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% 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) ->
?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}.
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