PluginReader.poll() - Code Metrics - Inspection of "- Added /proc readers for: cpu, diskspace, diskusa..." - s4z/plumd - Measure and Improve Code Quality continuously with Scrutinizer

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Push — master ( ee7b96...42a2db )

by Kenny

created 2016-08-02 16:04 UTC

PluginReader.poll() A

↳ Parent: PluginReader

Complexity

Conditions

Size

Total Lines

Duplication

Lines	22
Ratio	100 %

Importance

Changes	1
Bugs	1	Features	1

Metric	Value
cc	3
c	1
b	1
f	1
dl	22
loc	22
rs	9.2

# -*- coding: utf-8 -*-
"""Defines a class to read from a queue and write to a writer plugin.

.. moduleauthor:: Kenny Freeman <[email protected]>

"""
__author__ = 'Kenny Freeman'
__email__ = '[email protected]'
__license__ = "ISCL"
__docformat__ = 'reStructuredText'

import time
import Queue
import random
import threading
import traceback

import plumd
import plumd.util


class PluginReader(object):
    """Reads from a plugin instance by calling pobj.poll() and writes
    to a list of PluginWriters by calling <writerobj>.queue.put() - loops
    on a configured interval.

    :param log: A logger
    :type log: logging.get_logger()
    :param pobj: An instance of a Reader plugin.
    :type pobj: Reader
    :param pname: The configured name of the plugin.
    :type pname: str
    :param interval: The conigured polling interval for thep plugin.
    :type interval: int
    :raises: ConfigError, PluginLoadError
    """


    def __init__(self, log, pobj, pname):
        """Reads from a plugin instance by calling pobj.poll() and writes
        to a list of PluginWriters by calling <writerobj>.queue.put() - loops
        on a configured interval.

        :param log: A logger
        :type log: structlog.get_logger()
        :param pobj: An instance of a Reader plugin.
        :type pobj: Reader
        :param pname: The configured name of the plugin.
        :type pname: str
        :raises: ConfigError, PluginLoadError
        """
        self.log = log
        # poll() interval - get from plugins configuration
        self.interval = pobj.config.get('poll.interval')
        self._name = pname
        self.pobj = pobj
        # what writers should we write metrics to?
        self.writers = []
        # thread that polls for metrics and writes to writers
        self.thread = None
        self.stop_evt = threading.Event()


    @property
    def name(self):
        """Simply return our configured name.
        :rtype: str
        """
        return self._name


    def onstart(self):
        """Call the plugins onstart function."""
        try:
            self.pobj.onstart()
        except Exception as e:
            tb = traceback.format_exc()
            msg = "read: disabling reader {0}: exception in onstart: {1}: {2}"
            self.log.error(msg.format(self._name, e, tb))
            return


    def poll(self):

        """Calls the plugins poll() function and either returns a valid
        :class:`plumd.ResultSet` or None.

        :rtype: plumd.ResultSet
        """
        rset = None
        # plugins can raise pretty much any exception, wrap in catch all try
        try:
            rset = self.pobj.poll()
            if not isinstance(rset, plumd.ResultSet):
                msg = "read: invalid result set from reader {0}: {1}"
                self.log.error(msg.format(self._name, rset))
                rset = plumd.ResultSet()
        except Exception as e:
            # print a traceback and ensure the reader thread exits
            tb = traceback.format_exc()
            msg="read: disabling reader {0} due to exception in poll: {1} : {2}"
            self.log.error(msg.format(self._name, e, tb))
            self.stop_evt.set()
            rset = plumd.ResultSet()
        return rset


    def write(self, rset):
        """Iterates through each writer plugin and writes the
        :class:`plumd.ResultSet` to the writers input queue. Uses a
        :class:`plumd.utils.Interval` to determine if it will block when
        pushing to a writers queue. If there is time remaining in the current
        poll interval it will block. Also, if a writers queue is full it will
        drop the metric for that writer. Future versions may use persistance
        to queue result sets to disk if the backend metrics services are down.

