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sglang/scripts/ci/utils/runner_utilization_report.py
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#!/usr/bin/env python3
"""
Runner Utilization Report
Analyzes GitHub Actions job data to calculate runner utilization metrics.
Reports idle time, active time, and utilization percentage per runner label.
"""
import argparse
import json
import os
import random
import subprocess
import time
from collections import defaultdict
from concurrent.futures import ThreadPoolExecutor, as_completed
from datetime import datetime, timedelta, timezone
# Labels to skip when grouping runners (GitHub default labels)
DEFAULT_LABELS_TO_IGNORE = {"self-hosted", "Linux", "X64", "ARM64"}
GITHUB_HOSTED_LABELS = {"ubuntu-latest", "ubuntu-22.04", "ubuntu-24.04"}
def run_gh_command(args: list[str], max_retries: int = 10) -> dict:
"""Run gh CLI command and return JSON result.
Retries on transient failures (5xx, secondary rate limits, network
blips) with exponential backoff. The previous fail-fast behavior
combined with `except Exception: return None` in the threadpool
callers caused entire workflow runs to be silently dropped from
the utilization numerator whenever GH API hiccuped, severely
undercounting busy time on busy days.
"""
last_err = ""
for attempt in range(max_retries):
result = subprocess.run(
["gh", "api"] + args,
capture_output=True,
text=True,
)
if result.returncode == 0:
return json.loads(result.stdout)
last_err = result.stderr or "(no stderr)"
# Detect retryable conditions: HTTP 5xx, secondary rate limit, abuse
# detection, network resets. 4xx other than 429 are non-retryable.
retryable = any(
s in last_err
for s in (
"rate limit",
"abuse",
"Internal Server Error",
"502",
"503",
"504",
"Bad Gateway",
"Gateway Time-out",
"connection reset",
"Connection reset",
"EOF",
"timeout",
)
)
if not retryable:
break
# Exponential backoff with jitter, capped at 60s.
delay = min(60, (2**attempt) + random.uniform(0, 1))
time.sleep(delay)
raise Exception(f"gh api failed after {max_retries} attempts: {last_err[:300]}")
def get_workflow_runs(repo: str, hours: int = 24) -> list[dict]:
"""Get workflow runs from the last N hours."""
since = datetime.now(timezone.utc) - timedelta(hours=hours)
runs = []
page = 1
while True:
data = run_gh_command(
[
f"repos/{repo}/actions/runs?per_page=100&page={page}",
]
)
page_runs = data.get("workflow_runs", [])
# Filter by time
for run in page_runs:
created_at = parse_time(run.get("created_at"))
if created_at and created_at >= since:
runs.append(run)
elif created_at and created_at < since:
# Runs are ordered by created_at desc, so we can stop
return runs
if len(page_runs) < 100:
break
page += 1
if page > 50: # Safety limit (5000 runs)
break
return runs
def get_jobs_for_run(repo: str, run_id: int) -> list[dict]:
"""Get all jobs for a workflow run, including all retry attempts.
`filter=all` is required so that re-run attempts of the same job
appear separately. Each attempt consumed host time on the runner
pool, so for utilization we want them all summed in. The default
(`filter=latest`) only returns the most recent attempt and silently
hides time spent on prior retries.
"""
jobs = []
page = 1
while True:
data = run_gh_command(
[
f"repos/{repo}/actions/runs/{run_id}/jobs"
f"?per_page=100&page={page}&filter=all",
]
)
jobs.extend(data.get("jobs", []))
if len(data.get("jobs", [])) < 100:
break
page += 1
if page > 20: # Safety limit (2000 jobs per run)
break
return jobs
def get_runners(repo: str, online_only: bool = True) -> list[dict]:
"""Get all self-hosted runners with pagination. Returns empty if no permission."""
try:
all_runners = []
page = 1
while True:
data = run_gh_command(
[f"repos/{repo}/actions/runners?per_page=100&page={page}"]
)
runners = data.get("runners", [])
all_runners.extend(runners)
if len(runners) < 100:
break
page += 1
if page > 10: # Safety limit
break
if online_only:
all_runners = [r for r in all_runners if r.get("status") == "online"]
return all_runners
except Exception as e:
print(f"Warning: Cannot access runners API (need admin): {e}")
return []
def parse_time(time_str: str) -> datetime:
"""Parse ISO timestamp to datetime."""
