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Enforce write-once property #1

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jadeallenx wants to merge 20 commits from mra/write-once into master
pull from: mra/write-once
merge into: greg:master
Conversation 2 Commits 20 Files changed 13 +259 -113
1 changed files with 259 additions and 113 deletions
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src/machi_file_proxy.erl
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@ -68,6 +68,8 @@
-define(TOO_MANY_ERRORS_RATIO, 50).
-type op_stats() :: { Total :: non_neg_integer(), Errors :: non_neg_integer() }.
-type byte_sequence() :: { Offset :: non_neg_integer(),
Size :: pos_integer()|infinity }.
-record(state, {
data_dir :: string() | undefined,
@ -76,7 +78,8 @@
wedged = false :: boolean(),
csum_file :: string()|undefined,
csum_path :: string()|undefined,
last_write_offset = 0 :: non_neg_integer(),
eof_position = 0 :: non_neg_integer(),
unwritten_bytes = [] :: [byte_sequence()],
data_filehandle :: file:filehandle(),
csum_filehandle :: file:filehandle(),
tref :: reference(), %% timer ref
@ -103,13 +106,15 @@ sync(Pid, Type) ->
gen_server:call(Pid, {sync, Type}, ?TIMEOUT).
% @doc Read file at offset for length
-spec read(Pid :: pid(), Offset :: non_neg_integer(),
Length :: non_neg_integer()) -> {ok, Data :: binary(), Checksum :: binary()}|{error, term()}.
-spec read(Pid :: pid(),
Offset :: non_neg_integer(),
Length :: non_neg_integer()) -> {ok, Data :: binary(), Checksum :: binary()} |
{error, Reason :: term()}.
read(Pid, Offset, Length) ->
gen_server:call(Pid, {read, Offset, Length}, ?TIMEOUT).
% @doc Write data at offset
-spec write(Pid :: pid(), Offset :: non_neg_integer(), Data :: binary()) -> ok.
-spec write(Pid :: pid(), Offset :: non_neg_integer(), Data :: binary()) -> ok|{error, term()}.
write(Pid, Offset, Data) ->
write(Pid, Offset, [], Data).
@ -137,21 +142,14 @@ append(Pid, Data) ->
append(Pid, ClientMeta, Extra, Data) ->
gen_server:call(Pid, {append, ClientMeta, Extra, Data}, ?TIMEOUT).
%% TODO
%% read_repair(Filename, Offset, Data) ???
%% makes sense to me, but we could make the write path serve both purposes
%% I suppose...
%% gen_server callbacks
% @private
init({Filename, DataDir}) ->
CsumFile = machi_util:make_csum_filename(DataDir, Filename),
{_, DPath} = machi_util:make_data_filename(DataDir, Filename),
LastWriteOffset = case parse_csum_file(CsumFile) of
0 -> ?MINIMUM_OFFSET;
V -> V
end,
UnwrittenBytes = parse_csum_file(CsumFile),
{Eof, infinity} = lists:last(UnwrittenBytes),
{ok, FHd} = file:open(DPath, [read, write, binary, raw]),
{ok, FHc} = file:open(CsumFile, [append, binary, raw]),
Tref = schedule_tick(),
@ -163,7 +161,8 @@ init({Filename, DataDir}) ->
data_filehandle = FHd,
csum_filehandle = FHc,
tref = Tref,
last_write_offset = LastWriteOffset}}.
unwritten_bytes = UnwrittenBytes,
eof_position = Eof}}.
handle_call({sync, data}, _From, State = #state{ data_filehandle = FHd }) ->
R = file:sync(FHd),
@ -202,22 +201,23 @@ handle_call({read, _Offset, _Length}, _From,
{reply, {error, wedged}, State#state{writes = {T + 1, Err + 1}}};
handle_call({read, Offset, Length}, _From,
State = #state{last_write_offset = Last,
State = #state{eof_position = Eof,
reads = {T, Err}
}) when Offset + Length > Last ->
}) when Offset + Length > Eof ->
lager:error("Read request at offset ~p for ~p bytes is past the last write offset of ~p",
[Offset, Length, Last]),
[Offset, Length, Eof]),
{reply, {error, not_written}, State = #state{reads = {T + 1, Err + 1}}};
handle_call({read, Offset, Length}, _From,
State = #state{filename = F,
data_filehandle = FH,
unwritten_bytes = U,
reads = {T, Err}
}) ->
Checksum = get({Offset, Length}), %% N.B. Maybe be 'undefined'!
