logtail

   1 #!/usr/bin/python3
   2
   3 import sys, os, getopt, subprocess, time, select
   4
   5 class host(object):
   6     def __init__(self, hostname):
   7         self.hostname = hostname
   8         self.proc = None
   9         self.lastconn = 0
  10         self.outbuf = bytearray()
  11         self.errbuf = bytearray()
  12
  13     def gotline(self, buf, line):
  14         if buf == self.outbuf:
  15             sys.stdout.buffer.write(line + b"\n")
  16             sys.stdout.buffer.flush()
  17         elif buf == self.errbuf:
  18             sys.stderr.buffer.write(line + b"\n")
  19             sys.stderr.buffer.flush()
  20
  21     def handle(self, fp, buf):
  22         data = fp.read(4096)
  23         if data == b"":
  24             if len(self.outbuf) > 0:
  25                 self.gotline(self.outbuf, self.outbuf)
  26             if len(self.errbuf) > 0:
  27                 self.gotline(self.errbuf, self.errbuf)
  28             self.proc.wait()
  29             self.proc = None
  30             sys.stderr.write("loctail: disconnected from %s\n" % self.hostname)
  31         buf.extend(data)
  32         while True:
  33             p = buf.find(b'\n')
  34             if p < 0:
  35                 break
  36             self.gotline(buf, buf[:p])
  37             buf[:p + 1] = b""
  38
  39     def handleout(self):
  40         self.handle(self.proc.stdout, self.outbuf)
  41     def handleerr(self):
  42         self.handle(self.proc.stderr, self.errbuf)
  43
  44     def connect(self):
  45         self.proc = subprocess.Popen(["ssh", self.hostname, "tail", "-F", "/var/log/syslog"],
  46                                      bufsize=0, stdin=subprocess.DEVNULL, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
  47         self.lastconn = time.time()
  48
  49     def close(self):
  50         if self.proc is not None:
  51             self.proc.terminate()
  52             self.proc.wait()
  53             self.proc = None
  54
  55 def min2(arg, *args):
  56     ret = arg
  57     for arg in args:
  58         if ret is None or (arg is not None and arg < ret):
  59             ret = arg
  60     return ret
  61
  62 def tailloop(hosts):
  63     try:
  64         now = time.time()
  65         while True:
  66             rfd = []
  67             to = None
  68             for host in hosts:
  69                 if host.proc is not None:
  70                     rfd.append(host.proc.stdout)
  71                     rfd.append(host.proc.stderr)
  72                 else:
  73                     to = min2(to, host.lastconn + 10)
  74             rfd, wfd, efd = select.select(rfd, [], [], None if to is None else max(to - time.time(), 0))
  75             now = time.time()
  76             rfd = set(rfd)
  77             for host in hosts:
  78                 if host.proc is not None:
  79                     if host.proc.stdout in rfd:
  80                         host.handleout()
  81                     elif host.proc.stderr in rfd:
  82                         host.handleerr()
  83                 else:
  84                     if now > host.lastconn + 10:
  85                         host.connect()
  86     except KeyboardInterrupt:
  87         for host in hosts:
  88             host.close()
  89
  90 def usage(out):
  91     out.write("usage: logtail [-h] HOST...\n")
  92
  93 opts, args = getopt.getopt(sys.argv[1:], "h")
  94 for o, a in opts:
  95     if o == "-h":
  96         usage(sys.stdout)
  97         sys.exit(0)
  98 if len(args) < 1:
  99     usage(sys.stderr)
 100     sys.exit(1)
 101
 102 hosts = [host(arg) for arg in args]
 103 tailloop(hosts)