if not time_str:
return None
return datetime.fromisoformat(time_str.replace("Z", "+00:00"))
def calculate_concurrency_metrics(
jobs: list,
window_start: datetime,
window_end: datetime,
num_runners: int,
) -> dict:
"""Sweep-line algorithm: peak/avg concurrent, saturation time, peak queue."""
if not jobs:
return {
"peak_concurrent": 0,
"avg_concurrent": 0.0,
"saturation_seconds": 0,
"saturation_pct": 0.0,
"peak_queue": 0,
}
window_seconds = (window_end - window_start).total_seconds()
if window_seconds <= 0:
return {
"peak_concurrent": 0,
"avg_concurrent": 0.0,
"saturation_seconds": 0,
"saturation_pct": 0.0,
"peak_queue": 0,
}
running_events = []
for job in jobs:
start, end = job["start"], job["end"]
if end < window_start or start > window_end:
continue
running_events.append((max(start, window_start), 1))
running_events.append((min(end, window_end), -1))
queue_events = []
for job in jobs:
created_at = job.get("created_at")
started_at = job["start"]
if created_at and created_at < started_at:
if started_at < window_start or created_at > window_end:
continue
queue_events.append((max(created_at, window_start), 1))
queue_events.append((min(started_at, window_end), -1))
running_events.sort(key=lambda e: (e[0], e[1] == 1))
current_running = 0
peak_running = 0
prev_time = window_start
total_running_seconds = 0.0
saturation_seconds = 0.0
for event_time, delta in running_events:
td = (event_time - prev_time).total_seconds()
if td > 0:
total_running_seconds += current_running * td
if current_running >= num_runners:
saturation_seconds += td
current_running += delta
peak_running = max(peak_running, current_running)
prev_time = event_time
if prev_time < window_end:
td = (window_end - prev_time).total_seconds()
total_running_seconds += current_running * td
if current_running >= num_runners:
saturation_seconds += td
queue_events.sort(key=lambda e: (e[0], e[1] == 1))
current_queued = 0
peak_queue = 0
for _, delta in queue_events:
current_queued += delta
peak_queue = max(peak_queue, current_queued)
avg_concurrent = total_running_seconds / window_seconds if window_seconds > 0 else 0
return {
"peak_concurrent": peak_running,
"avg_concurrent": avg_concurrent,
"saturation_seconds": saturation_seconds,
"saturation_pct": (
(saturation_seconds / window_seconds * 100) if window_seconds > 0 else 0
),
"peak_queue": peak_queue,
}
_NON_GPU_WORKFLOW_HINTS = (
"lint",
"deploy",
"release",
"publish",
"docs",
"doc",
"mintlify",
"runner utilization", # this very script
"tag-and-rerun",
"auto", # auto-merge etc.
"label",
"stale",
"dependabot",
"codeql",
)
def _likely_no_gpu_jobs(workflow_name: str) -> bool:
"""Heuristic: skip per-run job-fetch for workflows that don't dispatch
to self-hosted GPU runners. The GH API rate limit (~5000 req/hr per
token) is the bottleneck on busy 24h windows where ~4000 workflow
runs fire — but only a fraction of those (pr-test, nightly-test,
pr-test-*kernel, etc.) actually run on GPU runners. Skipping the
docs/lint/release runs cuts the API call budget by 2-4x.
"""
if not workflow_name:
return False
n = workflow_name.lower()
return any(h in n for h in _NON_GPU_WORKFLOW_HINTS)
def calculate_utilization(repo: str, hours: int = 24, runner_filter: str = None):
"""Calculate runner utilization metrics."""
print(f"Fetching workflow runs from last {hours} hours...")
all_runs = get_workflow_runs(repo, hours)
runs = [r for r in all_runs if not _likely_no_gpu_jobs(r.get("name", ""))]
skipped = len(all_runs) - len(runs)
print(
f"Found {len(all_runs)} workflow runs "
f"({skipped} skipped as non-GPU: docs/lint/release/etc.)"
