From d97bd658d041822fddc9b5d55bf9a2225cf6afaf Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 12 Mar 2026 12:26:42 -0400
Subject: [PATCH 01/23] fix: add shutdown methods to executors and fix lithops
 memory leak

Add explicit shutdown() to SerialExecutor and DaskDelayedExecutor that
clears tracked futures. Enhance LithopsEagerFunctionExecutor.shutdown()
to clear cached _call_output on ResponseFutures before closing, preventing
memory accumulation across repeated map() calls. Add parametrized tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 virtualizarr/parallel.py            | 14 ++++++
 virtualizarr/tests/test_parallel.py | 74 ++++++++++++++++++++++++++++-
 2 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index 7341261d..7deeeebc 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -137,6 +137,9 @@ def map(
         """
         return map(fn, *iterables)
 
+    def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
+        self._futures.clear()
+
 
 class DaskDelayedExecutor(Executor):
     """
@@ -230,6 +233,9 @@ def map(
         # Compute all tasks
         return iter(dask.compute(*delayed_tasks))
 
+    def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
+        self._futures.clear()
+
 
 class LithopsEagerFunctionExecutor(Executor):
     """
@@ -372,4 +378,12 @@ def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
         wait
             Whether to wait for pending futures.
         """
+        # Free cached results from lithops ResponseFuture objects before shutdown.
+        # lithops.FunctionExecutor.futures is never cleared internally — each map()
+        # call extends it with new ResponseFutures that cache deserialized results
+        # in _call_output. Without this, memory accumulates across repeated calls.
+        for f in self.lithops_client.futures:
+            f._call_output = None
+        self.lithops_client.futures.clear()
+        self._futures.clear()
         self.lithops_client.__exit__(None, None, None)
diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 13c5fe03..4a9f604a 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -2,8 +2,13 @@
 
 import pytest
 
-from virtualizarr.parallel import LithopsEagerFunctionExecutor, get_executor
-from virtualizarr.tests import requires_lithops
+from virtualizarr.parallel import (
+    DaskDelayedExecutor,
+    LithopsEagerFunctionExecutor,
+    SerialExecutor,
+    get_executor,
+)
+from virtualizarr.tests import requires_dask, requires_lithops
 
 
 @requires_lithops
@@ -41,3 +46,68 @@ def test_get_executor_process_pool_mode():
 
     assert ctx is not None, "Expected executor to have a multiprocessing context"
     assert ctx.get_start_method() == "forkserver"
+
+
+def _make_executor(executor_cls):
+    """Create a pytest param for an executor class with appropriate marks."""
+    marks = {
+        "DaskDelayedExecutor": [requires_dask],
+        "LithopsEagerFunctionExecutor": [requires_lithops],
+    }
+    return pytest.param(
+        executor_cls,
+        id=executor_cls.__name__,
+        marks=marks.get(executor_cls.__name__, []),
+    )
+
+
+ALL_EXECUTORS = [
+    _make_executor(SerialExecutor),
+    _make_executor(DaskDelayedExecutor),
+    _make_executor(LithopsEagerFunctionExecutor),
+]
+
+
+@pytest.mark.parametrize("executor_cls", ALL_EXECUTORS)
+class TestExecutorShutdown:
+    def test_shutdown_clears_futures(self, executor_cls):
+        with executor_cls() as executor:
+            executor.submit(lambda: 42)
+            executor.submit(lambda: 99)
+            assert len(executor._futures) == 2
+
+        assert len(executor._futures) == 0
+
+    def test_shutdown_via_context_manager(self, executor_cls):
+        with executor_cls() as executor:
+            executor.submit(lambda: 42)
+            assert len(executor._futures) == 1
+
+        assert len(executor._futures) == 0
+
+    def test_shutdown_idempotent(self, executor_cls):
+        executor = executor_cls()
+        executor.submit(lambda: 1)
+        executor.shutdown()
+        executor.shutdown()
+        assert len(executor._futures) == 0
+
+
+@requires_lithops
+class TestLithopsExecutorShutdownSpecific:
+    def test_shutdown_clears_lithops_client_futures(self):
+        executor = LithopsEagerFunctionExecutor()
+        executor.submit(lambda: 42)
+
+        executor.shutdown()
+        assert len(executor.lithops_client.futures) == 0
+
+    def test_shutdown_clears_lithops_cached_results(self):
+        """Verify that shutdown clears _call_output on lithops ResponseFutures."""
+        with LithopsEagerFunctionExecutor() as executor:
+            executor.map(lambda x: x * 2, (1, 2, 3))
+            lithops_futures = list(executor.lithops_client.futures)
+            assert len(lithops_futures) > 0
+
+        # After shutdown, lithops futures list should be cleared
+        assert len(executor.lithops_client.futures) == 0

From 4f4c06111d7b678a663b6168e0c31af5c47965ac Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 12 Mar 2026 13:27:15 -0400
Subject: [PATCH 02/23] Add tests and constrain fix only to lithops

