djbdns/io.py

   1 r"""
   2 Functions that perform input/output. This forms a layer between the
   3 executable itself and the more libraryish modules.
   4 """
   5 from subprocess import Popen, PIPE
   6 from typing import TextIO
   7 from djbdns.dnscache import handle_dnscache_log
   8 from djbdns.tinydns import handle_tinydns_log
   9
  10 def parse_logfile(file : TextIO):
  11     r"""
  12     Process a single log ``file``.
  13
  14     Parameters
  15     ----------
  16
  17     file : typing.TextIO
  18         An open log file, or stdin.
  19
  20     Examples
  21     --------
  22
  23         >>> line = "@4000000063227a320c4f3114 7f000001:9d61:be69 - 0001 www.example.com\n"
  24         >>> from tempfile import NamedTemporaryFile
  25         >>> with NamedTemporaryFile(mode="w", delete=False) as f:
  26         ...     _ = f.write(line)
  27         >>> f = open(f.name, 'r')
  28         >>> parse_logfile(f)
  29         2022-09-14 21:04:40.206516500 dropped query (no authority) from 127.0.0.1:40289 (id 48745): a www.example.com
  30         >>> f.close()
  31         >>> from os import remove
  32         >>> remove(f.name)
  33
  34     """
  35     # Open a pipe to tai64nlocal. We'll write lines of our input file
  36     # (the log file) to it, and read back the same lines but with
  37     # friendly timestamps in them.
  38     with Popen(["tai64nlocal"],
  39                stdin=PIPE,
  40                stdout=PIPE,
  41                text=True,
  42                bufsize=0) as tai:
  43
  44         if not tai.stdin or not tai.stdout:
  45             # Mypy tells me that this can happen, based on the type
  46             # annotations in the standard library I guess?
  47             return
  48
  49         for line in file:
  50             tai.stdin.write(line)
  51             line = tai.stdout.readline()
  52
  53             friendly_line = handle_tinydns_log(line)
  54             if not friendly_line:
  55                 friendly_line = handle_dnscache_log(line)
  56                 if not friendly_line:
  57                     friendly_line = line
  58
  59             try:
  60                 print(friendly_line)
  61             except BrokenPipeError:
  62                 # If our stdout is being piped to another process and if
  63                 # that process closes the pipe, this error will be raised
  64                 # the next time we try to write to stdout.
  65                 break