Refactor Prometheus and Add Request Level Metrics (#2316)

2024-01-31 14:58:07 -08:00
parent d0d93b92b1
commit 93b38bea5d
7 changed files with 1230 additions and 98 deletions
--- a/vllm/engine/llm_engine.py
+++ b/vllm/engine/llm_engine.py
@@ -10,7 +10,7 @@ from vllm.config import (CacheConfig, ModelConfig, ParallelConfig,
                         SchedulerConfig, LoRAConfig)
 from vllm.core.scheduler import Scheduler, SchedulerOutputs
 from vllm.engine.arg_utils import EngineArgs
-from vllm.engine.metrics import record_metrics
+from vllm.engine.metrics import StatLogger, Stats
 from vllm.engine.ray_utils import RayWorkerVllm, initialize_cluster, ray
 from vllm.logger import init_logger
 from vllm.outputs import RequestOutput
@@ -28,8 +28,7 @@ if TYPE_CHECKING:
    from ray.util.placement_group import PlacementGroup

 logger = init_logger(__name__)
-
-_LOGGING_INTERVAL_SEC = 5
+_LOCAL_LOGGING_INTERVAL_SEC = 5


 class LLMEngine:
@@ -116,12 +115,10 @@ class LLMEngine:
        # Create the scheduler.
        self.scheduler = Scheduler(scheduler_config, cache_config, lora_config)

-        # Logging.
-        self.last_logging_time = 0.0
-        # List of (timestamp, num_tokens)
-        self.num_prompt_tokens: List[Tuple[float, int]] = []
-        # List of (timestamp, num_tokens)
-        self.num_generation_tokens: List[Tuple[float, int]] = []
+        # Metric Logging.
+        if self.log_stats:
+            self.stat_logger = StatLogger(
+                local_interval=_LOCAL_LOGGING_INTERVAL_SEC)

    def get_tokenizer_for_seq(self, sequence: Sequence):
        return self.tokenizer.get_lora_tokenizer(sequence.lora_request)
@@ -537,6 +534,7 @@ class LLMEngine:

    def _process_sequence_group_outputs(self, seq_group: SequenceGroup,
                                        outputs: SequenceGroupOutput) -> None:
+
        # Process prompt logprobs
        prompt_logprobs = outputs.prompt_logprobs
        if prompt_logprobs is not None:
@@ -732,10 +730,10 @@ class LLMEngine:
                    and not seq_group.prefix.computed):
                seq_group.prefix.computed = True

+        # Log stats.
        if self.log_stats:
-            # Log the system stats.
-            self._log_system_stats(scheduler_outputs.prompt_run,
-                                   scheduler_outputs.num_batched_tokens)
+            self.stat_logger.log(self._get_stats(scheduler_outputs))
+
        return request_outputs

    def step(self) -> List[RequestOutput]:
@@ -810,81 +808,73 @@ class LLMEngine:
        return self._process_model_outputs(output, scheduler_outputs)

    def do_log_stats(self) -> None:
-        self._log_system_stats(False, 0)
+        """Forced log when no requests active."""
+        if self.log_stats:
+            self.stat_logger.log(self._get_stats(scheduler_outputs=None))

-    def _log_system_stats(
-        self,
-        prompt_run: bool,
-        num_batched_tokens: int,
-    ) -> None:
+    def _get_stats(self,
+                   scheduler_outputs: Optional[SchedulerOutputs]) -> Stats:
+        """Get Stats to be Logged to Prometheus."""
        now = time.monotonic()
-        # Log the number of batched input tokens.
-        if prompt_run:
-            self.num_prompt_tokens.append((now, num_batched_tokens))
-        else:
-            self.num_generation_tokens.append((now, num_batched_tokens))

-        should_log = now - self.last_logging_time >= _LOGGING_INTERVAL_SEC
-        if not should_log:
-            return
+        # KV Cache Usage in %.
+        num_total_gpu = self.cache_config.num_gpu_blocks
+        num_free_gpu = self.scheduler.block_manager.get_num_free_gpu_blocks()
+        gpu_cache_usage = 1.0 - (num_free_gpu / num_total_gpu)