---
 virtualizarr/parallel.py            |  13 ++--
 virtualizarr/tests/test_parallel.py | 113 ++++++++++++++++++----------
 2 files changed, 80 insertions(+), 46 deletions(-)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index 7deeeebc..71d0b786 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -1,3 +1,4 @@
+import atexit
 import inspect
 import multiprocessing as mp
 import warnings
@@ -137,9 +138,6 @@ def map(
         """
         return map(fn, *iterables)
 
-    def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
-        self._futures.clear()
-
 
 class DaskDelayedExecutor(Executor):
     """
@@ -233,9 +231,6 @@ def map(
         # Compute all tasks
         return iter(dask.compute(*delayed_tasks))
 
-    def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
-        self._futures.clear()
-
 
 class LithopsEagerFunctionExecutor(Executor):
     """
@@ -386,4 +381,10 @@ def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
             f._call_output = None
         self.lithops_client.futures.clear()
         self._futures.clear()
+
+        # Lithops registers self.clean as an atexit handler (executors.py __init__),
+        # which prevents the FunctionExecutor from ever being garbage collected.
+        # Unregister it so the executor can be freed after shutdown.
+        atexit.unregister(self.lithops_client.clean)
+
         self.lithops_client.__exit__(None, None, None)
diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 4a9f604a..d592a017 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -1,4 +1,6 @@
+import gc
 import multiprocessing as mp
+import weakref
 
 import pytest
 
@@ -48,6 +50,26 @@ def test_get_executor_process_pool_mode():
     assert ctx.get_start_method() == "forkserver"
 
 
+@requires_lithops
+class TestLithopsExecutorShutdown:
+    def test_shutdown_clears_lithops_client_futures(self):
+        executor = LithopsEagerFunctionExecutor()
+        executor.submit(lambda: 42)
+
+        executor.shutdown()
+        assert len(executor.lithops_client.futures) == 0
+
+    def test_shutdown_clears_lithops_cached_results(self):
+        """Verify that shutdown clears _call_output on lithops ResponseFutures."""
+        with LithopsEagerFunctionExecutor() as executor:
+            executor.map(lambda x: x * 2, (1, 2, 3))
+            lithops_futures = list(executor.lithops_client.futures)
+            assert len(lithops_futures) > 0
+
+        # After shutdown, lithops futures list should be cleared
+        assert len(executor.lithops_client.futures) == 0
+
+
 def _make_executor(executor_cls):
     """Create a pytest param for an executor class with appropriate marks."""
     marks = {
@@ -69,45 +91,56 @@ def _make_executor(executor_cls):
 
 
 @pytest.mark.parametrize("executor_cls", ALL_EXECUTORS)
-class TestExecutorShutdown:
-    def test_shutdown_clears_futures(self, executor_cls):
-        with executor_cls() as executor:
-            executor.submit(lambda: 42)
-            executor.submit(lambda: 99)
-            assert len(executor._futures) == 2
+class TestExecutorMemory:
+    def test_executor_does_not_leak_after_context_manager(self, executor_cls):
+        """Executor and its futures should be GC-collectable after the with block."""
 
-        assert len(executor._futures) == 0
-
-    def test_shutdown_via_context_manager(self, executor_cls):
         with executor_cls() as executor:
-            executor.submit(lambda: 42)
-            assert len(executor._futures) == 1
-
-        assert len(executor._futures) == 0
-
-    def test_shutdown_idempotent(self, executor_cls):
-        executor = executor_cls()
-        executor.submit(lambda: 1)
-        executor.shutdown()
-        executor.shutdown()
-        assert len(executor._futures) == 0
-
-
-@requires_lithops
-class TestLithopsExecutorShutdownSpecific:
-    def test_shutdown_clears_lithops_client_futures(self):
-        executor = LithopsEagerFunctionExecutor()
-        executor.submit(lambda: 42)
-
-        executor.shutdown()
-        assert len(executor.lithops_client.futures) == 0
-
-    def test_shutdown_clears_lithops_cached_results(self):
-        """Verify that shutdown clears _call_output on lithops ResponseFutures."""
-        with LithopsEagerFunctionExecutor() as executor:
-            executor.map(lambda x: x * 2, (1, 2, 3))
-            lithops_futures = list(executor.lithops_client.futures)
-            assert len(lithops_futures) > 0
-
-        # After shutdown, lithops futures list should be cleared
-        assert len(executor.lithops_client.futures) == 0
+            # Use map() since lithops call_async requires a data argument
+            list(executor.map(lambda x: x * 2, range(5)))
+            ref = weakref.ref(executor)
+
+        # Drop the only local reference to the executor
+        del executor
+        gc.collect()
+
+        assert ref() is None, (
+            f"{executor_cls.__name__} was not garbage collected after shutdown"
+        )
+
+    def test_repeated_executor_use_does_not_grow_memory(self, executor_cls):
+        """Memory should not grow when creating and destroying executors repeatedly."""
+        import tracemalloc
+
+        def _run_once():
+            with executor_cls() as executor:
+                # Use map() to produce non-trivial results
+                return list(executor.map(lambda x: list(range(10_000)), range(5)))
+
+        # Warm up (first run may allocate caches, import modules, etc.)
+        _run_once()
+        gc.collect()
+
+        # Measure baseline: peak memory from a single run
+        tracemalloc.start()
+        _run_once()
+        gc.collect()
+        _, baseline_peak = tracemalloc.get_traced_memory()
+        tracemalloc.stop()
+
+        # Now run many iterations and check peak doesn't grow
+        tracemalloc.start()
+        n_iterations = 10
+        for _ in range(n_iterations):
+            _run_once()
+            gc.collect()
+        _, multi_peak = tracemalloc.get_traced_memory()
+        tracemalloc.stop()
+
+        # If memory leaks, peak will scale with n_iterations.
+        # Allow 1.2x the single-run peak to account for GC timing jitter.
+        assert multi_peak < 1.2 * baseline_peak, (
+            f"{executor_cls.__name__} leaked memory: single run peak "
+            f"{baseline_peak / 1024:.0f} KB, {n_iterations} runs peak "
+            f"{multi_peak / 1024:.0f} KB"
+        )

