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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 is used to track the status of long running tasks.
% Long running tasks register themselves, via a call to add_task/1, and then
% update their status properties via update/1. The status of a task is a
% list of properties. Each property is a tuple, with the first element being
% either an atom or a binary and the second element must be an EJSON value. When
% a task updates its status, it can override some or all of its properties.
% The properties {started_on, UnitTimestamp}, {updated_on, UnixTimestamp} and
% {pid, ErlangPid} are automatically added by this module.
% When a tracked task dies, its status will be automatically removed from
% memory. To get the tasks list, call the all/0 function.
-export([start_link/0, stop/0]).
-export([all/0, add_task/1, update/1, get/1, set_update_frequency/1]).
-export([is_task_added/0]).
-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").
-define(set(L, K, V), lists:keystore(K, 1, L, {K, V})).
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
stop() ->
gen_server:cast(?MODULE, stop).
all() ->
gen_server:call(?MODULE, all).
add_task(Props) ->
put(task_status_update, {{0, 0, 0}, 0}),
Ts = timestamp(),
TaskProps = lists:ukeysort(
1, [{started_on, Ts}, {updated_on, Ts} | Props]),
put(task_status_props, TaskProps),
gen_server:call(?MODULE, {add_task, TaskProps}).
is_task_added() ->
is_list(erlang:get(task_status_props)).
set_update_frequency(Msecs) ->
put(task_status_update, {{0, 0, 0}, Msecs * 1000}).
update(Props) ->
MergeProps = lists:ukeysort(1, Props),
TaskProps = lists:ukeymerge(1, MergeProps, erlang:get(task_status_props)),
put(task_status_props, TaskProps),
maybe_persist(TaskProps).
get(Props) when is_list(Props) ->
TaskProps = erlang:get(task_status_props),
[couch_util:get_value(P, TaskProps) || P <- Props];
get(Prop) ->
TaskProps = erlang:get(task_status_props),
couch_util:get_value(Prop, TaskProps).
maybe_persist(TaskProps0) ->
{LastUpdateTime, Frequency} = erlang:get(task_status_update),
case timer:now_diff(Now = now(), LastUpdateTime) >= Frequency of
true ->
put(task_status_update, {Now, Frequency}),
TaskProps = ?set(TaskProps0, updated_on, timestamp(Now)),
gen_server:cast(?MODULE, {update_status, self(), TaskProps});
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, TaskProps}, {From, _}, Server) ->
case ets:lookup(?MODULE, From) of
[] ->
true = ets:insert(?MODULE, {From, TaskProps}),
erlang:monitor(process, From),
{reply, ok, Server};
[_] ->
{reply, {add_task_error, already_registered}, Server}
end;
handle_call(all, _, Server) ->
All = ets:tab2list(?MODULE),
{reply, tasks_to_json(All), Server}.
handle_cast({update_status, Pid, NewProps}, Server) ->
case ets:lookup(?MODULE, Pid) of
[{Pid, _CurProps}] ->
?LOG_DEBUG("New task status for ~p: ~p", [Pid, NewProps]),
true = ets:insert(?MODULE, {Pid, NewProps});
_ ->
% Task finished/died in the meanwhile and we must have received
% a monitor message before this call - ignore.
ok
end,
{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}.
timestamp() ->
timestamp(now()).
timestamp({Mega, Secs, _}) ->
Mega * 1000000 + Secs.
tasks_to_json(Tasks) ->
[ [{pid, ?l2b(pid_to_list(Pid))} | Props] || {Pid, Props} <- Tasks].
|
