Allow debugging in distributed mode (#1920)

python/mlx/distributed_run.py

@@ -14,6 +14,8 @@ import time
 from collections import Counter
 from dataclasses import dataclass
 from pathlib import Path
+from queue import Empty as QueueEmpty
+from queue import Queue
 from select import select
 from subprocess import PIPE, Popen, run
 from typing import Optional
@@ -185,46 +187,54 @@ def parse_hostlist(parser, hostlist, repeats):
 
 
 def make_monitor_script(rank, hostfile, cwd, env, command, verbose):
+    # Imports that are used throughout
     script = ""
+    script += "import os\n"
+    script += "import sys\n"
+    script += "import tempfile\n"
+    script += "from pathlib import Path\n"
 
     # Write the PID to a file so we can kill the process if needed
-    script += "pidfile=$(mktemp)\n"
+    script += "_, pidfile = tempfile.mkstemp() \n"
-    script += "echo $$ >$pidfile\n"
+    script += "open(pidfile, 'w').write(str(os.getpid()))\n"
-    script += "echo $pidfile\n"
+    script += "print(pidfile, flush=True)\n"
 
     # Change the working directory if one was requested. Otherwise attempt to
-    # change to change to the current one but don't fail if it wasn't possible.
+    # change to the current one but don't fail if it wasn't possible.
     d = cwd or os.getcwd()
-    script += f"if [ -d {shlex.quote(d)} ]; then\n"
+    script += f"if Path({repr(d)}).exists():\n"
-    script += f"    cd {shlex.quote(d)}\n"
+    script += f"    os.chdir({repr(d)})\n"
     if cwd is not None:
-        script += "else\n"
+        script += "else:\n"
-        script += f"    echo Failed to change directory to {shlex.quote(d)} 1>&2\n"
+        script += (
-        script += f"    exit 1\n"
+            f"    print('Failed to change directory to', {repr(d)}, file=sys.stderr)\n"
-    script += "fi\n"
+        )
+        script += f"    sys.exit(1)\n"
 
     # Add the environment variables that were given to us
+    script += "env = dict(os.environ)\n"
     for e in env:
         key, *value = e.split("=", maxsplit=1)
         value = shlex.quote(value[0]) if len(value) > 0 else ""
         if not all(c.isalnum() or c == "_" for c in key):
             log_warning(f"'{e}' is an invalid environment variable so it is ignored")
             continue
-        script += f"export {key}={value}\n"
+        script += f"env[{repr(key)}] = {repr(value)}\n"
 
     # Add the environment variables to enable the ring distributed backend
     if hostfile != "":
-        script += "tmpfile=$(mktemp)\n"
+        script += "_, hostfile = tempfile.mkstemp()\n"
-        script += f"echo {shlex.quote(hostfile)} >$tmpfile\n"
+        script += "with open(hostfile, 'w') as f:\n"
+        script += f"    f.write({repr(hostfile)})\n"
         if verbose:
-            script += "export MLX_RING_VERBOSE=1\n"
+            script += "env['MLX_RING_VERBOSE'] = '1'\n"
-        script += "export MLX_HOSTFILE=$tmpfile\n"
+        script += "env['MLX_HOSTFILE'] = hostfile\n"
-        script += f"export MLX_RANK={rank}\n"
+        script += f"env['MLX_RANK'] = '{rank}'\n"
         script += "\n"
 
     # Replace the process with the script
-    script += shlex.join(["exec", *command])
+    script += f"command = [{','.join(map(repr, command))}]\n"
-    script += "\n"
+    script += "os.execve(command[0], command, env)\n"
 
     return script
 
@@ -233,28 +243,37 @@ def launch_ring(parser, hosts, args, command):
     stop = False
     exit_codes = [None] * len(hosts)
 
-    def node_thread(rank, host, hostfile):
+    def node_thread(rank, host, hostfile, input_queue):
         is_local = host == "127.0.0.1"
         script = make_monitor_script(
             rank, hostfile, args.cwd, args.env, command, args.verbose
         )
         script_b64 = base64.b64encode(script.encode()).decode()
-        cmd = f'echo "{script_b64}" | base64 -d | /bin/bash'
+        cmd = f'{sys.executable} -c "import base64; exec(base64.b64decode(\\"{script_b64}\\"));"'
         if not is_local:
             cmd = f"ssh {host} '{cmd}'"
         p = Popen(
             cmd,
             shell=True,
+            stdin=PIPE,
             stdout=PIPE,
             stderr=PIPE,
         )
         os.set_blocking(p.stdout.fileno(), False)
         os.set_blocking(p.stderr.fileno(), False)
+        os.set_blocking(p.stdin.fileno(), False)
 
         # Repeat the stdout and stderr to the local machine
+        to_read = [p.stdout.fileno(), p.stderr.fileno()]
+        to_write = [p.stdin.fileno()]
         pidfile = ""
+        stdin_buffer = b""
         while p.poll() is None:
-            rlist, _, _ = select([p.stdout.fileno(), p.stderr.fileno()], [], [], 1.0)
+            try:
+                stdin_buffer += input_queue.get_nowait()
+            except QueueEmpty:
+                pass
+            rlist, wlist, _ = select(to_read, to_write, [], 1.0)
             for fd in rlist:
                 is_stdout = fd == p.stdout.fileno()
                 outfile = sys.stdout if is_stdout else sys.stderr
@@ -266,6 +285,11 @@ def launch_ring(parser, hosts, args, command):
                     msg = msg[0] if msg else ""
 
                 outfile.write(msg)
+                outfile.flush()
+            for fd in wlist:
+                if len(stdin_buffer) > 0:
+                    n = os.write(fd, stdin_buffer)
+                    stdin_buffer = stdin_buffer[n:]
             if stop:
                 p.terminate()
                 break
@@ -310,16 +334,25 @@ def launch_ring(parser, hosts, args, command):
 
     log(args.verbose, "Running", shlex.join(command))
 
+    input_queues = []
     threads = []
     for i, h in enumerate(hosts):
         if i + 1 == len(hosts):
             time.sleep(1.0)
-        t = threading.Thread(target=node_thread, args=(i, h.ssh_hostname, hostfile))
+        input_queues.append(Queue())
+        t = threading.Thread(
+            target=node_thread, args=(i, h.ssh_hostname, hostfile, input_queues[-1])
+        )
         t.start()
         threads.append(t)
 
+    os.set_blocking(sys.stdin.fileno(), False)
     while not stop:
-        time.sleep(1.0)
+        rlist, _, _ = select([sys.stdin.fileno()], [], [], 1.0)
+        for fd in rlist:
+            stdin_buffer = os.read(fd, 8192)
+            for q in input_queues:
+                q.put(stdin_buffer)
         if any(t.is_alive() for t in threads):
             for i, t in enumerate(threads):
                 if not t.is_alive():
@@ -730,6 +763,8 @@ def main():
 
     if len(rest) == 0:
         parser.error("No script is provided")
+    if rest[0] == "--":
+        rest.pop(0)
 
     # Try to extract a list of hosts and corresponding ips
     if args.hostfile is not None: