Read and authenticate with credentials from password file when starti…

…ng Slurm worker manager (#4125)

* Read and authenticate with credentials from password file when starting Slurm worker manager

* clarify

codalab/worker_manager/slurm_batch_worker_manager.py

@@ -2,6 +2,7 @@
 import uuid
 import subprocess
 import getpass
+import os
 import re
 import sys
 import textwrap
@@ -108,6 +109,18 @@ def __init__(self, args):
         # A set of newly submitted job id to keep tracking worker status, as worker might not be created right away.
         self.submitted_jobs = self.load_worker_jobs()
 
+        # We're using a temporary CodaLabManager for the worker and worker managers by default,
+        # so we don't write out the state to state.json when users log in.
+        # If we always read from the password file, we can both leave state.json untouched,
+        # and users can always start the worker manager without logging in.
+        if args.password_file:
+            logger.info(
+                f"--password-file specified. Reading credentials from {args.password_file}..."
+            )
+            with open(args.password_file) as f:
+                os.environ["CODALAB_USERNAME"] = f.readline().strip()
+                os.environ["CODALAB_PASSWORD"] = f.readline().strip()
+
     def load_worker_jobs(self):
         """
         Load worker jobs that are created using SlurmWorkerManager and