pym/portage/dbapi/_MergeProcess.py

# Copyright 2010-2013 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2

import io
import platform
import signal
import sys
import traceback

import errno
import fcntl
import portage
from portage import os, _unicode_decode
from portage.util._ctypes import find_library
import portage.elog.messages
from portage.util._async.ForkProcess import ForkProcess

class MergeProcess(ForkProcess):
	"""
	Merge packages in a subprocess, so the Scheduler can run in the main
	thread while files are moved or copied asynchronously.
	"""

	__slots__ = ('mycat', 'mypkg', 'settings', 'treetype',
		'vartree', 'blockers', 'pkgloc', 'infloc', 'myebuild',
		'mydbapi', 'prev_mtimes', 'unmerge', '_elog_reader_fd', '_elog_reg_id',
		'_buf', '_elog_keys', '_locked_vdb')

	def _start(self):
		# Portage should always call setcpv prior to this
		# point, but here we have a fallback as a convenience
		# for external API consumers. It's important that
		# this metadata access happens in the parent process,
		# since closing of file descriptors in the subprocess
		# can prevent access to open database connections such
		# as that used by the sqlite metadata cache module.
		cpv = "%s/%s" % (self.mycat, self.mypkg)
		settings = self.settings
		if cpv != settings.mycpv or \
			"EAPI" not in settings.configdict["pkg"]:
			settings.reload()
			settings.reset()
			settings.setcpv(cpv, mydb=self.mydbapi)

		# This caches the libc library lookup in the current
		# process, so that it's only done once rather than
		# for each child process.
		if platform.system() == "Linux" and \
			"merge-sync" in settings.features:
			find_library("c")

		# Inherit stdin by default, so that the pdb SIGUSR1
		# handler is usable for the subprocess.
		if self.fd_pipes is None:
			self.fd_pipes = {}
		else:
			self.fd_pipes = self.fd_pipes.copy()
		self.fd_pipes.setdefault(0, portage._get_stdin().fileno())

		super(MergeProcess, self)._start()

	def _lock_vdb(self):
		"""
		Lock the vdb if FEATURES=parallel-install is NOT enabled,
		otherwise do nothing. This is implemented with
		vardbapi.lock(), which supports reentrance by the
		subprocess that we spawn.
		"""
		if "parallel-install" not in self.settings.features:
			self.vartree.dbapi.lock()
			self._locked_vdb = True

	def _unlock_vdb(self):
		"""
		Unlock the vdb if we hold a lock, otherwise do nothing.
		"""
		if self._locked_vdb:
			self.vartree.dbapi.unlock()
			self._locked_vdb = False

	def _elog_output_handler(self, fd, event):
		output = None
		if event & self.scheduler.IO_IN:
			try:
				output = os.read(fd, self._bufsize)
			except OSError as e:
				if e.errno not in (errno.EAGAIN, errno.EINTR):
					raise
		if output:
			lines = _unicode_decode(output).split('\n')
			if len(lines) == 1:
				self._buf += lines[0]
			else:
				lines[0] = self._buf + lines[0]
				self._buf = lines.pop()
				out = io.StringIO()
				for line in lines:
					funcname, phase, key, msg = line.split(' ', 3)
					self._elog_keys.add(key)
					reporter = getattr(portage.elog.messages, funcname)
					reporter(msg, phase=phase, key=key, out=out)

		if event & self.scheduler.IO_HUP:
			self.scheduler.source_remove(self._elog_reg_id)
			self._elog_reg_id = None
			os.close(self._elog_reader_fd)
			self._elog_reader_fd = None
			return False

		return True

	def _spawn(self, args, fd_pipes, **kwargs):
		"""
		Fork a subprocess, apply local settings, and call
		dblink.merge(). TODO: Share code with ForkProcess.
		"""

		elog_reader_fd, elog_writer_fd = os.pipe()

		fcntl.fcntl(elog_reader_fd, fcntl.F_SETFL,
			fcntl.fcntl(elog_reader_fd, fcntl.F_GETFL) | os.O_NONBLOCK)

		# FD_CLOEXEC is enabled by default in Python >=3.4.
		if sys.hexversion < 0x3040000:
			try:
				fcntl.FD_CLOEXEC
			except AttributeError:
				pass
			else:
				fcntl.fcntl(elog_reader_fd, fcntl.F_SETFD,
					fcntl.fcntl(elog_reader_fd, fcntl.F_GETFD) | fcntl.FD_CLOEXEC)

		blockers = None
		if self.blockers is not None:
			# Query blockers in the main process, since closing
			# of file descriptors in the subprocess can prevent
			# access to open database connections such as that
			# used by the sqlite metadata cache module.
			blockers = self.blockers()
		mylink = portage.dblink(self.mycat, self.mypkg, settings=self.settings,
			treetype=self.treetype, vartree=self.vartree,
			blockers=blockers, pipe=elog_writer_fd)
		fd_pipes[elog_writer_fd] = elog_writer_fd
		self._elog_reg_id = self.scheduler.io_add_watch(elog_reader_fd,
			self._registered_events, self._elog_output_handler)

