Add alternative worker commands, config options (#20)

* add alternative worker commands, config options

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* add support for Json worker args

* polls the scheduler for health check

* extra health checks for dask workers

* Handle dask not being on the path

* Revert sys.executable change

* Fix when worker args are not specified

* Clean up and add --cuda flag

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Jacob Tomlinson <jtomlinson@nvidia.com>

dask_databricks/cli.py

@@ -1,3 +1,4 @@
+import json
 import logging
 import os
 import socket
@@ -20,7 +21,16 @@ def main():
 
 
 @main.command()
-def run():
+@click.option('--worker-command', help='Custom worker command')
+@click.option('--worker-args', help='Additional worker arguments')
+@click.option(
+    "--cuda",
+    is_flag=True,
+    show_default=True,
+    default=False,
+    help="Use `dask cuda worker` from the dask-cuda package when starting workers.",
+)
+def run(worker_command, worker_args, cuda):
     """Run Dask processes on a Databricks cluster."""
     log = get_logger()
 
@@ -38,20 +48,52 @@ def run():
 
     if DB_IS_DRIVER == "TRUE":
         log.info("This node is the Dask scheduler.")
-        subprocess.Popen(["dask", "scheduler", "--dashboard-address", ":8787,:8087"])
+        scheduler_process = subprocess.Popen(["dask", "scheduler", "--dashboard-address", ":8787,:8087"])
+        time.sleep(5)  # give the scheduler time to start
+        if scheduler_process.poll() is not None:
+            log.error("Scheduler process has exited prematurely.")
+            sys.exit(1)
     else:
+        # Specify the same port for all workers
+        worker_port = 8786
         log.info("This node is a Dask worker.")
-        log.info(f"Connecting to Dask scheduler at {DB_DRIVER_IP}:8786")
+        log.info(f"Connecting to Dask scheduler at {DB_DRIVER_IP}:{worker_port}")
         while True:
             try:
                 sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
-                sock.connect((DB_DRIVER_IP, 8786))
+                sock.connect((DB_DRIVER_IP, worker_port))
                 sock.close()
                 break
             except ConnectionRefusedError:
                 log.info("Scheduler not available yet. Waiting...")
                 time.sleep(1)
-        subprocess.Popen(["dask", "worker", f"tcp://{DB_DRIVER_IP}:8786"])
+
+        # Construct the worker command
+        if worker_command:
+            worker_command = worker_command.split()
+        elif cuda:
+            worker_command = ["dask", "cuda", "worker"]
+        else:
+            worker_command = ["dask", "worker"]
+
+        if worker_args:
+            try:
+                # Try to decode the JSON-encoded worker_args
+                worker_args_list = json.loads(worker_args)
+                if not isinstance(worker_args_list, list):
+                    raise ValueError("The JSON-encoded worker_args must be a list.")
+            except json.JSONDecodeError:
+                # If decoding as JSON fails, split worker_args by spaces
+                worker_args_list = worker_args.split()
+
+            worker_command.extend(worker_args_list)
+        worker_command.append(f"tcp://{DB_DRIVER_IP}:{worker_port}")
+
+        worker_process = subprocess.Popen(worker_command)
+        time.sleep(5)  # give the worker time to start
+        if worker_process.poll() is not None:
+            log.error("Worker process has exited prematurely.")
+            sys.exit(1)
 
 
 if __name__ == "__main__":