{Resp, NewErr} = case do_read(FH, F, Checksum, Offset, Length) of
{Resp, NewErr} = case handle_read(FH, F, Checksum, Offset, Length, U) of
{ok, Bytes, Csum} ->
{{ok, Bytes, Csum}, Err};
eof ->
@ -236,7 +236,7 @@ handle_call({write, _Offset, _ClientMeta, _Data}, _From,
{reply, {error, wedged}, State#state{writes = {T + 1, Err + 1}}};
handle_call({write, Offset, ClientMeta, Data}, _From,
State = #state{last_write_offset = Last,
State = #state{unwritten_bytes = U,
filename = F,
writes = {T, Err},
data_filehandle = FHd,
@ -246,21 +246,25 @@ handle_call({write, Offset, ClientMeta, Data}, _From,
ClientCsumTag = proplists:get_value(client_csum_tag, ClientMeta, ?CSUM_TAG_NONE),
ClientCsum = proplists:get_value(client_csum, ClientMeta, <<>>),
{Resp, NewErr, NewLast} =
{Resp, NewErr, NewU} =
case check_or_make_tagged_csum(ClientCsumTag, ClientCsum, Data) of
{error, {bad_csum, Bad}} ->
lager:error("Bad checksum on write; client sent ~p, we computed ~p",
[ClientCsum, Bad]),
{{error, bad_csum}, Err + 1, Last};
{{error, bad_csum}, Err + 1, U};
TaggedCsum ->
case handle_write(FHd, FHc, F, TaggedCsum, Offset, Data) of
ok ->
{ok, Err, Last + Offset};
case handle_write(FHd, FHc, F, TaggedCsum, Offset, Data, U) of
{ok, NewU1} ->
{ok, Err, NewU1};
Error ->
{Error, Err + 1, Last}
{Error, Err + 1, U}
end
end,
{reply, Resp, State#state{writes = {T+1, NewErr}, last_write_offset = NewLast}};
{NewEof, infinity} = lists:last(NewU),
{reply, Resp, State#state{writes = {T+1, NewErr},
eof_position = NewEof,
unwritten_bytes = NewU
}};
%% APPENDS
@ -271,7 +275,8 @@ handle_call({append, _ClientMeta, _Extra, _Data}, _From,
{reply, {error, wedged}, State#state{appends = {T+1, Err+1}}};
handle_call({append, ClientMeta, Extra, Data}, _From,
State = #state{last_write_offset = Last,
State = #state{eof_position = EofP,
unwritten_bytes = U,
filename = F,
appends = {T, Err},
data_filehandle = FHd,
@ -280,23 +285,26 @@ handle_call({append, ClientMeta, Extra, Data}, _From,
ClientCsumTag = proplists:get_value(client_csum_tag, ClientMeta, ?CSUM_TAG_NONE),
ClientCsum = proplists:get_value(client_csum, ClientMeta, <<>>),
Size = iolist_size(Data),
{Resp, NewErr, NewLast} =
{Resp, NewErr, NewU} =
case check_or_make_tagged_csum(ClientCsumTag, ClientCsum, Data) of
{error, {bad_csum, Bad}} ->
lager:error("Bad checksum; client sent ~p, we computed ~p",
[ClientCsum, Bad]),
{{error, bad_csum}, Err + 1, Last};
{{error, bad_csum}, Err + 1, U};
TaggedCsum ->
case handle_write(FHd, FHc, F, TaggedCsum, Last, Data) of
ok ->
{{ok, F, Last}, Err, Last + Size + Extra};
case handle_write(FHd, FHc, F, TaggedCsum, EofP, Data, U) of
{ok, NewU1} ->
{{ok, F, EofP}, Err, NewU1};
Error ->
{Error, Err + 1, Last}
{Error, Err + 1, EofP, U}
end
end,
{reply, Resp, State#state{appends = {T+1, NewErr}, last_write_offset = NewLast}};
{NewEof, infinity} = lists:last(NewU),
{reply, Resp, State#state{appends = {T+1, NewErr},
eof_position = NewEof + Extra,
unwritten_bytes = NewU
}};
handle_call(Req, _From, State) ->
lager:warning("Unknown call: ~p", [Req]),
@ -430,34 +438,62 @@ map_offsets_to_csums(CsumList) ->
insert_offsets({Offset, Length, Checksum}) ->
put({Offset, Length}, Checksum).
