From 112d3fb86b07ed4450d17883cde78a0baf7ef53c Mon Sep 17 00:00:00 2001
From: Michael Tremer <michael.tremer@ipfire.org>
Date: Mon, 29 Sep 2014 14:03:46 +0000
Subject: [PATCH] Hold back further updates after failed updates for a while

Partly addresses #10603
---
 src/ddns/database.py  | 43 ++++++++++++++++++++++++++++++++++++++---
 src/ddns/providers.py | 45 ++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 82 insertions(+), 6 deletions(-)

diff --git a/src/ddns/database.py b/src/ddns/database.py
index 9301187..1e613c9 100644
--- a/src/ddns/database.py
+++ b/src/ddns/database.py
@@ -97,12 +97,49 @@ class DDNSDatabase(object):
 
 		return self.add_update(hostname, "failure", message=message)
 
-	def last_update(self, hostname, status="success"):
+	def last_update(self, hostname, status=None):
+		"""
+			Returns the timestamp of the last update (with the given status code).
+		"""
 		c = self._db.cursor()
 
 		try:
-			c.execute("SELECT timestamp FROM updates WHERE hostname = ? AND status = ? \
-				ORDER BY timestamp DESC LIMIT 1", (hostname, status))
+			if status:
+				c.execute("SELECT timestamp FROM updates WHERE hostname = ? AND status = ? \
+					ORDER BY timestamp DESC LIMIT 1", (hostname, status))
+			else:
+				c.execute("SELECT timestamp FROM updates WHERE hostname = ? \
+					ORDER BY timestamp DESC LIMIT 1", (hostname,))
+
+			for row in c:
+				return row[0]
+		finally:
+			c.close()
+
+	def last_update_status(self, hostname):
+		"""
+			Returns the update status of the last update.
+		"""
+		c = self._db.cursor()
+
+		try:
+			c.execute("SELECT status FROM updates WHERE hostname = ? \
+				ORDER BY timestamp DESC LIMIT 1", (hostname,))
+
+			for row in c:
+				return row[0]
+		finally:
+			c.close()
+
+	def last_update_failure_message(self, hostname):
+		"""
+			Returns the reason string for the last failed update (if any).
+		"""
+		c = self._db.cursor()
+
+		try:
+			c.execute("SELECT message FROM updates WHERE hostname = ? AND status = ? \
+				ORDER BY timestamp DESC LIMIT 1", (hostname, "failure"))
 
 			for row in c:
 				return row[0]
diff --git a/src/ddns/providers.py b/src/ddns/providers.py
index 797ef3d..16a6e7b 100644
--- a/src/ddns/providers.py
+++ b/src/ddns/providers.py
@@ -63,6 +63,10 @@ class DDNSProvider(object):
 	# the IP address has changed.
 	holdoff_days = 30
 
+	# holdoff time for update failures - Number of days no update
+	# is tried after the last one has failed.
+	holdoff_failure_days = 0.5
+
 	# True if the provider is able to remove records, too.
 	# Required to remove AAAA records if IPv6 is absent again.
 	can_remove_records = True
@@ -149,8 +153,8 @@ class DDNSProvider(object):
 		if force:
 			logger.debug(_("Updating %s forced") % self.hostname)
 
-		# Do nothing if no update is required
-		elif not self.requires_update:
+		# Do nothing if the last update has failed or no update is required
+		elif self.has_failure or not self.requires_update:
 			return
 
 		# Execute the update.
@@ -207,6 +211,41 @@ class DDNSProvider(object):
 
 		return False
 
+	@property
+	def has_failure(self):
+		"""
+			Returns True when the last update has failed and no retry
+			should be performed, yet.
+		"""
+		last_status = self.db.last_update_status(self.hostname)
+
+		# Return False if the last update has not failed.
+		if not last_status == "failure":
+			return False
+
+		# Determine when the holdoff time ends
+		last_update = self.db.last_update(self.hostname, status=last_status)
+		holdoff_end = last_update + datetime.timedelta(days=self.holdoff_failure_days)
+
+		now = datetime.datetime.utcnow()
+		if now < holdoff_end:
+			failure_message = self.db.last_update_failure_message(self.hostname)
+
+			logger.warning(_("An update has not been performed because earlier updates failed for %s") \
+				% self.hostname)
+
+			if failure_message:
+				logger.warning(_("Last failure message:"))
+
+				for line in failure_message.splitlines():
+					logger.warning("  %s" % line)
+
+			logger.warning(_("Further updates will be withheld until %s") % holdoff_end)
+
+			return True
+
+		return False
+
 	def ip_address_changed(self, protos):
 		"""
 			Returns True if this host is already up to date
@@ -243,7 +282,7 @@ class DDNSProvider(object):
 			return False
 
 		# Get the timestamp of the last successfull update
-		last_update = self.db.last_update(self.hostname)
+		last_update = self.db.last_update(self.hostname, status="success")
 
 		# If no timestamp has been recorded, no update has been
 		# performed. An update should be performed now.
-- 
2.39.2