)
# Try to get online runners from API
print("Fetching online runners...")
runners = get_runners(repo, online_only=True)
# Build label -> set of online runner names from API
api_label_runners = defaultdict(set)
if runners:
for runner in runners:
for label in runner.get("labels", []):
label_name = label.get("name", "")
if label_name not in DEFAULT_LABELS_TO_IGNORE:
api_label_runners[label_name].add(runner["name"])
print(f"Got {len(runners)} online runners from API")
else:
print("No runner API access, will use observed runners from job data")
# Track runners seen in jobs (for labels not in API or when API unavailable)
job_label_runners = defaultdict(set)
label_jobs = defaultdict(list) # label -> list of job_info
# Per-host accumulation: each physical machine appears once regardless of
# how many overlapping labels it advertises. This is what we use for the
# "Per Host Utilization" section (the source-of-truth view).
host_jobs = defaultdict(list) # runner_name -> list of job_info
host_labels = defaultdict(set) # runner_name -> set of labels it ran jobs under
# Fetch jobs for all runs in parallel. Cap concurrency lower than the
# GH API secondary rate-limit threshold to avoid bursts that silently
# drop runs even with retries.
total_runs = len(runs)
print(f"Fetching jobs for {total_runs} runs in parallel...")
def fetch_jobs_for_run(run):
"""Fetch jobs for a single run.
Returns (run_id, jobs, error_msg). `error_msg` is None on success.
We surface failures rather than silently dropping the run so the
caller can report how many runs' jobs are missing — silently
dropping previously caused 4-gpu-b200 (and every other label) to
report wildly different numbers depending on transient API hiccups.
"""
try:
return (run["id"], get_jobs_for_run(repo, run["id"]), None)
except Exception as e:
return (run["id"], None, str(e)[:200])
all_jobs = []
failed_runs = []
# Concurrency=4 with longer retry budget keeps us well below the GH
# API secondary rate-limit threshold (~10 req/s). On a 24h window
# with ~1500 GPU-relevant runs (post-filter), this completes in ~5
# min and almost never hits the rate limit.
with ThreadPoolExecutor(max_workers=4) as executor:
futures = [executor.submit(fetch_jobs_for_run, run) for run in runs]
completed = 0
for future in as_completed(futures):
completed += 1
if completed % 100 == 0:
print(
f"Fetched jobs for {completed}/{total_runs} runs "
f"({len(failed_runs)} failed so far)..."
)
run_id, jobs, err = future.result()
if err:
failed_runs.append((run_id, err))
elif jobs:
all_jobs.extend(jobs)
print(f"Processing {len(all_jobs)} jobs...")
if failed_runs:
print(
f"WARNING: {len(failed_runs)}/{total_runs} runs failed to fetch "
f"after retries. Utilization will be undercounted. "
f"First few errors:"
)
for rid, err in failed_runs[:5]:
print(f" run {rid}: {err}")
fetch_failure_pct = len(failed_runs) / total_runs * 100 if total_runs > 0 else 0
for job in all_jobs:
runner_name = job.get("runner_name")
if not runner_name:
continue
created_at = parse_time(job.get("created_at"))
started_at = parse_time(job.get("started_at"))
completed_at = parse_time(job.get("completed_at"))
if not started_at or not completed_at:
continue
duration = (completed_at - started_at).total_seconds()
queue_time = (started_at - created_at).total_seconds() if created_at else 0
job_info = {
"start": started_at,
"end": completed_at,
"created_at": created_at,
"duration": duration,
"queue_time": queue_time,
"job_name": job["name"],
"runner_name": runner_name,
}
# Per-host: every job on this physical machine, regardless of label.
host_jobs[runner_name].append(job_info)
# Use job labels directly (available in job data)
job_labels = job.get("labels", [])
for label in job_labels:
# Skip generic labels
if label in DEFAULT_LABELS_TO_IGNORE | GITHUB_HOSTED_LABELS:
continue
job_label_runners[label].add(runner_name)
label_jobs[label].append(job_info)
host_labels[runner_name].add(label)
# Merge API runners and job-observed runners
# Prefer API count (online runners) when available
all_labels = set(api_label_runners.keys()) | set(job_label_runners.keys())
# Filter labels if specified
if runner_filter:
all_labels = {lbl for lbl in all_labels if runner_filter in lbl}
print(f"Tracking {len(all_labels)} runner labels: {sorted(all_labels)}")
window_seconds = hours * 3600
window_end = datetime.now(timezone.utc)
window_start = window_end - timedelta(hours=hours)
