Decouple scheduler log printing from metrics collection (#20107)

python/sglang/srt/disaggregation/prefill.py

@@ -535,9 +535,8 @@ class SchedulerDisaggregationPrefillMixin:
                     self.send_kv_chunk(req, last_chunk=False, end_idx=req.tmp_end_idx)
                 req.time_stats.set_last_chunked_prefill_finish_time()
 
-        if self.current_scheduler_metrics_enabled:
         can_run_cuda_graph = getattr(result, "can_run_cuda_graph", False)
-            self.log_prefill_stats(
+        self.report_prefill_stats(
             prefill_stats=batch.prefill_stats,
             can_run_cuda_graph=can_run_cuda_graph,
             dp_cooperation_info=batch.dp_cooperation_info,

python/sglang/srt/dllm/mixin/scheduler.py

@@ -92,9 +92,8 @@ class SchedulerDllmMixin:
             self.stream_output(batch.reqs, batch.return_logprob)
             self.token_to_kv_pool_allocator.free_group_end()
 
-        if self.current_scheduler_metrics_enabled:
         can_run_cuda_graph = getattr(result, "can_run_cuda_graph", False)
-            self.log_prefill_stats(
+        self.report_prefill_stats(
             prefill_stats=batch.prefill_stats,
             can_run_cuda_graph=can_run_cuda_graph,
             dp_cooperation_info=batch.dp_cooperation_info,

python/sglang/srt/managers/scheduler.py

@@ -310,10 +310,6 @@ class Scheduler(
         self.enable_overlap = not server_args.disable_overlap_schedule
         self.enable_pdmux = server_args.enable_pdmux
         self.skip_tokenizer_init = server_args.skip_tokenizer_init
-        self.enable_metrics = server_args.enable_metrics
-        self.enable_metrics_for_all_schedulers = (
-            server_args.enable_metrics_for_all_schedulers
-        )
         self.stream_interval = server_args.stream_interval
         self.spec_algorithm = SpeculativeAlgorithm.from_string(
             server_args.speculative_algorithm

python/sglang/srt/managers/scheduler_output_processor_mixin.py

@@ -306,13 +306,8 @@ class SchedulerOutputProcessorMixin:
 
         self.stream_output(batch.reqs, batch.return_logprob, skip_stream_req)
 
-        if self.current_scheduler_metrics_enabled:
         can_run_cuda_graph = getattr(result, "can_run_cuda_graph", False)
-            if self.enable_metrics:
+        self.report_prefill_stats(
-                self.metrics_collector.increment_prefill_cuda_graph_pass(
-                    value=can_run_cuda_graph
-                )
-            self.log_prefill_stats(
             prefill_stats=batch.prefill_stats,
             can_run_cuda_graph=can_run_cuda_graph,
             dp_cooperation_info=batch.dp_cooperation_info,
@@ -485,11 +480,10 @@ class SchedulerOutputProcessorMixin:
         self.token_to_kv_pool_allocator.free_group_end()
 
         self.forward_ct_decode = (self.forward_ct_decode + 1) % (1 << 30)
-        if self.current_scheduler_metrics_enabled:
+        self.report_decode_stats(
-            if self.forward_ct_decode % self.server_args.decode_log_interval == 0:
+            can_run_cuda_graph,
-                self.log_decode_stats(can_run_cuda_graph, running_batch=batch)
+            running_batch=batch,
-            self.log_decode_stats_every_iteration(
+            num_accepted_tokens=result.num_accepted_tokens,
-                batch, num_accepted_tokens=result.num_accepted_tokens
         )
 
     def _mamba_prefix_cache_update(

python/sglang/srt/managers/scheduler_runtime_checker_mixin.py

@@ -271,8 +271,7 @@ class SchedulerRuntimeCheckerMixin:
         self._check_req_pool()
 
         if (
-            self.enable_metrics
+            self.current_scheduler_metrics_enabled
-            and self.current_scheduler_metrics_enabled
             and time.perf_counter() > self.metrics_collector.last_log_time + 30
         ):
             # During idle time, also collect metrics every 30 seconds.

python/sglang/srt/observability/scheduler_metrics_mixin.py

@@ -114,8 +114,10 @@ class SchedulerMetricsMixin:
         self.stats = SchedulerStats()
 
         # Metrics
-        self.current_scheduler_metrics_enabled = (
+        self.enable_metrics = self.server_args.enable_metrics
-            self.attn_tp_rank == 0 or self.enable_metrics_for_all_schedulers
+        self.is_stats_logging_rank = self.attn_tp_rank == 0
+        self.current_scheduler_metrics_enabled = self.enable_metrics and (
+            self.attn_tp_rank == 0 or self.server_args.enable_metrics_for_all_schedulers
         )
         if self.enable_metrics:
             if self.server_args.disaggregation_mode == DisaggregationMode.PREFILL.value:
@@ -158,7 +160,9 @@ class SchedulerMetricsMixin:
         if self.enable_kv_cache_events:
             self.init_kv_events(self.server_args.kv_events_config)
 
-        self.scheduler_status_logger = SchedulerStatusLogger.maybe_create()
+        self.scheduler_status_logger = SchedulerStatusLogger.maybe_create(
+            enable_metrics=self.enable_metrics
+        )
 
     def init_kv_events(self: Scheduler, kv_events_config: Optional[str]):
         if self.enable_kv_cache_events:
@@ -179,12 +183,18 @@ class SchedulerMetricsMixin:
         self.spec_total_num_accepted_tokens = 0
         self.spec_total_num_forward_ct = 0
 
