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Change the way we handle removes with a context #761

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merged 5 commits into from
Dec 18, 2013
Merged

Change the way we handle removes with a context #761

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e61b093
WIP on remove | add fix
russelldb Nov 13, 2013
e0f8f1c
WIP add `remove_all` to split_ops, add test for non-empty ctx
russelldb Nov 21, 2013
fe0fb93
Fix split eqc to set field element removes
russelldb Dec 9, 2013
133f318
WIP eqc for crdt update
russelldb Dec 10, 2013
f503ba4
Remove incomplete EQC test for now
russelldb Dec 13, 2013
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90 changes: 70 additions & 20 deletions src/riak_kv_crdt.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,7 @@

-ifdef(TEST).
-ifdef(EQC).
-export([test_split/0, test_split/1]).
-compile(export_all).
-include_lib("eqc/include/eqc.hrl").
-endif.
-include_lib("eunit/include/eunit.hrl").
Expand Down Expand Up @@ -190,11 +190,11 @@ update_crdt(Dict, Actor, ?CRDT_OP{mod=Mod, op=Ops, ctx=OpCtx}) when Mod==?MAP_TY
error ->
orddict:store(Mod, {undefined, to_record(Mod, InitialVal)}, Dict);
{ok, {Meta, LocalCRDT=?CRDT{value=LocalReplica}}} ->
Merged = Mod:merge(InitialVal, LocalReplica),
case Mod:update(PostOps, Actor, Merged) of
case Mod:update(PostOps, Actor, LocalReplica) of
{error, _}=E -> E;
{ok, NewVal} ->
orddict:store(Mod, {Meta, LocalCRDT?CRDT{value=NewVal}}, Dict)
Merged = Mod:merge(InitialVal, NewVal),
orddict:store(Mod, {Meta, LocalCRDT?CRDT{value=Merged}}, Dict)
end
end
end.
Expand Down Expand Up @@ -238,32 +238,40 @@ fetch_with_default(Mod, Dict) ->
%% essentially as a No Op (for example, and update to a nested Map
%% that has no operations. While this does not affect correctness, it
%% is not ideal.
split_ops(Ops) when is_list(Ops) ->
split_ops(Ops, [], []);
split_ops({AddOp, _}=Op) when AddOp == add;
AddOp == add_all ->
{{update, []}, {update, [Op]}};
split_ops({RemOp, _}=Op) when RemOp == remove;
RemOp == remove_all ->
{{update, [Op]}, {update, []}};
split_ops({update, Ops}) ->
{Pre, Post} = split_ops(Ops),
%% Map or Set update list
{Pre, Post} = split_ops(Ops, [], []),
{{update, Pre}, {update, Post}}.

split_ops([], Pre, Post) ->
{lists:reverse(Pre), lists:reverse(Post)};
split_ops([{remove, _Key}=Op | Rest], Pre, Post) ->
split_ops(Rest, [Op | Pre], Post);
split_ops([{remove_all, _ELems}=Op | Rest], Pre, Post) ->
split_ops([{remove_all, _Elems}=Op | Rest], Pre, Post) ->
split_ops(Rest, [Op | Pre], Post);
split_ops([{update, _Key, {remove, _}}=Op | Rest], Pre, Post) ->
split_ops(Rest, [Op | Pre], Post);
split_ops([{update, {_Name, ?MAP_TYPE}=Key, Op} | Rest], Pre0, Post0) ->
{Pre, Post} = split_ops(Op),
split_ops(Rest, [{update, Key, Pre} | Pre0], [{update, Key, Post} | Post0]);
split_ops([{update, Key, {remove, _}}=Op | Rest], Pre, Post) ->
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So, could this be solved by ensuring that any nested update (whether add or remove) in the map results in an increment to the clock and dot? I guess I'm just concerned that this is a larger issue with riak_dt_map.

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Can you explain the issue?

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Doesn't riak_dt_map already increment its clock and apply the dot to fields that contain nested removes? I guess that's my question.

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Yes, but the remove is applied to the context, so the increment is applied to the context. If the replica local copy has already incremented past that point for the field in question the update loses. That is the purpose of the patch, to ensure that the field update is applied in the adds list.

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So to answer your question: "Yes" and this is how we ensure that.