From d925fb7fed0b7659f39313908cc7c5d7dd6865f6 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 12 Mar 2026 15:35:28 -0400
Subject: [PATCH 03/23] Clean up claudes horrible tests

---
 virtualizarr/parallel.py            |  6 +++
 virtualizarr/tests/test_parallel.py | 60 ++++++++++++-----------------
 2 files changed, 30 insertions(+), 36 deletions(-)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index 71d0b786..7c728ef5 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -138,6 +138,9 @@ def map(
         """
         return map(fn, *iterables)
 
+    def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
+        self._futures.clear()
+
 
 class DaskDelayedExecutor(Executor):
     """
@@ -231,6 +234,9 @@ def map(
         # Compute all tasks
         return iter(dask.compute(*delayed_tasks))
 
+    def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
+        self._futures.clear()
+
 
 class LithopsEagerFunctionExecutor(Executor):
     """
diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index d592a017..542d4ae4 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -50,26 +50,6 @@ def test_get_executor_process_pool_mode():
     assert ctx.get_start_method() == "forkserver"
 
 
-@requires_lithops
-class TestLithopsExecutorShutdown:
-    def test_shutdown_clears_lithops_client_futures(self):
-        executor = LithopsEagerFunctionExecutor()
-        executor.submit(lambda: 42)
-
-        executor.shutdown()
-        assert len(executor.lithops_client.futures) == 0
-
-    def test_shutdown_clears_lithops_cached_results(self):
-        """Verify that shutdown clears _call_output on lithops ResponseFutures."""
-        with LithopsEagerFunctionExecutor() as executor:
-            executor.map(lambda x: x * 2, (1, 2, 3))
-            lithops_futures = list(executor.lithops_client.futures)
-            assert len(lithops_futures) > 0
-
-        # After shutdown, lithops futures list should be cleared
-        assert len(executor.lithops_client.futures) == 0
-
-
 def _make_executor(executor_cls):
     """Create a pytest param for an executor class with appropriate marks."""
     marks = {
@@ -89,25 +69,33 @@ def _make_executor(executor_cls):
     _make_executor(LithopsEagerFunctionExecutor),
 ]
 
-
 @pytest.mark.parametrize("executor_cls", ALL_EXECUTORS)
-class TestExecutorMemory:
-    def test_executor_does_not_leak_after_context_manager(self, executor_cls):
-        """Executor and its futures should be GC-collectable after the with block."""
-
+class TestExecutorShutdown:
+    def test_shutdown_clears_futures(self, executor_cls):
+        """Internal _futures list should be empty after shutdown."""
         with executor_cls() as executor:
-            # Use map() since lithops call_async requires a data argument
-            list(executor.map(lambda x: x * 2, range(5)))
-            ref = weakref.ref(executor)
-
-        # Drop the only local reference to the executor
-        del executor
-        gc.collect()
+            executor.submit(lambda x: x * 2, 1)
+            executor.submit(lambda x: x + 1, 2)
+            assert len(executor._futures) == 2
+            if executor_cls is LithopsEagerFunctionExecutor:
+                # grab refs before they get cleared
+                lithops_futures = list(executor.lithops_client.futures)
+                assert len(lithops_futures) ==2
+
+        assert len(executor._futures) == 0
+
+        # Lithops-specific: verify lithops internal futures are also cleared
+        if executor_cls is LithopsEagerFunctionExecutor:
+            assert len(executor.lithops_client.futures) == 0
+            assert all(f._call_output is None for f in lithops_futures)
+
+        # Testing idempotency
+        executor.shutdown()
+        assert len(executor._futures) == 0
 
