# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
# 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.
"""Session Handling for SQLAlchemy backend."""
import re
import time
import sqlalchemy
from sqlalchemy.exc import DisconnectionError, OperationalError
import sqlalchemy.orm
from sqlalchemy.pool import NullPool, StaticPool
from moniker.openstack.common import cfg
from moniker.openstack.common import log as logging
from moniker.openstack.common.gettextutils import _
LOG = logging.getLogger(__name__)
_MAKERS = {}
_ENGINES = {}
SQLOPTS = [
cfg.StrOpt('database_connection',
default='sqlite:///$state_path/moniker.sqlite',
help='The database driver to use'),
cfg.IntOpt('connection_debug', default=0,
help='Verbosity of SQL debugging information. 0=None,'
' 100=Everything'),
cfg.BoolOpt('connection_trace', default=False,
help='Add python stack traces to SQL as comment strings'),
cfg.BoolOpt('sqlite_synchronous', default=True,
help='If passed, use synchronous mode for sqlite'),
cfg.IntOpt('idle_timeout', default=3600,
help='timeout before idle sql connections are reaped'),
cfg.IntOpt('max_retries', default=10,
help='maximum db connection retries during startup. '
'(setting -1 implies an infinite retry count)'),
cfg.IntOpt('retry_interval', default=10,
help='interval between retries of opening a sql connection')
]
def get_session(config_group,
autocommit=True,
expire_on_commit=False,
autoflush=True):
"""Return a SQLAlchemy session."""
global _MAKERS
if config_group not in _MAKERS:
engine = get_engine(config_group)
_MAKERS[config_group] = get_maker(engine,
autocommit,
expire_on_commit,
autoflush)
session = _MAKERS[config_group]()
return session
def synchronous_switch_listener(dbapi_conn, connection_rec):
"""Switch sqlite connections to non-synchronous mode"""
dbapi_conn.execute("PRAGMA synchronous = OFF")
def add_regexp_listener(dbapi_con, con_record):
"""Add REGEXP function to sqlite connections."""
def regexp(expr, item):
reg = re.compile(expr)
return reg.search(unicode(item)) is not None
dbapi_con.create_function('regexp', 2, regexp)
def ping_listener(dbapi_conn, connection_rec, connection_proxy):
"""
Ensures that MySQL connections checked out of the
pool are alive.
Borrowed from:
http://groups.google.com/group/sqlalchemy/msg/a4ce563d802c929f
"""
try:
dbapi_conn.cursor().execute('select 1')
except dbapi_conn.OperationalError, ex:
if ex.args[0] in (2006, 2013, 2014, 2045, 2055):
LOG.warn('Got mysql server has gone away: %s', ex)
raise DisconnectionError("Database server went away")
else:
raise
def is_db_connection_error(args):
"""Return True if error in connecting to db."""
# NOTE(adam_g): This is currently MySQL specific and needs to be extended
# to support Postgres and others.
conn_err_codes = ('2002', '2003', '2006')
for err_code in conn_err_codes:
if args.find(err_code) != -1:
return True
return False
def get_engine(config_group):
"""Return a SQLAlchemy engine."""
global _ENGINES
database_connection = cfg.CONF[config_group].database_connection
if config_group not in _ENGINES:
connection_dict = sqlalchemy.engine.url.make_url(
database_connection)
engine_args = {
"pool_recycle": cfg.CONF[config_group].idle_timeout,
"echo": False,
'convert_unicode': True,
}
# Map our SQL debug level to SQLAlchemy's options
if cfg.CONF[config_group].connection_debug >= 100:
engine_args['echo'] = 'debug'
elif cfg.CONF[config_group].connection_debug >= 50:
engine_args['echo'] = True
if "sqlite" in connection_dict.drivername:
engine_args["poolclass"] = NullPool
if database_connection == "sqlite://":
engine_args["poolclass"] = StaticPool
engine_args["connect_args"] = {'check_same_thread': False}
_ENGINES[config_group] = sqlalchemy.create_engine(database_connection,
**engine_args)
if 'mysql' in connection_dict.drivername:
sqlalchemy.event.listen(_ENGINES[config_group],
'checkout',
ping_listener)
elif "sqlite" in connection_dict.drivername:
if not cfg.CONF[config_group].sqlite_synchronous:
sqlalchemy.event.listen(_ENGINES[config_group],
'connect',
synchronous_switch_listener)
sqlalchemy.event.listen(_ENGINES[config_group],
'connect',
add_regexp_listener)
if (cfg.CONF[config_group].connection_trace and
_ENGINES[config_group].dialect.dbapi.__name__ == 'MySQLdb'):
import MySQLdb.cursors
_do_query = debug_mysql_do_query()
setattr(MySQLdb.cursors.BaseCursor, '_do_query', _do_query)
try:
_ENGINES[config_group].connect()
except OperationalError, e:
if not is_db_connection_error(e.args[0]):
raise
remaining = cfg.CONF[config_group].max_retries
if remaining == -1:
remaining = 'infinite'
while True:
msg = _('SQL connection failed. %s attempts left.')
LOG.warn(msg % remaining)
if remaining != 'infinite':
remaining -= 1
time.sleep(cfg.CONF[config_group].retry_interval)
try:
_ENGINES[config_group].connect()
break
except OperationalError, e:
if (remaining != 'infinite' and remaining == 0) or \
not is_db_connection_error(e.args[0]):
raise
return _ENGINES[config_group]
def get_maker(engine, autocommit=True, expire_on_commit=False, autoflush=True):
"""Return a SQLAlchemy sessionmaker using the given engine."""
return sqlalchemy.orm.sessionmaker(bind=engine,
autocommit=autocommit,
autoflush=autoflush,
expire_on_commit=expire_on_commit)
def debug_mysql_do_query():
"""Return a debug version of MySQLdb.cursors._do_query"""
import MySQLdb.cursors
import traceback
old_mysql_do_query = MySQLdb.cursors.BaseCursor._do_query
def _do_query(self, q):
stack = ''
for file, line, method, function in traceback.extract_stack():
# exclude various common things from trace
if file.endswith('session.py') and method == '_do_query':
continue
if file.endswith('api.py') and method == 'wrapper':
continue
if file.endswith('utils.py') and method == '_inner':
continue
if file.endswith('exception.py') and method == '_wrap':
continue
# nova/db/api is just a wrapper around nova/db/sqlalchemy/api
if file.endswith('nova/db/api.py'):
continue
# only trace inside nova
index = file.rfind('nova')
if index == -1:
continue
stack += "File:%s:%s Method:%s() Line:%s | " \
% (file[index:], line, method, function)
# strip trailing " | " from stack
if stack:
stack = stack[:-3]
qq = "%s /* %s */" % (q, stack)
else:
qq = q
old_mysql_do_query(self, qq)
# return the new _do_query method
return _do_query