/usr/share/pyshared/psshlib/manager.py is in pssh 2.2.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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from errno import EINTR
import os
import select
import signal
import sys
import threading
try:
import queue
except ImportError:
import Queue as queue
from psshlib.askpass_server import PasswordServer
from psshlib import psshutil
READ_SIZE = 1 << 16
class FatalError(RuntimeError):
"""A fatal error in the PSSH Manager."""
pass
class Manager(object):
"""Executes tasks concurrently.
Tasks are added with add_task() and executed in parallel with run().
Returns a list of the exit statuses of the processes.
Arguments:
limit: Maximum number of commands running at once.
timeout: Maximum allowed execution time in seconds.
"""
def __init__(self, opts):
self.limit = opts.par
self.timeout = opts.timeout
self.askpass = opts.askpass
self.outdir = opts.outdir
self.errdir = opts.errdir
self.iomap = IOMap()
self.taskcount = 0
self.tasks = []
self.running = []
self.done = []
self.askpass_socket = None
def run(self):
"""Processes tasks previously added with add_task."""
try:
if self.outdir or self.errdir:
writer = Writer(self.outdir, self.errdir)
writer.start()
else:
writer = None
if self.askpass:
pass_server = PasswordServer()
pass_server.start(self.iomap, self.limit)
self.askpass_socket = pass_server.address
self.set_sigchld_handler()
try:
self.update_tasks(writer)
wait = None
while self.running or self.tasks:
# Opt for efficiency over subsecond timeout accuracy.
if wait is None or wait < 1:
wait = 1
self.iomap.poll(wait)
self.update_tasks(writer)
wait = self.check_timeout()
except KeyboardInterrupt:
# This exception handler tries to clean things up and prints
# out a nice status message for each interrupted host.
self.interrupted()
except KeyboardInterrupt:
# This exception handler doesn't print out any fancy status
# information--it just stops.
pass
if writer:
writer.signal_quit()
writer.join()
statuses = [task.exitstatus for task in self.done]
return statuses
def clear_sigchld_handler(self):
signal.signal(signal.SIGCHLD, signal.SIG_DFL)
def set_sigchld_handler(self):
# TODO: find out whether set_wakeup_fd still works if the default
# signal handler is used (I'm pretty sure it doesn't work if the
# signal is ignored).
signal.signal(signal.SIGCHLD, self.handle_sigchld)
# This should keep reads and writes from getting EINTR.
if hasattr(signal, 'siginterrupt'):
signal.siginterrupt(signal.SIGCHLD, False)
def handle_sigchld(self, number, frame):
"""Apparently we need a sigchld handler to make set_wakeup_fd work."""
# Write to the signal pipe (only for Python <2.5, where the
# set_wakeup_fd method doesn't exist).
if self.iomap.wakeup_writefd:
os.write(self.iomap.wakeup_writefd, '\0')
for task in self.running:
if task.proc:
task.proc.poll()
# Apparently some UNIX systems automatically resent the SIGCHLD
# handler to SIG_DFL. Reset it just in case.
self.set_sigchld_handler()
def add_task(self, task):
"""Adds a Task to be processed with run()."""
self.tasks.append(task)
def update_tasks(self, writer):
"""Reaps tasks and starts as many new ones as allowed."""
# Mask signals to work around a Python bug:
# http://bugs.python.org/issue1068268
# Since sigprocmask isn't in the stdlib, clear the SIGCHLD handler.
# Since signals are masked, reap_tasks needs to be called once for
# each loop.
keep_running = True
while keep_running:
self.clear_sigchld_handler()
self._start_tasks_once(writer)
self.set_sigchld_handler()
keep_running = self.reap_tasks()
def _start_tasks_once(self, writer):
"""Starts tasks once.
Due to http://bugs.python.org/issue1068268, signals must be masked
when this method is called.
"""
while 0 < len(self.tasks) and len(self.running) < self.limit:
task = self.tasks.pop(0)
self.running.append(task)
task.start(self.taskcount, self.iomap, writer, self.askpass_socket)
self.taskcount += 1
def reap_tasks(self):
"""Checks to see if any tasks have terminated.
After cleaning up, returns the number of tasks that finished.
