docker/clonedb/core/pipe_handler.py

"""
An handler for the stdout and the stderr output

@author: olivier.massot, 05-2020
"""
import logging
import os
import threading


class PipeHandler(threading.Thread):
    """ Handle the stdout/stderr output from a Popen object """

    def __init__(self, logger_name, default_level=logging.INFO):
        """ Setup the object with a logger and a loglevel
        and start the thread
        """
        threading.Thread.__init__(self)
        self.daemon = False
        self.fdRead, self.fdWrite = os.pipe()
        self.pipeReader = os.fdopen(self.fdRead, encoding='utf-8')
        self.start()

        self.logger = logging.getLogger(logger_name)
        self.default_level = default_level

    def fileno(self):
        """ Return the write file descriptor of the pipe
        """
        return self.fdWrite

    def process(self, line):
        """ Process the last line that was read
        """
        self.logger.log(self.default_level, line)

    def run(self):
        """ Run the thread, logging everything.
        """
        try:
            for line in iter(self.pipeReader.readline, ''):
                self.process(line.strip('\n'))
        except UnicodeDecodeError:
            self.process(' -- Error while decoding the incoming, unable to log --')
        finally:
            self.pipeReader.close()

    def close(self):
        """ Close the write end of the pipe.
        """
        os.close(self.fdWrite)