-        # Discard the old stats.
-        self.num_prompt_tokens = [(t, n) for t, n in self.num_prompt_tokens
-                                  if now - t < _LOGGING_INTERVAL_SEC]
-        self.num_generation_tokens = [(t, n)
-                                      for t, n in self.num_generation_tokens
-                                      if now - t < _LOGGING_INTERVAL_SEC]
+        num_total_cpu = self.cache_config.num_cpu_blocks
+        cpu_cache_usage = 0.
+        if num_total_cpu > 0:
+            num_free_cpu = self.scheduler.block_manager.get_num_free_cpu_blocks(
+            )
+            cpu_cache_usage = 1.0 - (num_free_cpu / num_total_cpu)

-        if len(self.num_prompt_tokens) > 1:
-            total_num_tokens = sum(n for _, n in self.num_prompt_tokens[:-1])
-            window = now - self.num_prompt_tokens[0][0]
-            avg_prompt_throughput = total_num_tokens / window
-        else:
-            avg_prompt_throughput = 0.0
-        if len(self.num_generation_tokens) > 1:
-            total_num_tokens = sum(n
-                                   for _, n in self.num_generation_tokens[:-1])
-            window = now - self.num_generation_tokens[0][0]
-            avg_generation_throughput = total_num_tokens / window
-        else:
-            avg_generation_throughput = 0.0
+        # Scheduler State
+        num_running = len(self.scheduler.running)
+        num_swapped = len(self.scheduler.swapped)
+        num_waiting = len(self.scheduler.waiting)

-        total_num_gpu_blocks = self.cache_config.num_gpu_blocks
-        num_free_gpu_blocks = (
-            self.scheduler.block_manager.get_num_free_gpu_blocks())
-        num_used_gpu_blocks = total_num_gpu_blocks - num_free_gpu_blocks
-        gpu_cache_usage = num_used_gpu_blocks / total_num_gpu_blocks
+        # Iteration stats if we have scheduler output.
+        num_prompt_tokens = 0
+        num_generation_tokens = 0
+        time_to_first_tokens = []
+        time_per_output_tokens = []
+        time_e2e_requests = []
+        if scheduler_outputs is not None:
+            prompt_run = scheduler_outputs.prompt_run

-        total_num_cpu_blocks = self.cache_config.num_cpu_blocks
-        if total_num_cpu_blocks > 0:
-            num_free_cpu_blocks = (
-                self.scheduler.block_manager.get_num_free_cpu_blocks())
-            num_used_cpu_blocks = total_num_cpu_blocks - num_free_cpu_blocks
-            cpu_cache_usage = num_used_cpu_blocks / total_num_cpu_blocks
-        else:
-            cpu_cache_usage = 0.0
+            # Number of Tokens.
+            if prompt_run:
+                num_prompt_tokens = scheduler_outputs.num_batched_tokens
+            else:
+                num_generation_tokens = scheduler_outputs.num_batched_tokens

-        record_metrics(
-            avg_prompt_throughput=avg_prompt_throughput,
-            avg_generation_throughput=avg_generation_throughput,
-            scheduler_running=len(self.scheduler.running),
-            scheduler_swapped=len(self.scheduler.swapped),
-            scheduler_waiting=len(self.scheduler.waiting),
+            # Latency Timings.
+            time_last_iters = []
+            for seq_group in scheduler_outputs.scheduled_seq_groups:
+                # Time since last token. (n.b. updates seq_group.last_token_time)
+                time_last_iters.append(seq_group.get_last_latency(now))
+                # Time since arrival for all finished requests.
+                if seq_group.is_finished():
+                    time_e2e_requests.append(now - seq_group.arrival_time)
+
+            time_to_first_tokens = time_last_iters if prompt_run else []
+            time_per_output_tokens = [] if prompt_run else time_last_iters
+
+        return Stats(
+            now=now,
+            num_running=num_running,
+            num_swapped=num_swapped,
+            num_waiting=num_waiting,
            gpu_cache_usage=gpu_cache_usage,
            cpu_cache_usage=cpu_cache_usage,
+            num_prompt_tokens=num_prompt_tokens,
+            num_generation_tokens=num_generation_tokens,
+            time_to_first_tokens=time_to_first_tokens,
+            time_per_output_tokens=time_per_output_tokens,
+            time_e2e_requests=time_e2e_requests,
        )

