fixup! Examples: Mark processes with daemon=True

Author: ReinierMaas

libs/opsqueue_python/tests/conftest.py

@@ -21,33 +21,47 @@ def _stack_dump_path(pid: int) -> Path:
     return Path(f"/tmp/opsqueue-pytest-stack-{pid}.log")
 
 
-def _linux_descendant_pids(parent_pid: int) -> dict[int, tuple[str, str]]:
-    children_file = Path(f"/proc/{parent_pid}/task/{parent_pid}/children")
-    try:
-        raw = children_file.read_text(encoding="utf-8").strip()
-    except OSError:
-        return {}
-
-    if not raw:
-        return {}
+def _linux_descendant_pids(parent_pid: int = os.getpid()) -> dict[int, tuple[str, str]]:
+    """
+    Returns a dictionary mapping descendant PIDs to their command name and command line. This is a
+    recursive function that will find all descendants of the given parent PID. The command name and
+    command line are read from the `/proc` filesystem, which is Linux-specific.
+    """
+    children = (
+        Path(f"/proc/{parent_pid}/task/{parent_pid}/children")
+        .read_text(encoding="utf-8")
+        .strip()
+    )
 
     def _child_command(pid: int) -> tuple[str, str]:
+        """
+        Returns the command name and command line of the given process id (pid).
+        """
         try:
-            return (
+            comm = (
                 Path(f"/proc/{pid}/comm").read_text(encoding="utf-8").strip()
-                or "<comm>",
+                or "<comm>"
+            )
+        except FileNotFoundError:
+            # Process might have exited between reading /proc/<pid>/children and now.
+            comm = "<comm>"
+        try:
+            cmdline = (
                 Path(f"/proc/{pid}/cmdline")
                 .read_text(encoding="utf-8")
                 .replace(
                     "\x00", " "
                 )  # Replace null bytes with spaces before stripping.
                 .strip()
-                or "<cmdline>",
+                or "<cmdline>"
             )
-        except OSError:
-            return ("<comm>", "<cmdline>")
+        except FileNotFoundError:
+            # Process might have exited between reading /proc/<pid>/children and now.
+            cmdline = "<cmdline>"
+
+        return (comm, cmdline)
 
-    pids = [int(pid_text) for pid_text in raw.split() if pid_text.isdigit()]
+    pids = [int(pid_text) for pid_text in children.split()]
     result = {pid: _child_command(pid) for pid in pids}
     for pid in pids:
         result.update(_linux_descendant_pids(pid))