Skip to content

python-logging.md

Latest commit

 

History

History
121 lines (80 loc) · 3.31 KB

python-logging.md

File metadata and controls

121 lines (80 loc) · 3.31 KB

Logging

BasicConfig list of options

logging attributes

setLoggerClass can be used to swap in a new logging class for use in all modules.

Loggers are in a hierarchy, defined by dot separated names.

  • foo is the parent of foo.bar
  • foo.bar is the parent of foo.bar.baz

Using __name__ names loggers in the same hierarchy as the module. This is a good default.

Each logger is created with level NOTSET, except for the root logger which is WARN. Loggers who's level is not set delegated to the first parent up the chain that has a level set.

the default python logging format is:

%(levelname)s:%(name)s:%(message)s

File Configuration

See logging.config

There are may gotch-ya

  • root must be in the logger list
  • root_logger must have a handlers key

Further, the resulting file is overly complex.

Dictionary Configuration

See logging.dictConfig and [schema](https://docs.python.org/3/library/logging.config.html#logging-config-dictschema].

Dictionaries could be loaded directly from YAML or JSON files.

version: 1
disable_existing_loggers: false

set disable_existing_loggers to true to disable all loggers not explicitly configured in the dictionary. Set to false to retain existing loggers.

formatters:
  formatConsole:
    format: '%(levelname)s:%(name)s:%(message)s'
  formatFile:
    format: '%(asctime)s:%(threadName)s:%(name)s:%(levelname)s:  %(message)s'

handlers:
  consoleHandler:
    class: logging.StreamHandler
    level: INFO
    formatter: formatConsole
    stream: ext://sys.stdout
  fileHandler:
    class : logging.FileHandler
    level: DEBUG
    formatter: formatFile
    mode: 'w'
    filename: logging/local-log.txt

mode w will overwrite the file, a will append to the file.

loggers:

  root:
    level: WARN
    handlers: [consoleHandler, fileHandler]
  mod_two: 
    level: DEBUG

Level

Level is determined by

  • Logger:
    • The current logger
    • Parent loggers (by name and the root)
  • Handlers
    • Handlers only handle their set or higher.

(Note: WARN is higher than INFO)

Logging exceptions

Capture stack trace with exc_info=True:

logger.error("Error message", exc_info=True)

Or, call logger.exception:

logger.exception("Error message")

which loggs as ERROR and includes the stack trace.

Logging to elasticsearch

For regular logging

formatters:
  # Create a formatter based on the ecs_logger std lib formatter
  ecsFmt:
    class:  ecs_logging.StdlibFormatter

handlers:
  # Create a handler that uses the elastic search formatter
  ecsHnd:
    class : logging.FileHandler
    level: DEBUG
    formatter: ecsFmt
    mode: 'w'
    filename: logging/local-log.json

Alternately, log directly to elastic search using python-elasticsearch-ecs-logger