Check number of delivered emails by postfix for netdata

postfix_delivered.py

#!/usr/bin/env python

import os, sys, time
import socket, threading
from pwd import getpwnam

class tail(object):
  def __init__(self, file):
    self.file = file

  def check(self):
    if not os.access(self.file, os.F_OK): raise
    if not os.access(self.file, os.R_OK): raise
    if os.path.isdir(self.file): raise

  def lines(self):
    self.check()
    while 1:
      s = 1
      try:
        with open(self.file) as f:
          f.seek(0, 2)
          while 1:
            l = f.readline()
            if not l:
              if not s: break
              time.sleep(s)
              s = 0
            else:
              yield l
        time.sleep(s)
      except: pass

class postfix_delivered(object):
  def __init__(self, sock = "/etc/postfix/postfix_delivered.sock"):
    self.sock = sock
    self.counter = 0

    try:
      os.unlink(self.sock)
    except OSError:
      if os.path.exists(self.sock): raise

    self.socket = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
    self.socket.bind(self.sock)

    try: id = getpwnam("netdata")[2]
    except KeyError: raise

    os.chown(self.sock, id, -1)

    self.socket.listen(5)

    self.lock = threading.Lock()

    self.thread = threading.Thread(target = self.run, args = ())
    self.thread.daemon = True
    self.thread.start()

  def run(self):
    while 1:
      c, _ = self.socket.accept()
      with self.lock:
        counter, self.counter = self.counter, 0
      try:
        c.sendall(str(counter))
      finally:
        c.close()

    self.socket.close()

  def inc(self):
    with self.lock:
      self.counter += 1

if __name__ == '__main__':
  pd = postfix_delivered()
  t = tail("/var/log/maillog")
  for line in t.lines():
    if not "status=sent" in line: continue
    pd.inc()