/usr/lib/python3/dist-packages/tooz/drivers/pgsql.py is in python3-tooz 1.59.0-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# Copyright © 2014 eNovance
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import contextlib
import hashlib
import logging
from oslo_utils import encodeutils
import psycopg2
import six
import tooz
from tooz import _retry
from tooz import coordination
from tooz import locking
from tooz import utils
LOG = logging.getLogger(__name__)
# See: psycopg/diagnostics_type.c for what kind of fields these
# objects may have (things like 'schema_name', 'internal_query'
# and so-on which are useful for figuring out what went wrong...)
_DIAGNOSTICS_ATTRS = tuple([
'column_name',
'constraint_name',
'context',
'datatype_name',
'internal_position',
'internal_query',
'message_detail',
'message_hint',
'message_primary',
'schema_name',
'severity',
'source_file',
'source_function',
'source_line',
'sqlstate',
'statement_position',
'table_name',
])
def _format_exception(e):
lines = [
"%s: %s" % (type(e).__name__,
encodeutils.exception_to_unicode(e).strip()),
]
if hasattr(e, 'pgcode') and e.pgcode is not None:
lines.append("Error code: %s" % e.pgcode)
# The reason this hasattr check is done is that the 'diag' may not always
# be present, depending on how new of a psycopg is installed... so better
# to be safe than sorry...
if hasattr(e, 'diag') and e.diag is not None:
diagnostic_lines = []
for attr_name in _DIAGNOSTICS_ATTRS:
if not hasattr(e.diag, attr_name):
continue
attr_value = getattr(e.diag, attr_name)
if attr_value is None:
continue
diagnostic_lines.append(" %s = %s" (attr_name, attr_value))
if diagnostic_lines:
lines.append('Diagnostics:')
lines.extend(diagnostic_lines)
return "\n".join(lines)
@contextlib.contextmanager
def _translating_cursor(conn):
try:
with conn.cursor() as cur:
yield cur
except psycopg2.Error as e:
utils.raise_with_cause(tooz.ToozError,
_format_exception(e),
cause=e)
class PostgresLock(locking.Lock):
"""A PostgreSQL based lock."""
def __init__(self, name, parsed_url, options):
super(PostgresLock, self).__init__(name)
self.acquired = False
self._conn = None
self._parsed_url = parsed_url
self._options = options
h = hashlib.md5()
h.update(name)
if six.PY2:
self.key = list(map(ord, h.digest()[0:2]))
else:
self.key = h.digest()[0:2]
def acquire(self, blocking=True, shared=False):
if shared:
raise tooz.NotImplemented
@_retry.retry(stop_max_delay=blocking)
def _lock():
# NOTE(sileht) One the same session the lock is not exclusive
# so we track it internally if the process already has the lock.
if self.acquired is True:
if blocking:
raise _retry.TryAgain
return False
if not self._conn or self._conn.closed:
self._conn = PostgresDriver.get_connection(self._parsed_url,
self._options)
with _translating_cursor(self._conn) as cur:
if blocking is True:
cur.execute("SELECT pg_advisory_lock(%s, %s);",
self.key)
cur.fetchone()
self.acquired = True
return True
else:
cur.execute("SELECT pg_try_advisory_lock(%s, %s);",
self.key)
if cur.fetchone()[0] is True:
self.acquired = True
return True
elif blocking is False:
self._conn.close()
return False
else:
raise _retry.TryAgain
try:
return _lock()
except Exception:
if self._conn:
self._conn.close()
raise
def release(self):
if not self.acquired:
return False
with _translating_cursor(self._conn) as cur:
cur.execute("SELECT pg_advisory_unlock(%s, %s);", self.key)
cur.fetchone()
self.acquired = False
self._conn.close()
return True
def __del__(self):
if self.acquired:
LOG.warning("unreleased lock %s garbage collected", self.name)
class PostgresDriver(coordination.CoordinationDriver):
"""A `PostgreSQL`_ based driver.
This driver users `PostgreSQL`_ database tables to
provide the coordination driver semantics and required API(s). It **is**
missing some functionality but in the future these not implemented API(s)
will be filled in.
.. _PostgreSQL: http://www.postgresql.org/
"""
CHARACTERISTICS = (
coordination.Characteristics.NON_TIMEOUT_BASED,
coordination.Characteristics.DISTRIBUTED_ACROSS_THREADS,
coordination.Characteristics.DISTRIBUTED_ACROSS_PROCESSES,
coordination.Characteristics.DISTRIBUTED_ACROSS_HOSTS,
)
"""
Tuple of :py:class:`~tooz.coordination.Characteristics` introspectable
enum member(s) that can be used to interogate how this driver works.
"""
def __init__(self, member_id, parsed_url, options):
"""Initialize the PostgreSQL driver."""
super(PostgresDriver, self).__init__(member_id, parsed_url, options)
self._parsed_url = parsed_url
self._options = utils.collapse(options)
def _start(self):
self._conn = self.get_connection(self._parsed_url, self._options)
def _stop(self):
self._conn.close()
def get_lock(self, name):
return PostgresLock(name, self._parsed_url, self._options)
@staticmethod
def watch_join_group(group_id, callback):
raise tooz.NotImplemented
@staticmethod
def unwatch_join_group(group_id, callback):
raise tooz.NotImplemented
@staticmethod
def watch_leave_group(group_id, callback):
raise tooz.NotImplemented
@staticmethod
def unwatch_leave_group(group_id, callback):
raise tooz.NotImplemented
@staticmethod
def watch_elected_as_leader(group_id, callback):
raise tooz.NotImplemented
@staticmethod
def unwatch_elected_as_leader(group_id, callback):
raise tooz.NotImplemented
@staticmethod
def get_connection(parsed_url, options):
host = options.get("host") or parsed_url.hostname
port = options.get("port") or parsed_url.port
dbname = options.get("dbname") or parsed_url.path[1:]
kwargs = {}
if parsed_url.username is not None:
kwargs["user"] = parsed_url.username
if parsed_url.password is not None:
kwargs["password"] = parsed_url.password
try:
return psycopg2.connect(host=host,
port=port,
database=dbname,
**kwargs)
except psycopg2.Error as e:
utils.raise_with_cause(coordination.ToozConnectionError,
_format_exception(e),
cause=e)
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