Switch to merklet

Still a WIP
This commit is contained in:
Mark Allen 2015-10-27 16:33:18 -05:00
parent 7f561f34e0
commit 5e571f6009
2 changed files with 55 additions and 189 deletions

View file

@ -18,18 +18,10 @@
%%
%% -------------------------------------------------------------------
%% @doc This manager maintains a Merkle tree per file per FLU. The leaf
%% nodes are stored in the same manner as the checksum data files, except
%% they are represented as
%%
%% `<<Length:64, Offset:32, 0>>' for unwritten bytes
%% `<<Length:64, Offset:32, 1>>' for trimmed bytes
%% `<<Length:64, Offset:32, Csum/binary>>' for written bytes
%%
%% In this case, the checksum tag is thrown away. The tree feeds these
%% leaf nodes into hashes representing 10 GB ranges, called Level 1. We aim for
%% around %% 10 hashes at level 2, and then 2 hashes level 3 and finally the
%% root.
%% @doc This manager maintains a Merkle tree per file per FLU as implemented
%% by the `merklet' library. Keys are encoded as `<<Offset:64, Size:32>>'
%% values encoded as `<<Tag:8, Csum/binary>>' *or* as <<0>> for unwritten
%% bytes, or <<1>> for trimmed bytes.
-module(machi_merkle_tree_mgr).
-behaviour(gen_server).
@ -41,8 +33,7 @@
start_link/3,
initialize/2,
update/5,
fetch/2,
fetch/3
fetch/2
]).
%% gen_server callbacks
@ -63,24 +54,14 @@
-record(mt, {
filename :: string(),
recalc = true :: boolean(),
root :: 'undefined' | binary(),
lvl1 = [] :: [ binary() ],
lvl2 = [] :: [ binary() ],
lvl3 = [] :: [ binary() ],
leaves = orddict:new() :: mt_entry()
tree :: merklet:tree()
}).
-type mt_entry() :: orddict:orddict().
-define(WRITTEN(Offset, Size, Csum), <<Offset:64/unsigned-big, Size:32/unsigned-big, Csum/binary>>).
-define(TRIMMED(Offset, Size), <<Offset:64/unsigned-big, Size:32/unsigned-big, 1>>).
-define(UNWRITTEN(Offset, Size), <<Offset:64/unsigned-big, Size:32/unsigned-big, 0>>).
-define(CHUNK_SIZE, (10*1024*1024)).
-define(LEVEL_SIZE, 10).
-define(H, sha).
-define(TRIMMED, <<1>>).
-define(UNWRITTEN, <<0>>).
-define(ENCODE(Offset, Size), <<Offset:64/unsigned-big, Size:32/unsigned-big>>).
-define(NEW_MERKLET, undefined).
-define(TIMEOUT, (10*1000)).
%% public API
@ -117,23 +98,11 @@ update(FluName, Filename, Offset, Length, Csum) ->
{update, Filename, Offset, Length, Csum}).
-spec fetch ( FluName :: atom(),
Filename :: string() ) -> {ok, [ Data :: binary() ]}.
%% @doc Returns the entire merkle tree for the given filename.
%% {@link fetch/3}
Filename :: string() ) -> {ok, 'undefined'|merklet:tree()}.
%% @doc Returns the merkle tree for the given filename.
fetch(FluName, Filename) ->
fetch(FluName, Filename, all).
-spec fetch( FluName :: atom(),
Filename :: string(),
Level :: 'root' | 'all'
) -> {ok, [ Data :: binary() ]}.
%% @doc Return the current merkle tree for the given filename.
%% If `root' is specified, returns a list with 1 element, the root
%% checksum of the tree. If `all' is specified, returns a list
%% with all levels.
fetch(FluName, Filename, Level) ->
gen_server:call(make_merkle_tree_mgr_name(FluName),
{fetch, Filename, Level}, ?TIMEOUT).
{fetch, Filename}, ?TIMEOUT).
%% gen_server callbacks
init({FluName, DataDir, Options}) ->
@ -146,8 +115,8 @@ init({FluName, DataDir, Options}) ->
end,
{ok, #state{fluname=FluName, datadir=DataDir, tid = Tid}}.
handle_call({fetch, Filename, Level}, _From, S = #state{ tid = Tid }) ->
Res = handle_fetch(Tid, Filename, Level),
handle_call({fetch, Filename}, _From, S = #state{ tid = Tid }) ->
Res = handle_fetch(Tid, Filename),
{reply, {ok, Res}, S};
handle_call(Req, _From, State) ->
lager:warning("Unknown call: ~p", [Req]),
