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# -*- coding: utf-8 -*- |
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"""Defines a class to read from a queue and write to a writer plugin. |
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.. moduleauthor:: Kenny Freeman <[email protected]> |
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""" |
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__author__ = 'Kenny Freeman' |
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__email__ = '[email protected]' |
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__license__ = "ISCL" |
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__docformat__ = 'reStructuredText' |
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import Queue |
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import threading |
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import traceback |
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class PluginWriter(object): |
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"""Writer plugin helper that provides a queue for reader plugins to queue |
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metrics onto. It runs a thread that writes to a plugin objects push(). |
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:param log: A logger |
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:type log: logging.RootLogger |
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:param pobj: An instance of a writer plugin. |
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:type pobj: writer |
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:param pname: The configured name of the plugin. |
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:type pname: str |
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:param qsize: The maximum queue size to set. |
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:type qsize: int |
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""" |
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def __init__(self, log, pobj, pname, qsize): |
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""" |
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Writer plugin helper that provides a queue for reader plugins to queue |
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metrics onto. It runs a thread that writes to a plugin objects push(). |
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:param log: A logger |
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:type log: logging.RootLogger |
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:param pobj: An instance of a writer plugin. |
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:type pobj: writer |
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:param pname: The configured name of the plugin. |
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:type pname: str |
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:param qsize: The maximum queue size to set. |
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:type qsize: int |
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""" |
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self.log = log |
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self._name = pname |
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# the queue readers enqueue metrics onto |
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self.queue = Queue.Queue(maxsize=qsize) |
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self.pobj = pobj |
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# the thread that dequeues metrics to pboj.push |
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self.thread = None |
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self.stop_evt = threading.Event() |
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@property |
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def name(self): |
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"""Simply return our configured name. |
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:rtype: str |
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""" |
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return self._name |
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def flush(self): |
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"""Flushes self.queue to self.pobj.push().""" |
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while not self.queue.empty(): |
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rset = self.queue.get() |
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# pretty much any exception can get raised in a plugins push call |
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try: |
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self.pobj.push(rset) |
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except Exception as e: |
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tb = traceback.format_exc() |
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msg = "write: disabling writer {0}: exception in flush: {1}: {2}" |
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self.log.debug(msg.format(self._name, e, tb)) |
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return |
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def dequeue(self): |
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"""Dequeues from self.queue to self.pobj.push().""" |
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# onstart needs to be called first |
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try: |
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self.pobj.onstart() |
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except Exception as e: |
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tb = traceback.format_exc() |
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msg = "write: disabling writer {0}: exception in dequeue: {1}: {2}" |
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self.log.error(msg.format(self._name, e, tb)) |
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self.queue = Queue.Queue(maxsize=1) |
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return |
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# can be stopped in between polls by setting self.run=>False |
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while not self.stop_evt.is_set(): |
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rset = self.queue.get(block=True) |
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# we push None values onto the queue when exiting |
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if rset is None: |
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msg = "write: dequeue for writer {0}: ignoring null value" |
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self.log.debug(msg.format(self._name)) |
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continue |
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try: |
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self.pobj.push(rset) |
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except Exception as e: |
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tb = traceback.format_exc() |
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msg = "write: disabling writer {0}: exception in push: {1}: {2}" |
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self.log.debug(msg.format(self._name, e, tb)) |
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self.stop_evt.set() |
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return |
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self.onstop() |
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def start(self): |
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"""Starts a writer thread that dequeues into pobj.push().""" |
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self.thread = threading.Thread(target=self.dequeue, group=None) |
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self.thread.start() |
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def stop(self): |
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"""Stops our thread, flush()s and calls pobj.stop().""" |
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self.stop_evt.set() |
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def onstop(self): |
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"""Calls the plugins onstop callable.""" |
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self.flush() |
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# this can raise pretty much any exception |
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try: |
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self.pobj.onstop() |
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except Exception as e: |
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tb = traceback.format_exc() |
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msg = "write: writer {0}: exception in onstop: {1}: {2}" |
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self.log.error(msg.format(self._name, e, tb)) |
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def join(self): |
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"""Joins our thread.""" |
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# this function assumes self.stop() has been called |
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# first we need to put a null entry onto the queue to wake the thread |
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# if it is waiting on a blocking call to self.queue.get() |
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if self.thread: |
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self.queue.put(None) |
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self.queue.put(None) |
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self.thread.join() |
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def __del__(self): |
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"""Mark __del__ in logs.""" |
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self.log.debug("write: del: {0}".format(self._name)) |
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s4z /
plumd
