88 lines
3.2 KiB
Python
88 lines
3.2 KiB
Python
"""
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Helper class to read output of a subprocess.
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Used to avoid deadlocks from the pipe buffer filling up and blocking the subprocess while it's
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being waited on.
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"""
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import threading
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class LoggerPipe(threading.Thread): # pylint: disable=too-many-instance-attributes
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"""Asynchronously reads the output of a subprocess and sends it to a logger."""
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# The start() and join() methods are not intended to be called directly on the LoggerPipe
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# instance. Since we override them for that effect, the super's version are preserved here.
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__start = threading.Thread.start
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__join = threading.Thread.join
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def __init__(self, logger, level, pipe_out):
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"""Initialize the LoggerPipe with the specified arguments."""
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threading.Thread.__init__(self)
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# Main thread should not call join() when exiting
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self.daemon = True
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self.__logger = logger
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self.__level = level
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self.__pipe_out = pipe_out
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self.__lock = threading.Lock()
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self.__condition = threading.Condition(self.__lock)
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self.__started = False
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self.__finished = False
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LoggerPipe.__start(self)
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def start(self):
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"""Start not implemented."""
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raise NotImplementedError("start should not be called directly")
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def run(self):
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"""Read the output from 'pipe_out' and logs each line to 'logger'."""
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with self.__lock:
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self.__started = True
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self.__condition.notify_all()
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# Close the pipe when finished reading all of the output.
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with self.__pipe_out:
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# Avoid buffering the output from the pipe.
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for line in iter(self.__pipe_out.readline, b""):
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# Replace null bytes in the output of the subprocess with a literal backslash ('\')
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# followed by a literal zero ('0') so tools like grep don't treat resmoke.py's
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# output as binary data.
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line = line.replace(b"\0", b"\\0")
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# Convert the output of the process from a bytestring to a UTF-8 string, and replace
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# any characters that cannot be decoded with the official Unicode replacement
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# character, U+FFFD. The log messages of MongoDB processes are not always valid
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# UTF-8 sequences. See SERVER-7506.
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line = line.decode("utf-8", "replace")
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self.__logger.log(self.__level, line.rstrip())
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with self.__lock:
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self.__finished = True
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self.__condition.notify_all()
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def join(self, timeout=None):
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"""Join not implemented."""
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raise NotImplementedError("join should not be called directly")
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def wait_until_started(self):
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"""Wait until started."""
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with self.__lock:
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while not self.__started:
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self.__condition.wait()
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def wait_until_finished(self):
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"""Wait until finished."""
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with self.__lock:
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while not self.__finished:
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self.__condition.wait()
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# No need to pass a timeout to join() because the thread should already be done after
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# notifying us it has finished reading output from the pipe.
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LoggerPipe.__join(self) # Tidy up the started thread.
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