91 lines
3.0 KiB
Python
91 lines
3.0 KiB
Python
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"""
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Structured logging primitives.
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Every log record is emitted as a single JSON object so Logstash can ingest it
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without grok patterns, and every record carries the request id of the HTTP
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request that produced it, which makes a single user action traceable end to end
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in Kibana.
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"""
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from __future__ import annotations
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import datetime as dt
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import json
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import logging
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import traceback
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from contextvars import ContextVar
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from typing import Any
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# Propagates the current request id to any code running in the same context,
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# including background threads started per request.
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_request_id: ContextVar[str] = ContextVar("request_id", default="-")
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# Attributes that ``logging`` puts on every record; anything else the caller
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# passed through ``extra=`` is treated as structured context and serialised.
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_STANDARD_ATTRS = frozenset(
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{
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"args", "asctime", "created", "exc_info", "exc_text", "filename",
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"funcName", "levelname", "levelno", "lineno", "module", "msecs",
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"message", "msg", "name", "pathname", "process", "processName",
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"relativeCreated", "stack_info", "thread", "threadName", "taskName",
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"request_id",
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}
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) # fmt: skip
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def set_request_id(value: str) -> None:
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_request_id.set(value)
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def get_request_id() -> str:
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return _request_id.get()
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class RequestIDFilter(logging.Filter):
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"""Attaches the ambient request id to every record."""
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def filter(self, record: logging.LogRecord) -> bool:
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record.request_id = getattr(record, "request_id", None) or get_request_id()
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return True
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class JSONFormatter(logging.Formatter):
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"""Renders a ``LogRecord`` as one line of JSON."""
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def __init__(self, service: str = "app", environment: str = "development") -> None:
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super().__init__()
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self.service = service
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self.environment = environment
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def format(self, record: logging.LogRecord) -> str:
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payload: dict[str, Any] = {
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"@timestamp": dt.datetime.fromtimestamp(record.created, tz=dt.UTC).isoformat(),
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"level": record.levelname,
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"logger": record.name,
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"message": record.getMessage(),
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"service": self.service,
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"environment": self.environment,
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"request_id": getattr(record, "request_id", "-"),
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}
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if record.exc_info:
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exc_type, exc_value, exc_tb = record.exc_info
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payload["error"] = {
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"type": getattr(exc_type, "__name__", str(exc_type)),
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"message": str(exc_value),
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"stack": "".join(traceback.format_exception(exc_type, exc_value, exc_tb))[:8000],
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}
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for key, value in record.__dict__.items():
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if key not in _STANDARD_ATTRS and not key.startswith("_"):
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payload[key] = _coerce(value)
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return json.dumps(payload, ensure_ascii=False, default=str)
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def _coerce(value: Any) -> Any:
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"""Keep the payload JSON serialisable without blowing up on odd types."""
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if isinstance(value, str | int | float | bool | type(None) | list | dict):
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return value
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return str(value)
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