From cd31eaa62c689c979c06900cab77749ef245d32b Mon Sep 17 00:00:00 2001
From: =?utf8?q?Stefan=20K=C3=B6gl?= <stefan@skoegl.net>
Date: Sun, 3 Dec 2017 20:59:06 +0100
Subject: [PATCH] Modify Podcast.update_interval with factor

When no new episodes are found, the factor increases the interval between
podcast updates.
---
 mygpo/data/feeddownloader.py                         | 11 +++++++++++
 .../0040_podcast_update_interval_factor.py           | 20 ++++++++++++++++++++
 mygpo/podcasts/models.py                             | 20 ++++++++++++++++----
 3 files changed, 47 insertions(+), 4 deletions(-)
 create mode 100644 mygpo/podcasts/migrations/0040_podcast_update_interval_factor.py

diff --git a/mygpo/data/feeddownloader.py b/mygpo/data/feeddownloader.py
index 9e7b3178..79dcbab0 100755
--- a/mygpo/data/feeddownloader.py
+++ b/mygpo/data/feeddownloader.py
@@ -239,8 +239,19 @@ class PodcastUpdater(object):
                                           released__isnull=False)\
                                   .order_by('released')
 
+        # Determine update interval
+
+        # Update interval is based on intervals between episodes
         podcast.update_interval = episode_updater.get_update_interval(episodes)
 
+        # factor is increased / decreased depending on whether the latest
+        # update has returned episodes
+        if episode_updater.episodes_added == 0:  # no episodes, incr factor
+            podcast.update_interval_factor *= 1.2
+        elif episode_updater.episodes_added > 1:  # new episodes, decr factor
+            newfactor = podcast.update_interval_factor / 1.2
+            podcast.update_interval_factor = max(1, newfactor)  # never below 1
+
         latest_episode = episodes.last()
         if latest_episode:
             podcast.latest_episode_timestamp = latest_episode.released
diff --git a/mygpo/podcasts/migrations/0040_podcast_update_interval_factor.py b/mygpo/podcasts/migrations/0040_podcast_update_interval_factor.py
new file mode 100644
index 00000000..57447b2d
--- /dev/null
+++ b/mygpo/podcasts/migrations/0040_podcast_update_interval_factor.py
@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.5 on 2017-12-03 19:53
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('podcasts', '0039_podcast_search_index_uptodate'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='podcast',
+            name='update_interval_factor',
+            field=models.FloatField(default=1),
+        ),
+    ]
diff --git a/mygpo/podcasts/models.py b/mygpo/podcasts/models.py
index 7e7ea056..f4596181 100644
--- a/mygpo/podcasts/models.py
+++ b/mygpo/podcasts/models.py
@@ -341,16 +341,20 @@ class PodcastQuerySet(MergedUUIDQuerySet):
 
     def order_by_next_update(self):
         """ Sort podcasts by next scheduled update """
-        NEXTUPDATE = "last_update + (update_interval || ' hours')::INTERVAL"
+        NEXTUPDATE = ("last_update + (update_interval * "
+                      "update_interval_factor || ' hours')::INTERVAL")
         q = self.extra(select={'_next_update': NEXTUPDATE})
         return q.order_by('_next_update')
 
     @property
     def next_update(self):
-        return self.last_update + timedelta(hours=self.update_interval)
+        interval = (timedelta(hours=self.update_interval) *
+                    self.update_interval_factor)
+        return self.last_update + interval
 
     def next_update_between(self, start, end):
-        NEXTUPDATE_BETWEEN = ("(last_update + (update_interval || "
+        NEXTUPDATE_BETWEEN = ("(last_update + (update_interval * "
+                              " update_interval_factor || "
                               "' hours')::INTERVAL) BETWEEN %s AND %s")
         return self.extra(
             where=[NEXTUPDATE_BETWEEN], params=[start, end]
@@ -570,9 +574,15 @@ class Podcast(UUIDModel, TitleModel, DescriptionModel, LinkModel,
     latest_episode_timestamp = models.DateTimeField(null=True)
     episode_count = models.PositiveIntegerField(default=0)
     hub = models.URLField(null=True)
+
+    # Interval between episodes, within a specified range
     update_interval = models.PositiveSmallIntegerField(null=False,
         default=DEFAULT_UPDATE_INTERVAL)
 
+    # factor to increase update_interval if an update does not find any
+    # new episodes
+    update_interval_factor = models.FloatField(default=1)
+
     # "order" value of the most recent episode (will be the highest of all)
     max_episode_order = models.PositiveIntegerField(null=True, default=None)
 
@@ -698,7 +708,9 @@ class Podcast(UUIDModel, TitleModel, DescriptionModel, LinkModel,
 
     @property
     def next_update(self):
-        return self.last_update + timedelta(hours=self.update_interval)
+        interval = (timedelta(hours=self.update_interval) *
+                    self.update_interval_factor)
+        return self.last_update + interval
 
 
 class EpisodeQuerySet(MergedUUIDQuerySet):
-- 
2.11.4.GIT