davisp commented on a change in pull request #470: Scheduling Replicator URL: https://github.com/apache/couchdb/pull/470#discussion_r110703225
########## File path: src/couch_replicator/src/couch_multidb_changes.erl ########## @@ -0,0 +1,830 @@ +% 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(couch_multidb_changes). + +-behaviour(gen_server). + + +-export([ + start_link/4 +]). + +-export([ + init/1, + terminate/2, + handle_call/3, + handle_info/2, + handle_cast/2, + code_change/3 +]). + +-export([ + changes_reader/3, + changes_reader_cb/3 +]). + +-include_lib("couch/include/couch_db.hrl"). +-include_lib("mem3/include/mem3.hrl"). + +-define(CTX, {user_ctx, #user_ctx{roles=[<<"_admin">>, <<"_replicator">>]}}). + +-define(AVG_DELAY_MSEC, 100). +-define(MAX_DELAY_MSEC, 60000). + +-record(state, { + tid :: ets:tid(), + mod :: atom(), + ctx :: term(), + suffix :: binary(), + event_server :: reference(), + scanner :: nil | pid(), + pids :: [{binary(), pid()}], + skip_ddocs :: boolean() +}). + +% Behavior API + +% For each db shard with a matching suffix, report created, +% deleted, found (discovered) and change events. + +-callback db_created(DbName :: binary(), Context :: term()) -> + Context :: term(). + +-callback db_deleted(DbName :: binary(), Context :: term()) -> + Context :: term(). + +-callback db_found(DbName :: binary(), Context :: term()) -> + Context :: term(). + +-callback db_change(DbName :: binary(), Change :: term(), Context :: term()) -> + Context :: term(). + + +% External API + + +% Opts list can contain: +% - `skip_ddocs` : Skip design docs + +-spec start_link(binary(), module(), term(), list()) -> + {ok, pid()} | ignore | {error, term()}. +start_link(DbSuffix, Module, Context, Opts) when + is_binary(DbSuffix), is_atom(Module), is_list(Opts) -> + gen_server:start_link(?MODULE, [DbSuffix, Module, Context, Opts], []). + + +% gen_server callbacks + +init([DbSuffix, Module, Context, Opts]) -> + process_flag(trap_exit, true), + Server = self(), + {ok, #state{ + tid = ets:new(?MODULE, [set, protected]), + mod = Module, + ctx = Context, + suffix = DbSuffix, + event_server = register_with_event_server(Server), + scanner = spawn_link(fun() -> scan_all_dbs(Server, DbSuffix) end), + pids = [], + skip_ddocs = proplists:is_defined(skip_ddocs, Opts) + }}. + + +terminate(_Reason, _State) -> + ok. + + +handle_call({change, DbName, Change}, _From, + #state{skip_ddocs=SkipDDocs, mod=Mod, ctx=Ctx} = State) -> + case {SkipDDocs, is_design_doc(Change)} of + {true, true} -> + {reply, ok, State}; + {_, _} -> + {reply, ok, State#state{ctx=Mod:db_change(DbName, Change, Ctx)}} + end; + +handle_call({checkpoint, DbName, EndSeq}, _From, #state{tid=Ets} = State) -> + case ets:lookup(Ets, DbName) of + [] -> + true = ets:insert(Ets, {DbName, EndSeq, false}); + [{DbName, _OldSeq, Rescan}] -> + true = ets:insert(Ets, {DbName, EndSeq, Rescan}) + end, + {reply, ok, State}. + + +handle_cast({resume_scan, DbName}, State) -> + {noreply, resume_scan(DbName, State)}. + + +handle_info({'$couch_event', DbName, Event}, #state{suffix = Suf} = State) -> + case Suf =:= couch_db:dbname_suffix(DbName) of + true -> + {noreply, db_callback(Event, DbName, State)}; + _ -> + {noreply, State} + end; + +handle_info({'DOWN', Ref, _, _, Info}, #state{event_server = Ref} = State) -> + {stop, {couch_event_server_died, Info}, State}; + +handle_info({'EXIT', From, normal}, #state{scanner = From} = State) -> + {noreply, State#state{scanner=nil}}; + +handle_info({'EXIT', From, Reason}, #state{scanner = From} = State) -> + {stop, {scanner_died, Reason}, State}; + +handle_info({'EXIT', From, Reason}, #state{pids = Pids} = State) -> + couch_log:debug("~p change feed exited ~p", [State#state.suffix, From]), + case lists:keytake(From, 2, Pids) of + {value, {DbName, From}, NewPids} -> + if Reason == normal -> ok; true -> + Fmt = "~s : Known change feed ~w died :: ~w", + couch_log:error(Fmt, [?MODULE, From, Reason]) + end, + NewState = State#state{pids = NewPids}, + case ets:lookup(State#state.tid, DbName) of + [{DbName, _EndSeq, true}] -> + {noreply, resume_scan(DbName, NewState)}; + _ -> + {noreply, NewState} + end; + false when Reason == normal -> + {noreply, State}; + false -> + Fmt = "~s(~p) : Unknown pid ~w died :: ~w", + couch_log:error(Fmt, [?MODULE, State#state.suffix, From, Reason]), + {stop, {unexpected_exit, From, Reason}, State} + end; + +handle_info(_Msg, State) -> + {noreply, State}. + + +code_change(_OldVsn, State, _Extra) -> + {ok, State}. + + +% Private functions + +-spec register_with_event_server(pid()) -> reference(). +register_with_event_server(Server) -> + Ref = erlang:monitor(process, couch_event_server), + couch_event:register_all(Server), + Ref. + + +-spec db_callback(created | deleted | updated, binary(), #state{}) -> #state{}. +db_callback(created, DbName, #state{mod = Mod, ctx = Ctx} = State) -> + State#state{ctx = Mod:db_created(DbName, Ctx)}; + +db_callback(deleted, DbName, #state{mod = Mod, ctx = Ctx} = State) -> + State#state{ctx = Mod:db_deleted(DbName, Ctx)}; + +db_callback(updated, DbName, State) -> + resume_scan(DbName, State); + +db_callback(_Other, _DbName, State) -> + State. + + +-spec resume_scan(binary(), #state{}) -> #state{}. +resume_scan(DbName, #state{pids=Pids, tid=Ets} = State) -> + case {lists:keyfind(DbName, 1, Pids), ets:lookup(Ets, DbName)} of + {{DbName, _}, []} -> + % Found existing change feed, but not entry in ETS + % Flag a need to rescan from begining + true = ets:insert(Ets, {DbName, 0, true}), + State; + {{DbName, _}, [{DbName, EndSeq, _}]} -> + % Found existing change feed and entry in ETS + % Flag a need to rescan from last ETS checkpoint + true = ets:insert(Ets, {DbName, EndSeq, true}), + State; + {false, []} -> + % No existing change feed running. No entry in ETS. + % This is first time seeing this db shard. + % Notify user with a found callback. Insert checkpoint + % entry in ETS to start from 0. And start a change feed. + true = ets:insert(Ets, {DbName, 0, false}), + Mod = State#state.mod, + Ctx = Mod:db_found(DbName, State#state.ctx), + Pid = start_changes_reader(DbName, 0), + State#state{ctx=Ctx, pids=[{DbName, Pid} | Pids]}; + {false, [{DbName, EndSeq, _}]} -> + % No existing change feed running. Found existing checkpoint. + % Start a new change reader from last checkpoint. + true = ets:insert(Ets, {DbName, EndSeq, false}), + Pid = start_changes_reader(DbName, EndSeq), + State#state{pids=[{DbName, Pid} | Pids]} + end. + + +start_changes_reader(DbName, Since) -> + spawn_link(?MODULE, changes_reader, [self(), DbName, Since]). + + +changes_reader(Server, DbName, Since) -> + {ok, Db} = couch_db:open_int(DbName, [?CTX, sys_db]), + ChangesArgs = #changes_args{ + include_docs = true, + since = Since, + feed = "normal", + timeout = infinity + }, + ChFun = couch_changes:handle_db_changes(ChangesArgs, {json_req, null}, Db), + ChFun({fun ?MODULE:changes_reader_cb/3, {Server, DbName}}). + + +changes_reader_cb({change, Change, _}, _, {Server, DbName}) -> + ok = gen_server:call(Server, {change, DbName, Change}, infinity), + {Server, DbName}; + +changes_reader_cb({stop, EndSeq}, _, {Server, DbName}) -> + ok = gen_server:call(Server, {checkpoint, DbName, EndSeq}, infinity), + {Server, DbName}; + +changes_reader_cb(_, _, Acc) -> + Acc. + + +scan_all_dbs(Server, DbSuffix) when is_pid(Server) -> + ok = scan_local_db(Server, DbSuffix), + {ok, Db} = mem3_util:ensure_exists( + config:get("mem3", "shards_db", "_dbs")), + ChangesFun = couch_changes:handle_changes(#changes_args{}, nil, Db, nil), + ChangesFun(fun({change, {Change}, _}, _) -> + DbName = couch_util:get_value(<<"id">>, Change), + case DbName of + <<"_design/", _/binary>> -> + ok; + _Else -> + case couch_replicator_utils:is_deleted(Change) of + true -> + ok; + false -> + [gen_server:cast(Server, {resume_scan, ShardName}) + || ShardName <- filter_shards(DbName, DbSuffix)], + ok + end + end; + (_, _) -> ok + end), + couch_db:close(Db). + + +filter_shards(DbName, DbSuffix) -> + case DbSuffix =:= couch_db:dbname_suffix(DbName) of + false -> + []; + true -> + try + [ShardName || #shard{name = ShardName} <- mem3:local_shards(DbName)] + catch + error:database_does_not_exist -> + [] + end + end. + + +scan_local_db(Server, DbSuffix) when is_pid(Server) -> + case couch_db:open_int(DbSuffix, [?CTX, sys_db, nologifmissing]) of + {ok, Db} -> + gen_server:cast(Server, {resume_scan, DbSuffix}), + ok = couch_db:close(Db); + _Error -> + ok + end. + + +is_design_doc({Change}) -> + case lists:keyfind(<<"id">>, 1, Change) of + false -> + false; + {_, Id} -> + is_design_doc_id(Id) + end. + + +is_design_doc_id(<<?DESIGN_DOC_PREFIX, _/binary>>) -> + true; + +is_design_doc_id(_) -> + false. + + +-ifdef(TEST). + +-include_lib("eunit/include/eunit.hrl"). +-include_lib("couch/include/couch_eunit.hrl"). + +-define(MOD, multidb_test_module). +-define(SUFFIX, <<"suff">>). +-define(DBNAME, <<"shards/40000000-5fffffff/acct/suff.0123456789">>). + +couch_multidb_changes_test_() -> + { + foreach, + fun setup/0, + fun teardown/1, + [ + t_handle_call_change(), + t_handle_call_change_filter_design_docs(), + t_handle_call_checkpoint_new(), + t_handle_call_checkpoint_existing(), + t_handle_info_created(), + t_handle_info_deleted(), + t_handle_info_updated(), + t_handle_info_other_event(), + t_handle_info_created_other_db(), + t_handle_info_scanner_exit_normal(), + t_handle_info_scanner_crashed(), + t_handle_info_event_server_exited(), + t_handle_info_unknown_pid_exited(), + t_handle_info_change_feed_exited(), + t_handle_info_change_feed_exited_and_need_rescan(), + t_spawn_changes_reader(), + t_changes_reader_cb_change(), + t_changes_reader_cb_stop(), + t_changes_reader_cb_other(), + t_handle_call_resume_scan_no_chfeed_no_ets_entry(), + t_handle_call_resume_scan_chfeed_no_ets_entry(), + t_handle_call_resume_scan_chfeed_ets_entry(), + t_handle_call_resume_scan_no_chfeed_ets_entry(), + t_start_link(), + t_start_link_no_ddocs(), + t_misc_gen_server_callbacks() + ] + }. + +setup() -> + mock_logs(), + mock_callback_mod(), + meck:expect(couch_event, register_all, 