		# If a concurrent emerge process tries to install a package
		# in the same SLOT as this one at the same time, there is an
		# extremely unlikely chance that the COUNTER values will not be
		# ordered correctly unless we lock the vdb here.
		# FEATURES=parallel-install skips this lock in order to
		# improve performance, and the risk is practically negligible.
		self._lock_vdb()
		counter = None
		if not self.unmerge:
			counter = self.vartree.dbapi.counter_tick()

		parent_pid = os.getpid()
		pid = None
		try:
			pid = os.fork()

			if pid != 0:
				if not isinstance(pid, int):
					raise AssertionError(
						"fork returned non-integer: %s" % (repr(pid),))

				os.close(elog_writer_fd)
				self._elog_reader_fd = elog_reader_fd
				self._buf = ""
				self._elog_keys = set()
				# Discard messages which will be collected by the subprocess,
				# in order to avoid duplicates (bug #446136).
				portage.elog.messages.collect_messages(key=mylink.mycpv)

				# invalidate relevant vardbapi caches
				if self.vartree.dbapi._categories is not None:
					self.vartree.dbapi._categories = None
				self.vartree.dbapi._pkgs_changed = True
				self.vartree.dbapi._clear_pkg_cache(mylink)

				return [pid]

			os.close(elog_reader_fd)

			# Use default signal handlers in order to avoid problems
			# killing subprocesses as reported in bug #353239.
			signal.signal(signal.SIGINT, signal.SIG_DFL)
			signal.signal(signal.SIGTERM, signal.SIG_DFL)

			portage.locks._close_fds()
			# We don't exec, so use close_fds=False
			# (see _setup_pipes docstring).
			portage.process._setup_pipes(fd_pipes, close_fds=False)

			portage.output.havecolor = self.settings.get('NOCOLOR') \
				not in ('yes', 'true')

			# Avoid wastful updates of the vdb cache.
			self.vartree.dbapi._flush_cache_enabled = False

			# In this subprocess we don't want PORTAGE_BACKGROUND to
			# suppress stdout/stderr output since they are pipes. We
			# also don't want to open PORTAGE_LOG_FILE, since it will
			# already be opened by the parent process, so we set the
			# "subprocess" value for use in conditional logging code
			# involving PORTAGE_LOG_FILE.
			if not self.unmerge:
				# unmerge phases have separate logs
				if self.settings.get("PORTAGE_BACKGROUND") == "1":
					self.settings["PORTAGE_BACKGROUND_UNMERGE"] = "1"
				else:
					self.settings["PORTAGE_BACKGROUND_UNMERGE"] = "0"
				self.settings.backup_changes("PORTAGE_BACKGROUND_UNMERGE")
			self.settings["PORTAGE_BACKGROUND"] = "subprocess"
			self.settings.backup_changes("PORTAGE_BACKGROUND")

			rval = 1
			try:
				if self.unmerge:
					if not mylink.exists():
						rval = os.EX_OK
					elif mylink.unmerge(
						ldpath_mtimes=self.prev_mtimes) == os.EX_OK:
						mylink.lockdb()
						try:
							mylink.delete()
						finally:
							mylink.unlockdb()
						rval = os.EX_OK
				else:
					rval = mylink.merge(self.pkgloc, self.infloc,
						myebuild=self.myebuild, mydbapi=self.mydbapi,
						prev_mtimes=self.prev_mtimes, counter=counter)
			except SystemExit:
				raise
			except:
				traceback.print_exc()
				# os._exit() skips stderr flush!
				sys.stderr.flush()
			finally:
				os._exit(rval)

		finally:
			if pid == 0 or (pid is None and os.getpid() != parent_pid):
				# Call os._exit() from a finally block in order
				# to suppress any finally blocks from earlier
				# in the call stack (see bug #345289). This
				# finally block has to be setup before the fork
				# in order to avoid a race condition.
				os._exit(1)

	def _unregister(self):
		"""
		Unregister from the scheduler and close open files.
		"""

		if not self.unmerge:
			# Populate the vardbapi cache for the new package
			# while its inodes are still hot.
			try:
				self.vartree.dbapi.aux_get(self.settings.mycpv, ["EAPI"])
			except KeyError:
				pass

		self._unlock_vdb()
		if self._elog_reg_id is not None:
			self.scheduler.source_remove(self._elog_reg_id)
			self._elog_reg_id = None
		if self._elog_reader_fd is not None:
			os.close(self._elog_reader_fd)
			self._elog_reader_fd = None
		if self._elog_keys is not None:
			for key in self._elog_keys:
				portage.elog.elog_process(key, self.settings,
					phasefilter=("prerm", "postrm"))
			self._elog_keys = None

		super(MergeProcess, self)._unregister()