diff options
Diffstat (limited to 'src/ddoc_cache/src/ddoc_cache_entry.erl')
| -rw-r--r-- | src/ddoc_cache/src/ddoc_cache_entry.erl | 327 |
1 files changed, 0 insertions, 327 deletions
diff --git a/src/ddoc_cache/src/ddoc_cache_entry.erl b/src/ddoc_cache/src/ddoc_cache_entry.erl deleted file mode 100644 index 5a1711dd8..000000000 --- a/src/ddoc_cache/src/ddoc_cache_entry.erl +++ /dev/null @@ -1,327 +0,0 @@ -% Licensed under the Apache License, Version 2.0 (the "License"); you may not -% use this file except in compliance with the License. You may obtain a copy of -% the License at -% -% http://www.apache.org/licenses/LICENSE-2.0 -% -% Unless required by applicable law or agreed to in writing, software -% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT -% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the -% License for the specific language governing permissions and limitations under -% the License. - --module(ddoc_cache_entry). --behaviour(gen_server). --vsn(1). - -% for the stacktrace macro only so far --include_lib("couch/include/couch_db.hrl"). - --export([ - dbname/1, - ddocid/1, - recover/1, - insert/2, - - start_link/2, - shutdown/1, - open/2, - accessed/1, - refresh/1 -]). - --export([ - init/1, - terminate/2, - handle_call/3, - handle_cast/2, - handle_info/2, - code_change/3 -]). - --export([ - do_open/1 -]). - --include("ddoc_cache.hrl"). - --ifndef(TEST). --define(ENTRY_SHUTDOWN_TIMEOUT, 5000). --else. --define(ENTRY_SHUTDOWN_TIMEOUT, 500). --endif. - --record(st, { - key, - val, - opener, - waiters, - ts, - accessed -}). - -dbname({Mod, Arg}) -> - Mod:dbname(Arg). - -ddocid({Mod, Arg}) -> - Mod:ddocid(Arg). - -recover({Mod, Arg}) -> - Mod:recover(Arg). - -insert({Mod, Arg}, Value) -> - Mod:insert(Arg, Value). - -start_link(Key, Default) -> - Pid = proc_lib:spawn_link(?MODULE, init, [{Key, Default}]), - {ok, Pid}. - -shutdown(Pid) -> - Ref = erlang:monitor(process, Pid), - ok = gen_server:cast(Pid, shutdown), - receive - {'DOWN', Ref, process, Pid, normal} -> - ok; - {'DOWN', Ref, process, Pid, Reason} -> - erlang:exit(Reason) - after ?ENTRY_SHUTDOWN_TIMEOUT -> - erlang:demonitor(Ref, [flush]), - erlang:exit({timeout, {entry_shutdown, Pid}}) - end. - -open(Pid, Key) -> - try - Resp = gen_server:call(Pid, open), - case Resp of - {open_ok, Val} -> - Val; - {open_error, {T, R, S}} -> - erlang:raise(T, R, S) - end - catch - error:database_does_not_exist -> - erlang:error(database_does_not_exist); - exit:_ -> - % Its possible that this process was evicted just - % before we tried talking to it. Just fallback - % to a standard recovery - recover(Key) - end. - -accessed(Pid) -> - gen_server:cast(Pid, accessed). - -refresh(Pid) -> - gen_server:cast(Pid, force_refresh). - -init({Key, undefined}) -> - true = ets:update_element(?CACHE, Key, {#entry.pid, self()}), - St = #st{ - key = Key, - opener = spawn_opener(Key), - waiters = [], - accessed = 1 - }, - ?EVENT(started, Key), - gen_server:enter_loop(?MODULE, [], St); -init({Key, Wrapped}) -> - Default = ddoc_cache_value:unwrap(Wrapped), - Updates = [ - {#entry.val, Default}, - {#entry.pid, self()} - ], - NewTs = os:timestamp(), - true = ets:update_element(?CACHE, Key, Updates), - true = ets:insert(?LRU, {{NewTs, Key, self()}}), - St = #st{ - key = Key, - val = {open_ok, {ok, Default}}, - opener = start_timer(), - waiters = [], - ts = NewTs, - accessed = 1 - }, - ?EVENT(default_started, Key), - gen_server:enter_loop(?MODULE, [], St, hibernate). - -terminate(_Reason, St) -> - #st{ - key = Key, - opener = Pid, - ts = Ts - } = St, - % We may have already deleted our cache entry - % during shutdown - Pattern = #entry{key = Key, pid = self(), _ = '_'}, - CacheMSpec = [{Pattern, [], [true]}], - true = ets:select_delete(?CACHE, CacheMSpec) < 2, - % We may have already deleted our LRU entry - % during shutdown - if - Ts == undefined -> - ok; - true -> - LruMSpec = [{{{Ts, Key, self()}}, [], [true]}], - true = ets:select_delete(?LRU, LruMSpec) < 2 - end, - % Blow away any current opener if it exists - if - not is_pid(Pid) -> ok; - true -> catch exit(Pid, kill) - end, - ok. - -handle_call(open, From, #st{opener = Pid} = St) when is_pid(Pid) -> - NewSt = St#st{ - waiters = [From | St#st.waiters] - }, - {noreply, NewSt}; -handle_call(open, _From, St) -> - {reply, St#st.val, St}; -handle_call(Msg, _From, St) -> - {stop, {bad_call, Msg}, {bad_call, Msg}, St}. - -handle_cast(accessed, St) -> - ?EVENT(accessed, St#st.key), - drain_accessed(), - NewSt = St#st{ - accessed = St#st.accessed + 1 - }, - {noreply, update_lru(NewSt)}; -handle_cast(force_refresh, St) -> - % If we had frequent design document updates - % they could end up racing accessed events and - % end up prematurely evicting this entry from - % cache. To prevent this we just make sure that - % accessed is set to at least 1 before we - % execute a refresh. - NewSt = - if - St#st.accessed > 0 -> St; - true -> St#st{accessed = 1} - end, - % We remove the cache entry value so that any - % new client comes to us for the refreshed - % value. - true = ets:update_element(?CACHE, St#st.key, {#entry.val, undefined}), - handle_cast(refresh, NewSt); -handle_cast(refresh, #st{accessed = 0} = St) -> - {stop, normal, St}; -handle_cast(refresh, #st{opener = Ref} = St) when is_reference(Ref) -> - #st{ - key = Key - } = St, - erlang:cancel_timer(Ref), - NewSt = St#st{ - opener = spawn_opener(Key), - accessed = 0 - }, - {noreply, NewSt}; -handle_cast(refresh, #st{opener = Pid} = St) when is_pid(Pid) -> - catch exit(Pid, kill), - receive - {'DOWN', _, _, Pid, _} -> ok - end, - NewSt = St#st{ - opener = spawn_opener(St#st.key), - accessed = 0 - }, - {noreply, NewSt}; -handle_cast(shutdown, St) -> - remove_from_cache(St), - {stop, normal, St}; -handle_cast(Msg, St) -> - {stop, {bad_cast, Msg}, St}. - -handle_info({'DOWN', _, _, Pid, Resp}, #st{key = Key, opener = Pid} = St) -> - case Resp of - {open_ok, Key, {ok, Val}} -> - update_cache(St, Val), - NewSt1 = St#st{ - val = {open_ok, {ok, Val}}, - opener = start_timer(), - waiters = [] - }, - NewSt2 = update_lru(NewSt1), - respond(St#st.waiters, {open_ok, {ok, Val}}), - {noreply, NewSt2}; - {Status, Key, Other} -> - NewSt = St#st{ - val = {Status, Other}, - opener = undefined, - waiters = undefined - }, - remove_from_cache(NewSt), - respond(St#st.waiters, {Status, Other}), - {stop, normal, NewSt} - end; -handle_info(Msg, St) -> - {stop, {bad_info, Msg}, St}. - -code_change(_, St, _) -> - {ok, St}. - -spawn_opener(Key) -> - {Pid, _} = erlang:spawn_monitor(?MODULE, do_open, [Key]), - Pid. - -start_timer() -> - TimeOut = config:get_integer( - "ddoc_cache", "refresh_timeout", ?REFRESH_TIMEOUT - ), - erlang:send_after(TimeOut, self(), {'$gen_cast', refresh}). - -do_open(Key) -> - try recover(Key) of - Resp -> - erlang:exit({open_ok, Key, Resp}) - catch ?STACKTRACE(T, R, S) - erlang:exit({open_error, Key, {T, R, S}}) - end. - -update_lru(#st{key = Key, ts = Ts} = St) -> - remove_from_lru(Ts, Key), - NewTs = os:timestamp(), - true = ets:insert(?LRU, {{NewTs, Key, self()}}), - St#st{ts = NewTs}. - -update_cache(#st{val = undefined} = St, Val) -> - true = ets:update_element(?CACHE, St#st.key, {#entry.val, Val}), - ?EVENT(inserted, St#st.key); -update_cache(#st{val = V1} = _St, V2) when {open_ok, {ok, V2}} == V1 -> - ?EVENT(update_noop, _St#st.key); -update_cache(St, Val) -> - true = ets:update_element(?CACHE, St#st.key, {#entry.val, Val}), - ?EVENT(updated, {St#st.key, Val}). - -remove_from_cache(St) -> - #st{ - key = Key, - ts = Ts - } = St, - Pattern = #entry{key = Key, pid = self(), _ = '_'}, - CacheMSpec = [{Pattern, [], [true]}], - 1 = ets:select_delete(?CACHE, CacheMSpec), - remove_from_lru(Ts, Key), - ?EVENT(removed, St#st.key), - ok. - -remove_from_lru(Ts, Key) -> - if - Ts == undefined -> - ok; - true -> - LruMSpec = [{{{Ts, Key, self()}}, [], [true]}], - 1 = ets:select_delete(?LRU, LruMSpec) - end. - -drain_accessed() -> - receive - {'$gen_cast', accessed} -> - drain_accessed() - after 0 -> - ok - end. - -respond(Waiters, Resp) -> - [gen_server:reply(W, Resp) || W <- Waiters]. |