@ -193,151 +162,47 @@ get_files(DataDir) ->
load_filename(Tid, DataDir, Filename) ->
CsumFile = machi_util:make_checksum_filename(DataDir, Filename),
case file:read_file(CsumFile) of
{error, enoent} ->
insert(Tid, Filename, {0, ?MINIMUM_OFFSET, unwritten});
{ok, Bin} ->
load_bin(Tid, Filename, Bin);
Error ->
throw(Error)
end.
load_bin(Tid, Filename, Bin) ->
{CsumL, _} = machi_csum_table:split_checksum_list_blob_decode(Bin),
iter_csum_list(Tid, Filename, CsumL).
iter_csum_list(Tid, Filename, []) ->
insert(Tid, Filename, {0, ?MINIMUM_OFFSET, unwritten});
iter_csum_list(Tid, Filename, L = [ {Last, _, _} | _ ]) ->
make_insert(Tid, Filename, Last, L).
make_insert(_Tid, _Filename, _Last, []) ->
ok;
%% case where Last offset matches Current, just insert current
make_insert(Tid, Filename, Last, [H={Last, Len, _Csum}|T]) ->
insert(Tid, Filename, H),
make_insert(Tid, Filename, Last+Len, T);
%% case where we have a hole
make_insert(Tid, Filename, Last, [H={Off, Len, _Csum}|T]) ->
Hole = Off - Last,
insert(Tid, Filename, {Last, Hole, unwritten}),
insert(Tid, Filename, H),
make_insert(Tid, Filename, Off+Len, T).
insert(Tid, Filename, {Offset, Length, trimmed}) ->
do_insert(Tid, Filename, Offset, Length, ?TRIMMED(Offset, Length));
insert(Tid, Filename, {Offset, Length, unwritten}) ->
do_insert(Tid, Filename, Offset, Length, ?UNWRITTEN(Offset, Length));
insert(Tid, Filename, {Offset, Length, <<_Tag:8, Csum/binary>>}) ->
do_insert(Tid, Filename, Offset, Length, ?WRITTEN(Offset, Length, Csum)).
do_insert(Tid, Filename, Offset, Length, Csum) ->
MT = case find(Tid, Filename) of
[] ->
#mt{ filename = Filename };
V ->
V
end,
ok = maybe_update(Tid, Offset, Length, Csum, MT),
{ok, T} = machi_csum_table:open(CsumFile, []),
%% docs say that the traversal order of ets:foldl is non-determinstic
%% but hopefully since csum_table uses an ordered set that's not true...
{_LastPosition, M} = machi_csum_table:foldl_chunks(fun insert_csum/2,
{?MINIMUM_OFFSET, ?NEW_MERKLET}, T),
true = ets:insert_new(Tid, #mt{ filename = Filename, tree = M}),
ok = machi_csum_table:close(T),
ok.
maybe_update(Tid, Offset, Length, Csum, MT) ->
case orddict:find({Offset, Length}, MT#mt.leaves) of
error ->
%% range not found in our orddict, so fill it in
do_update(Tid, Offset, Length, Csum, MT);
{ok, Csum} ->
%% trying to insert a value we already have that
%% matches
ok;
{ok, ?UNWRITTEN(Offset, Length)} ->
%% old value was unwritten, now we are filling it in
%% so that's legit
do_update(Tid, Offset, Length, Csum, MT);
{ok, ?TRIMMED(Offset, Length)} ->
%% XXX FIXME
%% Scott - range was trimmed - do we fill it in with new stuff?
ok;
{ok, Other} ->
%% we found a checksum that is different
%% this shouldn't happen because once we write a range, it's written
%% TODO - file corruption? insanity?
lager:error("Tried to update merkle tree for file ~p at offset ~p, length ~p, got checksum ~p and tried to insert ~p",
[MT#mt.filename, Offset, Length, Other, Csum]),
throw({weird, Other})
end.
insert_csum({Last, Size, _Csum}=In, {Last, MT}) ->
%% no gap here, insert a record
{Last+Size, update_merkle_tree(In, MT)};
insert_csum({Offset, Size, _Csum}=In, {Last, MT}) ->
%% gap here, insert unwritten record
%% *AND* insert written record
Hole = Offset - Last,
MT0 = update_merkle_tree({Last, Hole, unwritten}, MT),
{Offset+Size, update_merkle_tree(In, MT0)}.
do_update(Tid, Offset, Length, Csum, MT) ->
D = orddict:store({Offset, Length}, Csum, MT#mt.leaves),
true = ets:insert(Tid, MT#mt{ recalc = true, leaves = D }),
ok.
handle_fetch(Tid, Filename, root) ->
case find(Tid, Filename) of
[] -> undefined;