-        assert ref() is None, (
-            f"{executor_cls.__name__} was not garbage collected after shutdown"
-        )
 
+@pytest.mark.parametrize("executor_cls", ALL_EXECUTORS)
+class TestExecutorMemory:
     def test_repeated_executor_use_does_not_grow_memory(self, executor_cls):
         """Memory should not grow when creating and destroying executors repeatedly."""
         import tracemalloc
@@ -140,7 +128,7 @@ def _run_once():
         # If memory leaks, peak will scale with n_iterations.
         # Allow 1.2x the single-run peak to account for GC timing jitter.
         assert multi_peak < 1.2 * baseline_peak, (
-            f"{executor_cls.__name__} leaked memory: single run peak "
+            f"{executor_cls.__name__} does not release memory: single run peak "
             f"{baseline_peak / 1024:.0f} KB, {n_iterations} runs peak "
             f"{multi_peak / 1024:.0f} KB"
         )

From 46908c1bc88e3326fd9a783d9b8e38461d08e038 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 12 Mar 2026 19:36:43 +0000
Subject: [PATCH 04/23] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 virtualizarr/tests/test_parallel.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 542d4ae4..5a52046f 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -1,6 +1,5 @@
 import gc
 import multiprocessing as mp
-import weakref
 
 import pytest
 
@@ -69,6 +68,7 @@ def _make_executor(executor_cls):
     _make_executor(LithopsEagerFunctionExecutor),
 ]
 
+
 @pytest.mark.parametrize("executor_cls", ALL_EXECUTORS)
 class TestExecutorShutdown:
     def test_shutdown_clears_futures(self, executor_cls):
@@ -80,7 +80,7 @@ def test_shutdown_clears_futures(self, executor_cls):
             if executor_cls is LithopsEagerFunctionExecutor:
                 # grab refs before they get cleared
                 lithops_futures = list(executor.lithops_client.futures)
-                assert len(lithops_futures) ==2
+                assert len(lithops_futures) == 2
 
         assert len(executor._futures) == 0
 

From 4732cc33e4b962421babeef4491c6e440aef8f8d Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 12 Mar 2026 18:59:46 -0400
Subject: [PATCH 05/23] Alternative approach via lithops config

---
 virtualizarr/parallel.py            | 35 ++++++++++++++++++-----------
 virtualizarr/tests/test_parallel.py |  7 +++---
 2 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index 7c728ef5..ca3ecb40 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -277,6 +277,24 @@ def __call__(self, *args: P.args, **kwargs: P.kwargs) -> T:
     def __init__(self, **kwargs) -> None:
         import lithops  # type: ignore[import-untyped]
 
+
+        # Fix for unbounded memory growth on repeated `open_virtual_mfdataset` calls 
+        # see https://github.com/zarr-developers/VirtualiZarr/issues/926 
+        
+        # Users are encouraged to provide configs for lithops via file
+        # But just in case that someone imports this and configures it, they have to provide all
+        # details below explicitly as `config=` argument.
+        if not 'config' in kwargs:
+            _config_file = lithops.config.load_config()
+            if _config_file['lithops'].get('backend') == 'localhost':
+                # We currently only want to apply this fix for the localhost executor
+                kwargs['config'] = {
+                    "lithops":{
+                        "data_cleaner":False, #prevents atexit registration of `.lithops_client.clean` method
+                        "backend":'localhost', # if this is not provided lithops will default to aws lambda
+                        }
+                        }
+
         # Create Lithops client with optional configuration
         self.lithops_client = lithops.FunctionExecutor(**kwargs).__enter__()
 
@@ -379,18 +397,9 @@ def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
         wait
             Whether to wait for pending futures.
         """
-        # Free cached results from lithops ResponseFuture objects before shutdown.
-        # lithops.FunctionExecutor.futures is never cleared internally — each map()
-        # call extends it with new ResponseFutures that cache deserialized results
-        # in _call_output. Without this, memory accumulates across repeated calls.
-        for f in self.lithops_client.futures:
-            f._call_output = None
-        self.lithops_client.futures.clear()
-        self._futures.clear()
-
-        # Lithops registers self.clean as an atexit handler (executors.py __init__),
-        # which prevents the FunctionExecutor from ever being garbage collected.
-        # Unregister it so the executor can be freed after shutdown.
-        atexit.unregister(self.lithops_client.clean)
+        if wait:
+            # ensure all futures are completed before exiting
+            self.lithops_client.wait(show_progressbar=False)
 
