250 lines
7.9 KiB
Python
250 lines
7.9 KiB
Python
# -*- coding: utf-8 -*-
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#
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# Copyright © 2014 eNovance
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#
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# 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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import contextlib
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import logging
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from oslo_utils import encodeutils
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from oslo_utils.secretutils import md5
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import psycopg2
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import tooz
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from tooz import _retry
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from tooz import coordination
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from tooz import locking
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from tooz import utils
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LOG = logging.getLogger(__name__)
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# See: psycopg/diagnostics_type.c for what kind of fields these
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# objects may have (things like 'schema_name', 'internal_query'
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# and so-on which are useful for figuring out what went wrong...)
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_DIAGNOSTICS_ATTRS = tuple([
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'column_name',
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'constraint_name',
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'context',
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'datatype_name',
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'internal_position',
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'internal_query',
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'message_detail',
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'message_hint',
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'message_primary',
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'schema_name',
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'severity',
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'source_file',
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'source_function',
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'source_line',
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'sqlstate',
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'statement_position',
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'table_name',
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])
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def _format_exception(e):
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lines = [
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"%s: %s" % (type(e).__name__,
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encodeutils.exception_to_unicode(e).strip()),
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]
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if hasattr(e, 'pgcode') and e.pgcode is not None:
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lines.append("Error code: %s" % e.pgcode)
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# The reason this hasattr check is done is that the 'diag' may not always
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# be present, depending on how new of a psycopg is installed... so better
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# to be safe than sorry...
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if hasattr(e, 'diag') and e.diag is not None:
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diagnostic_lines = []
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for attr_name in _DIAGNOSTICS_ATTRS:
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if not hasattr(e.diag, attr_name):
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continue
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attr_value = getattr(e.diag, attr_name)
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if attr_value is None:
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continue
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diagnostic_lines.append(" %s = %s" (attr_name, attr_value))
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if diagnostic_lines:
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lines.append('Diagnostics:')
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lines.extend(diagnostic_lines)
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return "\n".join(lines)
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@contextlib.contextmanager
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def _translating_cursor(conn):
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try:
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with conn.cursor() as cur:
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yield cur
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except psycopg2.Error as e:
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utils.raise_with_cause(tooz.ToozError,
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_format_exception(e),
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cause=e)
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class PostgresLock(locking.Lock):
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"""A PostgreSQL based lock."""
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def __init__(self, name, parsed_url, options):
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super(PostgresLock, self).__init__(name)
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self.acquired = False
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self._conn = None
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self._parsed_url = parsed_url
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self._options = options
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h = md5(usedforsecurity=False)
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h.update(name)
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self.key = h.digest()[0:2]
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def acquire(self, blocking=True, shared=False):
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if shared:
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raise tooz.NotImplemented
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@_retry.retry(stop_max_delay=blocking)
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def _lock():
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# NOTE(sileht) One the same session the lock is not exclusive
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# so we track it internally if the process already has the lock.
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if self.acquired is True:
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if blocking:
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raise _retry.TryAgain
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return False
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if not self._conn or self._conn.closed:
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self._conn = PostgresDriver.get_connection(self._parsed_url,
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self._options)
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with _translating_cursor(self._conn) as cur:
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if blocking is True:
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cur.execute("SELECT pg_advisory_lock(%s, %s);",
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self.key)
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cur.fetchone()
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self.acquired = True
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return True
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else:
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cur.execute("SELECT pg_try_advisory_lock(%s, %s);",
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self.key)
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if cur.fetchone()[0] is True:
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self.acquired = True
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return True
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elif blocking is False:
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self._conn.close()
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return False
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else:
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raise _retry.TryAgain
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try:
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return _lock()
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except Exception:
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if self._conn:
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self._conn.close()
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raise
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def release(self):
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if not self.acquired:
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return False
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with _translating_cursor(self._conn) as cur:
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cur.execute("SELECT pg_advisory_unlock(%s, %s);", self.key)
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cur.fetchone()
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self.acquired = False
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self._conn.close()
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return True
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def __del__(self):
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if self.acquired:
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LOG.warning("unreleased lock %s garbage collected", self.name)
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class PostgresDriver(coordination.CoordinationDriver):
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"""A `PostgreSQL`_ based driver.
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This driver users `PostgreSQL`_ database tables to
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provide the coordination driver semantics and required API(s). It **is**
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missing some functionality but in the future these not implemented API(s)
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will be filled in.
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The PostgreSQL driver connection URI should look like::
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postgresql://[USERNAME[:PASSWORD]@]HOST:PORT?dbname=DBNAME
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.. _PostgreSQL: http://www.postgresql.org/
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"""
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CHARACTERISTICS = (
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coordination.Characteristics.NON_TIMEOUT_BASED,
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coordination.Characteristics.DISTRIBUTED_ACROSS_THREADS,
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coordination.Characteristics.DISTRIBUTED_ACROSS_PROCESSES,
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coordination.Characteristics.DISTRIBUTED_ACROSS_HOSTS,
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)
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"""
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Tuple of :py:class:`~tooz.coordination.Characteristics` introspectable
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enum member(s) that can be used to interogate how this driver works.
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"""
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def __init__(self, member_id, parsed_url, options):
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"""Initialize the PostgreSQL driver."""
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super(PostgresDriver, self).__init__(member_id, parsed_url, options)
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self._parsed_url = parsed_url
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self._options = utils.collapse(options)
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def _start(self):
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self._conn = self.get_connection(self._parsed_url, self._options)
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def _stop(self):
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self._conn.close()
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def get_lock(self, name):
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return PostgresLock(name, self._parsed_url, self._options)
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@staticmethod
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def watch_join_group(group_id, callback):
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raise tooz.NotImplemented
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@staticmethod
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def unwatch_join_group(group_id, callback):
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raise tooz.NotImplemented
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@staticmethod
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def watch_leave_group(group_id, callback):
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raise tooz.NotImplemented
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@staticmethod
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def unwatch_leave_group(group_id, callback):
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raise tooz.NotImplemented
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@staticmethod
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def watch_elected_as_leader(group_id, callback):
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raise tooz.NotImplemented
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@staticmethod
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def unwatch_elected_as_leader(group_id, callback):
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raise tooz.NotImplemented
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@staticmethod
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def get_connection(parsed_url, options):
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host = options.get("host") or parsed_url.hostname
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port = options.get("port") or parsed_url.port
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dbname = options.get("dbname") or parsed_url.path[1:]
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kwargs = {}
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if parsed_url.username is not None:
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kwargs["user"] = parsed_url.username
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if parsed_url.password is not None:
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kwargs["password"] = parsed_url.password
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try:
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return psycopg2.connect(host=host,
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port=port,
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database=dbname,
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**kwargs)
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except psycopg2.Error as e:
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utils.raise_with_cause(coordination.ToozConnectionError,
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_format_exception(e),
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cause=e)
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