Build Nginx live traffic monitor

This commit is contained in:
Jordan Wages 2026-09-17 17:47:16 -05:00
commit fb66a69bd7
9 changed files with 525 additions and 2 deletions

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app/main.py Normal file
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from __future__ import annotations
import argparse
import asyncio
import json
import math
import os
import statistics
import threading
import time
from collections import deque
from dataclasses import dataclass, field
from pathlib import Path
from typing import Any, AsyncIterator
from fastapi import FastAPI, Request
from fastapi.responses import FileResponse, StreamingResponse
from fastapi.staticfiles import StaticFiles
DEFAULT_LOG = "/var/log/nginx-traffic/traffic.log"
MAX_HOSTS = 1000
@dataclass
class Bucket:
incoming: int = 0
outgoing: int = 0
requests: int = 0
statuses: list[int] = field(default_factory=lambda: [0, 0, 0, 0])
request_times: list[float] = field(default_factory=list)
upstream_times: list[float] = field(default_factory=list)
class Series:
def __init__(self, retention: int):
self.retention = retention
self.buckets: dict[int, Bucket] = {}
def bucket(self, second: int) -> Bucket:
if second not in self.buckets:
self.buckets[second] = Bucket()
cutoff = second - self.retention + 1
for old in [key for key in self.buckets if key < cutoff]:
del self.buckets[old]
return self.buckets[second]
def percentile(values: list[float], p: float) -> float | None:
if not values:
return None
values = sorted(values)
index = (len(values) - 1) * p
low, high = math.floor(index), math.ceil(index)
if low == high:
return values[low]
return values[low] + (values[high] - values[low]) * (index - low)
def parse_line(line: str) -> dict[str, Any] | None:
"""Parse the configured, whitespace-delimited Nginx traffic format."""
fields = line.strip().split()
if len(fields) < 8:
return None
try:
timestamp = float(fields[0])
status = int(fields[3])
request_length = int(fields[4])
bytes_sent = int(fields[5])
request_time = float(fields[6])
upstream_raw = "".join(fields[7:])
upstream_values = [float(value) for value in upstream_raw.split(",") if value not in ("", "-")]
if not all(math.isfinite(value) and value >= 0 for value in
(timestamp, request_length, bytes_sent, request_time, *upstream_values)):
return None
if status < 100 or status > 599:
return None
except (ValueError, OverflowError):
return None
return {
"timestamp": timestamp,
"host": fields[1] or "(unknown)",
"incoming": request_length,
"outgoing": bytes_sent,
"status": status,
"request_time": request_time,
"upstream_time": statistics.fmean(upstream_values) if upstream_values else None,
}
class Telemetry:
def __init__(self, retention: int):
self.retention = max(60, min(retention, 86400))
self.global_series = Series(self.retention)
self.hosts: dict[str, Series] = {}
self.last_seen: dict[str, int] = {}
self.total_incoming = 0
self.total_outgoing = 0
self.lock = threading.RLock()
self.subscribers: set[asyncio.Queue[str]] = set()
def ingest(self, event: dict[str, Any]) -> None:
now = int(time.time())
second = int(event["timestamp"])
# Log timestamps are normally current, but clamping protects bounded
# storage if a clock-jumped or otherwise surprising line appears.
if second < now - self.retention:
return
second = min(second, now)
with self.lock:
self._add(self.global_series.bucket(second), event)
host = event["host"]
if host not in self.hosts:
if len(self.hosts) >= MAX_HOSTS:
oldest = min(self.last_seen, key=self.last_seen.get)
self.hosts.pop(oldest, None)
self.last_seen.pop(oldest, None)
self.hosts[host] = Series(self.retention)
self._add(self.hosts[host].bucket(second), event)
self.last_seen[host] = second
self.total_incoming += event["incoming"]
self.total_outgoing += event["outgoing"]
@staticmethod
def _add(bucket: Bucket, event: dict[str, Any]) -> None:
bucket.incoming += event["incoming"]
bucket.outgoing += event["outgoing"]
bucket.requests += 1
status_class = event["status"] // 100
if 2 <= status_class <= 5:
bucket.statuses[status_class - 2] += 1
if len(bucket.request_times) < 256:
bucket.request_times.append(event["request_time"])
if event["upstream_time"] is not None and len(bucket.upstream_times) < 256:
bucket.upstream_times.append(event["upstream_time"])
def subscribe(self) -> asyncio.Queue[str]:
queue: asyncio.Queue[str] = asyncio.Queue(maxsize=2)
with self.lock:
self.subscribers.add(queue)
return queue
def unsubscribe(self, queue: asyncio.Queue[str]) -> None:
with self.lock:
self.subscribers.discard(queue)
def snapshot(self, window: int) -> dict[str, Any]:
now = int(time.time())
start = now - window + 1
with self.lock:
points = [self._point(self.global_series.buckets.get(second), second) for second in range(start, now + 1)]
hosts = sorted(self.hosts, key=lambda host: self.last_seen.get(host, 0), reverse=True)
active = [host for host in hosts if self.last_seen.get(host, 0) >= now - 59]
host_points = {
host: [self._point(self.hosts[host].buckets.get(second), second) for second in range(start, now + 1)]
for host in hosts
}
current = self._summary(points[-60:])
current["total_incoming"] = self.total_incoming
current["total_outgoing"] = self.total_outgoing
current["active_hosts"] = len(active)
current["busiest_host"] = max(active, key=lambda host: sum(p["incoming"] + p["outgoing"] for p in host_points[host][-60:]), default=None)
