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Bugfix (part II) rare race between just-finished repair and flapping ending

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The prior commit wasn't sufficient: the range of transitions is wider than
assumed by that commit.  So, we take one of two options, with a TODO task
of researching the other option.
This commit is contained in:
Scott Lystig Fritchie 2015-07-07 14:28:45 +09:00
parent 96ca7b7082
commit 0f3d11e1bf
1 changed files with 34 additions and 7 deletions
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41
src/machi_chain_manager1.erl
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@ -1417,21 +1417,48 @@ react_to_env_C100(P_newprop, P_latest,
?REACT({c100, ?LINE, [sane]}),
erase(perhaps_reset_loop),
react_to_env_C110(P_latest, S);
_AnyOtherReturnValue ->
{expected_author2,_ExpectedAuthor2}=_ExpectedErr ->
case get(perhaps_reset_loop) of
undefined ->
put(perhaps_reset_loop, 1);
put(perhaps_reset_loop, 1),
?REACT({c100, ?LINE, [not_sane, get(why2), _ExpectedErr]}),
react_to_env_C300(P_newprop, P_latest, S);
X when X > 15 ->
Msg = lists:flatten(
io_lib:format("~P", [get(react), 300])),
exit({not_supposed_to_happen, ?MODULE, ?LINE, Msg});
%% Ha, yes, this is possible. For example:
%% outer: author=e,upi=[b,a,d],repair=[c,e]
%% inner: author=e,upi=[b,e], repair=[]
%% In this case, the transition from inner to outer by A30
%% has chosen the wrong author. We have two choices.
%% 1. Accept this transition, because it really was the
%% safe & transition-approved UPI+repeairing that we
%% were using while we were flapping. I'm 99% certain
%% that this is safe. TODO: Verify
%% 2. I'm not yet 100% certain that #1 is safe, so instead
%% we fall back to the one thing that we know is safe:
%% the 'none' projection, which lets the chain rebuild
%% itself normally during future iterations.
#projection_v1{epoch_number=Epoch_latest,
all_members=All_list,
members_dict=MembersDict} = P_latest,
P_none0 = make_none_projection(MyName, All_list, MembersDict),
P_none1 = P_none0#projection_v1{epoch_number=Epoch_latest},
Dbg = [{none_projection,true}],
P_none = machi_projection:update_checksum(
P_none1#projection_v1{dbg=Dbg}),
io:format(user, "YO: looping transition forced to none!\nNewProp: ~w\nLatest: ~w\nNone: ~w\n", [machi_projection:make_summary(P_newprop), machi_projection:make_summary(P_latest), machi_projection:make_summary(P_none)]),
%% Recurse to self!
react_to_env_C100(P_none, P_none, S);
X ->
put(perhaps_reset_loop, X+1)
end,
put(perhaps_reset_loop, X+1),
?REACT({c100, ?LINE, [not_sane, get(why2), _ExpectedErr]}),
react_to_env_C300(P_newprop, P_latest, S)
end;
_AnyOtherReturnValue ->
%% P_latest is not sane.
%% By process of elimination, P_newprop is best,
%% so let's write it.
?REACT({c100, ?LINE, [not_sane, get(why2), _AnyOtherReturnValue]}),
erase(perhaps_reset_loop),
react_to_env_C300(P_newprop, P_latest, S)
end.