diff options
Diffstat (limited to 'apps/mem3/src/mem3_cache.erl')
-rw-r--r-- | apps/mem3/src/mem3_cache.erl | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/apps/mem3/src/mem3_cache.erl b/apps/mem3/src/mem3_cache.erl new file mode 100644 index 00000000..2a29ca4c --- /dev/null +++ b/apps/mem3/src/mem3_cache.erl @@ -0,0 +1,92 @@ +-module(mem3_cache). +-behaviour(gen_server). +-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, + code_change/3]). + +-export([start_link/0]). + +-record(state, {changes_pid}). + +-include("mem3.hrl"). +-include_lib("couch/include/couch_db.hrl"). + +start_link() -> + gen_server:start_link({local, ?MODULE}, ?MODULE, [], []). + +init([]) -> + ets:new(partitions, [bag, public, named_table, {keypos,#shard.dbname}]), + {Pid, _} = spawn_monitor(fun() -> listen_for_changes(0) end), + {ok, #state{changes_pid = Pid}}. + +handle_call(_Call, _From, State) -> + {noreply, State}. + +handle_cast(_Msg, State) -> + {noreply, State}. + +handle_info({'DOWN', _, _, Pid, {badarg, [{ets,delete,[partitions,_]}|_]}}, + #state{changes_pid=Pid} = State) -> + % fatal error, somebody deleted our ets table + {stop, ets_table_error, State}; +handle_info({'DOWN', _, _, Pid, Reason}, #state{changes_pid=Pid} = State) -> + ?LOG_INFO("~p changes listener died ~p", [?MODULE, Reason]), + Seq = case Reason of {seq, EndSeq} -> EndSeq; _ -> 0 end, + timer:send_after(5000, {start_listener, Seq}), + {noreply, State}; +handle_info({start_listener, Seq}, State) -> + {NewPid, _} = spawn_monitor(fun() -> listen_for_changes(Seq) end), + {noreply, State#state{changes_pid=NewPid}}; +handle_info(_Msg, State) -> + {noreply, State}. + +terminate(_Reason, #state{changes_pid=Pid}) -> + exit(Pid, kill), + ok. + +code_change(_OldVsn, State, _Extra) -> + {ok, State}. + +%% internal functions + +listen_for_changes(Since) -> + DbName = ?l2b(couch_config:get("mem3", "db", "dbs")), + {ok, Db} = ensure_exists(DbName), + Args = #changes_args{ + feed = "continuous", + since = Since, + heartbeat = true, + include_docs = true + }, + ChangesFun = couch_changes:handle_changes(Args, nil, Db), + ChangesFun(fun changes_callback/2). + +ensure_exists(DbName) -> + Options = [{user_ctx, #user_ctx{roles=[<<"_admin">>]}}], + case couch_db:open(DbName, Options) of + {ok, Db} -> + {ok, Db}; + _ -> + couch_server:create(DbName, Options) + end. + +changes_callback(start, _) -> + {ok, nil}; +changes_callback({stop, EndSeq}, _) -> + exit({seq, EndSeq}); +changes_callback({change, {Change}, _}, _) -> + DbName = couch_util:get_value(<<"id">>, Change), + case couch_util:get_value(deleted, Change, false) of + true -> + ets:delete(partitions, DbName); + false -> + case couch_util:get_value(doc, Change) of + {error, Reason} -> + ?LOG_ERROR("missing partition table for ~s: ~p", [DbName, Reason]); + {Doc} -> + ets:delete(partitions, DbName), + ets:insert(partitions, mem3_util:build_shards(DbName, Doc)) + end + end, + {ok, couch_util:get_value(<<"seq">>, Change)}; +changes_callback(timeout, _) -> + {ok, nil}. |