openrvdas.logger.writers.email_writer

  1#!/usr/bin/env python3
  2
  3import getpass
  4import smtplib
  5import socket
  6import threading
  7import time
  8
  9from email.message import EmailMessage
 10
 11
 12from logger.writers.writer import Writer  # noqa: E402
 13
 14
 15class EmailWriter(Writer):
 16    """Send the record as an email message."""
 17
 18    def __init__(self, to, sender=None, subject=None, max_freq=3 * 60, **kwargs):
 19        """
 20        ```
 21        to           Comma-separated list of email addresses
 22
 23        sender       Identity of sender; default is <user>@<hostname>
 24                     if omitted
 25
 26        subject      Optional custom subject line; default is start of record
 27
 28        max_freq     maximum frequency, in seconds between messages, with which
 29                     to send email. Default is 3 minutes.
 30        ```
 31        NOTE: Of course, you'll need to make sure your machine has SMTP
 32        configured and running if you wish to send email anywhere other than
 33        localhost.
 34        """
 35        super().__init__(**kwargs)  # processes 'quiet' and type hints
 36
 37        if not sender:
 38            username = getpass.getuser()
 39            hostname = socket.gethostname()
 40            sender = username + '@' + hostname
 41        self.to = to
 42        self.sender = sender
 43        self.subject = subject
 44        self.max_freq = max_freq
 45
 46        self.queue = []
 47        self.queue_lock = threading.Lock()
 48        self.last_send = 0
 49
 50    ############################
 51    def _send_email(self, sleep=0):
 52        """Internal: Send record (and all previously queued but not sent) records
 53        as an email message."""
 54        time.sleep(sleep)
 55
 56        # Grab messages from queue
 57        with self.queue_lock:
 58            # If someone has snatched all the messages while we slept,
 59            # it's fine - just go home.
 60            if not self.queue:
 61                return
 62
 63            # Otherwise, snatch them all for ourselves
 64            message = '\n'.join(self.queue)
 65            self.queue = []
 66            self.last_send = time.time()
 67
 68        msg = EmailMessage()
 69        msg.set_content(message)
 70
 71        msg['To'] = self.to
 72        msg['From'] = self.sender
 73
 74        # If no subject specified, just wedge the message in, up to a
 75        # newline, which is a prohibited character for header fields
 76        if self.subject:
 77            msg['Subject'] = self.subject
 78        else:
 79            if message.find('\n') > 0:
 80                subject = message[:message.find('\n')]
 81            else:
 82                subject = message
 83            msg['Subject'] = subject
 84
 85        # Send the message via our own SMTP server.
 86        s = smtplib.SMTP('localhost')
 87        s.send_message(msg)
 88        s.quit()
 89
 90    ############################
 91    def write(self, record):
 92        """Send record as email, or queue to send if have already sent recently."""
 93        if not record:
 94            return
 95
 96        with self.queue_lock:
 97            # Stash record in queue
 98            self.queue.append(record)
 99
100            # How long before we can send next email?
101            now = time.time()
102            time_to_sleep = max(0, self.max_freq - (now - self.last_send))
103
104        # Start up a separate thread so we can go ahead and return while
105        # it possibly sleeps and waits.
106        threading.Thread(target=self._send_email, args=(time_to_sleep,),
107                         daemon=True).start()