Pyomo 6.10.1: fails with "Permission denied" on AWS lambda due to multiprocessing.Lock()

[bram-tv]

Summary

When running on AWS Lambda the code crashes with a "Permission denied" error when using pyomo 6.10.1 in combination with an S3 client provided via boto3 (i.e. boto3.client("s3")).

This crash happens due to the use of multiprocessing.Lock() (introduced in #3957 for #3908), this requires shared memory (/dev/shm) but that is not available on AWS Lambda.

(I have not yet attempted to run pyomo 6.10.1 on AWS Lambda without using the s3 client, if needed I could but in practice that would not be a useful scenario for us.)

Steps to reproduce the issue

import pyomo.environ as pyo
import boto3

def lambda_handler(event, context):
    # boto3.client('s3') imports s3transfer, which imports multiprocessing.
    # This springs Pyomo's deferred import hook, attempting to create a multiprocessing.Lock
    # which AWS Lambda immediately blocks.
    client = boto3.client("s3")
    return "Success"

Or without using boto3:

import pyomo.environ as pyo


def lambda_handler(event, context):
    import multiprocessing
    return "Success"

Error Message

Using boto3:

[ERROR] PermissionError: [Errno 13] Permission denied
Traceback (most recent call last):
  File "/var/lang/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/var/task/src/handler2.py", line 2, in <module>
    import boto3
  File "/var/task/boto3/__init__.py", line 17, in <module>
    from boto3.compat import _warn_deprecated_python
  File "/var/task/boto3/compat.py", line 21, in <module>
    from s3transfer.manager import TransferConfig
  File "/var/task/s3transfer/__init__.py", line 144, in <module>
    import s3transfer.compat
  File "/var/task/s3transfer/compat.py", line 94, in <module>
    from multiprocessing.managers import BaseManager  # noqa: F401,E402
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "/var/task/pyomo/common/dependencies.py", line 483, in exec_module
    deferred.resolve()
  File "/var/task/pyomo/common/dependencies.py", line 358, in resolve
    self._module, self._available = _perform_import(
  File "/var/task/pyomo/common/dependencies.py", line 798, in _perform_import
    callback(module, True)
  File "/var/task/pyomo/common/dependencies.py", line 979, in _finalize_multiprocessing
    capture_output_lock = module.Lock()
  File "/var/lang/lib/python3.10/multiprocessing/context.py", line 68, in Lock
    return Lock(ctx=self.get_context())
  File "/var/lang/lib/python3.10/multiprocessing/synchronize.py", line 162, in __init__
    SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
  File "/var/lang/lib/python3.10/multiprocessing/synchronize.py", line 57, in __init__
    sl = self._semlock = _multiprocessing.SemLock(

Direct import:

[ERROR] PermissionError: [Errno 13] Permission denied
Traceback (most recent call last):
  File "/var/task/src/handler3.py", line 5, in lambda_handler
    import multiprocessing
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "/var/task/pyomo/common/dependencies.py", line 483, in exec_module
    deferred.resolve()
  File "/var/task/pyomo/common/dependencies.py", line 358, in resolve
    self._module, self._available = _perform_import(
  File "/var/task/pyomo/common/dependencies.py", line 798, in _perform_import
    callback(module, True)
  File "/var/task/pyomo/common/dependencies.py", line 979, in _finalize_multiprocessing
    capture_output_lock = module.Lock()
  File "/var/lang/lib/python3.10/multiprocessing/context.py", line 68, in Lock
    return Lock(ctx=self.get_context())
  File "/var/lang/lib/python3.10/multiprocessing/synchronize.py", line 162, in __init__
    SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
  File "/var/lang/lib/python3.10/multiprocessing/synchronize.py", line 57, in __init__
    sl = self._semlock = _multiprocessing.SemLock(

Information on your system

Pyomo version: 6.10.1
Python version: 3.10
Operating system: AWS Lambda
How Pyomo was installed (PyPI, conda, source): PyPi

Other packages used:

• boto3: 1.43.31
• botocore: 1.43.31
• s3transfer: 0.19.0

Additional information

Testing the same setup with pyomo 6.10.0 works as expected.