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Doc update and clerk<->penciller changes

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Reviewing code to update comments revealed a weakness in the sequence of
events between penciller and clerk committing a manifest change wherby
an ill-timed crash could lead to files being deleted without the
manifest changing.

A different, and safer pattern now used between theses two actors.
This commit is contained in:
martinsumner 2016-10-09 22:33:45 +01:00
parent 4a8a2c1555
commit d2cc07a9eb
4 changed files with 119 additions and 66 deletions
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42
src/leveled_penciller.erl
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@ -7,8 +7,8 @@
%% Ledger.
%% - The Penciller provides re-write (compaction) work up to be managed by
%% the Penciller's Clerk
%% - The Penciller maintains a register of iterators who have requested
%% snapshots of the Ledger
%% - The Penciller can be cloned and maintains a register of clones who have
%% requested snapshots of the Ledger
%% - The accepts new dumps (in the form of lists of keys) from the Bookie, and
%% calls the Bookie once the process of pencilling this data in the Ledger is
%% complete - and the Bookie is free to forget about the data
@ -236,7 +236,7 @@
pcl_fetch/2,
pcl_checksequencenumber/3,
pcl_workforclerk/1,
pcl_promptmanifestchange/1,
pcl_promptmanifestchange/2,
pcl_confirmdelete/2,
pcl_close/1,
pcl_registersnapshot/2,
@ -307,8 +307,8 @@ pcl_checksequencenumber(Pid, Key, SQN) ->
pcl_workforclerk(Pid) ->
gen_server:call(Pid, work_for_clerk, infinity).
pcl_promptmanifestchange(Pid) ->
gen_server:cast(Pid, manifest_change).
pcl_promptmanifestchange(Pid, WI) ->
gen_server:cast(Pid, {manifest_change, WI}).
pcl_confirmdelete(Pid, FileName) ->
gen_server:call(Pid, {confirm_delete, FileName}, infinity).
@ -511,10 +511,11 @@ handle_call(close, _From, State) ->
handle_cast({update_snapshotcache, Tree, SQN}, State) ->
MemTableC = cache_tree_in_memcopy(State#state.memtable_copy, Tree, SQN),
{noreply, State#state{memtable_copy=MemTableC}};
handle_cast(manifest_change, State) ->
{ok, WI} = leveled_pclerk:clerk_returnmanifestchange(State#state.clerk,
false),
handle_cast({manifest_change, WI}, State) ->
{ok, UpdState} = commit_manifest_change(WI, State),
ok = leveled_pclerk:clerk_manifestchange(State#state.clerk,
confirm,
false),
{noreply, UpdState};
handle_cast(_Msg, State) ->
{noreply, State}.
@ -541,12 +542,18 @@ terminate(_Reason, State) ->
%% The cast may not succeed as the clerk could be synchronously calling
%% the penciller looking for a manifest commit
%%
MC = leveled_pclerk:clerk_returnmanifestchange(State#state.clerk, true),
MC = leveled_pclerk:clerk_manifestchange(State#state.clerk,
return,
true),
UpdState = case MC of
{ok, WI} ->
{ok, NewState} = commit_manifest_change(WI, State),
Clerk = State#state.clerk,
ok = leveled_pclerk:clerk_manifestchange(Clerk,
confirm,
true),
NewState;
no_change_required ->
no_change ->
State
end,
Dump = ets:tab2list(UpdState#state.memtable),
@ -1233,12 +1240,9 @@ simple_server_test() ->
?assertMatch(Key1, pcl_fetch(PCLr, {o,"Bucket0001", "Key0001"})),
?assertMatch(Key2, pcl_fetch(PCLr, {o,"Bucket0002", "Key0002"})),
?assertMatch(Key3, pcl_fetch(PCLr, {o,"Bucket0003", "Key0003"})),
S4 = pcl_pushmem(PCLr, KL3),
if S4 == pause -> timer:sleep(1000); true -> ok end,
S5 = pcl_pushmem(PCLr, [Key4]),
if S5 == pause -> timer:sleep(1000); true -> ok end,
S6 = pcl_pushmem(PCLr, KL4),
if S6 == pause -> timer:sleep(1000); true -> ok end,
maybe_pause_push(pcl_pushmem(PCLr, KL3)),
maybe_pause_push(pcl_pushmem(PCLr, [Key4])),
maybe_pause_push(pcl_pushmem(PCLr, KL4)),
?assertMatch(Key1, pcl_fetch(PCLr, {o,"Bucket0001", "Key0001"})),
?assertMatch(Key2, pcl_fetch(PCLr, {o,"Bucket0002", "Key0002"})),
?assertMatch(Key3, pcl_fetch(PCLr, {o,"Bucket0003", "Key0003"})),
@ -1268,10 +1272,8 @@ simple_server_test() ->
% in a new snapshot
Key1A = {{o,"Bucket0001", "Key0001"}, {4002, {active, infinity}, null}},
KL1A = lists:sort(leveled_sft:generate_randomkeys({4002, 2})),
S7 = pcl_pushmem(PCLr, [Key1A]),
if S7 == pause -> timer:sleep(1000); true -> ok end,
S8 = pcl_pushmem(PCLr, KL1A),
if S8 == pause -> timer:sleep(1000); true -> ok end,
maybe_pause_push(pcl_pushmem(PCLr, [Key1A])),
maybe_pause_push(pcl_pushmem(PCLr, KL1A)),
?assertMatch(true, pcl_checksequencenumber(PclSnap,
{o,"Bucket0001", "Key0001"},
1)),