#mt{ root = undefined } -> undefined;
#mt{ recalc = true } = MT -> hd(build_tree(Tid, MT));
#mt{ root = R, recalc = false } -> R
end;
handle_fetch(Tid, Filename, all) ->
case find(Tid, Filename) of
[] -> undefined;
#mt{ recalc = true } = MT -> build_tree(Tid, MT);
#mt{ recalc = false,
root = R,
lvl1 = L1,
lvl2 = L2,
lvl3 = L3 } -> [ R, L3, L2, L1 ]
end.
find(Tid, Filename) ->
insert(Tid, Filename, Term) ->
case ets:lookup(Tid, Filename) of
[] -> [];
[R] -> R
[] -> error(not_found); %% TODO: Something better?
[R] ->
NewMT = update_merkle_tree(Term, R#mt.tree),
%% we choose update_element because it
%% makes atomic changes so it is concurrent
%% safe. The regular 'insert' function
%% does not provide that guarantee.
true = ets:update_element(Tid, Filename, {#mt.tree, NewMT}),
ok
end.
build_tree(Tid, MT = #mt{ leaves = D }) ->
Leaves = lists:map(fun map_dict/1, orddict:to_list(D)),
io:format(user, "Leaves: ~p~n", [Leaves]),
Lvl1s = build_level_1(?CHUNK_SIZE, Leaves, 1, [ crypto:hash_init(?H) ]),
io:format(user, "Lvl1: ~p~n", [Lvl1s]),
Mod2 = length(Lvl1s) div ?LEVEL_SIZE,
Lvl2s = build_int_level(Mod2, Lvl1s, 1, [ crypto:hash_init(?H) ]),
io:format(user, "Lvl2: ~p~n", [Lvl2s]),
Mod3 = length(Lvl2s) div 2,
Lvl3s = build_int_level(Mod3, Lvl2s, 1, [ crypto:hash_init(?H) ]),
io:format(user, "Lvl3: ~p~n", [Lvl3s]),
Root = build_root(Lvl3s, crypto:hash_init(?H)),
io:format(user, "Root: ~p~n", [Root]),
ets:insert(Tid, MT#mt{ root = Root, lvl1 = Lvl1s, lvl2 = Lvl2s, lvl3 = Lvl3s, recalc = false }),
[Root, Lvl3s, Lvl2s, Lvl1s].
build_root([], Ctx) ->
crypto:hash_final(Ctx);
build_root([H|T], Ctx) ->
build_root(T, crypto:hash_update(Ctx, H)).
build_int_level(_Mod, [], _Cnt, [ Ctx | Rest ]) ->
lists:reverse( [ crypto:hash_final(Ctx) | Rest ] );
build_int_level(Mod, [H|T], Cnt, [ Ctx | Rest ]) when Cnt rem Mod == 0 ->
NewCtx = crypto:hash_init(?H),
build_int_level(Mod, T, Cnt + 1, [ crypto:hash_update(NewCtx, H), crypto:hash_final(Ctx) | Rest ]);
build_int_level(Mod, [H|T], Cnt, [ Ctx | Rest ]) ->
build_int_level(Mod, T, Cnt+1, [ crypto:hash_update(Ctx, H) | Rest ]).
map_dict({{Offset, Len}, Hash}) ->
{Offset + Len, Hash}.
build_level_1(_Size, [], _Multiple, [ Ctx | Rest ]) ->
lists:reverse([ crypto:hash_final(Ctx) | Rest ]);
build_level_1(Size, [{Pos, Hash}|T], Multiple, [ Ctx | Rest ]) when Pos > ( Size * Multiple ) ->
NewCtx = crypto:hash_init(?H),
build_level_1(Size, T, Multiple+1,
[ crypto:hash_update(NewCtx, Hash), crypto:hash_final(Ctx) | Rest ]);
build_level_1(Size, [{Pos, Hash}|T], Multiple, [ Ctx | Rest ]) when Pos =< ( Size * Multiple ) ->
io:format(user, "Size: ~p, Pos: ~p, Multiple: ~p~n", [Size, Pos, Multiple]),
build_level_1(Size, T, Multiple, [ crypto:hash_update(Ctx, Hash) | Rest ]).
handle_fetch(Tid, Filename) ->
case ets:lookup(Tid, Filename) of
[] -> undefined;
[R] -> R#mt.tree
end.
update_merkle_tree({Offset, Size, unwritten}, MT) ->
merklet:insert({?ENCODE(Offset, Size), ?UNWRITTEN}, MT);
update_merkle_tree({Offset, Size, trimmed}, MT) ->
merklet:insert({?ENCODE(Offset, Size), ?TRIMMED}, MT);
update_merkle_tree({Offset, Size, Csum}, MT) ->
merklet:insert({?ENCODE(Offset, Size), Csum}, MT).

View file

@ -91,8 +91,9 @@ test() ->
_ = machi_merkle_tree_mgr:start_link(test, ".", []),
machi_merkle_tree_mgr:initialize(test, ?TESTFILE),
timer:sleep(1000),
Root = machi_merkle_tree_mgr:fetch(test, ?TESTFILE, root),
?debugFmt("Root: ~p~n", [Root]),
All = machi_merkle_tree_mgr:fetch(test, ?TESTFILE),
?debugFmt("All: ~p~n", [All]),
timer:sleep(1000),
All = machi_merkle_tree_mgr:fetch(test, ?TESTFILE),
?debugFmt("All: ~p~n", [All]),
ok.