1, ok), + meck:expect(config, get, ["mem3", "shards_db", '_'], "_dbs"), + meck:expect(mem3_util, ensure_exists, 1, {ok, dbs}), + ChangesFun = meck:val(fun(_) -> ok end), + meck:expect(couch_changes, handle_changes, 4, ChangesFun), + meck:expect(couch_db, open_int, + fun(?DBNAME, [?CTX, sys_db]) -> {ok, db}; + (_, _) -> {not_found, no_db_file} + end), + meck:expect(couch_db, close, 1, ok), + mock_changes_reader(), + % create process to stand in for couch_ever_server + % mocking erlang:monitor doesn't, so give it real process to monitor + EvtPid = spawn_link(fun() -> receive looper -> ok end end), + true = register(couch_event_server, EvtPid), + EvtPid. + + +teardown(EvtPid) -> + unlink(EvtPid), + exit(EvtPid, kill), + meck:unload(). + + +t_handle_call_change() -> + ?_test(begin + State = mock_state(), + Change = change_row(<<"blah">>), + handle_call_ok({change, ?DBNAME, Change}, State), + ?assert(meck:validate(?MOD)), + ?assert(meck:called(?MOD, db_change, [?DBNAME, Change, zig])) + end). + +t_handle_call_change_filter_design_docs() -> + ?_test(begin + State0 = mock_state(), + State = State0#state{skip_ddocs = true}, + Change = change_row(<<"_design/blah">>), + handle_call_ok({change, ?DBNAME, Change}, State), + ?assert(meck:validate(?MOD)), + ?assertNot(meck:called(?MOD, db_change, [?DBNAME, Change, zig])) + end). + +t_handle_call_checkpoint_new() -> + ?_test(begin + Tid = mock_ets(), + State = mock_state(Tid), + handle_call_ok({checkpoint, ?DBNAME, 1}, State), + ?assertEqual([{?DBNAME, 1, false}], ets:tab2list(Tid)), + ets:delete(Tid) + end). + +t_handle_call_checkpoint_existing() -> + ?_test(begin + Tid = mock_ets(), + State = mock_state(Tid), + true = ets:insert(Tid, {?DBNAME, 1, true}), + handle_call_ok({checkpoint, ?DBNAME, 2}, State), + ?assertEqual([{?DBNAME, 2, true}], ets:tab2list(Tid)), + ets:delete(Tid) + end). + +t_handle_info_created() -> + ?_test(begin + State = mock_state(), + handle_info_check({'$couch_event', ?DBNAME, created}, State), + ?assert(meck:validate(?MOD)), + ?assert(meck:called(?MOD, db_created, [?DBNAME, zig])) + end). + +t_handle_info_deleted() -> + ?_test(begin + State = mock_state(), + handle_info_check({'$couch_event', ?DBNAME, deleted}, State), + ?assert(meck:validate(?MOD)), + ?assert(meck:called(?MOD, db_deleted, [?DBNAME, zig])) + end). + +t_handle_info_updated() -> + ?_test(begin + Tid = mock_ets(), + State = mock_state(Tid), + handle_info_check({'$couch_event', ?DBNAME, updated}, State), + ?assert(meck:validate(?MOD)), + ?assert(meck:called(?MOD, db_found, [?DBNAME, zig])) + end). + +t_handle_info_other_event() -> + ?_test(begin + State = mock_state(), + handle_info_check({'$couch_event', ?DBNAME, somethingelse}, State) Review comment: Seems like assertions for not calling db_created|deleted|found would be useful here. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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