# Per-host window-clamped busy time (each physical machine counted once).
# This is the source of truth for how loaded each host actually is.
host_busy_seconds = {}
for host, jobs in host_jobs.items():
busy = 0.0
for j in jobs:
cs = max(j["start"], window_start)
ce = min(j["end"], window_end)
if ce > cs:
busy += (ce - cs).total_seconds()
host_busy_seconds[host] = busy
results = []
for label in sorted(all_labels):
# Hosts to attribute to this label = union of currently-online
# runners advertising the label PLUS hosts that actually ran a
# job under it during the window. The union catches hosts that
# went offline mid-window (their busy time is still real
# capacity consumed) and hosts that came online late.
hosts = api_label_runners.get(label, set()) | job_label_runners.get(
label, set()
)
num_runners = len(hosts) if hosts else 1
# Pool busy time: sum of busy time across the hosts that could
# serve this label, regardless of which sibling label actually
# dispatched the job. This is the right denominator/numerator for
# asking "how saturated is the underlying hardware that this
# label depends on?" — sibling labels (e.g. `4-gpu-b200` and
# `4-gpu-b200-low-disk`) compete for the same physical machines,
# so their busy time should not be double-counted into separate
# capacity buckets.
active_seconds = sum(host_busy_seconds.get(h, 0.0) for h in hosts)
capacity_seconds = num_runners * window_seconds
utilization = (
(active_seconds / capacity_seconds * 100) if capacity_seconds > 0 else 0
)
# Job count + queue stats stay label-specific (only jobs that
# were dispatched under THIS label).
jobs = label_jobs.get(label, [])
queue_times = [j["queue_time"] for j in jobs if j["queue_time"] > 0]
avg_queue = sum(queue_times) / len(queue_times) if queue_times else 0
max_queue = max(queue_times) if queue_times else 0
# Concurrency / saturation / queue-depth metrics. Use observed
# peak as effective capacity if it's lower than the API count
# (e.g. for autoscaling pools where most listeners sit idle).
conc_initial = calculate_concurrency_metrics(
jobs, window_start, window_end, num_runners
)
effective_runners = (
min(num_runners, conc_initial["peak_concurrent"]) or num_runners
)
if effective_runners < num_runners and effective_runners > 0:
conc = calculate_concurrency_metrics(
jobs, window_start, window_end, effective_runners
)
else:
conc = conc_initial
results.append(
{
"label": label,
"num_runners": num_runners,
"effective_runners": effective_runners,
"num_jobs": len(jobs),
"total_active_hours": active_seconds / 3600,
"utilization_pct": utilization,
"avg_queue_min": avg_queue / 60,
"max_queue_min": max_queue / 60,
"peak_concurrent": conc_initial["peak_concurrent"],
"avg_concurrent": conc["avg_concurrent"],
"saturation_hours": conc["saturation_seconds"] / 3600,
"saturation_pct": conc["saturation_pct"],
"peak_queue": conc["peak_queue"],
}
)
return results, fetch_failure_pct
def format_report(
results: list[dict], hours: int, fetch_failure_pct: float = 0.0
) -> str:
"""One compact summary table — original schema, fixed columns.
Active (hrs) and Utilization now reflect the actual host pool's
busy time (sum across all jobs on the hosts that advertise this
label, regardless of which sibling label dispatched them). This
makes the column meaningful for shared host pools — e.g.
`4-gpu-b200` and `4-gpu-b200-low-disk` both consume the same
physical hosts, so their utilization now reflects real hardware
saturation instead of being divided across labels.
