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macos: update build process to use spawn instead of fork (#18205)

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Spack creates a separate process to do package installation. Different
operating systems and Python versions use different methods to create
it but up until Python 3.8 both Linux and Mac OS used "fork" (which
duplicates process memory, file descriptor table, etc.).

Python >= 3.8 on Mac OS prefers creating an entirely new process
(referred to as the "spawn" start method) because "fork" was found to
cause issues (in other words "spawn" is the default start method used
by multiprocessing.Process). Spack was dependent on the particular
behavior of fork to replicate process memory and transmit file
descriptors.

This PR refactors the Spack internals to support starting a child
process with the "spawn" method. To achieve this, it makes the
following changes:

- ensure that the package repository and other global state are
  transmitted to the child process
- ensure that file descriptors are transmitted to the child process in
  a way that works with multiprocessing and spawn
- make all the state needed for the build process and tests picklable
  (package, stage, etc.)
- move a number of locally-defined functions into global scope so that
  they can be pickled
- rework tests where needed to avoid using local functions

This PR also reworks sbang tests to work on macOS, where temporary
directories are deeper than the Linux sbang limit. We make the limit
platform-dependent (macOS supports 512-character shebangs)

See: #14102
This commit is contained in:
Peter Scheibel
2020-11-12 12:26:23 -08:00
committed by GitHub
parent 81cab3b271
commit bb42470211
27 changed files with 1052 additions and 563 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
lib/spack/llnl/util/lang.py
View File

@@ -568,6 +568,12 @@ def instance(self):
return self._instance
def __getattr__(self, name):
# When unpickling Singleton objects, the 'instance' attribute may be
# requested but not yet set. The final 'getattr' line here requires
# 'instance'/'_instance' to be defined or it will enter an infinite
# loop, so protect against that here.
if name in ['_instance', 'instance']:
raise AttributeError()
return getattr(self.instance, name)
def __getitem__(self, name):
@@ -596,6 +602,8 @@ def __init__(self, ref_function):
self.ref_function = ref_function
def __getattr__(self, name):
if name == 'ref_function':
raise AttributeError()
return getattr(self.ref_function(), name)
def __getitem__(self, name):

