Source code for

See the :class:`Logger` class.

import os
import pathlib
from abc import ABC, abstractmethod
from datetime import datetime
import gzip
from typing import Any, Optional, Callable, Type, Tuple, cast, Dict

from types import TracebackType

from typing_extensions import Literal
from pkg_resources import iter_entry_points

from ..message import Message
from ..listener import Listener
from .generic import BaseIOHandler, FileIOMessageWriter, MessageWriter
from .asc import ASCWriter
from .blf import BLFWriter
from .canutils import CanutilsLogWriter
from .csv import CSVWriter
from .sqlite import SqliteWriter
from .printer import Printer
from ..typechecking import StringPathLike, FileLike, AcceptedIOType

[docs]class Logger(MessageWriter): # pylint: disable=abstract-method """ Logs CAN messages to a file. The format is determined from the file suffix which can be one of: * .asc: :class:`can.ASCWriter` * .blf :class:`can.BLFWriter` * .csv: :class:`can.CSVWriter` * .db: :class:`can.SqliteWriter` * .log :class:`can.CanutilsLogWriter` * .txt :class:`can.Printer` Any of these formats can be used with gzip compression by appending the suffix .gz (e.g. filename.asc.gz). However, third-party tools might not be able to read these files. The **filename** may also be *None*, to fall back to :class:`can.Printer`. The log files may be incomplete until `stop()` is called due to buffering. .. note:: This class itself is just a dispatcher, and any positional and keyword arguments are passed on to the returned instance. """ fetched_plugins = False message_writers: Dict[str, Type[MessageWriter]] = { ".asc": ASCWriter, ".blf": BLFWriter, ".csv": CSVWriter, ".db": SqliteWriter, ".log": CanutilsLogWriter, ".txt": Printer, } @staticmethod def __new__( # type: ignore cls: Any, filename: Optional[StringPathLike], *args: Any, **kwargs: Any ) -> MessageWriter: """ :param filename: the filename/path of the file to write to, may be a path-like object or None to instantiate a :class:`~can.Printer` :raises ValueError: if the filename's suffix is of an unknown file type """ if filename is None: return Printer(*args, **kwargs) if not Logger.fetched_plugins: Logger.message_writers.update( { writer.load() for writer in iter_entry_points("") } ) Logger.fetched_plugins = True suffix = pathlib.PurePath(filename).suffix.lower() file_or_filename: AcceptedIOType = filename if suffix == ".gz": suffix, file_or_filename = Logger.compress(filename) try: return Logger.message_writers[suffix](file_or_filename, *args, **kwargs) except KeyError: raise ValueError( f'No write support for this unknown log format "{suffix}"' ) from None
[docs] @staticmethod def compress(filename: StringPathLike) -> Tuple[str, FileLike]: """ Return the suffix and io object of the decompressed file. File will automatically recompress upon close. """ real_suffix = pathlib.Path(filename).suffixes[-2].lower() mode = "ab" if real_suffix == ".blf" else "at" return real_suffix,, mode)
[docs] def on_message_received(self, msg: Message) -> None: pass
[docs]class BaseRotatingLogger(Listener, BaseIOHandler, ABC): """ Base class for rotating CAN loggers. This class is not meant to be instantiated directly. Subclasses must implement the :attr:`should_rollover` and `do_rollover` methods according to their rotation strategy. The rotation behavior can be further customized by the user by setting the :attr:`namer` and :attr:`rotator` attributes after instantiating the subclass. These attributes as well as the methods `rotation_filename` and `rotate` and the corresponding docstrings are carried over from the python builtin `BaseRotatingHandler`. Subclasses must set the `_writer` attribute upon initialization. :attr namer: If this attribute is set to a callable, the :meth:`rotation_filename` method delegates to this callable. The parameters passed to the callable are those passed to :meth:`rotation_filename`. :attr rotator: If this attribute is set to a callable, the :meth:`rotate` method delegates to this callable. The parameters passed to the callable are those passed to :meth:`rotate`. :attr rollover_count: An integer counter to track the number of rollovers. """ namer: Optional[Callable[[StringPathLike], StringPathLike]] = None rotator: Optional[Callable[[StringPathLike, StringPathLike], None]] = None rollover_count: int = 0 def __init__(self, *args: Any, **kwargs: Any) -> None: Listener.__init__(self) BaseIOHandler.__init__(self, None) self.writer_args = args self.writer_kwargs = kwargs # Expected to be set by the subclass self._writer: FileIOMessageWriter = None # type: ignore @property def writer(self) -> FileIOMessageWriter: """This attribute holds an instance of a writer class which manages the actual file IO.""" return self._writer
