[observability] add ServerArgs.stat_loggers for pluggable metrics backend (#24610)

Signed-off-by: Dongjun Na <kmu5544616@gmail.com>

python/sglang/srt/managers/tokenizer_manager.py

@@ -85,7 +85,11 @@ from sglang.srt.managers.tokenizer_manager_score_mixin import (
 )
 from sglang.srt.managers.utils import is_health_check_generate_req
 from sglang.srt.observability.cpu_monitor import start_cpu_monitor_thread
-from sglang.srt.observability.metrics_collector import TokenizerMetricsCollector
+from sglang.srt.observability.metrics_collector import (
+    STAT_LOGGER_ROLE_TOKENIZER,
+    TokenizerMetricsCollector,
+    resolve_collector_class,
+)
 from sglang.srt.observability.req_time_stats import (
     APIServerReqTimeStats,
     convert_time_to_realtime,
@@ -488,7 +492,12 @@ class TokenizerManager(TokenizerControlMixin, TokenizerManagerScoreMixin):
                     labels[label] = ""
             if self.server_args.extra_metric_labels:
                 labels.update(self.server_args.extra_metric_labels)
-            self.metrics_collector = TokenizerMetricsCollector(
+            tokenizer_collector_cls = resolve_collector_class(
+                self.server_args,
+                STAT_LOGGER_ROLE_TOKENIZER,
+                TokenizerMetricsCollector,
+            )
+            self.metrics_collector = tokenizer_collector_cls(
                 server_args=self.server_args,
                 labels=labels,
                 bucket_time_to_first_token=self.server_args.bucket_time_to_first_token,