+        #Exit context manager entered during __init__
         self.lithops_client.__exit__(None, None, None)
diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 5a52046f..556bdbb6 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -1,6 +1,6 @@
 import gc
 import multiprocessing as mp
-
+import tracemalloc
 import pytest
 
 from virtualizarr.parallel import (
@@ -98,7 +98,6 @@ def test_shutdown_clears_futures(self, executor_cls):
 class TestExecutorMemory:
     def test_repeated_executor_use_does_not_grow_memory(self, executor_cls):
         """Memory should not grow when creating and destroying executors repeatedly."""
-        import tracemalloc
 
         def _run_once():
             with executor_cls() as executor:
@@ -118,7 +117,7 @@ def _run_once():
 
         # Now run many iterations and check peak doesn't grow
         tracemalloc.start()
-        n_iterations = 10
+        n_iterations = 20
         for _ in range(n_iterations):
             _run_once()
             gc.collect()
@@ -127,7 +126,7 @@ def _run_once():
 
         # If memory leaks, peak will scale with n_iterations.
         # Allow 1.2x the single-run peak to account for GC timing jitter.
-        assert multi_peak < 1.2 * baseline_peak, (
+        assert multi_peak < 1.1 * baseline_peak, (
             f"{executor_cls.__name__} does not release memory: single run peak "
             f"{baseline_peak / 1024:.0f} KB, {n_iterations} runs peak "
             f"{multi_peak / 1024:.0f} KB"

From 031ffac5f94172be107998e89fba77f698c406a5 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 12 Mar 2026 22:59:58 +0000
Subject: [PATCH 06/23] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 virtualizarr/parallel.py            | 24 +++++++++++-------------
 virtualizarr/tests/test_parallel.py |  1 +
 2 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index ca3ecb40..d71c587a 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -1,4 +1,3 @@
-import atexit
 import inspect
 import multiprocessing as mp
 import warnings
@@ -277,23 +276,22 @@ def __call__(self, *args: P.args, **kwargs: P.kwargs) -> T:
     def __init__(self, **kwargs) -> None:
         import lithops  # type: ignore[import-untyped]
 
+        # Fix for unbounded memory growth on repeated `open_virtual_mfdataset` calls
+        # see https://github.com/zarr-developers/VirtualiZarr/issues/926
 
-        # Fix for unbounded memory growth on repeated `open_virtual_mfdataset` calls 
-        # see https://github.com/zarr-developers/VirtualiZarr/issues/926 
-        
         # Users are encouraged to provide configs for lithops via file
         # But just in case that someone imports this and configures it, they have to provide all
         # details below explicitly as `config=` argument.
-        if not 'config' in kwargs:
+        if "config" not in kwargs:
             _config_file = lithops.config.load_config()
-            if _config_file['lithops'].get('backend') == 'localhost':
+            if _config_file["lithops"].get("backend") == "localhost":
                 # We currently only want to apply this fix for the localhost executor
-                kwargs['config'] = {
-                    "lithops":{
-                        "data_cleaner":False, #prevents atexit registration of `.lithops_client.clean` method
-                        "backend":'localhost', # if this is not provided lithops will default to aws lambda
-                        }
-                        }
+                kwargs["config"] = {
+                    "lithops": {
+                        "data_cleaner": False,  # prevents atexit registration of `.lithops_client.clean` method
+                        "backend": "localhost",  # if this is not provided lithops will default to aws lambda
+                    }
+                }
 
         # Create Lithops client with optional configuration
         self.lithops_client = lithops.FunctionExecutor(**kwargs).__enter__()
@@ -401,5 +399,5 @@ def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
             # ensure all futures are completed before exiting
             self.lithops_client.wait(show_progressbar=False)
 
-        #Exit context manager entered during __init__
+        # Exit context manager entered during __init__
         self.lithops_client.__exit__(None, None, None)
diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 556bdbb6..c4861e26 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -1,6 +1,7 @@
 import gc
 import multiprocessing as mp
 import tracemalloc
+
 import pytest
 
 from virtualizarr.parallel import (

From 6414546a041b8b7cd06f2b001c32785ad2a9da86 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 12 Mar 2026 19:07:45 -0400
Subject: [PATCH 07/23] toms renaming suggestion

---
 virtualizarr/tests/test_parallel.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 556bdbb6..db03c355 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -62,14 +62,14 @@ def _make_executor(executor_cls):
     )
 
 
-ALL_EXECUTORS = [
+ALL_CUSTOM_EXECUTORS = [
     _make_executor(SerialExecutor),
     _make_executor(DaskDelayedExecutor),
     _make_executor(LithopsEagerFunctionExecutor),
 ]
 
 
-@pytest.mark.parametrize("executor_cls", ALL_EXECUTORS)
+@pytest.mark.parametrize("executor_cls", ALL_CUSTOM_EXECUTORS)
 class TestExecutorShutdown:
     def test_shutdown_clears_futures(self, executor_cls):
         """Internal _futures list should be empty after shutdown."""
@@ -94,7 +94,7 @@ def test_shutdown_clears_futures(self, executor_cls):
         assert len(executor._futures) == 0
 
 
-@pytest.mark.parametrize("executor_cls", ALL_EXECUTORS)
+@pytest.mark.parametrize("executor_cls", ALL_CUSTOM_EXECUTORS)
 class TestExecutorMemory:
     def test_repeated_executor_use_does_not_grow_memory(self, executor_cls):
         """Memory should not grow when creating and destroying executors repeatedly."""

