FIX: Parallel build JSON file issues

doc/changes/devel/13241.bugfix.rst

@@ -0,0 +1 @@
+Improved the configuration json to handle with parallel access with file lock configuration by :newcontrib:`Bruno Aristimunha`.

doc/changes/names.inc

@@ -35,6 +35,7 @@
 .. _Austin Hurst: https://github.com/a-hurst
 .. _Ben Beasley: https://github.com/musicinmybrain
 .. _Britta Westner: https://britta-wstnr.github.io
+.. _Bruno Aristimunha: https://bruaristimunha.github.io
 .. _Bruno Nicenboim: https://bnicenboim.github.io
 .. _btkcodedev: https://github.com/btkcodedev
 .. _buildqa: https://github.com/buildqa

environment.yml

@@ -11,6 +11,7 @@ dependencies:
   - dipy
   - edfio >=0.2.1
   - eeglabio
+  - filelock >=3.18.0
   - h5io >=0.2.4
   - h5py
   - imageio >=2.6.1

mne/forward/_lead_dots.py

@@ -12,7 +12,7 @@
 from numpy.polynomial import legendre
 
 from ..parallel import parallel_func
-from ..utils import _get_extra_data_path, fill_doc, logger, verbose
+from ..utils import _get_extra_data_path, _open_lock, fill_doc, logger, verbose
 
 ##############################################################################
 # FAST LEGENDRE (DERIVATIVE) POLYNOMIALS USING LOOKUP TABLE
@@ -80,11 +80,11 @@ def _get_legen_table(
         x_interp = np.linspace(-1, 1, n_interp + 1)
         lut = leg_fun(x_interp, n_coeff).astype(np.float32)
         if not force_calc:
-            with open(fname, "wb") as fid:
+            with _open_lock(fname, "wb") as fid:
                 fid.write(lut.tobytes())
     else:
         logger.info(f"Reading Legendre{extra_str} table...")
-        with open(fname, "rb", buffering=0) as fid:
+        with _open_lock(fname, "rb", buffering=0) as fid:
             lut = np.fromfile(fid, np.float32)
     lut.shape = lut_shape
 

mne/utils/__init__.pyi

@@ -88,6 +88,7 @@ __all__ = [
     "_julian_to_date",
     "_mask_to_onsets_offsets",
     "_on_missing",
+    "_open_lock",
     "_parse_verbose",
     "_path_like",
     "_pl",
@@ -280,6 +281,7 @@ from .config import (
     _get_numpy_libs,
     _get_root_dir,
     _get_stim_channel,
+    _open_lock,
     get_config,
     get_config_path,
     get_subjects_dir,

mne/utils/config.py

@@ -5,6 +5,7 @@
 # Copyright the MNE-Python contributors.
 
 import atexit
+import contextlib
 import json
 import multiprocessing
 import os
@@ -23,7 +24,13 @@
 from packaging.version import parse
 
 from ._logging import logger, warn
-from .check import _check_fname, _check_option, _check_qt_version, _validate_type
+from .check import (
+    _check_fname,
+    _check_option,
+    _check_qt_version,
+    _soft_import,
+    _validate_type,
+)
 from .docs import fill_doc
 from .misc import _pl
 
@@ -218,9 +225,53 @@ def set_memmap_min_size(memmap_min_size):
 )
 
 
+@contextlib.contextmanager
+def _open_lock(path, *args, **kwargs):
+    """
+    Context manager that opens a file with an optional file lock.
+
+    If the `filelock` package is available, a lock is acquired on a lock file
+    based on the given path (by appending '.lock').
+
+    Otherwise, a null context is used. The path is then opened in the
+    specified mode.
+
+    Parameters
+    ----------
+    path : str
+        The path to the file to be opened.
+    *args, **kwargs : optional
+        Additional arguments and keyword arguments to be passed to the
+        `open` function.
+
+    """
+    filelock = _soft_import(
+        "filelock", purpose="parallel config set and get", strict=False
+    )
+
+    lock_context = contextlib.nullcontext()  # default to no lock
+
+    if filelock is not None:
+        lock_path = f"{path}.lock"
+        try:
+            from filelock import FileLock
+
+            lock_context = FileLock(lock_path, timeout=5)
+            lock_context.acquire()
+        except TimeoutError:
+            warn(
+                "Could not acquire lock file after 5 seconds, consider deleting it "
+                f"if you know the corresponding file is usable:\n{lock_path}"
+            )
+            lock_context = contextlib.nullcontext()
+
+    with lock_context, open(path, *args, **kwargs) as fid:
+        yield fid
+
+
 def _load_config(config_path, raise_error=False):
     """Safely load a config file."""
-    with open(config_path) as fid:
+    with _open_lock(config_path, "r+") as fid:
         try:
             config = json.load(fid)
         except ValueError:
@@ -398,8 +449,29 @@ def set_config(key, value, home_dir=None, set_env=True):
     directory = op.dirname(config_path)
     if not op.isdir(directory):
         os.mkdir(directory)
-    with open(config_path, "w") as fid:
-        json.dump(config, fid, sort_keys=True, indent=0)
+
+    # Adapting the mode depend if you are create the file
+    # or no.
+    mode = "r+" if op.isfile(config_path) else "w+"
+
+    with _open_lock(config_path, mode) as fid:
+        try:
+            data = json.load(fid)
+        except (ValueError, json.JSONDecodeError) as exc:
+            logger.info(
+                f"Could not read the {config_path} json file during the writing."
+                f" Assuming it is empty. Got: {exc}"
+            )
+            data = {}
+
+        if value is None:
+            data.pop(key, None)
+        else:
+            data[key] = value
+
+        fid.seek(0)
+        fid.truncate()
+        json.dump(data, fid, sort_keys=True, indent=0)
 
