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+% 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(couch_task_status).
+-behaviour(gen_server).
+
+% This module allows is used to track the status of long running tasks.
+% Long running tasks register (add_task/3) then update their status (update/1)
+% and the task and status is added to tasks list. When the tracked task dies
+% it will be automatically removed the tracking. To get the tasks list, use the
+% all/0 function
+
+-export([start_link/0, stop/0]).
+-export([all/0, add_task/3, update/1, update/2, set_update_frequency/1]).
+
+-export([init/1, terminate/2, code_change/3]).
+-export([handle_call/3, handle_cast/2, handle_info/2]).
+
+-import(couch_util, [to_binary/1]).
+
+-include("couch_db.hrl").
+
+
+start_link() ->
+ gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
+
+
+stop() ->
+ gen_server:cast(?MODULE, stop).
+
+
+all() ->
+ gen_server:call(?MODULE, all).
+
+
+add_task(Type, TaskName, StatusText) ->
+ put(task_status_update, {{0, 0, 0}, 0}),
+ Msg = {
+ add_task,
+ to_binary(Type),
+ to_binary(TaskName),
+ to_binary(StatusText)
+ },
+ gen_server:call(?MODULE, Msg).
+
+
+set_update_frequency(Msecs) ->
+ put(task_status_update, {{0, 0, 0}, Msecs * 1000}).
+
+
+update(StatusText) ->
+ update("~s", [StatusText]).
+
+update(Format, Data) ->
+ {LastUpdateTime, Frequency} = get(task_status_update),
+ case timer:now_diff(Now = now(), LastUpdateTime) >= Frequency of
+ true ->
+ put(task_status_update, {Now, Frequency}),
+ Msg = ?l2b(io_lib:format(Format, Data)),
+ gen_server:cast(?MODULE, {update_status, self(), Msg});
+ false ->
+ ok
+ end.
+
+
+init([]) ->
+ % read configuration settings and register for configuration changes
+ ets:new(?MODULE, [ordered_set, protected, named_table]),
+ {ok, nil}.
+
+
+terminate(_Reason,_State) ->
+ ok.
+
+
+handle_call({add_task, Type, TaskName, StatusText}, {From, _}, Server) ->
+ case ets:lookup(?MODULE, From) of
+ [] ->
+ true = ets:insert(?MODULE, {From, {Type, TaskName, StatusText}}),
+ erlang:monitor(process, From),
+ {reply, ok, Server};
+ [_] ->
+ {reply, {add_task_error, already_registered}, Server}
+ end;
+handle_call(all, _, Server) ->
+ All = [
+ [
+ {type, Type},
+ {task, Task},
+ {status, Status},
+ {pid, ?l2b(pid_to_list(Pid))}
+ ]
+ ||
+ {Pid, {Type, Task, Status}} <- ets:tab2list(?MODULE)
+ ],
+ {reply, All, Server}.
+
+
+handle_cast({update_status, Pid, StatusText}, Server) ->
+ [{Pid, {Type, TaskName, _StatusText}}] = ets:lookup(?MODULE, Pid),
+ true = ets:insert(?MODULE, {Pid, {Type, TaskName, StatusText}}),
+ {noreply, Server};
+handle_cast(stop, State) ->
+ {stop, normal, State}.
+
+handle_info({'DOWN', _MonitorRef, _Type, Pid, _Info}, Server) ->
+ %% should we also erlang:demonitor(_MonitorRef), ?
+ ets:delete(?MODULE, Pid),
+ {noreply, Server}.
+
+
+code_change(_OldVsn, State, _Extra) ->
+ {ok, State}.
+