use logging in mlx server (#705)

llms/mlx_lm/server.py

@@ -2,6 +2,7 @@
 
 import argparse
 import json
+import logging
 import time
 import uuid
 import warnings
@@ -116,6 +117,8 @@ class APIHandler(BaseHTTPRequestHandler):
         content_length = int(self.headers["Content-Length"])
         raw_body = self.rfile.read(content_length)
         self.body = json.loads(raw_body.decode())
+        indent = "\t"  # Backslashes can't be inside of f-strings
+        logging.debug(f"Incoming Request Body: {json.dumps(self.body, indent=indent)}")
         assert isinstance(
             self.body, dict
         ), f"Request should be dict, but got {type(self.body)}"
@@ -240,6 +243,7 @@ class APIHandler(BaseHTTPRequestHandler):
         tokens = []
         finish_reason = "length"
         stop_sequence_suffix = None
+        logging.debug(f"Starting completion:")
         for (token, _), _ in zip(
             generate_step(
                 prompt=prompt,
@@ -253,6 +257,7 @@ class APIHandler(BaseHTTPRequestHandler):
             range(self.max_tokens),
         ):
             detokenizer.add_token(token)
+            logging.debug(detokenizer.text)
             tokens.append(token)
             stop_condition = stopping_criteria(
                 tokens, stop_id_sequences, self.tokenizer.eos_token_id
@@ -274,6 +279,8 @@ class APIHandler(BaseHTTPRequestHandler):
         response = self.generate_response(text, finish_reason, len(prompt), len(tokens))
 
         response_json = json.dumps(response).encode()
+        indent = "\t"  # Backslashes can't be inside of f-strings
+        logging.debug(f"Outgoing Response: {json.dumps(response, indent=indent)}")
 
         # Send an additional Content-Length header when it is known
         self.send_header("Content-Length", str(len(response_json)))
@@ -307,6 +314,7 @@ class APIHandler(BaseHTTPRequestHandler):
         # to check for stop conditions before writing to the stream.
         stop_sequence_buffer = []
         stop_sequence_suffix = None
+        logging.debug(f"Starting stream:")
         for (token, _), _ in zip(
             generate_step(
                 prompt=prompt,
@@ -319,6 +327,7 @@ class APIHandler(BaseHTTPRequestHandler):
             range(self.max_tokens),
         ):
             detokenizer.add_token(token)
+            logging.debug(detokenizer.text)
             tokens.append(token)
             stop_sequence_buffer.append(token)
 
@@ -425,7 +434,7 @@ def run(
         "mlx_lm.server is not recommended for production as "
         "it only implements basic security checks."
     )
-    print(f"Starting httpd at {host} on port {port}...")
+    logging.info(f"Starting httpd at {host} on port {port}...")
     httpd.serve_forever()
 
 
@@ -459,8 +468,20 @@ def main():
         action="store_true",
         help="Enable trusting remote code for tokenizer",
     )
+    parser.add_argument(
+        "--log-level",
+        type=str,
+        default="INFO",
+        choices=["DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"],
+        help="Set the logging level (default: INFO)",
+    )
     args = parser.parse_args()
 
+    logging.basicConfig(
+        level=getattr(logging, args.log_level.upper(), None),
+        format="%(asctime)s - %(levelname)s - %(message)s",
+    )
+
     # Building tokenizer_config
     tokenizer_config = {"trust_remote_code": True if args.trust_remote_code else None}