1 files changed, 118 insertions, 0 deletions
diff --git a/deps/mem3/src/mem3_cache.erl b/deps/mem3/src/mem3_cache.erl
new file mode 100644
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+++ b/deps/mem3/src/mem3_cache.erl
@@ -0,0 +1,118 @@
+% 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_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) ->
+    twig:log(notice, "~p changes listener died ~p", [?MODULE, Reason]),
+    Seq = case Reason of {seq, EndSeq} -> EndSeq; _ -> 0 end,
+    erlang:send_after(5000, self(), {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 = couch_config:get("mem3", "shard_db", "dbs"),
+    {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}, _}, _) ->
+    DbName = couch_util:get_value(<<"id">>, Change),
+    case DbName of <<"_design/", _/binary>> -> ok; _Else ->
+        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} ->
+                twig:log(error, "missing partition table for ~s: ~p", [DbName, Reason]);
+            {Doc} ->
+                ets:delete(partitions, DbName),
+                Shards = mem3_util:build_shards(DbName, Doc),
+                ets:insert(partitions, Shards),
+                [create_if_missing(Name) || #shard{name=Name, node=Node}
+                    <- Shards, Node =:= node()]
+            end
+        end
+    end,
+    {ok, couch_util:get_value(<<"seq">>, Change)};
+changes_callback(timeout, _) ->
+    {ok, nil}.
+
+create_if_missing(Name) ->
+    DbDir = couch_config:get("couchdb", "database_dir"),
+    Filename = filename:join(DbDir, ?b2l(Name) ++ ".couch"),
+    case filelib:is_regular(Filename) of
+    true ->
+        ok;
+    false ->
+        Options = [{user_ctx, #user_ctx{roles=[<<"_admin">>]}}],
+        case couch_server:create(Name, Options) of
+        {ok, Db} ->
+            couch_db:close(Db);
+        Error ->
+            twig:log(error, "~p tried to create ~s, got ~p", [?MODULE, Name, Error])
+        end
+    end.