bugfix: worker dies on smtp connection errors (#1821)

Catch socket.error exception when trying to connect smtp server in error email notification.

luigi/notifications.py

@@ -136,16 +136,20 @@ def send_email_smtp(config, sender, subject, message, recipients, image_png):
 
     smtp_login = config.get('core', 'smtp_login', None)
     smtp_password = config.get('core', 'smtp_password', None)
-    smtp = smtplib.SMTP(**kwargs) if not smtp_ssl else smtplib.SMTP_SSL(**kwargs)
-    smtp.ehlo_or_helo_if_needed()
-    if smtp.has_extn('starttls') and not smtp_without_tls:
-        smtp.starttls()
-    if smtp_login and smtp_password:
-        smtp.login(smtp_login, smtp_password)
 
-    msg_root = generate_email(sender, subject, message, recipients, image_png)
+    try:
+        smtp = smtplib.SMTP(**kwargs) if not smtp_ssl else smtplib.SMTP_SSL(**kwargs)
+        smtp.ehlo_or_helo_if_needed()
+        if smtp.has_extn('starttls') and not smtp_without_tls:
+            smtp.starttls()
+        if smtp_login and smtp_password:
+            smtp.login(smtp_login, smtp_password)
+
+        msg_root = generate_email(sender, subject, message, recipients, image_png)
 
-    smtp.sendmail(sender, recipients, msg_root.as_string())
+        smtp.sendmail(sender, recipients, msg_root.as_string())
+    except socket.error:
+        logger.error("Not able to connect to smtp server")
 
 
 def send_email_ses(config, sender, subject, message, recipients, image_png):

test/notifications_test.py

@@ -18,6 +18,7 @@
 from helpers import unittest
 import mock
 import sys
+import socket
 
 from helpers import with_config
 from luigi import notifications
@@ -258,6 +259,40 @@ def test_sends_smtp_email_without_tls(self):
                     .assert_called_once_with(self.sender, self.recipients,
                                              self.mocked_email_msg)
 
+    @with_config({"core": {"smtp_ssl": "False",
+                           "smtp_host": "my.smtp.local",
+                           "smtp_port": "999",
+                           "smtp_local_hostname": "ptms",
+                           "smtp_timeout": "1200",
+                           "smtp_login": "Robin",
+                           "smtp_password": "dooH",
+                           "smtp_without_tls": "True"}})
+    def test_sends_smtp_email_exceptions(self):
+        """
+        Call notificaions.send_email_smtp when it cannot connect to smtp server (socket.error)
+        starttls.
+        """
+        smtp_kws = {"host": "my.smtp.local",
+                    "port": 999,
+                    "local_hostname": "ptms",
+                    "timeout": 1200}
+
+        with mock.patch('smtplib.SMTP') as SMTP:
+            with mock.patch('luigi.notifications.generate_email') as generate_email:
+                SMTP.side_effect = socket.error()
+                generate_email.return_value \
+                    .as_string.return_value = self.mocked_email_msg
+
+                try:
+                    notifications.send_email_smtp(configuration.get_config(),
+                                                  *self.notification_args)
+                except socket.error:
+                    self.fail("send_email_smtp() raised expection unexpectedly")
+
+                SMTP.assert_called_once_with(**smtp_kws)
+                self.assertEqual(notifications.generate_email.called, False)
+                self.assertEqual(SMTP.sendemail.called, False)
+
 
 class TestSendgridEmail(unittest.TestCase, NotificationFixture):
     """