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#!/usr/bin/python2.6 -S
# Copyright 2011-2012 Canonical Ltd. This software is licensed under the
# GNU Affero General Public License version 3 (see the file LICENSE).
"""Confirm the database systems are ready to be patched as best we can."""
__all__ = [
'DatabasePreflight',
'KillConnectionsPreflight',
'NoConnectionCheckPreflight',
]
import _pythonpath
from datetime import timedelta
from optparse import OptionParser
import os.path
import time
import psycopg2
from lp.services.database.sqlbase import (
connect,
ISOLATION_LEVEL_AUTOCOMMIT,
sqlvalues,
)
from lp.services.scripts import (
db_options,
logger,
logger_options,
)
import replication.helpers
import upgrade
# Ignore connections by these users.
SYSTEM_USERS = frozenset(['postgres', 'slony', 'nagios', 'lagmon'])
# Fail checks if these users are connected. If a process should not be
# interrupted by a rollout, the database user it connects as should be
# added here. The preflight check will fail if any of these users are
# connected, so these systems will need to be shut down manually before
# a database update.
FRAGILE_USERS = frozenset([
'buildd_manager',
# process_accepted is fragile, but also fast so we likely shouldn't
# need to ever manually shut it down.
'process_accepted',
'process_upload',
'publish_distro',
'publish_ftpmaster',
])
# If these users have long running transactions, just kill 'em. Entries
# added here must come with a bug number, a if part of Launchpad holds
# open a long running transaction it is a bug we need to fix.
BAD_USERS = frozenset([
'karma', # Bug #863109
'rosettaadmin', # Bug #863122
'update-pkg-cache', # Bug #912144
'process_death_row', # Bug #912146
'langpack', # Bug #912147
])
# How lagged the cluster can be before failing the preflight check.
# If this is set too low, perfectly normal state will abort rollouts. If
# this is set too high, then we will have unacceptable downtime as
# replication needs to catch up before the database patches will apply.
MAX_LAG = timedelta(seconds=60)
class DatabasePreflight:
def __init__(self, log):
master_con = connect(isolation=ISOLATION_LEVEL_AUTOCOMMIT)
self.log = log
self.is_replicated = replication.helpers.slony_installed(master_con)
if self.is_replicated:
self.nodes = set(
replication.helpers.get_all_cluster_nodes(master_con))
for node in self.nodes:
node.con = psycopg2.connect(node.connection_string)
node.con.set_isolation_level(ISOLATION_LEVEL_AUTOCOMMIT)
# Create a list of nodes subscribed to the replicated sets we
# are modifying.
cur = master_con.cursor()
cur.execute("""
WITH subscriptions AS (
SELECT *
FROM _sl.sl_subscribe
WHERE sub_set = 1 AND sub_active IS TRUE)
SELECT sub_provider FROM subscriptions
UNION
SELECT sub_receiver FROM subscriptions
""")
lpmain_node_ids = set(row[0] for row in cur.fetchall())
self.lpmain_nodes = set(
node for node in self.nodes
if node.node_id in lpmain_node_ids)
# Store a reference to the lpmain origin.
lpmain_master_node_id = replication.helpers.get_master_node(
master_con, 1).node_id
self.lpmain_master_node = [
node for node in self.lpmain_nodes
if node.node_id == lpmain_master_node_id][0]
else:
node = replication.helpers.Node(None, None, None, True)
node.con = master_con
self.nodes = set([node])
self.lpmain_nodes = self.nodes
self.lpmain_master_node = node
def check_is_superuser(self):
"""Return True if all the node connections are as superusers."""
success = True
for node in self.nodes:
cur = node.con.cursor()
cur.execute("""
SELECT current_database(), pg_user.usesuper
FROM pg_user
WHERE usename = current_user
""")
dbname, is_super = cur.fetchone()
if is_super:
self.log.debug("Connected to %s as a superuser.", dbname)
else:
self.log.fatal("Not connected to %s as a superuser.", dbname)
success = False
return success
def check_open_connections(self):
"""False if any lpmain nodes have connections from non-system users.
We only check on subscribed nodes, as there will be active systems
connected to other nodes in the replication cluster (such as the
SSO servers).
System users are defined by SYSTEM_USERS.
"""
success = True
for node in self.lpmain_nodes:
cur = node.con.cursor()
cur.execute("""
SELECT datname, usename, COUNT(*) AS num_connections
FROM pg_stat_activity
WHERE
datname=current_database()
AND procpid <> pg_backend_pid()
GROUP BY datname, usename
""")
for datname, usename, num_connections in cur.fetchall():
if usename in SYSTEM_USERS:
self.log.debug(
"%s has %d connections by %s",
datname, num_connections, usename)
else:
self.log.fatal(
"%s has %d connections by %s",
datname, num_connections, usename)
success = False
if success:
self.log.info("Only system users connected to the cluster")
return success
def check_fragile_connections(self):
"""Fail if any FRAGILE_USERS are connected to the cluster.
If we interrupt these processes, we may have a mess to clean
up. If they are connected, the preflight check should fail.
"""
success = True
for node in self.lpmain_nodes:
cur = node.con.cursor()
cur.execute("""
SELECT datname, usename, COUNT(*) AS num_connections
FROM pg_stat_activity
WHERE
datname=current_database()
AND procpid <> pg_backend_pid()
AND usename IN %s
GROUP BY datname, usename
""" % sqlvalues(FRAGILE_USERS))
for datname, usename, num_connections in cur.fetchall():
self.log.fatal(
"Fragile system %s running. %s has %d connections.",
usename, datname, num_connections)
success = False
if success:
self.log.info(
"No fragile systems connected to the cluster (%s)"
% ', '.join(FRAGILE_USERS))
return success
def check_long_running_transactions(self, max_secs=60):
"""Return False if any nodes have long running transactions open.
max_secs defines what is long running. For database rollouts,
this will be short. Even if the transaction is benign like a
autovacuum task, we should wait until things have settled down.
