terom@5: """
terom@5:     Simple /sbin/lvm wrapper for handling snapshots.
terom@5: """
terom@5: 
terom@5: from pvl.backup.invoke import invoke, optargs, InvokeError
terom@5: 
terom@5: import contextlib
terom@5: import os.path
terom@5: import logging
terom@42: import time
terom@5: 
terom@5: log = logging.getLogger('pvl.backup.lvm')
terom@5: 
terom@42: # default snapshot size
terom@42: LVM_SNAPSHOT_SIZE   = '5G'
terom@42: 
terom@42: # number of seconds to wait for lvm snapshot to settle after unmount..
terom@42: LVM_SNAPSHOT_WAIT   = 5
terom@42: 
terom@61: # number of times to retry removal, due to lvm/udev bug..
terom@61: LVM_SNAPSHOT_RETRY  = 5
terom@61: 
terom@5: class LVMError (Exception) :
terom@5:     pass
terom@5: 
terom@5: class LVM (object) :
terom@5:     """
terom@5:         LVM VolumeGroup
terom@5:     """
terom@5: 
terom@5:     # path to lvm2 binary
terom@5:     LVM = '/sbin/lvm'
terom@5: 
terom@5:     
terom@5:     # VG name
terom@5:     name = None
terom@5: 
terom@69:     def __init__ (self, name, sudo=None) :
terom@69:         """
terom@69:             name    - VG name
terom@69:             sudo    - invoke sudo
terom@69:         """
terom@69: 
terom@5:         self.name = name
terom@69:         self.sudo = sudo
terom@5: 
terom@5:     def lv_name (self, lv) :
terom@5:         """
terom@5:             vg/lv name.
terom@5:         """
terom@5: 
terom@5:         return '{vg}/{lv}'.format(vg=self.name, lv=lv)
terom@5: 
terom@5:     def lv_path (self, lv) :
terom@5:         """
terom@5:             /dev/vg/lv path.
terom@5:         """
terom@5: 
terom@5:         return '/dev/{vg}/{lv}'.format(vg=self.name, lv=lv)
terom@5: 
terom@5:     def command (self, cmd, *args, **opts) :
terom@5:         """
terom@5:             Invoke a command with options/arguments, given via Python arguments/keyword arguments
terom@5:         """
terom@5:         
terom@5:         log.debug("{cmd} {opts} {args}".format(cmd=cmd, args=args, opts=opts))
terom@5: 
terom@5:         # invoke
terom@69:         invoke(self.LVM, [cmd] + optargs(*args, **opts), sudo=self.sudo)
terom@5: 
terom@5:     def volume (self, name) :
terom@5:         """
terom@5:             Return an LVMVolume for given named LV.
terom@5:         """
terom@5: 
terom@5:         return LVMVolume(self, name)
terom@5: 
terom@5:     @contextlib.contextmanager
terom@61:     def snapshot (self, base, wait=LVM_SNAPSHOT_WAIT, retry=LVM_SNAPSHOT_RETRY, **opts) :
terom@5:         """
terom@5:             A Context Manager for handling an LVMSnapshot.
terom@5: 
terom@5:             See LVMSnapshot.create()
terom@5: 
terom@5:             with lvm.snapshot(lv) as snapshot : ...
terom@42: 
terom@42:                 wait        - wait given interval for the snapshot device to settle before unmounting it
terom@61:                 retry       - retry removal given number of times
terom@42:                 **opts      - LVMSnapshot.create() options (e.g. size)
terom@5:         """
terom@5: 
terom@61:         log.debug("creating snapshot from {base}: wait={wait}, retry={retry} {opts}".format(base=base, wait=wait, retry=retry, opts=opts))
terom@42:         snapshot = LVMSnapshot.create(self, base, **opts)
terom@5: 
terom@5:         try :
terom@5:             log.debug("got: {0}".format(snapshot))
terom@5:             yield snapshot
terom@5: 
terom@5:         finally:
terom@61:             # XXX: there's some common udev bug with removing lvm snapshots
terom@61:             #       https://bugzilla.redhat.com/show_bug.cgi?id=577798
terom@61:             #       http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=618016
terom@61:             #       possibly fixed in lvm2 2.02.86?
terom@61:             # try to just patiently wait for it to settle down... then retry... if this isn't enough, we need some dmremove magic?
terom@61:             while True :
terom@61:                 # wait..
terom@61:                 if wait :
terom@61:                     log.debug("%s: cleanup: waiting %.2f seconds for snapshot volume to settle...", snapshot, wait)
terom@61:                     time.sleep(wait)
terom@29: 
terom@61:                 # lvremove
terom@61:                 try :
terom@61:                     log.debug("%s: cleanup", snapshot)
terom@61:                     snapshot.close()
terom@61: 
terom@61:                 except InvokeError as ex :
terom@61:                     if ex.exit != 5 :
terom@61:                         # lvremove sez "Can't remove open logical volume ..." -> exit(5);
terom@61:                         raise
terom@61:                     
terom@61:                     # retry counter?
