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143 lines
4.7 KiB
Python
143 lines
4.7 KiB
Python
#!/usr/bin/env python3
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"""
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Shared RFC 5424 syslog helper for DECNET service templates.
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Provides two functions consumed by every service's server.py:
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- syslog_line(service, hostname, event_type, severity, **fields) -> str
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- write_syslog_file(line: str) -> None
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- forward_syslog(line: str, log_target: str) -> None
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RFC 5424 structure:
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<PRI>1 TIMESTAMP HOSTNAME APP-NAME PROCID MSGID [SD-ELEMENT] MSG
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Facility: local0 (16), PEN for SD element ID: decnet@55555
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"""
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import logging
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import logging.handlers
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import os
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import socket
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from datetime import datetime, timezone
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from pathlib import Path
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from typing import Any
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# ─── Constants ────────────────────────────────────────────────────────────────
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_FACILITY_LOCAL0 = 16
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_SD_ID = "decnet@55555"
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_NILVALUE = "-"
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SEVERITY_EMERG = 0
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SEVERITY_ALERT = 1
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SEVERITY_CRIT = 2
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SEVERITY_ERROR = 3
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SEVERITY_WARNING = 4
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SEVERITY_NOTICE = 5
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SEVERITY_INFO = 6
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SEVERITY_DEBUG = 7
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_MAX_HOSTNAME = 255
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_MAX_APPNAME = 48
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_MAX_MSGID = 32
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_LOG_FILE_ENV = "DECNET_LOG_FILE"
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_DEFAULT_LOG_FILE = "/var/log/decnet/decnet.log"
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_MAX_BYTES = 10 * 1024 * 1024 # 10 MB
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_BACKUP_COUNT = 5
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# ─── Formatter ────────────────────────────────────────────────────────────────
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def _sd_escape(value: str) -> str:
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"""Escape SD-PARAM-VALUE per RFC 5424 §6.3.3."""
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return value.replace("\\", "\\\\").replace('"', '\\"').replace("]", "\\]")
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def _sd_element(fields: dict[str, Any]) -> str:
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if not fields:
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return _NILVALUE
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params = " ".join(f'{k}="{_sd_escape(str(v))}"' for k, v in fields.items())
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return f"[{_SD_ID} {params}]"
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def syslog_line(
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service: str,
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hostname: str,
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event_type: str,
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severity: int = SEVERITY_INFO,
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timestamp: datetime | None = None,
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msg: str | None = None,
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**fields: Any,
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) -> str:
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"""
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Return a single RFC 5424-compliant syslog line (no trailing newline).
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Args:
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service: APP-NAME (e.g. "http", "mysql")
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hostname: HOSTNAME (decky node name)
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event_type: MSGID (e.g. "request", "login_attempt")
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severity: Syslog severity integer (default: INFO=6)
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timestamp: UTC datetime; defaults to now
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msg: Optional free-text MSG
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**fields: Encoded as structured data params
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"""
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pri = f"<{_FACILITY_LOCAL0 * 8 + severity}>"
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ts = (timestamp or datetime.now(timezone.utc)).isoformat()
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host = (hostname or _NILVALUE)[:_MAX_HOSTNAME]
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appname = (service or _NILVALUE)[:_MAX_APPNAME]
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msgid = (event_type or _NILVALUE)[:_MAX_MSGID]
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sd = _sd_element(fields)
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message = f" {msg}" if msg else ""
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return f"{pri}1 {ts} {host} {appname} {_NILVALUE} {msgid} {sd}{message}"
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# ─── File handler ─────────────────────────────────────────────────────────────
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_file_logger: logging.Logger | None = None
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def _get_file_logger() -> logging.Logger:
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global _file_logger
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if _file_logger is not None:
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return _file_logger
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log_path = Path(os.environ.get(_LOG_FILE_ENV, _DEFAULT_LOG_FILE))
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try:
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log_path.parent.mkdir(parents=True, exist_ok=True)
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handler = logging.handlers.RotatingFileHandler(
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log_path,
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maxBytes=_MAX_BYTES,
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backupCount=_BACKUP_COUNT,
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encoding="utf-8",
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)
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except OSError:
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handler = logging.StreamHandler()
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handler.setFormatter(logging.Formatter("%(message)s"))
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_file_logger = logging.getLogger("decnet.syslog")
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_file_logger.setLevel(logging.DEBUG)
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_file_logger.propagate = False
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_file_logger.addHandler(handler)
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return _file_logger
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def write_syslog_file(line: str) -> None:
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"""Append a syslog line to the rotating log file."""
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try:
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_get_file_logger().info(line)
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except Exception:
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pass
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# ─── TCP forwarding ───────────────────────────────────────────────────────────
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def forward_syslog(line: str, log_target: str) -> None:
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"""Forward a syslog line over TCP to log_target (ip:port)."""
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if not log_target:
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return
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try:
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host, port = log_target.rsplit(":", 1)
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with socket.create_connection((host, int(port)), timeout=3) as s:
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s.sendall((line + "\n").encode())
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except Exception:
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pass
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