The user provide the method to get result(command on remote host), the check standard(a callback function), and information about target host(ip and username), and a timeout of execution time optional, with the envdet module, you can get the result: if the command output obey the check standard.
The application module, detapp.py:
import logging
from envdet import rcmd
logger = logging.getLogger('DetectApp')
logger.setLevel(logging.DEBUG)
fh = logging.FileHandler('detect.log')
fh.setLevel(logging.DEBUG)
ch = logging.StreamHandler()
ch.setLevel(logging.INFO)
formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
ch.setFormatter(formatter)
fh.setFormatter(formatter)
logger.addHandler(ch)
logger.addHandler(fh)
def isOracleJDK(str):
return 'Java(TM)' in str
res = rcmd('bvt', '10.0.2.47', 'java -version', isOracleJDK)
logger.info('Check result:%s' % res)
The environment detection module, envdet.py:
from subprocess import Popen, PIPE, STDOUT
import signal
import logging
logger = logging.getLogger('DetectApp.envdet')
def handler(signum, frame):
logger.error('Signal handler called with signal: %d' % signum)
raise IOError("Command execution timeout!")
def rcmd(user, host, cmd, check_handler, timeout=10):
signal.signal(signal.SIGALRM, handler)
signal.alarm(timeout)
cmdstr = "ssh %s@%s 'source /etc/profile;%s'" % (user, host, cmd)
p = Popen(cmdstr, close_fds=True, shell=True, stdout=PIPE, stderr=STDOUT)
fullres = line = ''
while p.poll() is None:
out = p.stdout.read(1)
fullres = fullres + out
if out=='\n':
logger.debug(line)
line = ''
else:
line = line + out
logger.debug('----ret of cmd %s is: %d----' % (cmd, p.returncode))
return check_handler(fullres)
The technical points here are:
-
Run shell command in Python and retrieve output and return code;
-
Use signal to limit the overall running time of commands on remote host over SSH;
-
The logging utility across multiple modules, notice the naming rules:
. . So if you rename the module name, rename it's logger accordingly.