        :param rset: a result set from a plugin poll() call.
        :type rset: plumd.ResultSet
        :param lint: an interval helper.
        :type lint: plumd.util.Interval
        """
        # only send result sets that have metrics
        if rset.nresults < 1:
            return

        # enqueue onto each writers queue, wait for any remaining time
        for wobj in self.writers:
            try:
                # allow queue puts to block for a short time
                # this cannot block for long as it will also block shutdown
                wobj.queue.put(rset, block=True, timeout=1)
            except Queue.Full:
                msg = "read: {0}: dropping metrics: writer plugin queue full: {1}"
                self.log.warn(msg.format(self._name, wobj.name))


    def read(self):
        """Calls the plugins onstart() function and then iterates over the
        plugins poll() function, pushing the result to each writer queue."""
        self.onstart()

        ## distribute metrics - don't everyone flood all at once
        time.sleep(random.randrange(int(self.pobj.config.get('delay.poll'))))

        # loop on calling the plugin objects poll and sending to writers
        while not self.stop_evt.is_set():
            # loop every self.interval seconds
            with plumd.util.Interval(self.interval, self.stop_evt) as lint:
                if self.stop_evt.is_set():
                    break
                rset = self.poll()
                # readers can return None values eg. a reader that polls
                # very often and periodically returns results
                if rset:
                    self.write(rset)
                # warn if loop time exceeded
                if lint.remaining < 0:
                    msg = "read: {0} reader loop time exceeded"
                    self.log.warn(msg.format(self._name))
        self.onstop()


    def start(self):
        """Calls pobj.onstart() and starts a thread to poll() metrics."""
        self.thread = threading.Thread(target=self.read, group=None)
        self.thread.start()


    def stop(self):
        """Stops the poll() thread and calls pobj.onstop()."""
        # set the stop event and the self.read thread falls through.
        self.stop_evt.set()


    def onstop(self):
        """Calls the plugins onstop callable."""
        # this can raise pretty much any exception
        try:
            self.pobj.onstop()
        except Exception as e:
            tb = traceback.format_exc()
            msg = "read: exception during onstop for reader {0}: {1}: {2}"
            self.log.error(msg.format(self._name, e, tb))


    def join(self, timeout):
        """Joins our thread."""
        if self.thread:
            self.thread.join(timeout)
            if self.thread.isAlive():
                msg = "read: plugin {0} shutdown timeout - blocking exit"
                self.log.error(msg.format(self._name))


    def __del__(self):
        """Logs __del__ calls."""
        self.log.debug("read: del: {0}".format(self._name))


1		# -- coding: utf-8 --
2		"""Defines a class to read from a queue and write to a writer plugin.
3
4		.. moduleauthor:: Kenny Freeman <[email protected]>
5
6		"""
7		__author__ = 'Kenny Freeman'
8		__email__ = '[email protected]'
9		__license__ = "ISCL"
10		__docformat__ = 'reStructuredText'
11
12		import time
13		import Queue
14		import random
15		import threading
16		import traceback
17
18		import plumd
19		import plumd.util
20
21
22		class PluginReader(object):
23		"""Reads from a plugin instance by calling pobj.poll() and writes
24		to a list of PluginWriters by calling <writerobj>.queue.put() - loops
25		on a configured interval.
26
27		:param log: A logger
28		:type log: logging.get_logger()
29		:param pobj: An instance of a Reader plugin.
30		:type pobj: Reader
31		:param pname: The configured name of the plugin.
32		:type pname: str
33		:param interval: The conigured polling interval for thep plugin.
34		:type interval: int
35		:raises: ConfigError, PluginLoadError
36		"""
37
38
39		def __init__(self, log, pobj, pname):
40		"""Reads from a plugin instance by calling pobj.poll() and writes
41		to a list of PluginWriters by calling <writerobj>.queue.put() - loops
42		on a configured interval.
43
44		:param log: A logger
45		:type log: structlog.get_logger()
46		:param pobj: An instance of a Reader plugin.
47		:type pobj: Reader
48		:param pname: The configured name of the plugin.
49		:type pname: str
50		:raises: ConfigError, PluginLoadError
51		"""
52		self.log = log
53		# poll() interval - get from plugins configuration
54		self.interval = pobj.config.get('poll.interval')
55		self._name = pname
56		self.pobj = pobj
57		# what writers should we write metrics to?
58		self.writers = []
59		# thread that polls for metrics and writes to writers
60		self.thread = None
61		self.stop_evt = threading.Event()
62
63
64		@property
65		def name(self):
66		"""Simply return our configured name.
67		:rtype: str
68		"""
69		return self._name
70
71
72		def onstart(self):
73		"""Call the plugins onstart function."""
74		try:
75		self.pobj.onstart()
76		except Exception as e:
77		tb = traceback.format_exc()
78		msg = "read: disabling reader {0}: exception in onstart: {1}: {2}"
79		self.log.error(msg.format(self._name, e, tb))
80		return
81
82
83	View Code Duplication	def poll(self):
		1 ignored issue – show Duplication introduced 2016-07-31 19:23 UTC by Report Bug Copy Issue Report This code seems to be duplicated in your project. Loading history...
84		"""Calls the plugins poll() function and either returns a valid
85		:class:`plumd.ResultSet` or None.
86
87		:rtype: plumd.ResultSet
88		"""
89		rset = None
90		# plugins can raise pretty much any exception, wrap in catch all try
91		try:
92		rset = self.pobj.poll()
93		if not isinstance(rset, plumd.ResultSet):
94		msg = "read: invalid result set from reader {0}: {1}"
95		self.log.error(msg.format(self._name, rset))
96		rset = plumd.ResultSet()
97		except Exception as e:
98		# print a traceback and ensure the reader thread exits
99		tb = traceback.format_exc()
100		msg="read: disabling reader {0} due to exception in poll: {1} : {2}"
101		self.log.error(msg.format(self._name, e, tb))
102		self.stop_evt.set()
103		rset = plumd.ResultSet()
104		return rset
105
106
107		def write(self, rset):
108		"""Iterates through each writer plugin and writes the
109		:class:`plumd.ResultSet` to the writers input queue. Uses a
110		:class:`plumd.utils.Interval` to determine if it will block when
111		pushing to a writers queue. If there is time remaining in the current
112		poll interval it will block. Also, if a writers queue is full it will
113		drop the metric for that writer. Future versions may use persistance
114		to queue result sets to disk if the backend metrics services are down.
115
116		:param rset: a result set from a plugin poll() call.
117		:type rset: plumd.ResultSet
118		:param lint: an interval helper.
119		:type lint: plumd.util.Interval
120		"""
121		# only send result sets that have metrics
122		if rset.nresults < 1:
123		return
124
125		# enqueue onto each writers queue, wait for any remaining time
126		for wobj in self.writers:
127		try:
128		# allow queue puts to block for a short time
129		# this cannot block for long as it will also block shutdown
130		wobj.queue.put(rset, block=True, timeout=1)
131		except Queue.Full:
132		msg = "read: {0}: dropping metrics: writer plugin queue full: {1}"
133		self.log.warn(msg.format(self._name, wobj.name))
134
135
136		def read(self):
137		"""Calls the plugins onstart() function and then iterates over the
138		plugins poll() function, pushing the result to each writer queue."""
139		self.onstart()
140
141		## distribute metrics - don't everyone flood all at once
142		time.sleep(random.randrange(int(self.pobj.config.get('delay.poll'))))
143
144		# loop on calling the plugin objects poll and sending to writers
145		while not self.stop_evt.is_set():
146		# loop every self.interval seconds
147		with plumd.util.Interval(self.interval, self.stop_evt) as lint:
148		if self.stop_evt.is_set():
149		break
150		rset = self.poll()
151		# readers can return None values eg. a reader that polls
152		# very often and periodically returns results
153		if rset:
154		self.write(rset)
155		# warn if loop time exceeded
156		if lint.remaining < 0:
157		msg = "read: {0} reader loop time exceeded"
158		self.log.warn(msg.format(self._name))
159		self.onstop()
160
161
162		def start(self):
163		"""Calls pobj.onstart() and starts a thread to poll() metrics."""
164		self.thread = threading.Thread(target=self.read, group=None)
165		self.thread.start()
166
167
168		def stop(self):
169		"""Stops the poll() thread and calls pobj.onstop()."""
170		# set the stop event and the self.read thread falls through.
171		self.stop_evt.set()
172
173
174		def onstop(self):
175		"""Calls the plugins onstop callable."""
176		# this can raise pretty much any exception
177		try:
178		self.pobj.onstop()
179		except Exception as e:
180		tb = traceback.format_exc()
181		msg = "read: exception during onstop for reader {0}: {1}: {2}"
182		self.log.error(msg.format(self._name, e, tb))
183
184
185		def join(self, timeout):
186		"""Joins our thread."""
187		if self.thread:
188		self.thread.join(timeout)
189		if self.thread.isAlive():
190		msg = "read: plugin {0} shutdown timeout - blocking exit"
191		self.log.error(msg.format(self._name))
192
193
194		def __del__(self):
195		"""Logs __del__ calls."""
196		self.log.debug("read: del: {0}".format(self._name))
197

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PluginReader.poll() A

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