[launcher] look ma, no more zombies (#714)

Co-authored-by: Jeff Rasley <jerasley@microsoft.com>

deepspeed/launcher/launch.py

@@ -13,6 +13,8 @@ import subprocess
 import os
 import json
 import base64
+import time
+import signal
 from collections import defaultdict
 from argparse import ArgumentParser, REMAINDER
 
@@ -122,11 +124,47 @@ def main():
             args.training_script,
             "--local_rank={}".format(local_rank)
         ] + args.training_script_args
+
+        sig_names = {2: "SIGINT", 15: "SIGTERM"}
+        last_return_code = None
+
+        def sigkill_handler(signum, frame):
+            for process in processes:
+                print(f"Killing subprocess {process.pid}")
+                try:
+                    process.kill()
+                except Exception as e:
+                    pass
+            if last_return_code is not None:
+                raise subprocess.CalledProcessError(returncode=last_return_code, cmd=cmd)
+            if signum in sig_names:
+                print(f"Main process received {sig_names[signum]}, exiting")
+            sys.exit(1)
+
+        # pass SIGINT/SIGTERM to children if the parent is being terminated
+        signal.signal(signal.SIGINT, sigkill_handler)
+        signal.signal(signal.SIGTERM, sigkill_handler)
+
         process = subprocess.Popen(cmd, env=current_env)
         processes.append(process)
 
-    for process in processes:
-        process.wait()
+    alive_processes = set(processes)
+    while len(alive_processes):
+        finished_processes = []
+        for process in alive_processes:
+            if process.poll() is None:
+                # the process is still running
+                continue
+            else:
+                if process.returncode != 0:
+                    last_return_code = process.returncode  # for sigkill_handler
+                    sigkill_handler(signal.SIGTERM, None)  # not coming back
+                else:
+                    # exited cleanly
+                    finished_processes.append(process)
+        alive_processes = set(alive_processes) - set(finished_processes)
+
+        time.sleep(1)
 
 
 if __name__ == "__main__":