-        logger.info("Avg prompt throughput: "
-                    f"{avg_prompt_throughput:.1f} tokens/s, "
-                    "Avg generation throughput: "
-                    f"{avg_generation_throughput:.1f} tokens/s, "
-                    f"Running: {len(self.scheduler.running)} reqs, "
-                    f"Swapped: {len(self.scheduler.swapped)} reqs, "
-                    f"Pending: {len(self.scheduler.waiting)} reqs, "
-                    f"GPU KV cache usage: {gpu_cache_usage * 100:.1f}%, "
-                    f"CPU KV cache usage: {cpu_cache_usage * 100:.1f}%")
-        self.last_logging_time = now
-
    def _decode_sequence(self, seq: Sequence, prms: SamplingParams) -> None:
        """Decodes the new token for a sequence."""
        (new_tokens, new_output_text, prefix_offset,
--- a/vllm/engine/metrics.py
+++ b/vllm/engine/metrics.py
@@ -1,4 +1,19 @@
-from aioprometheus import Gauge
+from vllm.logger import init_logger
+from aioprometheus import Counter, Gauge, Histogram
+
+import time
+import numpy as np
+from typing import List
+from dataclasses import dataclass
+
+logger = init_logger(__name__)
+
+labels = {}
+
+
+def add_global_metrics_labels(**kwargs):
+    labels.update(kwargs)
+

 # The begin-* and end* here are used by the documentation generator
 # to extract the metrics definitions.
@@ -9,12 +24,16 @@ gauge_avg_prompt_throughput = Gauge("vllm:avg_prompt_throughput_toks_per_s",
 gauge_avg_generation_throughput = Gauge(
    "vllm:avg_generation_throughput_toks_per_s",
    "Average generation throughput in tokens/s.")
+counter_prompt_tokens = Counter("vllm:prompt_tokens_total",
+                                "Number of prefill tokens processed.")
+counter_generation_tokens = Counter("vllm:generation_tokens_total",
+                                    "Number of generation tokens processed.")

 gauge_scheduler_running = Gauge(
    "vllm:num_requests_running",
-    "Number of requests that is currently running for inference.")
+    "Number of requests currently running on GPU.")
 gauge_scheduler_swapped = Gauge("vllm:num_requests_swapped",
-                                "Number requests swapped to CPU.")
+                                "Number of requests swapped to CPU.")
 gauge_scheduler_waiting = Gauge("vllm:num_requests_waiting",
                                "Number of requests waiting to be processed.")

@@ -24,28 +43,131 @@ gauge_gpu_cache_usage = Gauge(
 gauge_cpu_cache_usage = Gauge(
    "vllm:cpu_cache_usage_perc",
    "CPU KV-cache usage. 1 means 100 percent usage.")
+
+histogram_time_to_first_token = Histogram(
+    "vllm:time_to_first_token_seconds",
+    "Histogram of time to first token in seconds.",
+    buckets=[
+        0.001, 0.005, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.25, 0.5, 0.75, 1.0,
+        2.5, 5.0, 7.5, 10.0
+    ])
+histogram_time_per_output_tokens = Histogram(
+    "vllm:time_per_output_token_seconds",
+    "Histogram of time per output token in seconds.",
+    buckets=[
+        0.01, 0.025, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.75, 1.0, 2.5
+    ])
+histogram_e2e_request_latency = Histogram(
+    "vllm:e2e_request_latency_seconds",
+    "Histogram of end to end request latency in seconds.",
+    buckets=[1.0, 2.5, 5.0, 10.0, 15.0, 20.0, 30.0, 40.0, 50.0, 60.0])
 # end-metrics-definitions

-labels = {}
+
+@dataclass
+class Stats:
+    """Created by LLMEngine for use by StatLogger."""
+    now: float
+
+    # System stats.
+    num_running: int
+    num_waiting: int
+    num_swapped: int
+    gpu_cache_usage: float
+    cpu_cache_usage: float
+
+    # Raw stats from last model iteration.
+    num_prompt_tokens: int
+    num_generation_tokens: int
+    time_to_first_tokens: List[float]
+    time_per_output_tokens: List[float]
+    time_e2e_requests: List[float]


-def add_global_metrics_labels(**kwargs):
-    labels.update(kwargs)
+class StatLogger:
+    """StatLogger is used LLMEngine to log to Promethus and Stdout."""

+    def __init__(self, local_interval: float) -> None:
+        # Metadata for logging locally.
+        self.last_local_log = time.monotonic()
+        self.local_interval = local_interval

-def record_metrics(
-    avg_prompt_throughput: float,
-    avg_generation_throughput: float,
-    scheduler_running: int,
-    scheduler_swapped: int,
-    scheduler_waiting: int,
-    gpu_cache_usage: float,
-    cpu_cache_usage: float,
-):
-    gauge_avg_prompt_throughput.set(labels, avg_prompt_throughput)
-    gauge_avg_generation_throughput.set(labels, avg_generation_throughput)
-    gauge_scheduler_running.set(labels, scheduler_running)
-    gauge_scheduler_swapped.set(labels, scheduler_swapped)
-    gauge_scheduler_waiting.set(labels, scheduler_waiting)
-    gauge_gpu_cache_usage.set(labels, gpu_cache_usage)
-    gauge_cpu_cache_usage.set(labels, cpu_cache_usage)
+        # Tracked stats over current local logging interval.
+        self.num_prompt_tokens: List[int] = []
+        self.num_generation_tokens: List[int] = []
+
+    def _get_throughput(self, tracked_stats: List[int], now: float) -> float:
+        return float(np.sum(tracked_stats) / (now - self.last_local_log))
+
+    def _local_interval_elapsed(self, now: float) -> bool:
+        elapsed_time = now - self.last_local_log
+        return elapsed_time > self.local_interval
+
+    def _log_prometheus(self, stats: Stats) -> None:
+        # Set system stat gauges.
+        gauge_scheduler_running.set(labels, stats.num_running)
+        gauge_scheduler_swapped.set(labels, stats.num_swapped)
+        gauge_scheduler_waiting.set(labels, stats.num_waiting)
+        gauge_gpu_cache_usage.set(labels, stats.gpu_cache_usage)
+        gauge_cpu_cache_usage.set(labels, stats.cpu_cache_usage)
+
+        # Add to token counters.
+        counter_prompt_tokens.add(labels, stats.num_prompt_tokens)
+        counter_generation_tokens.add(labels, stats.num_generation_tokens)
+
+        # Observe request level latencies in histograms.
+        for ttft in stats.time_to_first_tokens:
+            histogram_time_to_first_token.observe(labels, ttft)
+        for tpot in stats.time_per_output_tokens:
+            histogram_time_per_output_tokens.observe(labels, tpot)
+        for e2e in stats.time_e2e_requests:
+            histogram_e2e_request_latency.observe(labels, e2e)
+
+    def _log_prometheus_interval(self, prompt_throughput: float,
+                                 generation_throughput: float) -> None:
+        # Logs metrics to prometheus that are computed every logging_interval.
+        # Support legacy gauge metrics that make throughput calculations on the vLLM side.
+        # Moving forward, we should use counters like counter_prompt_tokens, counter_generation_tokens
+        # Which log raw data and calculate summaries using rate() on the grafana/prometheus side.
+        # See https://github.com/vllm-project/vllm/pull/2316#discussion_r1464204666
+        gauge_avg_prompt_throughput.set(labels, prompt_throughput)
+        gauge_avg_generation_throughput.set(labels, generation_throughput)
+
+    def log(self, stats: Stats) -> None:
+        """Called by LLMEngine.
+           Logs to prometheus and tracked stats every iteration. 
+           Logs to Stdout every self.local_interval seconds."""
+
+        # Log to prometheus.
+        self._log_prometheus(stats)
+
+        # Save tracked stats for token counters.
+        self.num_prompt_tokens.append(stats.num_prompt_tokens)
+        self.num_generation_tokens.append(stats.num_generation_tokens)
+
+        # Log locally every local_interval seconds.
+        if self._local_interval_elapsed(stats.now):
+
+            # Compute summary metrics for tracked stats (and log them to promethus if applicable).
+            prompt_throughput = self._get_throughput(self.num_prompt_tokens,
+                                                     now=stats.now)
+            generation_throughput = self._get_throughput(
+                self.num_generation_tokens, now=stats.now)
+            self._log_prometheus_interval(
+                prompt_throughput=prompt_throughput,
+                generation_throughput=generation_throughput)
+
+            # Log to stdout.
+            logger.info(
+                f"Avg prompt throughput: {prompt_throughput:.1f} tokens/s, "
+                f"Avg generation throughput: {generation_throughput:.1f} tokens/s, "
+                f"Running: {stats.num_running} reqs, "
+                f"Swapped: {stats.num_swapped} reqs, "
+                f"Pending: {stats.num_waiting} reqs, "
+                f"GPU KV cache usage: {stats.gpu_cache_usage * 100:.1f}%, "
+                f"CPU KV cache usage: {stats.cpu_cache_usage * 100:.1f}%")
+
+            # Reset tracked stats for next interval.
+            self.num_prompt_tokens = []
+            self.num_generation_tokens = []
+            self.last_local_log = stats.now