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-rw-r--r--src/mem3_nodes.erl117
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}.