"""
lines = [
"# Runner Utilization Report",
"",
f"**Time window:** Last {hours} hours · "
f"**Generated:** {datetime.now(timezone.utc).strftime('%Y-%m-%d %H:%M UTC')}",
"",
]
if fetch_failure_pct > 1.0:
lines.append(
f"⚠️ **Data completeness warning**: {fetch_failure_pct:.0f}% of "
f"GPU-relevant workflow runs failed to fetch jobs after retries "
f"(GH API rate limit). Active hours and utilization below are "
f"under-counted by approximately this fraction."
)
lines.append("")
lines.extend(
[
"| Label | Runners | Jobs | Active (hrs) | Utilization | Avg Queue | Max Queue |",
"|-------|---------|------|--------------|-------------|-----------|-----------|",
]
)
for r in results:
bar = "█" * int(r["utilization_pct"] / 10) + "░" * (
10 - int(r["utilization_pct"] / 10)
)
lines.append(
f"| {r['label']} | {r['num_runners']} | {r['num_jobs']} | "
f"{r['total_active_hours']:.1f} | "
f"{r['utilization_pct']:.1f}% {bar} | "
f"{r['avg_queue_min']:.1f}m | {r['max_queue_min']:.1f}m |"
)
# Concurrency Analysis section
lines.extend(
[
"",
"## Concurrency Analysis",
"",
"| Label | Runners (API/Effective) | Peak Concurrent | Avg Concurrent | Saturation Time | Peak Queue |",
"|-------|-------------------------|-----------------|----------------|-----------------|------------|",
]
)
for r in results:
effective = r["effective_runners"]
avg_pct = (r["avg_concurrent"] / effective * 100) if effective > 0 else 0
runner_str = (
f"{r['num_runners']}/{effective}"
if effective != r["num_runners"]
else str(r["num_runners"])
)
lines.append(
f"| {r['label']} | {runner_str} | "
f"{r['peak_concurrent']} | "
f"{r['avg_concurrent']:.1f} ({avg_pct:.0f}%) | "
f"{r['saturation_hours']:.1f}h ({r['saturation_pct']:.0f}%) | "
f"{r['peak_queue']} jobs |"
)
# Recommendations
lines.extend(["", "## Recommendations", ""])
has_recs = False
for r in results:
label = r["label"]
sat_pct = r["saturation_pct"]
peak_q = r["peak_queue"]
effective = r["effective_runners"]
avg_pct = (r["avg_concurrent"] / effective * 100) if effective > 0 else 0
if sat_pct > 50 or peak_q > 5:
lines.append(
f"⚠️ **{label}**: High saturation ({sat_pct:.0f}%) "
f"with queue buildup ({peak_q} jobs). Consider adding runners."
)
has_recs = True
elif sat_pct > 20 or peak_q > 0:
lines.append(
f"📊 **{label}**: Moderate saturation ({sat_pct:.0f}%), "
f"peak queue {peak_q} jobs. Monitor for trends."
)
has_recs = True
elif avg_pct < 30 and r["num_jobs"] > 0:
lines.append(
f"💡 **{label}**: Low average utilization ({avg_pct:.0f}%). "
f"Runner pool may be oversized."
)
has_recs = True
else:
lines.append(f"✓ **{label}**: Healthy utilization with minimal queueing.")
if not has_recs and results:
lines.append("All runner pools have healthy utilization.")
return "\n".join(lines)
def main():
parser = argparse.ArgumentParser(description="Generate runner utilization report")
parser.add_argument("--repo", default="sgl-project/sglang", help="GitHub repo")
parser.add_argument("--hours", type=int, default=24, help="Time window in hours")
parser.add_argument(
"--filter", type=str, help="Filter runner labels (e.g., '5090', 'h200')"
)
parser.add_argument("--output", type=str, help="Output file (default: stdout)")
args = parser.parse_args()
results, fetch_failure_pct = calculate_utilization(
args.repo, args.hours, args.filter
)
report = format_report(results, args.hours, fetch_failure_pct)
if args.output:
with open(args.output, "w") as f:
f.write(report)
print(f"Report written to {args.output}")
else:
print(report)
# Also write to GITHUB_STEP_SUMMARY if available
summary_file = os.environ.get("GITHUB_STEP_SUMMARY")
if summary_file:
with open(summary_file, "a") as f:
f.write(report)
if __name__ == "__main__":
main()