215
lib/spack/llnl/util/tty/log.py
View File

@@ -21,7 +21,6 @@
from six import StringIO
import llnl.util.tty as tty
from llnl.util.lang import fork_context
try:
import termios
@@ -237,6 +236,8 @@ def __exit__(self, exc_type, exception, traceback):
"""If termios was available, restore old settings."""
if self.old_cfg:
self._restore_default_terminal_settings()
if sys.version_info >= (3,):
atexit.unregister(self._restore_default_terminal_settings)
# restore SIGSTP and SIGCONT handlers
if self.old_handlers:
@@ -288,6 +289,109 @@ def _file_descriptors_work(*streams):
return False
class FileWrapper(object):
"""Represents a file. Can be an open stream, a path to a file (not opened
yet), or neither. When unwrapped, it returns an open file (or file-like)
object.
"""
def __init__(self, file_like):
# This records whether the file-like object returned by "unwrap" is
# purely in-memory. In that case a subprocess will need to explicitly
# transmit the contents to the parent.
self.write_in_parent = False
self.file_like = file_like
if isinstance(file_like, string_types):
self.open = True
elif _file_descriptors_work(file_like):
self.open = False
else:
self.file_like = None
self.open = True
self.write_in_parent = True
self.file = None
def unwrap(self):
if self.open:
if self.file_like:
self.file = open(self.file_like, 'w')
else:
self.file = StringIO()
return self.file
else:
# We were handed an already-open file object. In this case we also
# will not actually close the object when requested to.
return self.file_like
def close(self):
if self.file:
self.file.close()
class MultiProcessFd(object):
"""Return an object which stores a file descriptor and can be passed as an
argument to a function run with ``multiprocessing.Process``, such that
the file descriptor is available in the subprocess."""
def __init__(self, fd):
self._connection = None
self._fd = None
if sys.version_info >= (3, 8):
self._connection = multiprocessing.connection.Connection(fd)
else:
self._fd = fd
@property
def fd(self):
if self._connection:
return self._connection._handle
else:
return self._fd
def close(self):
if self._connection:
self._connection.close()
else:
os.close(self._fd)
def close_connection_and_file(multiprocess_fd, file):
# MultiprocessFd is intended to transmit a FD
# to a child process, this FD is then opened to a Python File object
# (using fdopen). In >= 3.8, MultiprocessFd encapsulates a
# multiprocessing.connection.Connection; Connection closes the FD
# when it is deleted, and prints a warning about duplicate closure if
# it is not explicitly closed. In < 3.8, MultiprocessFd encapsulates a
# simple FD; closing the FD here appears to conflict with
# closure of the File object (in < 3.8 that is). Therefore this needs
# to choose whether to close the File or the Connection.
if sys.version_info >= (3, 8):
multiprocess_fd.close()
else:
file.close()
@contextmanager
def replace_environment(env):
"""Replace the current environment (`os.environ`) with `env`.
If `env` is empty (or None), this unsets all current environment
variables.
"""
env = env or {}
old_env = os.environ.copy()
try:
os.environ.clear()
for name, val in env.items():
os.environ[name] = val
yield
finally:
os.environ.clear()
for name, val in old_env.items():
os.environ[name] = val
class log_output(object):
"""Context manager that logs its output to a file.
@@ -324,7 +428,8 @@ class log_output(object):
work within test frameworks like nose and pytest.
"""
def __init__(self, file_like=None, echo=False, debug=0, buffer=False):
def __init__(self, file_like=None, echo=False, debug=0, buffer=False,
env=None):
"""Create a new output log context manager.
Args:
@@ -352,6 +457,7 @@ def __init__(self, file_like=None, echo=False, debug=0, buffer=False):
self.echo = echo
self.debug = debug
self.buffer = buffer
self.env = env # the environment to use for _writer_daemon
self._active = False # used to prevent re-entry
@@ -393,18 +499,7 @@ def __enter__(self):
"file argument must be set by either __init__ or __call__")
# set up a stream for the daemon to write to
self.close_log_in_parent = True
self.write_log_in_parent = False
if isinstance(self.file_like, string_types):
self.log_file = open(self.file_like, 'w')
elif _file_descriptors_work(self.file_like):
self.log_file = self.file_like
self.close_log_in_parent = False
else:
self.log_file = StringIO()
self.write_log_in_parent = True
self.log_file = FileWrapper(self.file_like)
# record parent color settings before redirecting. We do this
# because color output depends on whether the *original* stdout
@@ -419,6 +514,8 @@ def __enter__(self):
# OS-level pipe for redirecting output to logger
read_fd, write_fd = os.pipe()
read_multiprocess_fd = MultiProcessFd(read_fd)
# Multiprocessing pipe for communication back from the daemon
# Currently only used to save echo value between uses
self.parent_pipe, child_pipe = multiprocessing.Pipe()
@@ -427,24 +524,28 @@ def __enter__(self):
try:
# need to pass this b/c multiprocessing closes stdin in child.
try:
input_stream = os.fdopen(os.dup(sys.stdin.fileno()))
except BaseException:
input_stream = None # just don't forward input if this fails