-spec parse_csum_file( Filename :: string() ) -> [byte_sequence()].
parse_csum_file(Filename) ->
%% using file:read_file works as long as the files are "small"
{ok, CsumData} = file:read_file(Filename),
{DecodedCsums, _Junk} = machi_flu1:split_checksum_list_blob_decode(CsumData),
case DecodedCsums of
[] -> 0;
Sort = lists:sort(DecodedCsums),
case Sort of
[] -> [{?MINIMUM_OFFSET, infinity}];
_ ->
map_offsets_to_csums(DecodedCsums),
{Offset, Size, _Csum} = lists:last(DecodedCsums),
Offset + Size
{First, _, _} = hd(Sort),
build_unwritten_bytes_list(Sort, First, [])
end.
-spec do_read(FHd :: file:filehandle(),
-spec handle_read(FHd :: file:filehandle(),
Filename :: string(),
TaggedCsum :: undefined|binary(),
Offset :: non_neg_integer(),
Size :: non_neg_integer()) -> eof |
{ok, Bytes :: binary(), Csum :: binary()} |
Size :: non_neg_integer(),
Unwritten :: [byte_sequence()]
) -> {ok, Bytes :: binary(), Csum :: binary()} |
eof |
{error, bad_csum} |
{error, partial_read} |
{error, not_written} |
{error, Other :: term() }.
do_read(FHd, Filename, undefined, Offset, Size) ->
do_read(FHd, Filename, machi_util:make_tagged_csum(none), Offset, Size);
% @private Attempt a read operation on the given offset and length.
% <li>
% <ul> If the byte range is not yet written, `{error, not_written}' is
% returned.</ul>
% <ul> If the checksum given does not match what comes off the disk,
% `{error, bad_csum}' is returned.</ul>
% <ul> If the number of bytes that comes off the disk is not the requested length,
% `{error, partial_read}' is returned.</ul>
% <ul> If the offset is at or beyond the current file boundary, `eof' is returned.</ul>
% <ul> If some kind of POSIX error occurs, the OTP version of that POSIX error
% tuple is returned.</ul>
% </li>
%
% On success, `{ok, Bytes, Checksum}' is returned.
handle_read(FHd, Filename, undefined, Offset, Size, U) ->
handle_read(FHd, Filename, machi_util:make_tagged_csum(none), Offset, Size, U);
handle_read(FHd, Filename, TaggedCsum, Offset, Size, U) ->
case is_byte_range_unwritten(Offset, Size, U) of
true ->
{error, not_written};
false ->
do_read(FHd, Filename, TaggedCsum, Offset, Size)
end.
% @private Implements the disk read
do_read(FHd, Filename, TaggedCsum, Offset, Size) ->
case file:pread(FHd, Offset, Size) of
eof ->
eof;
{ok, Bytes} when byte_size(Bytes) == Size ->
{Type, Ck} = machi_util:unmake_tagged_csum(TaggedCsum),
case check_or_make_tagged_csum(Type, Ck, Bytes) of
@ -468,12 +504,10 @@ do_read(FHd, Filename, TaggedCsum, Offset, Size) ->
TaggedCsum ->
{ok, Bytes, TaggedCsum}
end;
{ok, Partial} ->
lager:error("In file ~p, offset ~p, wanted to read ~p bytes, but got ~p",
[Filename, Offset, Size, byte_size(Partial)]),
{error, partial_read};
Other ->
lager:error("While reading file ~p, offset ~p, length ~p, got ~p",
[Filename, Offset, Size, Other]),
@ -485,29 +519,41 @@ do_read(FHd, Filename, TaggedCsum, Offset, Size) ->
Filename :: string(),
TaggedCsum :: binary(),
Offset :: non_neg_integer(),
Data :: binary() ) -> ok |
Data :: binary(),
Unwritten :: [byte_sequence()]
) -> {ok, NewU :: [byte_sequence()]} |
{error, written} |
{error, Reason :: term()}.
handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data) ->
handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data, U) ->
Size = iolist_size(Data),
case is_byte_range_unwritten(Offset, Size, U) of
false ->
case get({Offset, Size}) of
undefined ->
{error, written};
TaggedCsum ->
case do_read(FHd, Filename, TaggedCsum, Offset, Size) of
eof ->
lager:warning("This should never happen: got eof while reading at offset ~p in file ~p that's supposedly written",
[Offset, Filename]),
{error, server_insanity};
{ok, _, _} ->
{ok, U};
_ ->
{error, written}
end
end;
true ->
try
do_write(FHd, FHc, Filename, TaggedCsum, Offset, Size, Data)
do_write(FHd, FHc, Filename, TaggedCsum, Offset, Size, Data, U)
catch
%%% XXX FIXME: be more specific on badmatch that might
%%% occur around line 520 when we write the checksum
%%% occur around line 533 when we write the checksum
%%% file entry for the data blob we just put on the disk
error:Reason ->
{error, Reason}
end;
{ok, _, _} ->
% yep, we did that write! Honest.
ok;
{error, Error} ->
lager:error("During write to ~p, offset ~p, got error ~p; returning {error, written}",
[Filename, Offset, Error]),
{error, written}
end
end.
-spec do_write( FHd :: file:descriptor(),
@ -516,18 +562,118 @@ handle_write(FHd, FHc, Filename, TaggedCsum, Offset, Data) ->
TaggedCsum :: binary(),
Offset :: non_neg_integer(),
Size :: non_neg_integer(),
Data :: binary() ) -> ok|term().
do_write(FHd, FHc, Filename, TaggedCsum, Offset, Size, Data) ->
Data :: binary(),
Unwritten :: [byte_sequence()]
) -> {ok, NewUnwritten :: [byte_sequence()]} |
{error, Reason :: term()}.
do_write(FHd, FHc, Filename, TaggedCsum, Offset, Size, Data, U) ->
case file:pwrite(FHd, Offset, Data) of
ok ->
lager:debug("Successful write in file ~p at offset ~p, length ~p",
[Filename, Offset, Size]),
EncodedCsum = encode_csum_file_entry(Offset, Size, TaggedCsum),
ok = file:write(FHc, EncodedCsum),
lager:debug("Successful write to checksum file for ~p.", [Filename]),
ok;
put({Offset, Size}, TaggedCsum),
NewU = update_unwritten(Offset, Size, U),
lager:debug("Successful write to checksum file for ~p; unwritten bytes are now: ~p",
[Filename, NewU]),
{ok, NewU};
Other ->
lager:error("Got ~p during write to file ~p at offset ~p, length ~p",
[Other, Filename, Offset, Size]),
{error, Other}
end.
-spec is_byte_range_unwritten( Offset :: non_neg_integer(),
Size :: pos_integer(),
Unwritten :: [byte_sequence()] ) -> boolean().
% @private Given an offset and a size, return `true' if a byte range has
% <b>not</b> been written. Otherwise, return `false'.
is_byte_range_unwritten(Offset, Size, Unwritten) ->
case length(Unwritten) of
0 ->
lager:critical("Unwritten byte list has 0 entries! This should never happen."),
false;
1 ->
{Eof, infinity} = hd(Unwritten),
Offset >= Eof;
_ ->
case lookup_unwritten(Offset, Size, Unwritten) of
{ok, _} -> true;
not_found -> false
end
end.