We ignore transactions held open by BAD_USERS. These are bugs
that need to be fixed, but we have determined that rudely aborting
them is fine for now and there is no need to block a rollout on
their behalf.
"""
success = True
for node in self.nodes:
cur = node.con.cursor()
cur.execute("""
SELECT
datname, usename,
age(current_timestamp, xact_start) AS age, current_query
FROM pg_stat_activity
WHERE
age(current_timestamp, xact_start) > interval '%d secs'
AND datname=current_database()
""" % max_secs)
for datname, usename, age, current_query in cur.fetchall():
if usename in BAD_USERS:
self.log.info(
"%s has transactions by %s open %s (ignoring)",
datname, usename, age)
else:
self.log.fatal(
"%s has transaction by %s open %s",
datname, usename, age)
success = False
if success:
self.log.info("No long running transactions detected.")
return success
def check_replication_lag(self):
"""Return False if the replication cluster is badly lagged."""
if not self.is_replicated:
self.log.debug("Not replicated - no replication lag.")
return True
# Check replication lag on every node just in case there are
# disagreements.
max_lag = timedelta(seconds=-1)
for node in self.nodes:
cur = node.con.cursor()
cur.execute("""
SELECT current_database(),
max(st_lag_time) AS lag FROM _sl.sl_status
""")
dbname, lag = cur.fetchone()
if lag > max_lag:
max_lag = lag
self.log.debug(
"%s reports database lag of %s.", dbname, lag)
if max_lag <= MAX_LAG:
self.log.info("Database cluster lag is ok (%s)", max_lag)
return True
else:
self.log.fatal("Database cluster lag is high (%s)", max_lag)
return False
def check_can_sync(self):
"""Return True if a sync event is acknowledged by all nodes.
We only wait 30 seconds for the sync, because we require the
cluster to be quiescent.
"""
if self.is_replicated:
success = replication.helpers.sync(30, exit_on_fail=False)
if success:
self.log.info(
"Replication events are being propagated.")
else:
self.log.fatal(
"Replication events are not being propagated.")
self.log.fatal(
"One or more replication daemons may be down.")
self.log.fatal(
"Bounce the replication daemons and check the logs.")
return success
else:
return True
def report_patches(self):
"""Report what patches are due to be applied from this tree."""
con = self.lpmain_master_node.con
upgrade.log = self.log
for patch_num, patch_file in upgrade.get_patchlist(con):
self.log.info("%s is pending", os.path.basename(patch_file))
def check_all(self):
"""Run all checks.
If any failed, return False. Otherwise return True.
"""
if not self.check_is_superuser():
# No point continuing - results will be bogus without access
# to pg_stat_activity
return False
self.report_patches()
success = True
if not self.check_replication_lag():
success = False
if not self.check_can_sync():
success = False
# Do checks on open transactions last to minimize race
# conditions.
if not self.check_open_connections():
success = False
if not self.check_long_running_transactions():
success = False
if not self.check_fragile_connections():
success = False
return success
class NoConnectionCheckPreflight(DatabasePreflight):
def check_open_connections(self):
return True
class KillConnectionsPreflight(DatabasePreflight):
def check_open_connections(self):
"""Kill all non-system connections to Launchpad databases.
We only check on subscribed nodes, as there will be active systems
connected to other nodes in the replication cluster (such as the
SSO servers).
System users are defined by SYSTEM_USERS.
"""
# We keep trying to terminate connections every 0.5 seconds for
# up to 10 seconds.
num_tries = 20
seconds_to_pause = 0.5
for loop_count in range(num_tries):
all_clear = True
for node in self.lpmain_nodes:
cur = node.con.cursor()
cur.execute("""
SELECT
procpid, datname, usename,
pg_terminate_backend(procpid)
FROM pg_stat_activity
WHERE
datname=current_database()
AND procpid <> pg_backend_pid()
AND usename NOT IN %s
""" % sqlvalues(SYSTEM_USERS))
for procpid, datname, usename, ignored in cur.fetchall():
all_clear = False
if loop_count == num_tries - 1:
self.log.fatal(
"Unable to kill %s [%s] on %s",
usename, procpid, datname)
elif usename in BAD_USERS:
self.log.info(
"Killed %s [%s] on %s", usename, procpid, datname)
else:
self.log.warning(
"Killed %s [%s] on %s", usename, procpid, datname)
if all_clear:
break
# Wait a little for any terminated connections to actually
# terminate.
time.sleep(seconds_to_pause)
return all_clear
def main():
parser = OptionParser()
db_options(parser)
logger_options(parser)
parser.add_option(
"--skip-connection-check", dest='skip_connection_check',
default=False, action="store_true",
help="Don't check open connections.")
parser.add_option(
"--kill-connections", dest='kill_connections',
default=False, action="store_true",
help="Kill non-system connections instead of reporting an error.")
(options, args) = parser.parse_args()
if args:
parser.error("Too many arguments")
if options.kill_connections and options.skip_connection_check:
parser.error(
"--skip-connection-check conflicts with --kill-connections")
log = logger(options)
if options.kill_connections:
preflight_check = KillConnectionsPreflight(log)
elif options.skip_connection_check:
preflight_check = NoConnectionCheckPreflight(log)
else:
preflight_check = DatabasePreflight(log)
if preflight_check.check_all():
log.info('Preflight check succeeded. Good to go.')
return 0
else:
log.error('Preflight check failed.')
return 1
if __name__ == '__main__':
raise SystemExit(main())
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