self.process = fork_context.Process(
target=_writer_daemon,
args=(
input_stream, read_fd, write_fd, self.echo, self.log_file,
child_pipe
input_multiprocess_fd = MultiProcessFd(
os.dup(sys.stdin.fileno())
)
)
self.process.daemon = True # must set before start()
self.process.start()
os.close(read_fd) # close in the parent process
except BaseException:
# just don't forward input if this fails
input_multiprocess_fd = None
with replace_environment(self.env):
self.process = multiprocessing.Process(
target=_writer_daemon,
args=(
input_multiprocess_fd, read_multiprocess_fd, write_fd,
self.echo, self.log_file, child_pipe
)
)
self.process.daemon = True # must set before start()
self.process.start()
finally:
if input_stream:
input_stream.close()
if input_multiprocess_fd:
input_multiprocess_fd.close()
read_multiprocess_fd.close()
# Flush immediately before redirecting so that anything buffered
# goes to the original stream
@@ -515,18 +616,21 @@ def __exit__(self, exc_type, exc_val, exc_tb):
sys.stderr = self._saved_stderr
# print log contents in parent if needed.
if self.write_log_in_parent:
if self.log_file.write_in_parent:
string = self.parent_pipe.recv()
self.file_like.write(string)
if self.close_log_in_parent:
self.log_file.close()
# recover and store echo settings from the child before it dies
self.echo = self.parent_pipe.recv()
try:
self.echo = self.parent_pipe.recv()
except EOFError:
# This may occur if some exception prematurely terminates the
# _writer_daemon. An exception will have already been generated.
pass
# join the daemon process. The daemon will quit automatically
# when the write pipe is closed; we just wait for it here.
# now that the write pipe is closed (in this __exit__, when we restore
# stdout with dup2), the logger daemon process loop will terminate. We
# wait for that here.
self.process.join()
# restore old color and debug settings
@@ -555,7 +659,8 @@ def force_echo(self):
sys.stdout.flush()
def _writer_daemon(stdin, read_fd, write_fd, echo, log_file, control_pipe):
def _writer_daemon(stdin_multiprocess_fd, read_multiprocess_fd, write_fd, echo,
log_file_wrapper, control_pipe):
"""Daemon used by ``log_output`` to write to a log file and to ``stdout``.
The daemon receives output from the parent process and writes it both
@@ -592,26 +697,39 @@ def _writer_daemon(stdin, read_fd, write_fd, echo, log_file, control_pipe):
``StringIO`` in the parent. This is mainly for testing.
Arguments:
stdin (stream): input from the terminal
read_fd (int): pipe for reading from parent's redirected stdout
write_fd (int): parent's end of the pipe will write to (will be
immediately closed by the writer daemon)
stdin_multiprocess_fd (int): input from the terminal
read_multiprocess_fd (int): pipe for reading from parent's redirected
stdout
echo (bool): initial echo setting -- controlled by user and
preserved across multiple writer daemons
log_file (file-like): file to log all output
log_file_wrapper (FileWrapper): file to log all output
control_pipe (Pipe): multiprocessing pipe on which to send control
information to the parent
"""
# If this process was forked, then it will inherit file descriptors from
# the parent process. This process depends on closing all instances of
# write_fd to terminate the reading loop, so we close the file descriptor
# here. Forking is the process spawning method everywhere except Mac OS
# for Python >= 3.8 and on Windows
if sys.version_info < (3, 8) or sys.platform != 'darwin':
os.close(write_fd)
# Use line buffering (3rd param = 1) since Python 3 has a bug
# that prevents unbuffered text I/O.
in_pipe = os.fdopen(read_fd, 'r', 1)
os.close(write_fd)
in_pipe = os.fdopen(read_multiprocess_fd.fd, 'r', 1)
if stdin_multiprocess_fd:
stdin = os.fdopen(stdin_multiprocess_fd.fd)
else:
stdin = None
# list of streams to select from
istreams = [in_pipe, stdin] if stdin else [in_pipe]
force_echo = False # parent can force echo for certain output
log_file = log_file_wrapper.unwrap()
try:
with keyboard_input(stdin) as kb:
while True:
@@ -672,10 +790,13 @@ def _writer_daemon(stdin, read_fd, write_fd, echo, log_file, control_pipe):
# send written data back to parent if we used a StringIO
if isinstance(log_file, StringIO):
control_pipe.send(log_file.getvalue())
log_file.close()
log_file_wrapper.close()
close_connection_and_file(read_multiprocess_fd, in_pipe)
if stdin_multiprocess_fd:
close_connection_and_file(stdin_multiprocess_fd, stdin)
# send echo value back to the parent so it can be preserved.
control_pipe.send(echo)
# send echo value back to the parent so it can be preserved.
control_pipe.send(echo)
def _retry(function):

3
lib/spack/llnl/util/tty/pty.py
View File

@@ -24,7 +24,6 @@
import traceback
import llnl.util.tty.log as log
from llnl.util.lang import fork_context
from spack.util.executable import which
@@ -234,7 +233,7 @@ def start(self, **kwargs):
``minion_function``.
"""
self.proc = fork_context.Process(
self.proc = multiprocessing.Process(
target=PseudoShell._set_up_and_run_controller_function,
args=(self.controller_function, self.minion_function,
self.controller_timeout, self.sleep_time),