-spec lookup_unwritten( Offset :: non_neg_integer(),
Size :: pos_integer(),
Unwritten :: [byte_sequence()]
) -> {ok, byte_sequence()} | not_found.
% @private Given an offset and a size, scan the list of unwritten bytes and
% look for a "hole" where a write might be allowed if any exist. If a
% suitable byte sequence is found, the function returns a tuple of {ok,
% {Position, Space}} is returned. `not_found' is returned if no suitable
% space is located.
lookup_unwritten(_Offset, _Size, []) ->
not_found;
lookup_unwritten(Offset, _Size, [H={Pos, infinity}|_Rest]) when Offset >= Pos ->
{ok, H};
lookup_unwritten(Offset, Size, [H={Pos, Space}|_Rest])
when Offset >= Pos andalso Offset < Pos+Space
andalso Size =< (Space - (Offset - Pos)) ->
{ok, H};
lookup_unwritten(Offset, Size, [_H|Rest]) ->
lookup_unwritten(Offset, Size, Rest).
-spec update_unwritten( Offset :: non_neg_integer(),
Size :: pos_integer(),
Unwritten :: [byte_sequence()] ) -> NewUnwritten :: [byte_sequence()].
% @private Given an offset, a size and the unwritten byte list, return an updated
% and sorted unwritten byte list accounting for any completed write operation.
update_unwritten(Offset, Size, Unwritten) ->
case lookup_unwritten(Offset, Size, Unwritten) of
not_found ->
lager:error("Couldn't find byte sequence tuple for a write which earlier found a valid spot to write!!! This should never happen!"),
Unwritten;
{ok, {Offset, Size}} ->
%% we neatly filled in our hole...
lists:keydelete(Offset, 1, Unwritten);
{ok, S={Pos, _}} ->
lists:sort(lists:keydelete(Pos, 1, Unwritten) ++
update_byte_range(Offset, Size, S))
end.
-spec update_byte_range( Offset :: non_neg_integer(),
Size :: pos_integer(),
Sequence :: byte_sequence() ) -> Updates :: [byte_sequence()].
% @private Given an offset and size and a byte sequence tuple where a
% write took place, return a list of updates to the list of unwritten bytes
% accounting for the space occupied by the just completed write.
update_byte_range(Offset, Size, {Eof, infinity}) when Offset == Eof ->
[{Offset + Size, infinity}];
update_byte_range(Offset, Size, {Eof, infinity}) when Offset > Eof ->
[{Eof, (Offset - Eof)}, {Offset+Size, infinity}];
update_byte_range(Offset, Size, {Pos, Space}) when Offset == Pos andalso Size < Space ->
[{Offset + Size, Space - Size}];
update_byte_range(Offset, Size, {Pos, Space}) when Offset > Pos ->
[{Pos, Offset - Pos}, {Offset+Size, ( (Pos+Space) - (Offset + Size) )}].
-spec build_unwritten_bytes_list( CsumData :: [{ Offset :: non_neg_integer(),
Size :: pos_integer(),
Checksum :: binary() }],
LastOffset :: non_neg_integer(),
Acc :: list() ) -> [byte_sequence()].
% @private Given a <b>sorted</b> list of checksum data tuples, return a sorted
% list of unwritten byte ranges. The output list <b>always</b> has at least one
% entry: the last tuple in the list is guaranteed to be the current end of
% bytes written to a particular file with the special space moniker
% `infinity'.
build_unwritten_bytes_list([], Last, Acc) ->
NewAcc = [ {Last, infinity} | Acc ],
lists:reverse(NewAcc);
build_unwritten_bytes_list([{CurrentOffset, CurrentSize, _Csum}|Rest], LastOffset, Acc) when
CurrentOffset /= LastOffset ->
Hole = CurrentOffset - LastOffset,
build_unwritten_bytes_list(Rest, (CurrentOffset+CurrentSize), [{LastOffset, Hole}|Acc]);
build_unwritten_bytes_list([{CO, CS, _Ck}|Rest], _LastOffset, Acc) ->
build_unwritten_bytes_list(Rest, CO + CS, Acc).