Increase the execution interval for the tracker stats importer

[josecelano]

Relates to: torrust/torrust-demo#1

There is a background task that imports torrent stats from the Tracker. The Tracker Statistics Importer checks every 100 milliseconds if there are torrents to import. It executes a SQL query to fetch torrents that have not been updated in the last hour:

	"torrent_id"	INTEGER NOT NULL,
	"tracker_url"	VARCHAR(256) NOT NULL,
	"seeders"	INTEGER NOT NULL DEFAULT 0,
	"leechers"	INTEGER NOT NULL DEFAULT 0,
	"updated_at"	TEXT DEFAULT 1000-01-01 00:00:00,
	FOREIGN KEY("torrent_id") REFERENCES "torrust_torrents"("torrent_id") ON DELETE CASCADE,
	UNIQUE("torrent_id","tracker_url"),
	PRIMARY KEY("torrent_id")
);

The field updated_at stores the last update date. You can configure the importer in the config file:

[tracker_statistics_importer]
torrent_info_update_interval = 3600

That configuration means the Index should try to update torrents at least every hour.

It seems querying the database every 100 milliseconds is overloading the demo server. Although it's a tiny instance, we should increase the interval. It could be a configuration option or even calculated manually in the future.

According to the data I've collected we could increase it from 100 milliseconds to 2000 milliseconds.