initial POC

system_monitor.py

@@ -0,0 +1,146 @@
+#!/usr/bin/env python3
+"""Collect Linux host metrics and store them in an RRD database."""
+
+from __future__ import annotations
+
+import argparse
+import configparser
+import os
+from pathlib import Path
+import subprocess
+import time
+
+
+DEFAULT_CONFIG = "/etc/cheap-system-monitor.conf"
+DS_NAMES = (
+    "load1", "load5", "load15", "cpu_user", "cpu_system", "cpu_nice",
+    "net_in", "net_out", "disk_root", "disk_1", "disk_2", "memory",
+)
+
+
+def read_config(filename: str) -> configparser.SectionProxy:
+    parser = configparser.ConfigParser()
+    parser.read_dict({"monitor": {
+        "rrd_file": "/var/lib/cheap-system-monitor/system.rrd",
+        "mountpoints": "/",
+        "interfaces": "auto",
+        "cpu_sample_seconds": "1.0",
+    }})
+    if not parser.read(filename):
+        raise SystemExit(f"Configuration file not found: {filename}")
+    return parser["monitor"]
+
+
+def run_rrdtool(*arguments: str) -> None:
+    try:
+        subprocess.run(["rrdtool", *arguments], check=True)
+    except FileNotFoundError:
+        raise SystemExit("rrdtool is not installed (try: sudo apt install rrdtool)")
+    except subprocess.CalledProcessError as error:
+        raise SystemExit(f"rrdtool failed with exit status {error.returncode}")
+
+
+def create_rrd(path: Path) -> None:
+    path.parent.mkdir(parents=True, exist_ok=True)
+    ds = [
+        "DS:load1:GAUGE:180:0:U", "DS:load5:GAUGE:180:0:U",
+        "DS:load15:GAUGE:180:0:U", "DS:cpu_user:GAUGE:180:0:100",
+        "DS:cpu_system:GAUGE:180:0:100", "DS:cpu_nice:GAUGE:180:0:100",
+        "DS:net_in:DERIVE:180:0:U", "DS:net_out:DERIVE:180:0:U",
+        "DS:disk_root:GAUGE:180:0:100", "DS:disk_1:GAUGE:180:0:100",
+        "DS:disk_2:GAUGE:180:0:100", "DS:memory:GAUGE:180:0:100",
+    ]
+    # 1-minute data for a day, 5-minute data for two weeks, hourly for a year.
+    archives = [
+        "RRA:AVERAGE:0.5:1:1440", "RRA:MAX:0.5:1:1440",
+        "RRA:AVERAGE:0.5:5:4032", "RRA:MAX:0.5:5:4032",
+        "RRA:AVERAGE:0.5:60:8784", "RRA:MAX:0.5:60:8784",
+    ]
+    run_rrdtool("create", str(path), "--step", "60", *ds, *archives)
+
+
+def read_cpu() -> tuple[int, int, int, int]:
+    fields = Path("/proc/stat").read_text().splitlines()[0].split()
+    if fields[0] != "cpu" or len(fields) < 8:
+        raise RuntimeError("unexpected /proc/stat format")
+    values = [int(value) for value in fields[1:]]
+    user, nice, system, idle = values[:4]
+    idle += values[4] if len(values) > 4 else 0  # include iowait
+    # Linux reports guest time as already included in user/nice, so only the
+    # first eight fields belong in the total (through steal time).
+    return user, system, nice, sum(values[:8])
+
+
+def cpu_percentages(sample_seconds: float) -> tuple[float, float, float]:
+    before = read_cpu()
+    time.sleep(sample_seconds)
+    after = read_cpu()
+    total = after[3] - before[3]
+    if total <= 0:
+        return 0.0, 0.0, 0.0
+    return tuple(100.0 * (after[i] - before[i]) / total for i in range(3))
+
+
+def memory_percent() -> float:
+    entries = {}
+    for line in Path("/proc/meminfo").read_text().splitlines():
+        key, value = line.split(":", 1)
+        entries[key] = int(value.split()[0])
+    total = entries["MemTotal"]
+    available = entries.get("MemAvailable", entries.get("MemFree", 0))
+    return 100.0 * (total - available) / total
+
+
+def disk_percent(mountpoint: str) -> float:
+    stats = os.statvfs(mountpoint)
+    used = stats.f_blocks - stats.f_bfree
+    available = stats.f_bavail
+    return 100.0 * used / (used + available) if used + available else 0.0
+
+
+def network_counters(interface_setting: str) -> tuple[int, int]:
+    wanted = {item.strip() for item in interface_setting.split(",") if item.strip()}
+    automatic = not wanted or wanted == {"auto"}
+    received = transmitted = 0
+    for line in Path("/proc/net/dev").read_text().splitlines()[2:]:
+        interface, data = line.split(":", 1)
+        interface = interface.strip()
+        if (automatic and interface == "lo") or (not automatic and interface not in wanted):
+            continue
+        fields = data.split()
+        received += int(fields[0])
+        transmitted += int(fields[8])
+    return received, transmitted
+
+
+def collect(config: configparser.SectionProxy) -> list[float | int | str]:
+    load = os.getloadavg()
+    cpu = cpu_percentages(config.getfloat("cpu_sample_seconds"))
+    net = network_counters(config["interfaces"])
+    mounts = [item.strip() for item in config["mountpoints"].split(",") if item.strip()]
+    if not mounts or mounts[0] != "/":
+        mounts.insert(0, "/")
+    if len(mounts) > 3:
+        raise SystemExit("At most three mountpoints are supported (including /)")
+    disks: list[float | str] = [disk_percent(item) for item in mounts]
+    disks.extend(["U"] * (3 - len(disks)))
+    return [*load, *cpu, *net, *disks, memory_percent()]
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--config", default=DEFAULT_CONFIG)
+    parser.add_argument("--create-only", action="store_true")
+    args = parser.parse_args()
+    config = read_config(args.config)
+    rrd_file = Path(config["rrd_file"])
+    if not rrd_file.exists():
+        create_rrd(rrd_file)
+    if not args.create_only:
+        values = collect(config)
+        update = "N:" + ":".join(str(round(v, 3)) if isinstance(v, float) else str(v) for v in values)
+        run_rrdtool("update", str(rrd_file), "--template", ":".join(DS_NAMES), update)
+
+
+if __name__ == "__main__":
+    main()