false ->
Acc
end;
_ ->
Acc
end end,
false,
SkipList),
case Hash rem ?SKIP_WIDTH of
0 ->
{LHS, RHS} = lists:splitwith(fun({K, _V}) -> K < Key end, SubList),
SkpL1 = lists:keyreplace(MarkerKey, 1, SkipList, {MarkerKey, RHS}),
SkpL2 = [{Key, lists:ukeysort(1, [{Key, Value}|LHS])}|SkpL1],
lists:ukeysort(1, SkpL2);
_ ->
UpdSubList = lists:ukeysort(1, [{Key, Value}|SubList]),
lists:keyreplace(MarkerKey, 1, SkipList, {MarkerKey, UpdSubList})
end.
skiplist_generate(UnsortedKVL) ->
KVL = lists:ukeysort(1, UnsortedKVL),
Slots = length(KVL) div ?SKIP_WIDTH,
SkipList0 = lists:map(fun(X) ->
N = X * ?SKIP_WIDTH,
{K, _V} = lists:nth(N, KVL),
{K, lists:sublist(KVL,
N - ?SKIP_WIDTH + 1,
?SKIP_WIDTH)}
end,
lists:seq(1, length(KVL) div ?SKIP_WIDTH)),
case Slots * ?SKIP_WIDTH < length(KVL) of
true ->
{LastK, _V} = lists:last(KVL),
SkipList0 ++ [{LastK, lists:nthtail(Slots * ?SKIP_WIDTH, KVL)}];
false ->
SkipList0
end.
skiplist_get(SkipList, Key) ->
SubList = lists:foldl(fun({SkipKey, SL}, Acc) ->
case {Acc, SkipKey} of
{null, SkipKey} when SkipKey >= Key ->
SL;
_ ->
Acc
end end,
null,
SkipList),
case SubList of
null ->
not_found;
SubList ->
case lists:keyfind(Key, 1, SubList) of
false ->
not_found;
{Key, V} ->
{Key, V}
end
end.
skiplist_range(SkipList, Start, End) ->
R = lists:foldl(fun({Mark, SL}, {PassedStart, PassedEnd, Acc, PrevList}) ->
case {PassedStart, PassedEnd} of
{true, true} ->
{true, true, Acc, null};
{false, false} ->
case Start > Mark of
true ->
{false, false, Acc, SL};
false ->
RHS = splitlist_start(Start, PrevList ++ SL),
case leveled_codec:endkey_passed(End, Mark) of
true ->
EL = splitlist_end(End, RHS),
{true, true, EL, null};
false ->
{true, false, RHS, null}
end
end;
{true, false} ->
case leveled_codec:endkey_passed(End, Mark) of
true ->
EL = splitlist_end(End, SL),
{true, true, Acc ++ EL, null};
false ->
{true, false, Acc ++ SL, null}
end
end end,
{false, false, [], []},
SkipList),
{_Bool1, _Bool2, SubList, _PrevList} = R,
SubList.
splitlist_start(StartKey, SL) ->
{_LHS, RHS} = lists:splitwith(fun({K, _V}) -> K < StartKey end, SL),
RHS.
splitlist_end(EndKey, SL) ->
{LHS, _RHS} = lists:splitwith(fun({K, _V}) ->
not leveled_codec:endkey_passed(EndKey, K)
end,
SL),
LHS.
%%%============================================================================
%%% Internal Functions
%%%============================================================================
hash_to_slot(Key) ->
H = erlang:phash2(Key),
{H bsr element(2, ?SLOT_WIDTH), H band (element(1, ?SLOT_WIDTH) - 1)}.
merge_nexttree(Tree, TreeAcc, StartKey, EndKey) ->
Iter = gb_trees:iterator_from(StartKey, Tree),
merge_nexttree(Iter, TreeAcc, EndKey).
merge_nexttree(Iter, TreeAcc, EndKey) ->
case gb_trees:next(Iter) of
none ->
TreeAcc;
{Key, Value, NewIter} ->
case leveled_codec:endkey_passed(EndKey, Key) of
true ->
TreeAcc;
false ->
merge_nexttree(NewIter,
gb_trees:enter(Key, Value, TreeAcc),
EndKey)
end
end.
