chewbranca commented on a change in pull request #610: Optimize ddoc cache
URL: https://github.com/apache/couchdb/pull/610#discussion_r123586231
##########
File path: src/ddoc_cache/src/ddoc_cache_opener.erl
##########
@@ -32,195 +32,96 @@
]).
-export([
- open_doc/2,
- open_doc/3,
- open_validation_funs/1,
- evict_docs/2,
- lookup/1,
- match_newest/1,
- recover_doc/2,
- recover_doc/3,
- recover_validation_funs/1
+ open/1
]).
--export([
- handle_db_event/3
-]).
--export([
- fetch_doc_data/1
-]).
-
--define(CACHE, ddoc_cache_lru).
--define(OPENING, ddoc_cache_opening).
--type dbname() :: iodata().
--type docid() :: iodata().
--type doc_hash() :: <<_:128>>.
--type revision() :: {pos_integer(), doc_hash()}.
+-include("ddoc_cache.hrl").
--record(opener, {
- key,
- pid,
- clients
-}).
-record(st, {
- db_ddocs,
- evictor
+ db_ddocs
}).
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
--spec open_doc(dbname(), docid()) -> {ok, #doc{}}.
-open_doc(DbName, DocId) ->
- Resp = gen_server:call(?MODULE, {open, {DbName, DocId}}, infinity),
- handle_open_response(Resp).
--spec open_doc(dbname(), docid(), revision()) -> {ok, #doc{}}.
-open_doc(DbName, DocId, Rev) ->
- Resp = gen_server:call(?MODULE, {open, {DbName, DocId, Rev}}, infinity),
- handle_open_response(Resp).
-
--spec open_validation_funs(dbname()) -> {ok, [fun()]}.
-open_validation_funs(DbName) ->
- Resp = gen_server:call(?MODULE, {open, {DbName, validation_funs}},
infinity),
- handle_open_response(Resp).
-
--spec evict_docs(dbname(), [docid()]) -> ok.
-evict_docs(DbName, DocIds) ->
- gen_server:cast(?MODULE, {evict, DbName, DocIds}).
-
-lookup(Key) ->
- try ets_lru:lookup_d(?CACHE, Key) of
- {ok, _} = Resp ->
- Resp;
- _ ->
- missing
- catch
- error:badarg ->
- recover
- end.
-
-match_newest(Key) ->
- try ets_lru:match_object(?CACHE, Key, '_') of
+open(Key) ->
+ try ets:lookup(?CACHE, Key) of
[] ->
- missing;
- Docs ->
- Sorted = lists:sort(
- fun (#doc{deleted=DelL, revs=L}, #doc{deleted=DelR, revs=R}) ->
- {not DelL, L} > {not DelR, R}
- end, Docs),
- {ok, hd(Sorted)}
- catch
- error:badarg ->
- recover
+ couch_stats:increment_counter([ddoc_cache, miss]),
+ Resp = gen_server:call(?MODULE, {open, Key}, infinity),
+ ddoc_cache_entry:handle_resp(Resp);
+ [#entry{val = Val}] ->
+ couch_stats:increment_counter([ddoc_cache, hit]),
+ ddoc_cache_lru:accessed(Key),
Review comment:
I'm concerned about sending a message here with every successful lookup.
We've seen this to be problematic in couch_server, and I think we might run
into similar issues here. Every single time `ddoc_cache_lru:accessed/1` is
called it can trigger 1 khash read, 1 khash write, one ets lookup, one
`is_process_alive` check, one ets delete, and one ets insert. I could see this
getting overwhelmed in a hurry.
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