 
 def _get_extra_data_path(home_dir=None):

mne/utils/tests/test_config.py

@@ -2,9 +2,12 @@
 # License: BSD-3-Clause
 # Copyright the MNE-Python contributors.
 
+import json
 import os
 import platform
+import random
 import re
+import time
 from functools import partial
 from pathlib import Path
 from urllib.error import URLError
@@ -232,3 +235,103 @@ def bad_open(url, timeout, msg):
     out = out.getvalue()
     assert "devel, " in out
     assert "updating.html" not in out
+
+
+def _worker_update_config_loop(home_dir, worker_id, iterations=10):
+    """Util function to update config in parallel.
+
+    Worker function that repeatedly reads the config (via get_config)
+    and then updates it (via set_config) with a unique key/value pair.
+    A short random sleep is added to encourage interleaving.
+
+    Dummy function to simulate a worker that reads and updates the config.
+
+    Parameters
+    ----------
+    home_dir : str
+        The home directory where the config file is located.
+    worker_id : int
+        The ID of the worker (for creating unique keys).
+    iterations : int
+        The number of iterations to run the loop.
+
+    """
+    for i in range(iterations):
+        # Read current configuration (to simulate a read-modify cycle)
+        _ = get_config(home_dir=home_dir)
+        # Create a unique key/value pair.
+        new_key = f"worker_{worker_id}_{i}"
+        new_value = f"value_{worker_id}_{i}"
+        # Update the configuration (our set_config holds the lock over the full cycle)
+        set_config(new_key, new_value, home_dir=home_dir)
+        time.sleep(random.uniform(0, 0.05))
+    return worker_id
+
+
+def test_parallel_get_set_config(tmp_path: Path):
+    """Test that uses parallel workers to get and set config.
+
+    All the workers update the same configuration file concurrently. In a
+    correct implementation with proper path file locking, the final
+    config file remains valid JSON and includes all expected updates.
+
+    """
+    pytest.importorskip("joblib")
+    pytest.importorskip("filelock")
+    from joblib import Parallel, delayed
+
+    # Use the temporary directory as our home directory.
+    home_dir = str(tmp_path)
+    # get_config_path will return home_dir/.mne/mne-python.json
+    config_file = get_config_path(home_dir=home_dir)
+
+    # if the config file already exists, remove it
+    if os.path.exists(config_file):
+        os.remove(config_file)
+
+    # Ensure that the .mne directory exists.
+    config_dir = tmp_path / ".mne"
+    config_dir.mkdir(exist_ok=True)
+
+    # Write an initial (valid) config file.
+    initial_config = {"initial": "True"}
+    with open(config_file, "w") as f:
+        json.dump(initial_config, f)
+
+    n_workers = 50
+    iterations = 10
+
+    # Launch multiple workers concurrently using joblib.
+    Parallel(n_jobs=10)(
+        delayed(_worker_update_config_loop)(home_dir, worker_id, iterations)
+        for worker_id in range(n_workers)
+    )
+
+    # Now, read back the config file.
+    final_config = get_config(home_dir=home_dir)
+    expected_keys = set()
+    expected_values = set()
+    # For each worker and iteration, check that the expected key/value pair is present.
+    for worker_id in range(n_workers):
+        for i in range(iterations):
+            expected_key = f"worker_{worker_id}_{i}"
+            expected_value = f"value_{worker_id}_{i}"
+
+            assert final_config.get(expected_key) == expected_value, (
+                f"Missing or incorrect value for key {expected_key}"
+            )
+            expected_keys.add(expected_key)
+            expected_values.add(expected_value)
+
+    # include the initial key/value pair
+    # that was written before the workers started
+
+    assert len(expected_keys - set(final_config.keys())) == 0
+    assert len(expected_values - set(final_config.values())) == 0
+
+    # Check that the final config is valid JSON.
+    with open(config_file) as f:
+        try:
+            json.load(f)
+        except json.JSONDecodeError as e:
+            pytest.fail(f"Config file is not valid JSON: {e}")

pyproject.toml

@@ -93,6 +93,7 @@ full-no-qt = [
   "dipy",
   "edfio >= 0.2.1",
   "eeglabio",
+  "filelock>=3.18.0",
   "h5py",
   "imageio >= 2.6.1",
   "imageio-ffmpeg >= 0.4.1",