Remote exception names are cut to 128 identifier characters before a class is built for them

backend/fluksio/flow/workers.py

@@ -17,6 +17,7 @@ import itertools
 import logging
 import os
 import queue
+import re
 import select
 import signal
 import subprocess
@@ -102,6 +103,8 @@ class NodeCancelled(RemoteError):
 #: node code chose, so an unbounded cache is a node raising a class named after
 #: its loop counter.
 MAX_REMOTE_TYPES = 256
+#: How long one of those names may be. A remote worker's comes off the wire.
+MAX_REMOTE_NAME = 128
 
 _remote_types: dict[str, type[RemoteError]] = {}
 
@@ -113,6 +116,7 @@ def _remote_class(name: str) -> type[RemoteError]:
     the author still reads ``ValueError: bad input`` rather than the name of
     the transport that carried it.
     """
+    name = re.sub(r"\W", "_", name[:MAX_REMOTE_NAME]) or "RemoteError"
     cls = _remote_types.get(name)
     if cls is not None:
         return cls

backend/tests/flow/test_remote.py

@@ -21,7 +21,12 @@ from fluksio.flow.remote import (
     RemoteWorkerHub,
     WorkerInventory,
 )
-from fluksio.flow.workers import NodeTimeout, RemoteError
+from fluksio.flow.workers import (
+    MAX_REMOTE_NAME,
+    NodeTimeout,
+    RemoteError,
+    _remote_class,
+)
 
 
 @pytest.fixture
@@ -149,6 +154,13 @@ def test_a_failure_keeps_its_class_across_the_socket(loop):
     assert str(caught[0]) == "bad input"
 
 
+def test_a_class_name_off_the_wire_is_bounded_and_identifier_safe():
+    cls = _remote_class("Bad Name\n" + "x" * 10_000)
+    assert cls.__name__.isidentifier()
+    assert len(cls.__name__) == MAX_REMOTE_NAME
+    assert issubclass(cls, RemoteError)
+
+
 def test_a_worker_that_goes_away_fails_the_call_rather_than_hanging(loop):
     hub = RemoteWorkerHub()
     worker, socket = attach(hub, loop)