"""
still_running = []
finished_count = 0
for task in self.running:
if task.running():
still_running.append(task)
else:
self.finished(task)
finished_count += 1
self.running = still_running
return finished_count
def check_timeout(self):
"""Kills timed-out processes and returns the lowest time left."""
if self.timeout <= 0:
return None
min_timeleft = None
for task in self.running:
timeleft = self.timeout - task.elapsed()
if timeleft <= 0:
task.timedout()
continue
if min_timeleft is None or timeleft < min_timeleft:
min_timeleft = timeleft
if min_timeleft is None:
return 0
else:
return max(0, min_timeleft)
def interrupted(self):
"""Cleans up after a keyboard interrupt."""
for task in self.running:
task.interrupted()
self.finished(task)
for task in self.tasks:
task.cancel()
self.finished(task)
def finished(self, task):
"""Marks a task as complete and reports its status to stdout."""
self.done.append(task)
n = len(self.done)
task.report(n)
class IOMap(object):
"""A manager for file descriptors and their associated handlers.
The poll method dispatches events to the appropriate handlers.
"""
def __init__(self):
self.readmap = {}
self.writemap = {}
# Setup the wakeup file descriptor to avoid hanging on lost signals.
wakeup_readfd, wakeup_writefd = os.pipe()
self.register_read(wakeup_readfd, self.wakeup_handler)
# TODO: remove test when we stop supporting Python <2.5
if hasattr(signal, 'set_wakeup_fd'):
signal.set_wakeup_fd(wakeup_writefd)
self.wakeup_writefd = None
else:
self.wakeup_writefd = wakeup_writefd
def register_read(self, fd, handler):
"""Registers an IO handler for a file descriptor for reading."""
self.readmap[fd] = handler
def register_write(self, fd, handler):
"""Registers an IO handler for a file descriptor for writing."""
self.writemap[fd] = handler
def unregister(self, fd):
"""Unregisters the given file descriptor."""
if fd in self.readmap:
del self.readmap[fd]
if fd in self.writemap:
del self.writemap[fd]
def poll(self, timeout=None):
"""Performs a poll and dispatches the resulting events."""
if not self.readmap and not self.writemap:
return
rlist = list(self.readmap)
wlist = list(self.writemap)
try:
rlist, wlist, _ = select.select(rlist, wlist, [], timeout)
except select.error:
_, e, _ = sys.exc_info()
errno = e.args[0]
if errno == EINTR:
return
else:
raise
for fd in rlist:
handler = self.readmap[fd]
handler(fd, self)
for fd in wlist:
handler = self.writemap[fd]
handler(fd, self)
def wakeup_handler(self, fd, iomap):
"""Handles read events on the signal wakeup pipe.
This ensures that SIGCHLD signals aren't lost.
"""
try:
os.read(fd, READ_SIZE)
except (OSError, IOError):
_, e, _ = sys.exc_info()
errno, message = e.args
if errno != EINTR:
sys.stderr.write('Fatal error reading from wakeup pipe: %s\n'
% message)
raise FatalError
class Writer(threading.Thread):
"""Thread that writes to files by processing requests from a Queue.
Until AIO becomes widely available, it is impossible to make a nonblocking
write to an ordinary file. The Writer thread processes all writing to
ordinary files so that the main thread can work without blocking.
"""
OPEN = object()
EOF = object()
ABORT = object()
def __init__(self, outdir, errdir):
threading.Thread.__init__(self)
# A daemon thread automatically dies if the program is terminated.
self.setDaemon(True)
self.queue = queue.Queue()
self.outdir = outdir
self.errdir = errdir
self.host_counts = {}
self.files = {}
def run(self):
while True:
filename, data = self.queue.get()
if filename == self.ABORT:
return
if data == self.OPEN:
self.files[filename] = open(filename, 'wb', buffering=1)
psshutil.set_cloexec(self.files[filename])
else:
dest = self.files[filename]
if data == self.EOF:
dest.close()
else:
dest.write(data)
def open_files(self, host):
"""Called from another thread to create files for stdout and stderr.
Returns a pair of filenames (outfile, errfile). These filenames are
used as handles for future operations. Either or both may be None if
outdir or errdir or not set.
"""
outfile = errfile = None
if self.outdir or self.errdir:
count = self.host_counts.get(host, 0)
self.host_counts[host] = count + 1
if count:
filename = "%s.%s" % (host, count)
else:
filename = host
if self.outdir:
outfile = os.path.join(self.outdir, filename)
self.queue.put((outfile, self.OPEN))
if self.errdir:
errfile = os.path.join(self.errdir, filename)
self.queue.put((errfile, self.OPEN))
return outfile, errfile
def write(self, filename, data):
"""Called from another thread to enqueue a write."""
self.queue.put((filename, data))
def close(self, filename):
"""Called from another thread to close the given file."""
self.queue.put((filename, self.EOF))
def signal_quit(self):
"""Called from another thread to request the Writer to quit."""
self.queue.put((self.ABORT, None))
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