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Aha, I think I see now.

split_ops(Rest, [Op | Pre], [{add, Key} | Post]);
split_ops([{update, Key, {remove_all, _}}=Op | Rest], Pre, Post) ->
split_ops(Rest, [Op | Pre], [{add, Key} | Post]);
split_ops([{update, {_Name, _}=Key, {update, Ops}} | Rest], Pre0, Post0) when is_list(Ops) ->
{Pre, Post} = split_ops(Ops,[], []),
Pre1 = maybe_prepend(Key, Pre, Pre0),
Post1 = maybe_prepend(Key, Post, Post0),
split_ops(Rest, Pre1, [{add, Key} | Post1]);
split_ops([Op | Rest], Pre, Post) ->
split_ops(Rest, Pre, [Op | Post]).


maybe_prepend(_Key, [], Acc) ->
Acc;
maybe_prepend(Key, Ops, Acc) ->
[{update,Key,{update, Ops}} | Acc].
%% This uses an exported but marked INTERNAL
%% function of `riak_object:set_contents' to preserve
%% non-crdt sibling values and Metadata
Expand Down Expand Up @@ -417,6 +425,46 @@ get_context(Type, Value) ->
%% ===================================================================
-ifdef(TEST).

pre_post_test() ->
M = riak_dt_map:new(),
{ok, M2} = riak_dt_map:update({update, [{update, {<<"s">>, riak_dt_orswot}, {add_all, [<<"a">>, <<"b">>, <<"c">>]}}]}, a, M),
Context = M2,
{ok, M3} = riak_dt_map:update({update, [{update, {<<"s">>, riak_dt_orswot}, {add, [<<"d">>]}}]}, a, M2),
{ok, M4} = riak_dt_map:update({update, [{remove, {<<"s">>, riak_dt_orswot}}]}, a, M3),
Op = {update, [{update, {<<"s">>, riak_dt_orswot}, {remove, <<"a">>}}]},
{Pre, Post} = split_ops(Op),
?debugFmt("Pre ~p~n post ~p~n", [Pre,Post]),
{ok, PreMerge} = riak_dt_map:update(Pre, a, Context),
Local = M4,
{ok, Local2} = riak_dt_map:update(Post, a, Local),
PostMerge = riak_dt_map:merge(PreMerge, Local2),
?debugFmt("local ~p~n", [PostMerge]),
%% Set field should be present, since it's a field update (an
%% element remove) "concurrent" with field removal.
%% Expect the field to be present, and it's value to be [b,c]
Set = riak_dt_map:value({get, {<<"s">>, riak_dt_orswot}}, PostMerge),
?assertNot(error == Set),
?assertEqual([<<"b">>, <<"c">>], lists:sort(Set)).

pre_post_empty_test() ->
M = riak_dt_map:new(),
{ok, M2} = riak_dt_map:update({update, [{update, {<<"s">>, riak_dt_orswot}, {add_all, [<<"a">>, <<"b">>, <<"c">>]}}]}, a, M),
Context = M2,
Op = {update, [{update, {<<"s">>, riak_dt_orswot}, {remove, <<"a">>}}]},
{Pre, Post} = split_ops(Op),
?debugFmt("Pre ~p~n post ~p~n", [Pre,Post]),
{ok, PreMerge} = riak_dt_map:update(Pre, a, Context),
Local = M,
{ok, Local2} = riak_dt_map:update(Post, a, Local),
PostMerge = riak_dt_map:merge(PreMerge, Local2),
?debugFmt("local ~p~n", [PostMerge]),
%% Set field should be present, since it's a field update (an
%% element remove) "concurrent" with field removal.
%% Expect the field to be present, and it's value to be [b,c]
Set = riak_dt_map:value({get, {<<"s">>, riak_dt_orswot}}, PostMerge),
?assertNot(error == Set),
?assertEqual([<<"b">>, <<"c">>], lists:sort(Set)).

-ifdef(EQC).
-define(QC_OUT(P),
eqc:on_output(fun(Str, Args) ->
Expand Down Expand Up @@ -444,13 +492,11 @@ prop_split() ->
io:format("Split Pre ~p~n", [Pre]),
io:format("Split Post ~p~n", [Post])
end,
collect(length(AgOps),
collect(depth(AgOps, 0),
collect(with_title("operation length"), length(AgOps),
collect(with_title("operation depth"), depth(AgOps, 0),
conjunction([
{pre, only_rem_ops(Pre)},
{pre_depth, equals(depth(Pre, 0), depth(AgOps, 0))},
{post, only_add_ops(Post)},
{post_depth, equals(depth(Post, 0), depth(AgOps, 0))}
{post, only_add_ops(Post)}
])))
)
end).
Expand Down Expand Up @@ -489,13 +535,17 @@ only_rem_ops({update, Ops}) ->
only_rem_ops(Ops) ->
only_type_ops(fun is_rem_op/1, Ops).

is_add_op({update, {_Name, ?MAP_TYPE}, {update, Ops}}) ->
is_add_op({update, {_Name, _}, {update, Ops}}) ->
only_add_ops(Ops);
is_add_op(Op) ->
not is_rem_op(Op).

is_rem_op({update, {_Name, ?MAP_TYPE}, {update, Ops}}) ->
is_rem_op({update, {_Name, _}, {update, Ops}}) ->
only_rem_ops(Ops);
is_rem_op({update, {_Name, _}, {remove, _E}}) ->
true;
is_rem_op({update, {_Name, _}, {remove_all, _Es}}) ->
true;
is_rem_op({remove, _Key}) ->
true;
is_rem_op({remove_all, _Elems}) ->
Expand Down