%%%============================================================================
%%% Test
%%%============================================================================
-ifdef(TEST).
generate_randomkeys(Seqn, Count, BucketRangeLow, BucketRangeHigh) ->
generate_randomkeys(Seqn,
Count,
gb_trees:empty(),
BucketRangeLow,
BucketRangeHigh).
generate_randomkeys(_Seqn, 0, Acc, _BucketLow, _BucketHigh) ->
Acc;
generate_randomkeys(Seqn, Count, Acc, BucketLow, BRange) ->
BNumber =
case BRange of
0 ->
string:right(integer_to_list(BucketLow), 4, $0);
_ ->
BRand = random:uniform(BRange),
string:right(integer_to_list(BucketLow + BRand), 4, $0)
end,
KNumber = string:right(integer_to_list(random:uniform(1000)), 4, $0),
{K, V} = {{o, "Bucket" ++ BNumber, "Key" ++ KNumber, null},
{Seqn, {active, infinity}, null}},
generate_randomkeys(Seqn + 1,
Count - 1,
gb_trees:enter(K, V, Acc),
BucketLow,
BRange).
compare_method_test() ->
R = lists:foldl(fun(_X, {LedgerSQN, L0Size, L0Index, L0TreeList}) ->
LM1 = generate_randomkeys(LedgerSQN + 1,
2000, 1, 500),
add_to_index(L0Index, L0Size, LM1, LedgerSQN,
L0TreeList)
end,
{0, 0, new_index(), []},
lists:seq(1, 16)),
{SQN, Size, Index, TreeList} = R,
?assertMatch(32000, SQN),
?assertMatch(true, Size =< 32000),
TestList = gb_trees:to_list(generate_randomkeys(1, 2000, 1, 800)),
S0 = lists:foldl(fun({Key, _V}, Acc) ->
R0 = lists:foldr(fun(Tree, {Found, KV}) ->
case Found of
true ->
{true, KV};
false ->
L0 = gb_trees:lookup(Key, Tree),
case L0 of
none ->
{false, not_found};
{value, Value} ->
{true, {Key, Value}}
end
end
end,
{false, not_found},
TreeList),
[R0|Acc]
end,
[],
TestList),
S1 = lists:foldl(fun({Key, _V}, Acc) ->
R0 = check_levelzero(Key, Index, TreeList),
[R0|Acc]
end,
[],
TestList),
?assertMatch(S0, S1),
StartKey = {o, "Bucket0100", null, null},
EndKey = {o, "Bucket0200", null, null},
SWa = os:timestamp(),
FetchFun = fun(Slot) -> lists:nth(Slot, TreeList) end,
DumpList = to_list(length(TreeList), FetchFun),
Q0 = lists:foldl(fun({K, V}, Acc) ->
P = leveled_codec:endkey_passed(EndKey, K),
case {K, P} of
{K, false} when K >= StartKey ->
gb_trees:enter(K, V, Acc);
_ ->
Acc
end
end,
gb_trees:empty(),
DumpList),
Sz0 = gb_trees:size(Q0),
io:format(user, "Crude method took ~w microseconds resulting in tree of "
++ "size ~w~n",
[timer:now_diff(os:timestamp(), SWa), Sz0]),
SWb = os:timestamp(),
Q1 = merge_trees(StartKey, EndKey, TreeList, gb_trees:empty()),
Sz1 = gb_trees:size(Q1),
io:format(user, "Merge method took ~w microseconds resulting in tree of "
++ "size ~w~n",
[timer:now_diff(os:timestamp(), SWb), Sz1]),
?assertMatch(Sz0, Sz1).
