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# -*- coding: utf-8 -*-
#
# 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 psycopg2
import six
import tooz
from tooz import coordination
from tooz.drivers import _retry
from tooz import locking
from tooz import utils
# 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__, utils.exception_message(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:
raise coordination.ToozError(_format_exception(e))
class PostgresLock(locking.Lock):
"""A PostgreSQL based lock."""
def __init__(self, name, connection):
super(PostgresLock, self).__init__(name)
self._conn = connection
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):
if blocking is True:
with _translating_cursor(self._conn) as cur:
cur.execute("SELECT pg_advisory_lock(%s, %s);", self.key)
return True
elif blocking is False:
with _translating_cursor(self._conn) as cur:
cur.execute("SELECT pg_try_advisory_lock(%s, %s);", self.key)
return cur.fetchone()[0]
else:
def _acquire():
with _translating_cursor(self._conn) as cur:
cur.execute("SELECT pg_try_advisory_lock(%s, %s);",
self.key)
if cur.fetchone()[0] is True:
return True
raise _retry.Retry
kwargs = _retry.RETRYING_KWARGS.copy()
kwargs['stop_max_delay'] = blocking
return _retry.Retrying(**kwargs).call(_acquire)
def release(self):
with _translating_cursor(self._conn) as cur:
cur.execute("SELECT pg_advisory_unlock(%s, %s);", self.key)
return cur.fetchone()[0]
class PostgresDriver(coordination.CoordinationDriver):
"""A PostgreSQL based driver."""
def __init__(self, member_id, parsed_url, options):
"""Initialize the PostgreSQL driver."""
super(PostgresDriver, self).__init__()
self._host = options.get("host", [None])[-1]
self._port = parsed_url.port or options.get("port", [None])[-1]
self._dbname = parsed_url.path[1:] or options.get("dbname", [None])[-1]
self._username = parsed_url.username
self._password = parsed_url.password
def _start(self):
try:
self._conn = psycopg2.connect(host=self._host,
port=self._port,
user=self._username,
password=self._password,
database=self._dbname)
except psycopg2.Error as e:
raise coordination.ToozConnectionError(_format_exception(e))
def _stop(self):
self._conn.close()
def get_lock(self, name):
return PostgresLock(name, self._conn)
@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
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