[docs] def rotation_filename(self, default_name: StringPathLike) -> StringPathLike: """Modify the filename of a log file when rotating. This is provided so that a custom filename can be provided. The default implementation calls the :attr:`namer` attribute of the handler, if it's callable, passing the default name to it. If the attribute isn't callable (the default is `None`), the name is returned unchanged. :param default_name: The default name for the log file. """ if not callable(self.namer): return default_name return self.namer(default_name)
[docs] def rotate(self, source: StringPathLike, dest: StringPathLike) -> None: """When rotating, rotate the current log. The default implementation calls the :attr:`rotator` attribute of the handler, if it's callable, passing the source and dest arguments to it. If the attribute isn't callable (the default is `None`), the source is simply renamed to the destination. :param source: The source filename. This is normally the base filename, e.g. `"test.log"` :param dest: The destination filename. This is normally what the source is rotated to, e.g. `"test_#001.log"`. """ if not callable(self.rotator): if os.path.exists(source): os.rename(source, dest) else: self.rotator(source, dest)
[docs] def on_message_received(self, msg: Message) -> None: """This method is called to handle the given message. :param msg: the delivered message """ if self.should_rollover(msg): self.do_rollover() self.rollover_count += 1 self.writer.on_message_received(msg)
def _get_new_writer(self, filename: StringPathLike) -> FileIOMessageWriter: """Instantiate a new writer after stopping the old one. :param filename: Path-like object that specifies the location and name of the log file. The log file format is defined by the suffix of `filename`. :return: An instance of a writer class. """ # Close the old writer first if self._writer is not None: self._writer.stop() logger = Logger(filename, *self.writer_args, **self.writer_kwargs) if isinstance(logger, FileIOMessageWriter): return logger elif isinstance(logger, Printer) and logger.file is not None: return cast(FileIOMessageWriter, logger) else: raise Exception( "The Logger corresponding to the arguments is not a FileIOMessageWriter or " "can.Printer" )
[docs] def stop(self) -> None: """Stop handling new messages. Carry out any final tasks to ensure data is persisted and cleanup any open resources. """ self.writer.stop()
def __enter__(self) -> "BaseRotatingLogger": return self def __exit__( self, exc_type: Optional[Type[BaseException]], exc_val: Optional[BaseException], exc_tb: Optional[TracebackType], ) -> Literal[False]: return self._writer.__exit__(exc_type, exc_val, exc_tb)
[docs] @abstractmethod def should_rollover(self, msg: Message) -> bool: """Determine if the rollover conditions are met."""
[docs] @abstractmethod def do_rollover(self) -> None: """Perform rollover."""
[docs]class SizedRotatingLogger(BaseRotatingLogger): """Log CAN messages to a sequence of files with a given maximum size. The logger creates a log file with the given `base_filename`. When the size threshold is reached the current log file is closed and renamed by adding a timestamp and the rollover count. A new log file is then created and written to. This behavior can be customized by setting the :attr:`namer` and :attr:`rotator` attribute. Example:: from can import Notifier, SizedRotatingLogger from can.interfaces.vector import VectorBus bus = VectorBus(channel=[0], app_name="CANape", fd=True) logger = SizedRotatingLogger( base_filename="my_logfile.asc", max_bytes=5 * 1024 ** 2, # =5MB ) logger.rollover_count = 23 # start counter at 23 notifier = Notifier(bus=bus, listeners=[logger]) The SizedRotatingLogger currently supports the formats * .asc: :class:`can.ASCWriter` * .blf :class:`can.BLFWriter` * .csv: :class:`can.CSVWriter` * .log :class:`can.CanutilsLogWriter` * .txt :class:`can.Printer` (if pointing to a file) .. note:: The :class:`can.SqliteWriter` is not supported yet. The log files on disk may be incomplete due to buffering until :meth:`~can.Listener.stop` is called. """ def __init__( self, base_filename: StringPathLike, *args: Any, max_bytes: int = 0, **kwargs: Any, ) -> None: """ :param base_filename: A path-like object for the base filename. The log file format is defined by the suffix of `base_filename`. :param max_bytes: The size threshold at which a new log file shall be created. If set to 0, no rollover will be performed. """ super().__init__(*args, **kwargs) self.base_filename = os.path.abspath(base_filename) self.max_bytes = max_bytes self._writer = self._get_new_writer(self.base_filename)
[docs] def should_rollover(self, msg: Message) -> bool: if self.max_bytes <= 0: return False if self.writer.file.tell() >= self.max_bytes: return True return False
[docs] def do_rollover(self) -> None: if self.writer: self.writer.stop() sfn = self.base_filename dfn = self.rotation_filename(self._default_name()) self.rotate(sfn, dfn) self._writer = self._get_new_writer(self.base_filename)
def _default_name(self) -> StringPathLike: """Generate the default rotation filename.""" path = pathlib.Path(self.base_filename) new_name = ( path.stem + "_" +"%Y-%m-%dT%H%M%S") + "_" + f"#{self.rollover_count:03}" + path.suffix ) return str(path.parent / new_name)