From 3f9aa440991227ada5555b7c8b6e1c24a6cdcdfb Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Mon, 16 Mar 2026 14:12:17 -0400
Subject: [PATCH 08/23] Update lithops dependency version in pyproject.toml

---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index 9317afa7..8275304a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -133,7 +133,7 @@ dev = [
     "pytest-xdist",
     "ruff",
     "s3fs",
-    "lithops",
+    "lithops>3.6.4",
     "dask",
 ]
 

From af2c83edd427ac12358d998442058e6add1f9553 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Mon, 16 Mar 2026 14:14:15 -0400
Subject: [PATCH 09/23] Revert lithops dependency version constraint

---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index 8275304a..9317afa7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -133,7 +133,7 @@ dev = [
     "pytest-xdist",
     "ruff",
     "s3fs",
-    "lithops>3.6.4",
+    "lithops",
     "dask",
 ]
 

From 0cb839d325b0e8d2b040bd5053452c0ad9f8a8ee Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 14:46:42 -0400
Subject: [PATCH 10/23] Mark Lithops executor tests as flaky

---
 virtualizarr/tests/test_parallel.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index e9abcc89..a63bc9ee 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -56,7 +56,7 @@ def _make_executor(executor_cls):
     """Create a pytest param for an executor class with appropriate marks."""
     marks = {
         "DaskDelayedExecutor": [requires_dask],
-        "LithopsEagerFunctionExecutor": [requires_lithops],
+        "LithopsEagerFunctionExecutor": [requires_lithops, pytest.mark.flaky],
     }
     return pytest.param(
         executor_cls,

From 05316e6a5df2f70693863da2863568c765772b6c Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 14:55:25 -0400
Subject: [PATCH 11/23] rerun flaky tests

---
 virtualizarr/tests/test_parallel.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index a63bc9ee..da64799a 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -56,7 +56,7 @@ def _make_executor(executor_cls):
     """Create a pytest param for an executor class with appropriate marks."""
     marks = {
         "DaskDelayedExecutor": [requires_dask],
-        "LithopsEagerFunctionExecutor": [requires_lithops, pytest.mark.flaky],
+        "LithopsEagerFunctionExecutor": [requires_lithops, pytest.mark.flaky(max_runs=3)],
     }
     return pytest.param(
         executor_cls,

From 23d2654e0943cc366554b2069564cfca967df5dd Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 19 Mar 2026 18:55:46 +0000
Subject: [PATCH 12/23] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 virtualizarr/tests/test_parallel.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index da64799a..cb2c03cf 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -56,7 +56,10 @@ def _make_executor(executor_cls):
     """Create a pytest param for an executor class with appropriate marks."""
     marks = {
         "DaskDelayedExecutor": [requires_dask],
-        "LithopsEagerFunctionExecutor": [requires_lithops, pytest.mark.flaky(max_runs=3)],
+        "LithopsEagerFunctionExecutor": [
+            requires_lithops,
+            pytest.mark.flaky(max_runs=3),
+        ],
     }
     return pytest.param(
         executor_cls,

From 748f50d0e862a99309193491c8ac521d89bb488a Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 15:22:21 -0400
Subject: [PATCH 13/23] Fix LithopsEagerFunctionExecutor.shutdown() not
 clearing futures

The shutdown method was not clearing `lithops_client.futures` or freeing
output memory, causing test failures on Python 3.12 and 3.13.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 virtualizarr/parallel.py            | 7 +++++++
 virtualizarr/tests/test_parallel.py | 5 +----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index d71c587a..2fcadd68 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -399,5 +399,12 @@ def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
             # ensure all futures are completed before exiting
             self.lithops_client.wait(show_progressbar=False)
 
+        self._futures.clear()
+
+        # Free output memory and clear lithops internal futures list
+        for f in self.lithops_client.futures:
+            f._call_output = None
+        self.lithops_client.futures.clear()
+
         # Exit context manager entered during __init__
         self.lithops_client.__exit__(None, None, None)
diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index cb2c03cf..e9abcc89 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -56,10 +56,7 @@ def _make_executor(executor_cls):
     """Create a pytest param for an executor class with appropriate marks."""
     marks = {
         "DaskDelayedExecutor": [requires_dask],
-        "LithopsEagerFunctionExecutor": [
-            requires_lithops,
-            pytest.mark.flaky(max_runs=3),
-        ],
+        "LithopsEagerFunctionExecutor": [requires_lithops],
     }
     return pytest.param(
         executor_cls,

