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#!/usr/local/cpanel/bin/python-packman
import argparse
import fcntl
import os
import select
import signal
import subprocess
import sys
import time
class Script(object):
rpm_bin = '/usr/bin/rpm'
yum_bin = '/usr/bin/yum'
lock_error_text = b'''error: can't create transaction lock on'''
def __init__(self) -> None:
self.max_wait = 300
self.saw_lock_error = False
self.lockfile_name = subprocess.check_output('/usr/bin/rpm -E %_rpmlock_path'.split()).strip()
if not self.lockfile_name:
raise RuntimeError('get rpm lock path: empty')
self.lockfile = open(self.lockfile_name, 'wb+')
self.stdout = open(os.dup(sys.stdout.fileno()), 'wb')
self.stderr = open(os.dup(sys.stderr.fileno()), 'wb', buffering=0)
def run(self, args=None):
parser = argparse.ArgumentParser()
parser.add_argument('rpm_or_yum', choices=[Script.rpm_bin, Script.yum_bin])
args, wrapped_args = parser.parse_known_args(args=args)
cmd = [args.rpm_or_yum] + wrapped_args
start = time.time()
try:
while True:
time_elapsed = time.time() - start
if self.max_wait < time_elapsed:
raise TimeExceeded()
rc = self.try_cmd(cmd)
if 0 == rc:
return 0
if self.saw_lock_error:
alarm_timeout = int(self.max_wait - time_elapsed)
self.err(b'lock error detected; waiting on rpm lock\n')
def handle_alarm(signo, frame):
raise TimeExceeded()
signal.signal(signal.SIGALRM, handle_alarm)
signal.alarm(alarm_timeout)
fcntl.lockf(self.lockfile, fcntl.LOCK_EX)
signal.alarm(0)
self.err(b'lock acquired\n')
# We waited on lock as a cheap way to know when it was available. We have to give it up so that the
# subprocess can acquire it, but it's possible some other process will get the lock between now and
# then so that's why we're in this loop. You might be thinking you could carry this lock across an
# execve call and that _is_ possible, however there is no guarantee that this lock is the first one
# the subprocess will acquire and so you might end up deadlocking.
fcntl.lockf(self.lockfile, fcntl.LOCK_UN)
else:
return rc
except TimeExceeded as e:
self.err(b'error: max wait time has elapsed; returning error result\n')
return 99
def err(self, msg):
self.stderr.write(msg)
# self.stderr.flush()
def try_cmd(self, args):
self.saw_lock_error = False
devnull = open(os.devnull, 'rb')
proc = subprocess.Popen(args, stdin=devnull, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
def out_cb(line, script):
script.stdout.write(line)
script.stdout.flush()
def error_cb(line, script):
if Script.lock_error_text in line:
script.saw_lock_error = True
# some Cpanel code looks for '^error:' text, so we prefix retryable errors with our name so that a
# successful retry will not be detected as an error that needs review.
line = b'retry_rpm.py: ' + line
script.err(line)
readers = [
LineReader(proc.stdout, out_cb, self),
LineReader(proc.stderr, error_cb, self),
]
while readers:
readable, _, _ = select.select(readers, [], [], 1.0)
for w in readable:
if not w.read():
readers.remove(w)
return proc.wait()
class LineReader(object):
def __init__(self, fl, cb, arg):
self.file = fl
os.set_blocking(self.file.fileno(), False)
self.cb = cb
self.arg = arg
def fileno(self):
return self.file.fileno()
def read(self):
lines = 0
for line in self.file:
lines += 1
self.cb(line, self.arg)
any_lines = 0 < lines
return any_lines
class TimeExceeded(Exception):
pass
if __name__ == '__main__':
sys.exit(Script().run())