support prometheus metrics (#1853)

Co-authored-by: Lianmin Zheng <lianminzheng@gmail.com>
Co-authored-by: Byron Hsu <byronhsu1230@gmail.com>

python/sglang/srt/managers/schedule_policy.py

@@ -17,6 +17,7 @@ limitations under the License.
 
 import os
 import random
+import time
 from collections import defaultdict
 from contextlib import contextmanager
 from enum import Enum, auto
@@ -306,6 +307,7 @@ class PrefillAdder:
             ):
                 # Non-chunked prefill
                 self.can_run_list.append(req)
+                req.queued_time = time.time()
                 self.tree_cache.inc_lock_ref(req.last_node)
                 self._prefill_one_req(
                     prefix_len,
@@ -324,6 +326,7 @@ class PrefillAdder:
                 req.extend_input_len = trunc_len
                 req.fill_ids = req.fill_ids[: len(req.prefix_indices) + trunc_len]
                 self.can_run_list.append(req)
+                req.queued_time = time.time()
                 self.new_inflight_req = req
                 self.tree_cache.inc_lock_ref(req.last_node)
                 self._prefill_one_req(prefix_len, trunc_len, 0)