def mysql_failover(master, dry_run, skip_lock,
ignore_dr_slave, trust_me_its_dead, kill_old_master):
""" Promte a new MySQL master
Args:
master - Hostaddr object of the master instance to be demoted
dry_run - Do not change state, just do sanity testing and exit
skip_lock - Do not take a promotion lock
ignore_dr_slave - Ignore the existance of a dr_slave
trust_me_its_dead - Do not test to see if the master is dead
kill_old_master - Send a mysqladmin kill command to the old master
Returns:
new_master - The new master server
"""
log.info('Master to demote is {master}'.format(master=master))
zk = host_utils.MysqlZookeeper()
(replica_set, _) = zk.get_replica_set_from_instance(master, rtypes=['master'])
log.info('Replica set is detected as '
'{replica_set}'.format(replica_set=replica_set))
# take a lock here to make sure nothing changes underneath us
if not skip_lock and not dry_run:
log.info('Taking promotion lock on replica set')
lock_identifier = get_promotion_lock(replica_set)
else:
lock_identifier = None
# giant try. If there any problems we roll back from the except
try:
master_conn = False
slave = zk.get_mysql_instance_from_replica_set(replica_set=replica_set,
repl_type=host_utils.REPLICA_ROLE_SLAVE)
log.info('Slave/new master is detected as {slave}'.format(slave=slave))
if ignore_dr_slave:
log.info('Intentionally ignoring a dr_slave')
dr_slave = None
else:
dr_slave = zk.get_mysql_instance_from_replica_set(replica_set,
host_utils.REPLICA_ROLE_DR_SLAVE)
log.info('DR slave is detected as {dr_slave}'.format(dr_slave=dr_slave))
if dr_slave:
if dr_slave == slave:
raise Exception('Slave and dr_slave appear to be the same')
replicas = set([slave, dr_slave])
else:
replicas = set([slave])
# let's make sure that what we think is the master, actually is
confirm_replica_topology(master, replicas)
# We use master_conn as a mysql connection to the master server, if
# it is False, the master is dead
if trust_me_its_dead:
master_conn = None
else:
master_conn = is_master_alive(master, replicas)
slave_conn = mysql_lib.connect_mysql(slave)
# Test to see if the slave is setup for replication. If not, we are hosed
log.info('Testing to see if Slave/new master is setup to write '
'replication logs')
try:
mysql_lib.get_master_status(slave_conn)
except mysql_lib.ReplicationError:
log.error('New master {slave} is not setup to write replicaiton '
'logs!'.format(slave=slave))
raise
log.info('Slave/new master is setup to write replication logs')
if kill_old_master:
log.info('Killing old master, we hope you know what you are doing')
mysql_lib.shutdown_mysql(master)
master_conn = None
if master_conn:
log.info('Master is considered alive')
dead_master = False
confirm_max_replica_lag(replicas, MAX_ALIVE_MASTER_SLAVE_LAG_SECONDS,
dead_master=dead_master)
else:
log.info('Master is considered dead')
dead_master = True
confirm_max_replica_lag(replicas, MAX_DEAD_MASTER_SLAVE_LAG_SECONDS,
dead_master=dead_master)
if dry_run:
log.info('In dry_run mode, so exiting now')
# Using os._exit in order to not get catch in the giant try
os._exit(0)
log.info('Preliminary sanity checks complete, starting promotion')
if master_conn:
log.info('Setting read_only on master')
mysql_lib.set_global_variable(master_conn, 'read_only', True)
log.info('Confirming no writes to old master')
# If there are writes with the master in read_only mode then the
# promotion can not proceed.
# A likely reason is a client has the SUPER privilege.
confirm_no_writes(master_conn)
log.info('Waiting for replicas to be caught up')
confirm_max_replica_lag(replicas, 0,
timeout=MAX_ALIVE_MASTER_SLAVE_LAG_SECONDS,
dead_master=dead_master)
log.info('Setting up replication from old master ({master})'
'to new master ({slave})'.format(master=master,
slave=slave))
mysql_lib.setup_replication(new_master=slave, new_replica=master)
else:
log.info('Starting up a zk connection to make sure we can connect')
kazoo_client = environment_specific.get_kazoo_client()
if not kazoo_client:
raise Exception('Could not conect to zk')
log.info('Confirming replica has processed all replication '
' logs')
confirm_no_writes(slave_conn)
log.info('Looks like no writes being processed by replica via '
'replication or other means')
if len(replicas) > 1:
log.info('Confirming relpica servers in sync')
confirm_max_replica_lag(replicas, MAX_DEAD_MASTER_SLAVE_LAG_SECONDS,
replicas_synced=True,
dead_master=dead_master)
except:
log.info('Starting rollback')
if master_conn:
log.info('Releasing read_only on old master')
mysql_lib.set_global_variable(master_conn, 'read_only', False)
log.info('Clearing replication settings on old master')
mysql_lib.reset_slave(master_conn)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Rollback complete, reraising exception')
raise
if dr_slave:
try:
mysql_lib.setup_replication(new_master=slave, new_replica=dr_slave)
except Exception as e:
log.error(e)
log.error('Setting up replication on the dr_slave failed. '
'Failing forward!')
log.info('Updating zk')
zk_write_attempt = 0
while True:
try:
modify_mysql_zk.swap_master_and_slave(slave, dry_run=False)
break
except:
if zk_write_attempt > MAX_ZK_WRITE_ATTEMPTS:
log.info('Final failure writing to zk, bailing')
raise
else:
log.info('Write to zk failed, trying again')
zk_write_attempt = zk_write_attempt+1
log.info('Removing read_only from new master')
mysql_lib.set_global_variable(slave_conn, 'read_only', False)
log.info('Removing replication configuration from new master')
mysql_lib.reset_slave(slave_conn)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Failover complete')
if not master_conn:
log.info('As master is dead, will try to launch a replacement. Will '
'sleep 20 seconds first to let things settle')
time.sleep(20)
launch_replacement_db_host.launch_replacement_db_host(master)
def mysql_failover(master, dry_run, skip_lock, ignore_dr_slave,
trust_me_its_dead, kill_old_master):
""" Promote a new MySQL master
Args:
master - Hostaddr object of the master instance to be demoted
dry_run - Do not change state, just do sanity testing and exit
skip_lock - Do not take a promotion lock
ignore_dr_slave - Ignore the existance of a dr_slave
trust_me_its_dead - Do not test to see if the master is dead
kill_old_master - Send a mysqladmin kill command to the old master
Returns:
new_master - The new master server
"""
log.info('Master to demote is {master}'.format(master=master))
zk = host_utils.MysqlZookeeper()
(replica_set, _) = zk.get_replica_set_from_instance(master,
rtypes=['master'])
log.info('Replica set is detected as '
'{replica_set}'.format(replica_set=replica_set))
# take a lock here to make sure nothing changes underneath us
if not skip_lock and not dry_run:
log.info('Taking promotion lock on replica set')
lock_identifier = get_promotion_lock(replica_set)
else:
lock_identifier = None
# giant try. If there any problems we roll back from the except
try:
master_conn = False
slave = zk.get_mysql_instance_from_replica_set(
replica_set=replica_set, repl_type=host_utils.REPLICA_ROLE_SLAVE)
log.info('Slave/new master is detected as {slave}'.format(slave=slave))
if ignore_dr_slave:
log.info('Intentionally ignoring a dr_slave')
dr_slave = None
else:
dr_slave = zk.get_mysql_instance_from_replica_set(
replica_set, host_utils.REPLICA_ROLE_DR_SLAVE)
log.info(
'DR slave is detected as {dr_slave}'.format(dr_slave=dr_slave))
if dr_slave:
if dr_slave == slave:
raise Exception('Slave and dr_slave appear to be the same')
replicas = set([slave, dr_slave])
else:
replicas = set([slave])
# We use master_conn as a mysql connection to the master server, if
# it is False, the master is dead
if trust_me_its_dead:
master_conn = None
else:
master_conn = is_master_alive(master, replicas)
# Test to see if the slave is setup for replication. If not, we are hosed
log.info('Testing to see if Slave/new master is setup to write '
'replication logs')
mysql_lib.get_master_status(slave)
if kill_old_master and not dry_run:
log.info('Killing old master, we hope you know what you are doing')
mysql_lib.shutdown_mysql(master)
master_conn = None
if master_conn:
log.info('Master is considered alive')
dead_master = False
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_NORMAL,
dead_master)
else:
log.info('Master is considered dead')
dead_master = True
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_LOOSE,
dead_master)
if dry_run:
log.info('In dry_run mode, so exiting now')
# Using os._exit in order to not get catch in the giant try
os._exit(environment_specific.DRY_RUN_EXIT_CODE)
log.info('Preliminary sanity checks complete, starting promotion')
if master_conn:
log.info('Setting read_only on master')
mysql_lib.set_global_variable(master, 'read_only', True)
log.info('Confirming no writes to old master')
