Crate flexi_logger

A flexible and easy-to-use logger that writes logs to stderr and/or to files or other output streams.

To read the log specification from an environment variable and get the log written to stderr, start flexi_logger e.g. like this:

flexi_logger::Logger::try_with_env().unwrap().start().unwrap();

See

• The builder Logger for a full description of all configuration options,
• module code_examples for various concrete examples of flexi_logger initialization
• the module writers for the usage of additional log writers,
• and the README for how to get started.

There are configuration options to e.g.

• decide whether you want to write your logs to stderr or to a file,
• configure the path and the filenames of the log files,
• use file rotation,
• specify the line format for the log lines,
• apply a stateful filter before log lines are really written,
• define additional log output streams, e.g for alert or security messages,
• support changing the log specification while the program is running,

flexi_logger uses a similar syntax as env_logger for specifying which logs should really be written (but is more graceful with the syntax, and can provide error information).

By default, i.e. if feature colors is not switched off, the log lines that appear on your terminal are coloured. In case the chosen colors don’t fit to your terminal’s color theme, you can adapt the colors to improve readability. See the documentation of method Logger::set_palette for a description how this can be done.

Modules

• code_examples
  Examples for the flexi_logger initialization.
• error_info
  Error codes of flexi_logger.
• filter
  This module contains two traits which allow adding a stateful filter using Logger::filter.
• trctrc
  Use flexi_logger functionality with tracing.
• writers
  Describes how to extend flexi_logger with additional log writers.

Structs

• DeferredNow
  Deferred timestamp creation.
• FileSpec
  Builder object for specifying the name and path of the log output file.
• LogSpecBuilder
  Builder for LogSpecification.
• LogSpecification
  Immutable struct that defines which loglines are to be written, based on the module, the log level, and the text.
• LogfileSelector
  Used in LoggerHandle::existing_log_files.
• Logger
  The entry-point for using flexi_logger.
• LoggerHandle
  Allows reconfiguring the logger while the program is running, and shuts down the logger when it is dropped.
• ModuleFilter
  Defines which loglevel filter to use for the specified module.
• Record
  Re-exports from log crate The “payload” of a log message.

Enums

• AdaptiveFormat
  Helps to use coloring only if the output goes to a tty.
• Age
  The age after which a log file rotation will be triggered, when Criterion::Age is chosen.
• Cleanup
  Defines the strategy for handling older log files.
• Criterion
  Criterion when to rotate the log file.
• Duplicate
  Used to control which messages are to be duplicated to stderr, when log_to_file() is used.
• ErrorChannel
  Enum for defining the output channel for flexi_logger’s own error messages.
• FlexiLoggerError
  Describes errors in the initialization of flexi_logger.
• Level
  Re-exports from log crate An enum representing the available verbosity levels of the logger.
• LevelFilter
  Re-exports from log crate An enum representing the available verbosity level filters of the logger.
• Naming
  The naming convention for rotated log files.
• WriteMode
  Describes whether the log output should be written synchronously or asynchronously, and if and how I/O should be buffered and flushed.

Constants

• DEFAULT_BUFFER_CAPACITY
  Default buffer capacity (8k), when buffering is used.
• DEFAULT_FLUSH_INTERVAL
  Default flush interval (1s), when flushing is used.
• DEFAULT_MESSAGE_CAPA
  Default capacity for the message buffers; a higher value reduces allocations when longer log lines are used.
• DEFAULT_POOL_CAPA
  Default size of the message pool; a higher value could further reduce allocations during log file rotation and cleanup.
• TS_DASHES_BLANK_COLONS_DOT_BLANK
  Time stamp format that is used by the provided format functions.

Functions

• colored_default_formatcolors
  A colored version of the logline-formatter default_format.
• colored_detailed_formatcolors
  A colored version of the logline-formatter detailed_format.
• colored_opt_formatcolors
  A colored version of the logline-formatter opt_format.
• colored_with_threadcolors
  A colored version of the logline-formatter with_thread.
• default_format
  A logline-formatter that produces log lines like
  INFO [my_prog::some_submodule] Task successfully read from conf.json.
• detailed_format
  A logline-formatter that produces log lines like
  [2016-01-13 15:25:01.640870 +01:00] INFO [foo::bar] src/foo/bar.rs:26: Task successfully read from conf.json
• init
  Shortest form to get started.
• json_formatjson
  A logline-formatter that produces log lines in json format.
• opt_format
  A logline-formatter that produces log lines with timestamp and file location, like
  [2016-01-13 15:25:01.640870 +01:00] INFO [src/foo/bar:26] Task successfully read from conf.json
  
• stylecolors
  Helper function that is used in the provided coloring format functions to apply colors based on the log level and the effective color palette.
• with_thread
  A logline-formatter that produces log lines like
  [2016-01-13 15:25:01.640870 +01:00] T[taskreader] INFO [src/foo/bar:26] Task successfully read from conf.json

Type Aliases

• FormatFunction
  Function type for format functions.