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| -rw-r--r-- | src/mem3_nodes.erl | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/src/mem3_nodes.erl b/src/mem3_nodes.erl new file mode 100644 index 00000000..9b3f32f3 --- /dev/null +++ b/src/mem3_nodes.erl @@ -0,0 +1,117 @@ +-module(mem3_nodes). +-behaviour(gen_server). +-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, + code_change/3]). + +-export([start_link/0, get_nodelist/0]). + +-include("mem3.hrl"). + +-record(state, {changes_pid, update_seq, nodes}). + +start_link() -> + gen_server:start_link({local, ?MODULE}, ?MODULE, [], []). + +get_nodelist() -> + gen_server:call(?MODULE, get_nodelist). + +init([]) -> + {Nodes, UpdateSeq} = initialize_nodelist(), + {Pid, _} = spawn_monitor(fun() -> listen_for_changes(UpdateSeq) end), + {ok, #state{changes_pid = Pid, update_seq = UpdateSeq, nodes = Nodes}}. + +handle_call(get_nodelist, _From, State) -> + {reply, State#state.nodes, State}; +handle_call({add_node, Node}, _From, #state{nodes=Nodes} = State) -> + gen_event:notify(mem3_events, {add_node, Node}), + {reply, ok, State#state{nodes = lists:umerge([Node], Nodes)}}; +handle_call({remove_node, Node}, _From, #state{nodes=Nodes} = State) -> + gen_event:notify(mem3_events, {remove_node, Node}), + {reply, ok, State#state{nodes = lists:delete(Node, Nodes)}}; +handle_call(_Call, _From, State) -> + {noreply, State}. + +handle_cast(_Msg, State) -> + {noreply, State}. + +handle_info({'DOWN', _, _, Pid, Reason}, #state{changes_pid=Pid} = State) -> + ?LOG_INFO("~p changes listener died ~p", [?MODULE, Reason]), + StartSeq = State#state.update_seq, + Seq = case Reason of {seq, EndSeq} -> EndSeq; _ -> StartSeq end, + timer:send_after(5000, start_listener), + {noreply, State#state{update_seq = Seq}}; +handle_info(start_listener, #state{update_seq = Seq} = State) -> + {NewPid, _} = spawn_monitor(fun() -> listen_for_changes(Seq) end), + {noreply, State#state{changes_pid=NewPid}}; +handle_info(_Info, State) -> + {noreply, State}. + +terminate(_Reason, _State) -> + ok. + +code_change(_OldVsn, State, _Extra) -> + {ok, State}. + +%% internal functions + +initialize_nodelist() -> + DbName = couch_config:get("mem3", "nodedb", "nodes"), + {ok, Db} = ensure_exists(DbName), + {ok, _, Nodes0} = couch_btree:fold(Db#db.id_tree, fun first_fold/3, [], []), + % add self if not already present + case lists:member(node(), Nodes0) of + true -> + Nodes = Nodes0; + false -> + Doc = #doc{id = couch_util:to_binary(node())}, + {ok, _} = couch_db:update_doc(Db, Doc, []), + Nodes = [node() | Nodes0] + end, + couch_db:close(Db), + {lists:sort(Nodes), Db#db.update_seq}. + +first_fold(#full_doc_info{id = <<"_design/", _/binary>>}, _, Acc) -> + {ok, Acc}; +first_fold(#full_doc_info{id=Id}, _, Acc) -> + {ok, [mem3_util:to_atom(Id) | Acc]}. + +listen_for_changes(Since) -> + DbName = ?l2b(couch_config:get("mem3", "nodedb", "nodes")), + {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) when is_list(DbName) -> + ensure_exists(list_to_binary(DbName)); +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}, _}, _) -> + Node = couch_util:get_value(<<"id">>, Change), + case Node of <<"_design/", _/binary>> -> ok; _ -> + case couch_util:get_value(deleted, Change, false) of + false -> + gen_server:call(?MODULE, {add_node, mem3_util:to_atom(Node)}); + true -> + gen_server:call(?MODULE, {remove_node, mem3_util:to_atom(Node)}) + end + end, + {ok, couch_util:get_value(<<"seq">>, Change)}; +changes_callback(timeout, _) -> + {ok, nil}. |