-    def log_prefill_stats(
+    def report_prefill_stats(
         self: Scheduler,
         prefill_stats: PrefillStats,
         can_run_cuda_graph: bool,
         dp_cooperation_info: Optional[DPCooperationInfo] = None,
     ):
+        if (
+            not self.is_stats_logging_rank
+            and not self.current_scheduler_metrics_enabled
+        ):
+            return
+
         gap_latency = time.perf_counter() - self.last_prefill_stats_tic
         self.last_prefill_stats_tic = time.perf_counter()
         self.last_input_throughput = self.last_prefill_tokens / gap_latency
@@ -267,9 +277,13 @@ class SchedulerMetricsMixin:
 
         msg += f"{graph_backend[self.device]}: {can_run_cuda_graph}"
 
+        if self.is_stats_logging_rank:
             logger.info(msg)
 
-        if self.enable_metrics:
+        if self.current_scheduler_metrics_enabled:
+            self.metrics_collector.increment_prefill_cuda_graph_pass(
+                value=can_run_cuda_graph
+            )
             self.metrics_collector.increment_realtime_tokens(
                 prefill_compute_tokens=prefill_stats.log_input_tokens,
                 prefill_cache_tokens=prefill_stats.log_hit_tokens,
@@ -332,11 +346,34 @@ class SchedulerMetricsMixin:
             self._emit_kv_metrics()
         self._publish_kv_events()
 
-    def log_decode_stats(
+    def report_decode_stats(
-        self: Scheduler, can_run_cuda_graph: bool, running_batch: ScheduleBatch = None
+        self: Scheduler,
+        can_run_cuda_graph: bool,
+        running_batch: ScheduleBatch = None,
+        num_accepted_tokens: int = 0,
     ):
         batch = running_batch or self.running_batch
 
+        # Every-iteration work: realtime token counting + status logger
+        if self.current_scheduler_metrics_enabled:
+            self.metrics_collector.increment_realtime_tokens(
+                # TODO unify this w/ the bumping logic in `Scheduler.num_generated_tokens` accumulator
+                decode_tokens=batch.batch_size() + num_accepted_tokens,
+                dp_cooperation_info=batch.dp_cooperation_info,
+            )
+
+            if x := self.scheduler_status_logger:
+                x.maybe_dump(batch, self.waiting_queue)
+
+        # Periodic work: log + heavy metrics at decode_log_interval
+        if self.forward_ct_decode % self.server_args.decode_log_interval != 0:
+            return
+        if (
+            not self.is_stats_logging_rank
+            and not self.current_scheduler_metrics_enabled
+        ):
+            return
+
         gap_latency = time.perf_counter() - self.last_decode_stats_tic
         self.last_decode_stats_tic = time.perf_counter()
         self.last_gen_throughput = self.num_generated_tokens / gap_latency
@@ -455,8 +492,9 @@ class SchedulerMetricsMixin:
             f"#queue-req: {len(self.waiting_queue)}"
         )
 
+        if self.is_stats_logging_rank:
             logger.info(msg)
-        if self.enable_metrics:
+        if self.current_scheduler_metrics_enabled:
             priority_enabled = self.enable_priority_scheduling
             # Basics
             self.stats.num_running_reqs = QueueCount.from_reqs(
@@ -524,19 +562,6 @@ class SchedulerMetricsMixin:
             self._emit_kv_metrics()
         self._publish_kv_events()
 
-    def log_decode_stats_every_iteration(
-        self: Scheduler, batch: ScheduleBatch, num_accepted_tokens: int
-    ):
-        if self.enable_metrics:
-            self.metrics_collector.increment_realtime_tokens(
-                # TODO unify this w/ the bumping logic in `Scheduler.num_generated_tokens` accumulator
-                decode_tokens=batch.batch_size() + num_accepted_tokens,
-                dp_cooperation_info=batch.dp_cooperation_info,
-            )
-
-        if x := self.scheduler_status_logger:
-            x.maybe_dump(batch, self.waiting_queue)
-
     def log_batch_result_stats(
         self: Scheduler,
         batch: ScheduleBatch,

python/sglang/srt/server_args.py

@@ -3905,7 +3905,7 @@ class ServerArgs:
             "--decode-log-interval",
             type=int,
             default=ServerArgs.decode_log_interval,
-            help="The log interval of decode batch.",
+            help="The log and metrics reporting interval (in decode iterations) for decode batches.",
         )
         parser.add_argument(
             "--enable-request-time-stats-logging",

python/sglang/srt/utils/scheduler_status_logger.py

@@ -20,11 +20,17 @@ class SchedulerStatusLogger:
         self.rank = dist.get_rank() if dist.is_initialized() else 0
 
     @staticmethod
-    def maybe_create() -> Optional["SchedulerStatusLogger"]:
+    def maybe_create(enable_metrics: bool) -> Optional["SchedulerStatusLogger"]:
         target = envs.SGLANG_LOG_SCHEDULER_STATUS_TARGET.get()
         if not target:
             return None
 
+        if not enable_metrics:
+            raise ValueError(
+                "SGLANG_LOG_SCHEDULER_STATUS_TARGET is set but --enable-metrics "
+                "is not active. Status dumps require --enable-metrics to work."
+            )
+
         return SchedulerStatusLogger(
             targets=[t.strip() for t in target.split(",") if t.strip()],
             dump_interval=envs.SGLANG_LOG_SCHEDULER_STATUS_INTERVAL.get(),

test/registered/utils/test_scheduler_status_logger.py

@@ -33,7 +33,7 @@ class TestSchedulerStatusLogger(CustomTestCase):
             "Qwen/Qwen3-0.6B",
             DEFAULT_URL_FOR_TEST,
             timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
-            other_args=["--skip-server-warmup"],
+            other_args=["--skip-server-warmup", "--enable-metrics"],
             env=env,
         )
         cls.addClassCleanup(kill_process_tree, cls.process.pid)