return {"type": "telemetry", "now": now, "points": points, "hosts": hosts, "host_points": host_points, "summary": current}
@staticmethod
def _point(bucket: Bucket | None, second: int) -> dict[str, Any]:
if not bucket:
return {"time": second, "incoming": 0, "outgoing": 0, "requests": 0, "status": [0, 0, 0, 0], "latency": None, "p95": None, "upstream": None}
return {"time": second, "incoming": bucket.incoming, "outgoing": bucket.outgoing, "requests": bucket.requests, "status": bucket.statuses, "latency": statistics.fmean(bucket.request_times) if bucket.request_times else None, "p95": percentile(bucket.request_times, .95), "upstream": statistics.fmean(bucket.upstream_times) if bucket.upstream_times else None}
@staticmethod
def _summary(points: list[dict[str, Any]]) -> dict[str, Any]:
seconds = max(1, len(points))
total_requests = sum(point["requests"] for point in points)
statuses = [sum(point["status"][index] for point in points) for index in range(4)]
latencies = [point["latency"] for point in points if point["latency"] is not None]
upstream = [point["upstream"] for point in points if point["upstream"] is not None]
return {"incoming": sum(point["incoming"] for point in points) / seconds, "outgoing": sum(point["outgoing"] for point in points) / seconds, "requests": total_requests / seconds, "status": statuses, "latency": statistics.fmean(latencies) if latencies else None, "p95": percentile(latencies, .95), "upstream": statistics.fmean(upstream) if upstream else None}
async def follow_log(path: str, telemetry: Telemetry, stop: asyncio.Event) -> None:
handle = None
inode = None
pending = ""
while not stop.is_set():
try:
stat = await asyncio.to_thread(os.stat, path)
if handle is None:
handle = await asyncio.to_thread(open, path, "r", encoding="utf-8", errors="replace")
await asyncio.to_thread(handle.seek, 0, os.SEEK_END)
inode = (stat.st_dev, stat.st_ino)
elif inode != (stat.st_dev, stat.st_ino):
# Drain what is currently available from the renamed file before switching.
for line in handle:
event = parse_line(line)
if event:
telemetry.ingest(event)
handle.close()
handle = await asyncio.to_thread(open, path, "r", encoding="utf-8", errors="replace")
inode = (stat.st_dev, stat.st_ino)
# Never join a partial line from the old inode to a new file.
pending = ""
data = await asyncio.to_thread(handle.read)
if data:
pending += data
lines = pending.split("\n")
pending = lines.pop()
for line in lines:
event = parse_line(line)
if event:
telemetry.ingest(event)
await asyncio.sleep(.15)
except FileNotFoundError:
if handle:
data = handle.read()
if data:
pending += data
await asyncio.sleep(.5)
except (OSError, ValueError):
if handle:
handle.close()
handle, inode = None, None
await asyncio.sleep(.5)
if handle:
handle.close()
def create_app(log_path: str = DEFAULT_LOG, retention: int = 3600) -> FastAPI:
telemetry = Telemetry(retention)
stop = asyncio.Event()
app = FastAPI(title="Nginx Live Traffic Monitor")
app.mount("/static", StaticFiles(directory=Path(__file__).parent / "static"), name="static")
@app.on_event("startup")
async def startup() -> None:
app.state.task = asyncio.create_task(follow_log(log_path, telemetry, stop))
app.state.publisher = asyncio.create_task(publish())
@app.on_event("shutdown")
async def shutdown() -> None:
stop.set()
for task in (getattr(app.state, "task", None), getattr(app.state, "publisher", None)):
if task:
task.cancel()
async def publish() -> None:
while not stop.is_set():
payload = json.dumps(telemetry.snapshot(3600), separators=(",", ":"))
with telemetry.lock:
subscribers = list(telemetry.subscribers)
for queue in subscribers:
try:
queue.put_nowait(payload)
except asyncio.QueueFull:
try:
queue.get_nowait()
except asyncio.QueueEmpty:
pass
queue.put_nowait(payload)
await asyncio.sleep(1)
@app.get("/")
async def index() -> FileResponse:
return FileResponse(Path(__file__).parent / "static" / "index.html")
@app.get("/api/telemetry")
async def telemetry_api(window: int = 300) -> dict[str, Any]:
return telemetry.snapshot(max(60, min(window, 3600)))
@app.get("/api/events")
async def events(request: Request, window: int = 300) -> StreamingResponse:
queue = telemetry.subscribe()
initial = json.dumps(telemetry.snapshot(max(60, min(window, 3600))), separators=(",", ":"))
async def stream() -> AsyncIterator[str]:
try:
yield f"data: {initial}\n\n"
while True:
if await request.is_disconnected():
break
try:
payload = await asyncio.wait_for(queue.get(), timeout=15)
yield f"data: {payload}\n\n"
except asyncio.TimeoutError:
yield ": keep-alive\n\n"
finally:
telemetry.unsubscribe(queue)
return StreamingResponse(stream(), media_type="text/event-stream", headers={"Cache-Control": "no-cache", "X-Accel-Buffering": "no"})
app.state.telemetry = telemetry
return app
def main() -> None:
parser = argparse.ArgumentParser(description="Live Nginx traffic dashboard")
parser.add_argument("--log-path", default=os.getenv("TRAFFIC_LOG_PATH", DEFAULT_LOG))
parser.add_argument("--host", default=os.getenv("LISTEN_ADDRESS", "127.0.0.1"))
parser.add_argument("--port", type=int, default=int(os.getenv("LISTEN_PORT", "8080")))
parser.add_argument("--retention", type=int, default=int(os.getenv("TELEMETRY_RETENTION", "3600")))
args = parser.parse_args()
import uvicorn
uvicorn.run(create_app(args.log_path, args.retention), host=args.host, port=args.port)
if __name__ == "__main__":
main()