Manage runtime environments (#452)

* Add `Env` class that manages all runtime environments.
* Changed `NPKIT_DUMP_DIR` to `MSCCLPP_NPKIT_DUMP_DIR`.

python/test/test_mscclpp.py

@@ -27,6 +27,7 @@ from mscclpp import (
     Transport,
     is_nvls_supported,
     npkit,
+    env,
 )
 import mscclpp.comm as mscclpp_comm
 from mscclpp.utils import KernelBuilder, GpuBuffer, pack
@@ -36,6 +37,19 @@ from .mscclpp_mpi import MpiGroup, parametrize_mpi_groups, mpi_group
 ethernet_interface_name = "eth0"
 
 
+@parametrize_mpi_groups(1)
+def test_env(mpi_group: MpiGroup):
+    e = env()
+    assert isinstance(e.debug, str)
+    with pytest.raises(AttributeError):
+        # all attributes should be read-only
+        e.debug = "INFO"
+
+    # should be the same object
+    e2 = env()
+    assert e == e2
+
+
 def all_ranks_on_the_same_node(mpi_group: MpiGroup):
     if (ethernet_interface_name in ni.interfaces()) is False:
         pytest.skip(f"{ethernet_interface_name} is not an interface to use on this node")
@@ -624,8 +638,8 @@ def test_executor(mpi_group: MpiGroup, filename: str):
     project_dir = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
     mscclpp_group = mscclpp_comm.CommGroup(mpi_group.comm)
     executor = Executor(mscclpp_group.communicator)
-    npkit_dump_dir = os.getenv("NPKIT_DUMP_DIR")
-    if npkit_dump_dir is not None:
+    npkit_dump_dir = env().npkit_dump_dir
+    if npkit_dump_dir != "":
         npkit.init(mscclpp_group.my_rank)
     execution_plan = ExecutionPlan(os.path.join(project_dir, "test", "execution-files", filename))