narration 0.2.13

Narration is a logging library starting a server receiving log records from other process.

narration

Logging is easy, but setup is messy and boring in multi processes contexts, due to the various way python can spawn processes (fork, spawn, forkserver) via explicit or implicit spawning context.

Narration handles the following logging setup boiler plate:

• main process’s logger writes log record emitted by the process itself or its child processes

• child process’s logger’s handler forward log records to the main process only

Installation

Install python virtual envs needed by tox/IDE

bash make.sh --setup-python-dev-envs

pip install narration

Usage

• Create your loggers as you like (eg: logging.basicConfig(…))

• On the master process, setup the logger to act as server:

import narration
import multiprocessing
import logging

ctx = mutiprocessing.get_context()
m = ctx.Manager()

logger=logging.getLogger()
client_handler_settings = narration.setup_server_handlers(logger=logger, ctx=ctx, ctx_manager=m)
logger.debug("Main process ready")

pool = multiprocessing.pool.Pool(10, child_process_worker_function, [client_handler_settings] , 2, ctx)

• On the child process, setup the logger to act as ‘emitting’ client:

import narration
import multiprocessing
import logging

# Child process must receive the 'client_handler_settings' payload when starting the process

# Re-create a logger, replacing handlers/formatting (if any) with handler to forrward records to the master process
logger=logging.getLogger()
narration.setup_client_handlers(logger=logger, handler_name_to_client_handler_settings=client_handler_settings)
logger.debug("Child process ready")

• Child process log records will be sent to the master process’s logger’s original handlers for procesing.

Main process ready
Child process ready