# If there are writes with the master in read_only mode then the
# promotion can not proceed.
# A likely reason is a client has the SUPER privilege.
confirm_no_writes(master)
log.info('Waiting for replicas to be caught up')
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_NONE,
dead_master, True,
mysql_lib.NORMAL_HEARTBEAT_LAG)
log.info('Setting up replication from old master ({master}) '
'to new master ({slave})'.format(master=master,
slave=slave))
mysql_lib.setup_replication(new_master=slave, new_replica=master)
else:
log.info('Starting up a zk connection to make sure we can connect')
kazoo_client = environment_specific.get_kazoo_client()
if not kazoo_client:
raise Exception('Could not conect to zk')
log.info('Confirming replica has processed all replication '
' logs')
confirm_no_writes(slave)
log.info('Looks like no writes being processed by replica via '
'replication or other means')
if len(replicas) > 1:
log.info('Confirming replica servers are synced')
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_LOOSE,
dead_master, True)
except:
log.info('Starting rollback')
if master_conn:
log.info('Releasing read_only on old master')
mysql_lib.set_global_variable(master, 'read_only', False)
log.info('Clearing replication settings on old master')
mysql_lib.reset_slave(master)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Rollback complete, reraising exception')
raise
if dr_slave:
try:
mysql_lib.setup_replication(new_master=slave, new_replica=dr_slave)
except Exception as e:
log.error(e)
log.error('Setting up replication on the dr_slave failed. '
'Failing forward!')
log.info('Updating zk')
zk_write_attempt = 0
while True:
try:
modify_mysql_zk.swap_master_and_slave(slave, dry_run=False)
break
except:
if zk_write_attempt > MAX_ZK_WRITE_ATTEMPTS:
log.info('Final failure writing to zk, bailing')
raise
else:
log.info('Write to zk failed, trying again')
zk_write_attempt = zk_write_attempt + 1
log.info('Removing read_only from new master')
mysql_lib.set_global_variable(slave, 'read_only', False)
log.info('Removing replication configuration from new master')
mysql_lib.reset_slave(slave)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Failover complete')
# we don't really care if this fails, but we'll print a message anyway.
try:
environment_specific.generic_json_post(
environment_specific.CHANGE_FEED_URL, {
'type': 'MySQL Failover',
'environment': replica_set,
'description': "Failover from {m} to {s}".format(m=master,
s=slave),
'author': host_utils.get_user(),
'automation': False,
'source': "mysql_failover.py on {}".format(host_utils.HOSTNAME)
})
except Exception as e:
log.warning("Failover completed, but change feed "
"not updated: {}".format(e))
if not master_conn:
log.info('As master is dead, will try to launch a replacement. Will '
'sleep 20 seconds first to let things settle')
time.sleep(20)
launch_replacement_db_host.launch_replacement_db_host(master)
def finish_shard_migration(source_replica_set,
dry_run=False,
confirm_row_counts=True):
""" Run a partial failover to finish a migration
Args:
source_replica_set - The source replica set for the migration
dry_run - Just run verifications, do not failover shards
confirm_row_counts - If true, confirm row counts of slaves, otherwise
check estimated row counts
"""
if host_utils.get_security_role(
) not in environment_specific.ROLE_TO_MIGRATE:
raise Exception(environment_specific.ROLE_ERROR_MSG)
# Figure out what we are working on based on the lock present on the
# source_replica_set
migration = start_shard_migration.check_migration_lock(source_replica_set)
if migration['status'] != start_shard_migration.STATUS_FAILOVER_READY:
raise Exception('Migration is not ready to run')
destination_replica_set = migration['destination_replica_set']
source_replica_set = migration['source_replica_set']
mig_databases = set(migration['mig_databases'].split(', '))
non_mig_databases = set(migration['non_mig_databases'].split(', '))
mig_lock_identifier = migration['lock_identifier']
# Figure out some more data based on the lock
zk = host_utils.MysqlZookeeper()