skiplist_test() ->
KL = gb_trees:to_list(generate_randomkeys(1, 4000, 1, 200)),
SWaD = os:timestamp(),
_D = lists:foldl(fun({K, V}, AccD) -> dict:store(K, V, AccD) end,
dict:new(),
KL),
io:format(user, "Loading dict with 4000 keys in ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWaD)]),
SWa = os:timestamp(),
SkipList = skiplist_generate(KL),
io:format(user, "Generating skip list with 4000 keys in ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWa)]),
CheckList1 = lists:sublist(KL, 1200, 100),
CheckList2 = lists:sublist(KL, 1600, 100),
CheckList3 = lists:sublist(KL, 2000, 100),
CheckList4 = lists:sublist(KL, 2400, 100),
CheckList5 = lists:sublist(KL, 2800, 100),
CheckList6 = lists:sublist(KL, 1, 10),
CheckList7 = lists:nthtail(3800, KL),
CheckList8 = lists:sublist(KL, 3000, 1),
CheckAll = CheckList1 ++ CheckList2 ++ CheckList3 ++
CheckList4 ++ CheckList5 ++ CheckList6 ++ CheckList7,
SWb = os:timestamp(),
lists:foreach(fun({K, V}) ->
?assertMatch({K, V}, skiplist_get(SkipList, K))
end,
CheckAll),
io:format(user, "Finding 520 keys took ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWb)]),
SWc = os:timestamp(),
KR1 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList1)),
element(1, lists:last(CheckList1))),
io:format("Result length ~w ~n", [length(KR1)]),
CompareL1 = length(lists:usort(CheckList1)),
?assertMatch(CompareL1, length(KR1)),
KR2 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList2)),
element(1, lists:last(CheckList2))),
CompareL2 = length(lists:usort(CheckList2)),
?assertMatch(CompareL2, length(KR2)),
KR3 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList3)),
element(1, lists:last(CheckList3))),
CompareL3 = length(lists:usort(CheckList3)),
?assertMatch(CompareL3, length(KR3)),
KR4 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList4)),
element(1, lists:last(CheckList4))),
CompareL4 = length(lists:usort(CheckList4)),
?assertMatch(CompareL4, length(KR4)),
KR5 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList5)),
element(1, lists:last(CheckList5))),
CompareL5 = length(lists:usort(CheckList5)),
?assertMatch(CompareL5, length(KR5)),
KR6 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList6)),
element(1, lists:last(CheckList6))),
CompareL6 = length(lists:usort(CheckList6)),
?assertMatch(CompareL6, length(KR6)),
KR7 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList7)),
element(1, lists:last(CheckList7))),
CompareL7 = length(lists:usort(CheckList7)),
?assertMatch(CompareL7, length(KR7)),
KR8 = skiplist_range(SkipList,
element(1, lists:nth(1, CheckList8)),
element(1, lists:last(CheckList8))),
CompareL8 = length(lists:usort(CheckList8)),
?assertMatch(CompareL8, length(KR8)),
KL_OOR1 = gb_trees:to_list(generate_randomkeys(1, 4, 201, 202)),
KR9 = skiplist_range(SkipList,
element(1, lists:nth(1, KL_OOR1)),
element(1, lists:last(KL_OOR1))),
?assertMatch([], KR9),
KL_OOR2 = gb_trees:to_list(generate_randomkeys(1, 4, 0, 0)),
KR10 = skiplist_range(SkipList,
element(1, lists:nth(1, KL_OOR2)),
element(1, lists:last(KL_OOR2))),
?assertMatch([], KR10),
io:format(user, "Finding 10 ranges took ~w microseconds~n",
2016-11-24 23:31:13 +00:00
[timer:now_diff(os:timestamp(), SWc)]),
AltKL = gb_trees:to_list(generate_randomkeys(1, 1000, 1, 200)),
SWd = os:timestamp(),
lists:foreach(fun({K, _V}) ->
skiplist_get(SkipList, K)
end,
AltKL),
io:format(user, "Finding 1000 mainly missing keys took ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWd)]).
