Add email on Flask error

app/__init__.py

@@ -37,5 +37,9 @@ csrf = CsrfProtect(app)
 mail = Mail(app)
 pages = FlatPages(app)
 
+if not app.debug:
+	from .maillogger import register_mail_error_handler
+	register_mail_error_handler(app, mail)
+
 from . import models, tasks
 from .views import *

app/maillogger.py

@@ -0,0 +1,109 @@
+import logging
+from enum import Enum
+from app.tasks.emails import sendEmailRaw
+
+def _has_newline(line):
+	"""Used by has_bad_header to check for \\r or \\n"""
+	if line and ("\r" in line or "\n" in line):
+		return True
+	return False
+
+def _is_bad_subject(subject):
+	"""Copied from: flask_mail.py class Message def has_bad_headers"""
+	if _has_newline(subject):
+		for linenum, line in enumerate(subject.split("\r\n")):
+			if not line:
+				return True
+			if linenum > 0 and line[0] not in "\t ":
+				return True
+			if _has_newline(line):
+				return True
+			if len(line.strip()) == 0:
+				return True
+	return False
+
+
+class FlaskMailSubjectFormatter(logging.Formatter):
+	def format(self, record):
+		record.message = record.getMessage()
+		if self.usesTime():
+			record.asctime = self.formatTime(record, self.datefmt)
+		s = self.formatMessage(record)
+		return s
+
+class FlaskMailTextFormatter(logging.Formatter):
+	pass
+
+# TODO: hier nog niet tevreden over (vooral logger.error(..., exc_info, stack_info))
+class FlaskMailHTMLFormatter(logging.Formatter):
+	pre_template = "<h1>%s</h1><pre>%s</pre>"
+	def formatException(self, exc_info):
+		formatted_exception = logging.Handler.formatException(self, exc_info)
+		return FlaskMailHTMLFormatter.pre_template % ("Exception information", formatted_exception)
+	def formatStack(self, stack_info):
+		return FlaskMailHTMLFormatter.pre_template % ("<h1>Stack information</h1><pre>%s</pre>", stack_info)
+
+
+# see: https://github.com/python/cpython/blob/3.6/Lib/logging/__init__.py (class Handler)
+
+class FlaskMailHandler(logging.Handler):
+	def __init__(self, mailer, subject_template, level=logging.NOTSET):
+		logging.Handler.__init__(self, level)
+		self.mailer = mailer
+		self.send_to = mailer.app.config["MAIL_UTILS_ERROR_SEND_TO"]
+		self.subject_template = subject_template
+		self.html_formatter = None
+
+	def setFormatter(self, text_fmt, html_fmt=None):
+		"""
+		Set the formatters for this handler. Provide at least one formatter.
+		When no text_fmt is provided, no text-part is created for the email body.
+		"""
+		assert (text_fmt, html_fmt) != (None, None), "At least one formatter should be provided"
+		if type(text_fmt)==str:
+			text_fmt = FlaskMailTextFormatter(text_fmt)
+		self.formatter = text_fmt
+		if type(html_fmt)==str:
+			html_fmt = FlaskMailHTMLFormatter(html_fmt)
+		self.html_formatter = html_fmt
+
+	def getSubject(self, record):
+		fmt = FlaskMailSubjectFormatter(self.subject_template)
+		subject = fmt.format(record)
+		#Since templates can cause header problems, and we rather have a incomplete email then an error, we fix this
+		if _is_bad_subject(subject):
+			subject="FlaskMailHandler log-entry from %s [original subject is replaced, because it would result in a bad header]" % self.mailer.app.name
+		return subject
+
+	def emit(self, record):
+		text = self.format(record)				if self.formatter	  else None
+		html = self.html_formatter.format(record) if self.html_formatter else None
+		sendEmailRaw.delay(self.send_to, self.getSubject(record), text, html)
+
+
+def register_mail_error_handler(app, mailer):
+	subject_template = "ContentDB crashed (%(module)s > %(funcName)s)"
+	text_template = """
+Message type: %(levelname)s
+Location:	 %(pathname)s:%(lineno)d
+Module:	   %(module)s
+Function:	 %(funcName)s
+Time:		 %(asctime)s
+Message:
+%(message)s"""
+	html_template = """
+<style>th { text-align: right}</style><table>
+<tr><th>Message type:</th><td>%(levelname)s</td></tr>
+<tr>	<th>Location:</th><td>%(pathname)s:%(lineno)d</td></tr>
+<tr>	  <th>Module:</th><td>%(module)s</td></tr>
+<tr>	<th>Function:</th><td>%(funcName)s</td></tr>
+<tr>		<th>Time:</th><td>%(asctime)s</td></tr>
+</table>
+<h2>Message</h2>
+<pre>%(message)s</pre>"""
+
+	import logging
+	mail_handler = FlaskMailHandler(mailer, subject_template)
+	mail_handler.setLevel(logging.ERROR)
+	mail_handler.setFormatter(text_template, html_template)
+	app.logger.addHandler(mail_handler)

app/tasks/emails.py

@@ -26,3 +26,13 @@ def sendVerifyEmail(newEmail, token):
 	msg.body = "This is a verification email!"
 	msg.html = render_template("emails/verify.html", token=token)
 	mail.send(msg)
+
+@celery.task()
+def sendEmailRaw(to, subject, text, html):
+	from flask_mail import Message
+	msg = Message(subject, recipients=to)
+	if text:
+		msg.body = text
+	if html:
+		msg.html = html
+	mail.send(msg)

config.example.cfg

@@ -22,3 +22,4 @@ MAIL_DEFAULT_SENDER=""
 MAIL_SERVER=""
 MAIL_PORT=587
 MAIL_USE_TLS=True
+MAIL_UTILS_ERROR_SEND_TO=[""]