djbdns/io.py

   1 from subprocess import Popen, PIPE
   2 from typing import TextIO
   3 from djbdns.dnscache import handle_dnscache_log
   4 from djbdns.tinydns import handle_tinydns_log
   5
   6 def parse_logfile(file : TextIO):
   7     r"""
   8     Process a single log ``file``.
   9
  10     Parameters
  11     ----------
  12
  13     file : typing.TextIO
  14         An open log file, or stdin.
  15
  16     Examples
  17     --------
  18
  19         >>> line = "@4000000063227a320c4f3114 7f000001:9d61:be69 - 0001 www.example.com\n"
  20         >>> from tempfile import NamedTemporaryFile
  21         >>> with NamedTemporaryFile(mode="w", delete=False) as f:
  22         ...     _ = f.write(line)
  23         >>> f = open(f.name, 'r')
  24         >>> parse_logfile(f)
  25         2022-09-14 21:04:40.206516500 dropped query (no authority) from 127.0.0.1:40289 (id 48745): a www.example.com
  26         >>> f.close()
  27         >>> from os import remove
  28         >>> remove(f.name)
  29
  30     """
  31     # Open a pipe to tai64nlocal. We'll write lines of our input file
  32     # (the log file) to it, and read back the same lines but with
  33     # friendly timestamps in them.
  34     tai = Popen(["tai64nlocal"], stdin=PIPE, stdout=PIPE, text=True, bufsize=0)
  35
  36     for line in file:
  37         tai.stdin.write(line)
  38         line = tai.stdout.readline()
  39
  40         friendly_line = handle_tinydns_log(line)
  41         if not friendly_line:
  42             friendly_line = handle_dnscache_log(line)
  43             if not friendly_line:
  44                 friendly_line = line
  45
  46         try:
  47             print(friendly_line)
  48         except BrokenPipeError:
  49             # If our stdout is being piped to another process and if
  50             # that process closes the pipe, this error will be raised
  51             # the next time we try to write to stdout.
  52             break
  53
  54     # Ensure that the pipe gets closed.
  55     tai.communicate()