chewbranca commented on a change in pull request #610: Optimize ddoc cache URL: https://github.com/apache/couchdb/pull/610#discussion_r125153291
########## File path: src/ddoc_cache/src/ddoc_cache_entry.erl ########## @@ -0,0 +1,280 @@ +% 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). + + +-export([ + dbname/1, + ddocid/1, + recover/1, + + start_link/1, + 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"). + + +-record(st, { + key, + val, + opener, + waiters, + ts +}). + + +dbname({Mod, Arg}) -> + Mod:dbname(Arg). + + +ddocid({Mod, Arg}) -> + Mod:ddocid(Arg). + + +recover({Mod, Arg}) -> + Mod:recover(Arg). + + +start_link(Key) -> + Pid = proc_lib:spawn_link(?MODULE, init, [Key]), + {ok, Pid}. + + +shutdown(Pid) -> + ok = gen_server:call(Pid, shutdown). + + +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 exit:_ -> + % Its possible that this process was evicted just + % before we tried talking to it. Just fallback + % to a standard recovery Review comment: It would be good to update this comment to indicate this is also the fallback for when `Pid` executes `spawn_opener` and that opener pid fails for whatever reason, resulting in the not `open_ok` clause of `handle_info({'DOWN', _, _, Pid, Resp}, #st{key = Key, opener = Pid} = St) ->` to be hit leading to `{stop, normal, NewSt}` which will be caught by this clause as `Pid` dies. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
