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}.