Fix bug in reset_seed() that incorrectly converts the PL_SEED_WORKERS environment variable str read to bool

CHANGELOG.md

@@ -614,6 +614,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed undesired side effects being caused by `Trainer` patching dataloader methods on the `LightningModule` ([#9764](https://github.com/PyTorchLightning/pytorch-lightning/pull/9764))
 
 
+- Fixed an issue with `pl.utilities.seed.reset_seed` converting the `PL_SEED_WORKERS` environment variable to `bool` ([#10099](https://github.com/PyTorchLightning/pytorch-lightning/pull/10099))
+
+
 ## [1.4.9] - 2021-09-30
 
 - Fixed `lr_find` to generate same results on multiple calls ([#9704](https://github.com/PyTorchLightning/pytorch-lightning/pull/9704))

pytorch_lightning/utilities/seed.py

@@ -88,9 +88,9 @@ def reset_seed() -> None:
     If :func:`pytorch_lightning.utilities.seed.seed_everything` is unused, this function will do nothing.
     """
     seed = os.environ.get("PL_GLOBAL_SEED", None)
-    workers = os.environ.get("PL_SEED_WORKERS", False)
+    workers = os.environ.get("PL_SEED_WORKERS", "0")
     if seed is not None:
-        seed_everything(int(seed), workers=bool(workers))
+        seed_everything(int(seed), workers=bool(int(workers)))
 
 
 def pl_worker_init_function(worker_id: int, rank: Optional[int] = None) -> None:  # pragma: no cover

tests/utilities/test_seed.py

@@ -56,12 +56,19 @@ def test_reset_seed_no_op():
     assert "PL_GLOBAL_SEED" not in os.environ
 
 
-def test_reset_seed_everything():
+@pytest.mark.parametrize("workers", (True, False))
+def test_reset_seed_everything(workers):
     """Test that we can reset the seed to the initial value set by seed_everything()"""
     assert "PL_GLOBAL_SEED" not in os.environ
-    seed_utils.seed_everything(123)
-    assert os.environ["PL_GLOBAL_SEED"] == "123"
+    assert "PL_SEED_WORKERS" not in os.environ
+
+    seed_utils.seed_everything(123, workers)
     before = torch.rand(1)
+    assert os.environ["PL_GLOBAL_SEED"] == "123"
+    assert os.environ["PL_SEED_WORKERS"] == str(int(workers))
+
     seed_utils.reset_seed()
     after = torch.rand(1)
+    assert os.environ["PL_GLOBAL_SEED"] == "123"
+    assert os.environ["PL_SEED_WORKERS"] == str(int(workers))
     assert torch.allclose(before, after)