Add a utility for running functions in parallel.

teuthology/parallel.py

@@ -0,0 +1,27 @@
+import gevent
+import logging
+
+log = logging.getLogger(__name__)
+
+def run(func, all_args):
+    tasks = []
+    for args in all_args:
+        assert isinstance(args, list), 'args must be a list of lists'
+        tasks.append(gevent.spawn(func, *args))
+    gevent.sleep(0)
+
+    try:
+        while tasks:
+            task = tasks[-1]
+            try:
+                task.get(block=True, timeout=5)
+            except gevent.Timeout:
+                continue
+            else:
+                tasks.pop()
+    except:
+        log.exception('Exception from parallel greenlet')
+        for task in tasks:
+            log.error('KILLING TASK')
+            task.kill(block=True)
+        raise