From 263656e0e5a874fa9239839b06fd3afb77bb0bfb Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 15:24:03 -0400
Subject: [PATCH 14/23] add comment

---
 virtualizarr/parallel.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index 2fcadd68..5f4339e0 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -399,6 +399,7 @@ def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
             # ensure all futures are completed before exiting
             self.lithops_client.wait(show_progressbar=False)
 
+        # Python <= 3.13 requires manual clearing of the futures, python 3.14 clears futures during wait
         self._futures.clear()
 
         # Free output memory and clear lithops internal futures list

From b9ba3cadafa3d651dcf935538f37646ef02d0b4a Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:03:24 -0400
Subject: [PATCH 15/23] Test against lithops fork with job_manager thread join
 fix

Temporarily point lithops dep to jbusecke/lithops@fix-join-job-manager-localhostv2
to verify the upstream fix resolves the memory growth test on Linux CI.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index a99ac862..b31ae47f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -133,7 +133,7 @@ dev = [
     "pytest-xdist",
     "ruff",
     "s3fs",
-    "lithops",
+    "lithops @ git+https://github.com/jbusecke/lithops.git@fix-join-job-manager-localhostv2",
     "dask",
 ]
 

From 63481f847f2640a61aa93316e8f1dccaeda849f1 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:09:30 -0400
Subject: [PATCH 16/23] Add sleep between memory test iterations to allow
 background threads to exit

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 virtualizarr/tests/test_parallel.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index e9abcc89..f9f6a67d 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -1,5 +1,6 @@
 import gc
 import multiprocessing as mp
+import time
 import tracemalloc
 
 import pytest
@@ -97,6 +98,13 @@ def test_shutdown_clears_futures(self, executor_cls):
         assert len(executor._futures) == 0
 
 
+@requires_lithops
+def test_lithops_executor_data_cleaner_disabled():
+    """data_cleaner must be False to prevent atexit registration of lithops' clean method."""
+    with LithopsEagerFunctionExecutor() as executor:
+        assert executor.lithops_client.data_cleaner is False
+
+
 @pytest.mark.parametrize("executor_cls", ALL_CUSTOM_EXECUTORS)
 class TestExecutorMemory:
     def test_repeated_executor_use_does_not_grow_memory(self, executor_cls):
@@ -124,6 +132,7 @@ def _run_once():
         for _ in range(n_iterations):
             _run_once()
             gc.collect()
+            time.sleep(0.5)  # allow background threads to exit and be GC'd
         _, multi_peak = tracemalloc.get_traced_memory()
         tracemalloc.stop()
 

From 68a60e969e644440db9e961dd7cac9ed9fd4918b Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:10:03 -0400
Subject: [PATCH 17/23] Move sleep to after the loop to allow background
 threads to exit before measuring

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 virtualizarr/tests/test_parallel.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index f9f6a67d..7bc79229 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -132,7 +132,7 @@ def _run_once():
         for _ in range(n_iterations):
             _run_once()
             gc.collect()
-            time.sleep(0.5)  # allow background threads to exit and be GC'd
+        time.sleep(2)  # allow background threads to exit and be GC'd before measuring
         _, multi_peak = tracemalloc.get_traced_memory()
         tracemalloc.stop()
 

From ba61353caaaeb080d00eb0ea6e98e0b844f575c3 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:14:48 -0400
Subject: [PATCH 18/23] Increase sleep to 30s to give background threads more
 time to exit

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 virtualizarr/tests/test_parallel.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 7bc79229..2b2d5c72 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -132,7 +132,7 @@ def _run_once():
         for _ in range(n_iterations):
             _run_once()
             gc.collect()
-        time.sleep(2)  # allow background threads to exit and be GC'd before measuring
+        time.sleep(30)  # allow background threads to exit and be GC'd before measuring
         _, multi_peak = tracemalloc.get_traced_memory()
         tracemalloc.stop()
 

From 71a43b44184fb65a109b68c3c7e50950a7996820 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:24:18 -0400
Subject: [PATCH 19/23] Revert lithops dep back to released version

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index b31ae47f..a99ac862 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -133,7 +133,7 @@ dev = [
     "pytest-xdist",
     "ruff",
     "s3fs",
-    "lithops @ git+https://github.com/jbusecke/lithops.git@fix-join-job-manager-localhostv2",
+    "lithops",
     "dask",
 ]
 

From 394c019c4015f18a8f1f29c91cd208611d1608cc Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:44:02 -0400
Subject: [PATCH 20/23] remove the memory growth test

---
 virtualizarr/parallel.py            |  1 -
 virtualizarr/tests/test_parallel.py | 40 -----------------------------
 2 files changed, 41 deletions(-)

diff --git a/virtualizarr/parallel.py b/virtualizarr/parallel.py
index 5f4339e0..2fcadd68 100644
--- a/virtualizarr/parallel.py
+++ b/virtualizarr/parallel.py
@@ -399,7 +399,6 @@ def shutdown(self, wait: bool = True, *, cancel_futures: bool = False) -> None:
             # ensure all futures are completed before exiting
             self.lithops_client.wait(show_progressbar=False)
 