hash_index_test() ->
KeyCount = 4000,
SlotWidth = element(1, ?SLOT_WIDTH),
HI0 = new_index(),
MHI0 = new_index(),
KL0 = gb_trees:to_list(generate_randomkeys(1, KeyCount, 1, 200)),
CheckList1 = lists:sublist(KL0, 1200, 100),
CheckList2 = lists:sublist(KL0, 1600, 100),
CheckList3 = lists:sublist(KL0, 2000, 100),
CheckList4 = lists:sublist(KL0, 2400, 100),
CheckList5 = lists:sublist(KL0, 2800, 100),
CheckList6 = lists:sublist(KL0, 1, 10),
CheckList7 = lists:nthtail(3800, KL0),
CheckAll = CheckList1 ++ CheckList2 ++ CheckList3 ++
CheckList4 ++ CheckList5 ++ CheckList6 ++ CheckList7,
SWa = os:timestamp(),
{HashIndex1, SkipList1, _TC} =
lists:foldl(fun({K, V}, {HI, SL, C}) ->
{H, S} = hash_to_slot(K),
{UpdHI, UpdC} = addhash_to_index(HI, H, S, C),
UpdSL = skiplist_put(SL, K, V, H),
{UpdHI, UpdSL, UpdC} end,
{HI0, ?EMPTY_SKIPLIST, 0},
KL0),
io:format(user, "Dynamic load of skiplist took ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWa)]),
{LL, LN} = lists:foldl(fun({K, SL}, {Count, Number}) ->
{Count + length(SL), Number + 1} end,
{0, 0},
SkipList1),
io:format(user,
"Skip list has ~w markers with total members of ~w~n",
[LN, LL]),
?assertMatch(true, LL / LN > ?SKIP_WIDTH / 2 ),
?assertMatch(true, LL / LN < ?SKIP_WIDTH * 2 ),
SWb = os:timestamp(),
lists:foreach(fun({K, V}) ->
?assertMatch({K, V},
skiplist_get(SkipList1, K))
end,
CheckAll),
io:format(user, "Fetching ~w keys from skiplist took ~w microseconds~n",
[KeyCount, timer:now_diff(os:timestamp(), SWb)]),
SWc = os:timestamp(),
{HI1, _C1} = lists:foldl(fun({K, _V}, {HI, C}) ->
{H, S} = hash_to_slot(K),
addhash_to_index(HI, H, S, C) end,
{HI0, 0},
KL0),
io:format(user, "Adding ~w keys to hashindex took ~w microseconds~n",
[KeyCount, timer:now_diff(os:timestamp(), SWc)]),
?assertMatch(SlotWidth, array:size(HI1)),
SWd = os:timestamp(),
{MHI1, TC1} = merge_indexes(HI1, MHI0, 0, 0),
io:format(user, "First merge to hashindex took ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWd)]),
?assertMatch(SlotWidth, array:size(MHI1)),
KL1 = gb_trees:to_list(generate_randomkeys(1, KeyCount, 1, 200)),
SWe = os:timestamp(),
HI2 = new_index(),
{HI3, _C2} = lists:foldl(fun({K, _V}, {HI, C}) ->
{H, S} = hash_to_slot(K),
addhash_to_index(HI, H, S, C) end,
{HI2, 0},
KL1),
io:format(user, "Adding ~w keys to hashindex took ~w microseconds~n",
[KeyCount, timer:now_diff(os:timestamp(), SWe)]),
SWf = os:timestamp(),
{MHI2, TC2} = merge_indexes(HI3, MHI1, TC1, 1),
io:format(user, "Second merge to hashindex took ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWf)]),
?assertMatch(SlotWidth, array:size(MHI2)),
SWg = os:timestamp(),
HI4 = new_index(),
{HI5, _C3} = lists:foldl(fun({K, _V}, {HI, C}) ->
{H, S} = hash_to_slot(K),
addhash_to_index(HI, H, S, C) end,
{HI4, 0},
KL1),
io:format(user, "Adding ~w keys to hashindex took ~w microseconds~n",
[KeyCount, timer:now_diff(os:timestamp(), SWg)]),
SWh = os:timestamp(),
{MHI3, _TC3} = merge_indexes(HI5, MHI2, TC2, 2),
io:format(user, "Third merge to hashindex took ~w microseconds~n",
[timer:now_diff(os:timestamp(), SWh)]),
?assertMatch(SlotWidth, array:size(MHI2)).
-endif.