terom@61:                     if retry :
terom@61:                         log.warn("%s: cleanup: lvremove failed, retrying...", snapshot)
terom@61:                         retry -= 1
terom@61: 
terom@61:                         # retry
terom@61:                         continue
terom@61: 
terom@61:                     else :
terom@61:                         # failed
terom@61:                         log.error("%s: cleanup: lvremove failed, aborting...", snapshot)
terom@61:                         raise
terom@61: 
terom@61:                 else :
terom@61:                     # done
terom@61:                     break
terom@5: 
terom@10:     def __str__ (self) :
terom@10:         return self.name
terom@10: 
terom@5:     def __repr__ (self) :
terom@5:         return "LVM(name={name})".format(name=repr(self.name))
terom@5: 
terom@5: class LVMVolume (object) :
terom@5:     """
terom@5:         LVM Logical Volume.
terom@5:     """
terom@5: 
terom@5:     # VG
terom@5:     lvm = None
terom@5: 
terom@5:     # name
terom@5:     name = None
terom@5: 
terom@5:     def __init__ (self, lvm, name) :
terom@5:         self.lvm = lvm
terom@5:         self.name = name
terom@5: 
terom@5:     @property
terom@5:     def lvm_path (self) :
terom@5:         return self.lvm.lv_name(self.name)
terom@5: 
terom@5:     @property
terom@5:     def dev_path (self) :
terom@5:         return self.lvm.lv_path(self.name)
terom@5: 
terom@5:     def verify_exists (self) :
terom@5:         """
terom@5:             Verify that the LV exists.
terom@5: 
terom@5:             Raises an LVMError otherwise.
terom@5:         """
terom@5: 
terom@5:         # lvdisplay
terom@5:         try :
terom@5:             self.lvm.command('lvs', self.lvm_path)
terom@5: 
terom@5:         except InvokeError :
terom@5:             raise LVMError("Unable to lvdisplay LV: {path}".format(path=self.lvm_path))
terom@5: 
terom@5:         # dev
terom@5:         if not self.test_dev() :
terom@5:             raise LVMError("LV dev does not exist: {path}".format(path=self.dev_path))
terom@5: 
terom@5:     def verify_missing (self) :
terom@5:         """
terom@5:             Verify that the LV does NOT exist.
terom@5: 
terom@5:             Raises an LVMError otherwise.
terom@5:         """
terom@5: 
terom@5:         if self.test_dev() :
terom@5:             raise Exception("LV already exists: {path}".format(path=self.dev_path))
terom@5: 
terom@5:     def test_dev (self) :
terom@5:         """
terom@5:             Tests for existance of device file, returning True/False.
terom@5:         """
terom@5: 
terom@5:         return os.path.exists(self.dev_path)
terom@5: 
terom@10:     def __str__ (self) :
terom@10:         return self.lvm_path
terom@10: 
terom@5:     def __repr__ (self) :
terom@5:         return "LVMVolume(lvm={lvm}, name={name})".format(
terom@5:                 lvm     = repr(self.lvm),
terom@5:                 name    = repr(self.name),
terom@5:         )
terom@5: 
terom@5: class LVMSnapshot (LVMVolume) :
terom@5:     """
terom@5:         LVM snapshot
terom@5:     """
terom@5: 
terom@5:     # base lv
terom@5:     base = None
terom@5: 
terom@5:     @classmethod
terom@5:     def create (cls, lvm, base, tag, size=LVM_SNAPSHOT_SIZE) :
terom@5:         """
terom@5:             Create a new LVM snapshot of the given LV.
terom@5:             
terom@5:             Returns a (snapshot_name, dev_path) tuple.
terom@5:         """
terom@5: 
terom@5:         # snapshot name
terom@5:         name = '{name}-{tag}'.format(name=base.name, tag=tag)
terom@5: 
terom@5:         # snapshot instance
terom@42:         snapshot = cls(lvm, base, name, size=size)
terom@5: 
terom@5:         ## verify
terom@5:         # base should exist
terom@5:         base.verify_exists()
terom@5: 
terom@5:         # snapshot should not
terom@5:         snapshot.verify_missing()
terom@5:         
terom@5:         ## create
terom@5:         snapshot.open()
terom@5: 
terom@5:         # verify
terom@5:         if not snapshot.test_dev() :
terom@5:             raise LVMError("Failed to find new snapshot LV device: {path}".format(path=snapshot.dev_path))
terom@5: 
terom@5:         # yay
terom@5:         return snapshot
terom@5: 
terom@5:     def __init__ (self, lvm, base, name, size=LVM_SNAPSHOT_SIZE) :
terom@5:         LVMVolume.__init__(self, lvm, name)
terom@5: 
terom@5:         self.base = base
terom@5:         self.size = size
terom@5: 
terom@5:     def open (self) :
terom@5:         """
terom@5:             Create snapshot volume.
terom@5:         """
terom@5: 
terom@5:         # create
terom@5:         self.lvm.command('lvcreate', self.base.lvm_path, snapshot=True, name=self.name, size=self.size)
terom@5: 
terom@5:     def close (self) :
terom@5:         """
terom@5:             Remove snapshot volume.
terom@5:         """
terom@5: 
terom@61:         # don't typo me!
terom@5:         self.lvm.command('lvremove', '-f', self.lvm_path)
terom@5: 
terom@5:     def __repr__ (self) :
terom@5:         return "LVMSnapshot(lvm={lvm}, base={base}, name={name})".format(
terom@5:                 lvm     = str(self.lvm),
terom@5:                 base    = str(self.base),
terom@5:                 name    = repr(self.name),
terom@5:         )
terom@5: 
terom@5: