115 lines
4.1 KiB
Python
115 lines
4.1 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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Generic SheepDog Connection Utilities.
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"""
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import eventlet
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import io
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from oslo_concurrency import processutils
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from os_brick import exception
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from os_brick.i18n import _
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class SheepdogVolumeIOWrapper(io.RawIOBase):
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"""File-like object with Sheepdog backend."""
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def __init__(self, addr, port, volume, snapshot_name=None):
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self._addr = addr
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self._port = port
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self._vdiname = volume
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self._snapshot_name = snapshot_name
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self._offset = 0
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# SheepdogVolumeIOWrapper instance becomes invalid
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# if a write error occurs.
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self._valid = True
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def _execute(self, cmd, data=None):
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try:
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# NOTE(yamada-h): processutils.execute causes busy waiting
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# under eventlet.
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# To avoid wasting CPU resources, it should not be used for
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# the command which takes long time to execute.
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# For workaround, we replace a subprocess module with
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# the original one while only executing a read/write command.
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_processutils_subprocess = processutils.subprocess
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processutils.subprocess = eventlet.patcher.original('subprocess')
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return processutils.execute(*cmd, process_input=data)[0]
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except (processutils.ProcessExecutionError, OSError):
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self._valid = False
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raise exception.VolumeDriverException(name=self._vdiname)
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finally:
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processutils.subprocess = _processutils_subprocess
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def read(self, length=None):
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if not self._valid:
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raise exception.VolumeDriverException(name=self._vdiname)
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cmd = ['dog', 'vdi', 'read', '-a', self._addr, '-p', self._port]
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if self._snapshot_name:
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cmd.extend(('-s', self._snapshot_name))
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cmd.extend((self._vdiname, self._offset))
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if length:
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cmd.append(length)
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data = self._execute(cmd)
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self._offset += len(data)
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return data
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def write(self, data):
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if not self._valid:
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raise exception.VolumeDriverException(name=self._vdiname)
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length = len(data)
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cmd = ('dog', 'vdi', 'write', '-a', self._addr, '-p', self._port,
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self._vdiname, self._offset, length)
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self._execute(cmd, data)
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self._offset += length
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return length
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def seek(self, offset, whence=0):
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if not self._valid:
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raise exception.VolumeDriverException(name=self._vdiname)
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if whence == 0:
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# SEEK_SET or 0 - start of the stream (the default);
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# offset should be zero or positive
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new_offset = offset
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elif whence == 1:
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# SEEK_CUR or 1 - current stream position; offset may be negative
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new_offset = self._offset + offset
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else:
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# SEEK_END or 2 - end of the stream; offset is usually negative
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# TODO(yamada-h): Support SEEK_END
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raise IOError(_("Invalid argument - whence=%s not supported.") %
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whence)
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if new_offset < 0:
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raise IOError(_("Invalid argument - negative seek offset."))
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self._offset = new_offset
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def tell(self):
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return self._offset
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def flush(self):
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pass
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def fileno(self):
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"""Sheepdog does not have support for fileno so we raise IOError.
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Raising IOError is recommended way to notify caller that interface is
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not supported - see http://docs.python.org/2/library/io.html#io.IOBase
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"""
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raise IOError(_("fileno is not supported by SheepdogVolumeIOWrapper"))
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