root / lib / watcher / state.py @ b459a848
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# Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Module keeping state for Ganeti watcher.
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"""
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import os |
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import time |
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import logging |
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from ganeti import utils |
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from ganeti import serializer |
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from ganeti import errors |
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# Delete any record that is older than 8 hours; this value is based on
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# the fact that the current retry counter is 5, and watcher runs every
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# 5 minutes, so it takes around half an hour to exceed the retry
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# counter, so 8 hours (16*1/2h) seems like a reasonable reset time
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RETRY_EXPIRATION = 8 * 3600 |
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KEY_RESTART_COUNT = "restart_count"
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KEY_RESTART_WHEN = "restart_when"
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KEY_BOOT_ID = "bootid"
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def OpenStateFile(path): |
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"""Opens the state file and acquires a lock on it.
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@type path: string
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@param path: Path to state file
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"""
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# The two-step dance below is necessary to allow both opening existing
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# file read/write and creating if not existing. Vanilla open will truncate
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# an existing file -or- allow creating if not existing.
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statefile_fd = os.open(path, os.O_RDWR | os.O_CREAT) |
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# Try to acquire lock on state file. If this fails, another watcher instance
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# might already be running or another program is temporarily blocking the
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# watcher from running.
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try:
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utils.LockFile(statefile_fd) |
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except errors.LockError, err:
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logging.error("Can't acquire lock on state file %s: %s", path, err)
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return None |
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return os.fdopen(statefile_fd, "w+") |
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class WatcherState(object): |
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"""Interface to a state file recording restart attempts.
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"""
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def __init__(self, statefile): |
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"""Open, lock, read and parse the file.
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@type statefile: file
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@param statefile: State file object
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"""
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self.statefile = statefile
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try:
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state_data = self.statefile.read()
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if not state_data: |
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self._data = {}
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else:
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self._data = serializer.Load(state_data)
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except Exception, msg: # pylint: disable=W0703 |
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# Ignore errors while loading the file and treat it as empty
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self._data = {}
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logging.warning(("Invalid state file. Using defaults."
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" Error message: %s"), msg)
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if "instance" not in self._data: |
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self._data["instance"] = {} |
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if "node" not in self._data: |
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self._data["node"] = {} |
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self._orig_data = serializer.Dump(self._data) |
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def Save(self, filename): |
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"""Save state to file, then unlock and close it.
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"""
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assert self.statefile |
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serialized_form = serializer.Dump(self._data)
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if self._orig_data == serialized_form: |
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logging.debug("Data didn't change, just touching status file")
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os.utime(filename, None)
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return
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# We need to make sure the file is locked before renaming it, otherwise
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# starting ganeti-watcher again at the same time will create a conflict.
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fd = utils.WriteFile(filename, |
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data=serialized_form, |
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prewrite=utils.LockFile, close=False)
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self.statefile = os.fdopen(fd, 'w+') |
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def Close(self): |
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"""Unlock configuration file and close it.
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"""
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assert self.statefile |
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# Files are automatically unlocked when closing them
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self.statefile.close()
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self.statefile = None |
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def GetNodeBootID(self, name): |
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"""Returns the last boot ID of a node or None.
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"""
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ndata = self._data["node"] |
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if name in ndata and KEY_BOOT_ID in ndata[name]: |
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return ndata[name][KEY_BOOT_ID]
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return None |
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def SetNodeBootID(self, name, bootid): |
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"""Sets the boot ID of a node.
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"""
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assert bootid
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ndata = self._data["node"] |
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ndata.setdefault(name, {})[KEY_BOOT_ID] = bootid |
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def NumberOfRestartAttempts(self, instance_name): |
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"""Returns number of previous restart attempts.
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@type instance_name: string
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@param instance_name: the name of the instance to look up
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"""
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idata = self._data["instance"] |
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if instance_name in idata: |
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return idata[instance_name][KEY_RESTART_COUNT]
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return 0 |
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def MaintainInstanceList(self, instances): |
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"""Perform maintenance on the recorded instances.
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@type instances: list of string
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@param instances: the list of currently existing instances
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"""
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idict = self._data["instance"] |
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# First, delete obsolete instances
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obsolete_instances = set(idict).difference(instances)
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for inst in obsolete_instances: |
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logging.debug("Forgetting obsolete instance %s", inst)
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idict.pop(inst, None)
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# Second, delete expired records
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earliest = time.time() - RETRY_EXPIRATION |
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expired_instances = [i for i in idict |
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if idict[i][KEY_RESTART_WHEN] < earliest]
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for inst in expired_instances: |
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logging.debug("Expiring record for instance %s", inst)
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idict.pop(inst, None)
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def RecordRestartAttempt(self, instance_name): |
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"""Record a restart attempt.
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@type instance_name: string
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@param instance_name: the name of the instance being restarted
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"""
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idata = self._data["instance"] |
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inst = idata.setdefault(instance_name, {}) |
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inst[KEY_RESTART_WHEN] = time.time() |
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inst[KEY_RESTART_COUNT] = inst.get(KEY_RESTART_COUNT, 0) + 1 |
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def RemoveInstance(self, instance_name): |
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"""Update state to reflect that a machine is running.
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This method removes the record for a named instance (as we only
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track down instances).
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@type instance_name: string
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@param instance_name: the name of the instance to remove from books
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"""
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idata = self._data["instance"] |
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idata.pop(instance_name, None)
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