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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,init/1,terminate/2,handle_call/3,handle_cast/2,handle_info/2,
code_change/3,add_task/3,update/1,update/2,all/0,set_update_frequency/1]).
-include("couch_db.hrl").
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
to_binary(L) when is_list(L) ->
?l2b(L);
to_binary(B) when is_binary(B) ->
B.
add_task(Type, TaskName, StatusText) ->
put(task_status_update, {{0,0,0}, 0}),
gen_server:call(?MODULE, {add_task, to_binary(Type),
to_binary(TaskName), to_binary(StatusText)}).
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}),
gen_server:cast(?MODULE, {update_status, self(), ?l2b(io_lib:format(Format, Data))});
false ->
ok
end.
% returns a list of proplists. Each proplist describes a running task.
all() ->
[[{type,Type},
{task,Task},
{status,Status},
{pid,?l2b(pid_to_list(Pid))}] ||
{Pid, {Type,Task,Status}} <- ets:tab2list(tasks_by_pid)].
init([]) ->
% read configuration settings and register for configuration changes
ets:new(tasks_by_pid, [ordered_set, protected, named_table]),
{ok, nil}.
terminate(_Reason,_State) ->
ok.
handle_call({add_task,Type,TaskName,StatusText}, {From, _}, Server) ->
case ets:lookup(tasks_by_pid, From) of
[] ->
true = ets:insert(tasks_by_pid, {From,{Type,TaskName,StatusText}}),
erlang:monitor(process, From),
{reply, ok, Server};
[_] ->
{reply, {add_task_error, already_registered}, Server}
end.
handle_cast({update_status, Pid, StatusText}, Server) ->
[{Pid, {Type,TaskName,_StatusText}}] = ets:lookup(tasks_by_pid, Pid),
true = ets:insert(tasks_by_pid, {Pid, {Type,TaskName,StatusText}}),
{noreply, Server}.
handle_info({'DOWN', _MonitorRef, _Type, Pid, _Info}, Server) ->
ets:delete(tasks_by_pid, Pid),
{noreply, Server}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
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