extract work queue and use it to drive broken attach in parallel

test_runner/fixtures/work_queue.py

@@ -0,0 +1,46 @@
+import queue
+import threading
+from typing import Callable, Generic, List, Optional, TypeVar
+
+T = TypeVar("T")
+U = TypeVar("U")
+V = TypeVar("V")
+
+
+def do(nthreads: int, inputs: List[T], work_fn: Callable[[T], U]) -> List[U]:
+    class Item(Generic[V]):
+        _item: V
+
+        def __init__(self, item: V):
+            self._item = item
+
+    # duplicate the tenant in remote storage
+    def worker(input_queue: queue.Queue[Item[T]], output_queue: queue.Queue[U]):
+        while True:
+            item = input_queue.get()
+            if item is None:
+                return
+            output = work_fn(item._item)
+            output_queue.put(Item(output))
+
+    input_queue: queue.Queue[Optional["Item[T]"]] = queue.Queue()
+    output_queue: queue.Queue[Optional["Item[U]"]] = queue.Queue()
+    for t in inputs:
+        input_queue.put(Item(t))
+    workers = []
+    for _ in range(0, nthreads):
+        w = threading.Thread(target=worker, args=[input_queue, output_queue])
+        workers.append(w)
+        w.start()
+        input_queue.put(None)
+    for w in workers:
+        w.join()
+
+    outputs = []
+    while True:
+        try:
+            output = output_queue.get(block=False)
+            outputs.append(output)
+        except queue.Empty:
+            break
+    return outputs