Fix ResourceWarning by avoiding garbage collection altogether

.travis.yml

@@ -1,15 +1,13 @@
 # Config file for automatic testing at travis-ci.org
 
 language: python
-dist: xenial
+dist: bionic
 python:
-  - "3.9-dev"
+  - "3.10-dev"
+  - "3.9"
   - "3.8"
   - "3.7"
   - "3.6"
-  - "3.5"
-  - "2.7"
-  - "pypy"
   - "pypy3"
 
 # Command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## Unreleased
+- Avoid `ResourceWarning: unclosed file <...>` warning by keeping a strong reference to the lock files. Lock files were weakly referenced on purpose, so that they could stay alive until the interpreter decides to remove them.
+- Drop support for python 2.7 and 3.5. Only python >= 3.6 is supported now.
 
 ## 0.2.0
 - Removed logic that falls back to copying a file when `file_movable=True` but the file does not appear to be movable. Do not try to be smart.

dogpile_filesystem/registry.py

@@ -5,7 +5,20 @@
 
 logger = logging.getLogger(__name__)
 
-file_lock = ProcessLocalRegistry(lambda path: open(path, "w+b"))
+_registry = {}
+
+
+def _open_file(path):
+    """Open a file and keep a reference to it, in order to avoid ResourceWarnings when the interpreter
+    closes the file automatically when garbage collected."""
+    try:
+        return _registry[path]
+    except KeyError:
+        f = _registry[path] = open(path, "w+b", buffering=0)
+        return f
+
+
+file_lock = ProcessLocalRegistry(creator=_open_file)
 
 
 def _lock_creator(identifier):
@@ -14,4 +27,4 @@ def _lock_creator(identifier):
     return RangedFileReentrantLock(file_o, offset)
 
 
-locks = ProcessLocalRegistry(_lock_creator)
+locks = ProcessLocalRegistry(creator=_lock_creator)

setup.py

@@ -19,18 +19,19 @@
         "License :: OSI Approved :: MIT License",
         "Natural Language :: English",
         "Operating System :: POSIX",
-        "Programming Language :: Python :: 2",
-        "Programming Language :: Python :: 2.7",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: Implementation",
         "Programming Language :: Python :: Implementation :: CPython",
         "Programming Language :: Python :: Implementation :: PyPy",
     ],
     description="File System Backends for Dogpile Cache",
     install_requires=["dogpile.cache"],
+    python_requires=">=3.6",
     license="MIT license",
     long_description=readme + "\n\n" + history,
     long_description_content_type="text/markdown",

tests/test_locking.py

@@ -36,7 +36,24 @@ def other_thread():
         mutex.release()
 
 
-def test_dogpile_lock_processes(region):
+def _other_process(
+    backend_name, region_expiration_time, backend_arguments, proc_result
+):
+    import dogpile.cache
+
+    region = dogpile.cache.make_region("test_region")
+    region.configure(
+        backend=backend_name,
+        expiration_time=region_expiration_time,
+        arguments=backend_arguments,
+    )
+    o_mutex = region.backend.get_mutex("asd")
+    proc_result.value = o_mutex.acquire(False)
+
+
+def test_dogpile_lock_processes(
+    region, backend_name, region_expiration_time, backend_arguments
+):
     mutex = region.backend.get_mutex("asd")
 
     mutex.acquire()
@@ -47,11 +64,15 @@ def test_dogpile_lock_processes(region):
     proc_result = multiprocessing.Value("d", 42)
     assert proc_result.value == 42
 
-    def other_process():
-        o_mutex = region.backend.get_mutex("asd")
-        proc_result.value = o_mutex.acquire(False)
-
-    t = multiprocessing.Process(target=other_process)
+    t = multiprocessing.Process(
+        target=_other_process,
+        kwargs={
+            "backend_name": backend_name,
+            "region_expiration_time": region_expiration_time,
+            "backend_arguments": backend_arguments,
+            "proc_result": proc_result,
+        },
+    )
     t.start()
     t.join()
 

tox.ini

@@ -1,26 +1,21 @@
 [tox]
 envlist =
     py38-linters,
-    py27-dp{06,07,08,09},
-    py35-dp{06,07,08,09},
-    py36-dp{06,07,08,09,10,latest},
-    py37-dp{06,07,08,09,10,latest},
-    py38-dp{06,07,08,09,10,latest},
-    py39-dp{06,07,08,09,10,latest},
-    pypy-dp{06,07,08,09},
-    pypy3-dp{06,07,08,09,10,latest}
+    py36-dp{10,11,latest},
+    py37-dp{10,11,latest},
+    py38-dp{10,11,latest},
+    py39-dp{10,11,latest},
+    py310-dp{10,11,latest},
+    pypy3-dp{10,11,latest}
 
-[testenv:py37-linters]
+[testenv:py38-linters]
 deps = black
 commands = black --check --verbose setup.py dogpile_filesystem tests
 
 [testenv]
 deps =
     dp10: dogpile.cache~=1.0.0
-    dp09: dogpile.cache~=0.9.0
-    dp08: dogpile.cache~=0.8.0
-    dp07: dogpile.cache~=0.7.0
-    dp06: dogpile.cache~=0.6.0
+    dp11: dogpile.cache~=1.1.0
     dplatest: dogpile.cache
     -r{toxinidir}/requirements_dev.txt
 commands =