-        # Python <= 3.13 requires manual clearing of the futures, python 3.14 clears futures during wait
         self._futures.clear()
 
         # Free output memory and clear lithops internal futures list
diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 2b2d5c72..76681a3c 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -103,43 +103,3 @@ def test_lithops_executor_data_cleaner_disabled():
     """data_cleaner must be False to prevent atexit registration of lithops' clean method."""
     with LithopsEagerFunctionExecutor() as executor:
         assert executor.lithops_client.data_cleaner is False
-
-
-@pytest.mark.parametrize("executor_cls", ALL_CUSTOM_EXECUTORS)
-class TestExecutorMemory:
-    def test_repeated_executor_use_does_not_grow_memory(self, executor_cls):
-        """Memory should not grow when creating and destroying executors repeatedly."""
-
-        def _run_once():
-            with executor_cls() as executor:
-                # Use map() to produce non-trivial results
-                return list(executor.map(lambda x: list(range(10_000)), range(5)))
-
-        # Warm up (first run may allocate caches, import modules, etc.)
-        _run_once()
-        gc.collect()
-
-        # Measure baseline: peak memory from a single run
-        tracemalloc.start()
-        _run_once()
-        gc.collect()
-        _, baseline_peak = tracemalloc.get_traced_memory()
-        tracemalloc.stop()
-
-        # Now run many iterations and check peak doesn't grow
-        tracemalloc.start()
-        n_iterations = 20
-        for _ in range(n_iterations):
-            _run_once()
-            gc.collect()
-        time.sleep(30)  # allow background threads to exit and be GC'd before measuring
-        _, multi_peak = tracemalloc.get_traced_memory()
-        tracemalloc.stop()
-
-        # If memory leaks, peak will scale with n_iterations.
-        # Allow 1.2x the single-run peak to account for GC timing jitter.
-        assert multi_peak < 1.1 * baseline_peak, (
-            f"{executor_cls.__name__} does not release memory: single run peak "
-            f"{baseline_peak / 1024:.0f} KB, {n_iterations} runs peak "
-            f"{multi_peak / 1024:.0f} KB"
-        )

From d1822a31130eb63e9d34054788b99bbb94f48980 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 19 Mar 2026 21:44:32 +0000
Subject: [PATCH 21/23] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 virtualizarr/tests/test_parallel.py | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 76681a3c..8625437e 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -1,7 +1,4 @@
-import gc
 import multiprocessing as mp
-import time
-import tracemalloc
 
 import pytest
 

From d8c0ab199815cdeca2caef03bb2927191cb22f43 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:51:57 -0400
Subject: [PATCH 22/23] Add .shutdown() method to custom executors

Added `.shutdown()` method to custom executors to prevent unbounded memory increase in lithops.
---
 docs/releases.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/releases.md b/docs/releases.md
index ecb83f39..04fb8a18 100644
--- a/docs/releases.md
+++ b/docs/releases.md
@@ -42,6 +42,8 @@
   By [Tom Nicholas](https://github.com/TomNicholas).
 - Fix `ZarrParser` not correctly parsing scalar variables from v2 native zarr stores ([#936](https://github.com/zarr-developers/VirtualiZarr/pull/936)).
   By [Julius Buseceke](https://github.com/jbusecke)
+- Add `.shutdown()` method to custom executors (dask, lithops) preventing unbounded memory increase in the case of lithops ([#925](https://github.com/zarr-developers/VirtualiZarr/pull/925)).
+  By [Julius Buseceke](https://github.com/jbusecke)
 
 ### Documentation
 

From 887edac031e5588a854180f4157e92a8e0313a01 Mon Sep 17 00:00:00 2001
From: Julius Busecke <14314623+jbusecke@users.noreply.github.com>
Date: Thu, 19 Mar 2026 17:57:30 -0400
Subject: [PATCH 23/23] satisfy linter

---
 virtualizarr/tests/test_parallel.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virtualizarr/tests/test_parallel.py b/virtualizarr/tests/test_parallel.py
index 8625437e..d274cb58 100644
--- a/virtualizarr/tests/test_parallel.py
+++ b/virtualizarr/tests/test_parallel.py
@@ -97,6 +97,6 @@ def test_shutdown_clears_futures(self, executor_cls):
 
 @requires_lithops
 def test_lithops_executor_data_cleaner_disabled():
-    """data_cleaner must be False to prevent atexit registration of lithops' clean method."""
+    """Data_cleaner must be False to prevent atexit registration of lithops' clean method."""
     with LithopsEagerFunctionExecutor() as executor:
         assert executor.lithops_client.data_cleaner is False