1 files changed, 136 insertions, 0 deletions
diff --git a/deps/mem3/src/mem3_nodes.erl b/deps/mem3/src/mem3_nodes.erl
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+++ b/deps/mem3/src/mem3_nodes.erl
@@ -0,0 +1,136 @@
+% Copyright 2010 Cloudant
+%
+% 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(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, get_node_info/2]).
+
+-include("mem3.hrl").
+-include_lib("couch/include/couch_db.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).
+
+get_node_info(Node, Key) ->
+    gen_server:call(?MODULE, {get_node_info, Node, Key}).
+
+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, lists:sort(dict:fetch_keys(State#state.nodes)), State};
+handle_call({get_node_info, Node, Key}, _From, State) ->
+    case dict:find(Node, State#state.nodes) of
+        {ok, NodeInfo} ->
+            {reply, couch_util:get_value(Key, NodeInfo), State};
+        error ->
+            {reply, error, State}
+    end;
+handle_call({add_node, Node, NodeInfo}, _From, #state{nodes=Nodes} = State) ->
+    gen_event:notify(mem3_events, {add_node, Node}),
+    {reply, ok, State#state{nodes = dict:store(Node, NodeInfo, Nodes)}};
+handle_call({remove_node, Node}, _From, #state{nodes=Nodes} = State) ->
+    gen_event:notify(mem3_events, {remove_node, Node}),
+    {reply, ok, State#state{nodes = dict:erase(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) ->
+    twig:log(notice, "~p changes listener died ~p", [?MODULE, Reason]),
+    StartSeq = State#state.update_seq,
+    Seq = case Reason of {seq, EndSeq} -> EndSeq; _ -> StartSeq end,
+    erlang:send_after(5000, self(), 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", "node_db", "nodes"),
+    {ok, Db} = mem3_util:ensure_exists(DbName),
+    {ok, _, {_, Nodes0}} = couch_btree:fold(Db#db.id_tree, fun first_fold/3,
+                                       {Db, dict:new()}, []),
+    % add self if not already present
+    case dict:find(node(), Nodes0) of
+    {ok, _} ->
+        Nodes = Nodes0;
+    error ->
+        Doc = #doc{id = couch_util:to_binary(node())},
+        {ok, _} = couch_db:update_doc(Db, Doc, []),
+        Nodes = dict:store(node(), [], Nodes0)
+    end,
+    couch_db:close(Db),
+    {Nodes, Db#db.update_seq}.
+
+first_fold(#full_doc_info{id = <<"_design/", _/binary>>}, _, Acc) ->
+    {ok, Acc};
+first_fold(#full_doc_info{deleted=true}, _, Acc) ->
+    {ok, Acc};
+first_fold(#full_doc_info{id=Id}=DocInfo, _, {Db, Dict}) ->
+    {ok, #doc{body={Props}}} = couch_db:open_doc(Db, DocInfo),
+    {ok, {Db, dict:store(mem3_util:to_atom(Id), Props, Dict)}}.
+
+listen_for_changes(Since) ->
+    DbName = couch_config:get("mem3", "node_db", "nodes"),
+    {ok, Db} = mem3_util: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).
+
+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 ->
+            {Props} = couch_util:get_value(doc, Change),
+            gen_server:call(?MODULE, {add_node, mem3_util:to_atom(Node), Props});
+        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}.