source_master = zk.get_mysql_instance_from_replica_set(source_replica_set)
destination_master = zk.get_mysql_instance_from_replica_set(
destination_replica_set)
log.info('Will migrate {dbs} from {s} to {d}'
''.format(dbs=mig_databases,
s=source_replica_set,
d=destination_replica_set))
try:
dest_lock_identifier = None
src_lock_identifier = None
read_only_set = False
if not dry_run:
log.info('Taking promotion locks')
dest_lock_identifier = mysql_failover.get_promotion_lock(
destination_replica_set)
src_lock_identifier = mysql_failover.get_promotion_lock(
source_replica_set)
# Check replication
log.info('Checking replication')
check_replication_for_migration(source_replica_set,
destination_replica_set)
# Check schema and data
log.info('Checking schema and row counts')
verify_schema_for_migration(source_replica_set,
destination_replica_set, mig_databases,
confirm_row_counts)
log.info('Confirming that no real tables exists on blackhole dbs')
verify_blackhole_dbs(destination_master, non_mig_databases)
if dry_run:
log.info('In dry_run mode, existing now')
os._exit(environment_specific.DRY_RUN_EXIT_CODE)
log.info('Preliminary sanity checks complete, starting migration')
log.info('Setting read_only on master servers')
read_only_set = True
mysql_lib.set_global_variable(source_master, 'read_only', True)
# We don't strictly need to set read_only on the destination_master
# but it seems sane out of paranoia
mysql_lib.set_global_variable(destination_master, 'read_only', True)
log.info('Confirming no writes to old master')
mysql_failover.confirm_no_writes(source_master)
log.info('Waiting for replicas to be caught up')
wait_for_repl_sync(destination_master)
log.info('Breaking replication from source to destination')
mysql_lib.reset_slave(destination_master)
log.info('Renaming migrated dbs on source master')
fix_orphaned_shards.rename_db_to_drop(source_master,
mig_databases,
skip_check=True)
log.info('Modifying shard mapping')
migrate_shard_mapping(source_replica_set, destination_replica_set,
mig_databases)
log.info('Dropping blackhole dbs on destination')
for db in non_mig_databases:
mysql_lib.drop_db(destination_master, db)
start_shard_migration.finish_migration_log(
mig_lock_identifier, start_shard_migration.STATUS_FINISHED)
except:
raise
finally:
if read_only_set:
log.info('Remove read_only settings')
mysql_lib.set_global_variable(source_master, 'read_only', False)
mysql_lib.set_global_variable(destination_master, 'read_only',
False)
if dest_lock_identifier:
log.info('Releasing destination promotion lock')
mysql_failover.release_promotion_lock(dest_lock_identifier)
if src_lock_identifier:
log.info('Releasing source promotion lock')
mysql_failover.release_promotion_lock(src_lock_identifier)
# No exception got reraised in the the except, things must have worked
log.info('To drop migrated dbs on source, wait a bit and then run:')
log.info('/usr/local/bin/mysql_utils/fix_orphaned_shards.py -a '
'drop -i {}'.format(source_master))
def mysql_failover(master, dry_run, skip_lock, ignore_dr_slave,
trust_me_its_dead, kill_old_master):
""" Promte a new MySQL master
Args:
master - Hostaddr object of the master instance to be demoted
dry_run - Do not change state, just do sanity testing and exit
skip_lock - Do not take a promotion lock
ignore_dr_slave - Ignore the existance of a dr_slave
trust_me_its_dead - Do not test to see if the master is dead
kill_old_master - Send a mysqladmin kill command to the old master
Returns:
new_master - The new master server
"""
log.info('Master to demote is {master}'.format(master=master))
zk = host_utils.MysqlZookeeper()
(replica_set, _) = zk.get_replica_set_from_instance(master,
rtypes=['master'])
log.info('Replica set is detected as '
'{replica_set}'.format(replica_set=replica_set))
# take a lock here to make sure nothing changes underneath us
if not skip_lock and not dry_run:
log.info('Taking promotion lock on replica set')
lock_identifier = get_promotion_lock(replica_set)
else:
lock_identifier = None
# giant try. If there any problems we roll back from the except
try:
master_conn = False
slave = zk.get_mysql_instance_from_replica_set(
replica_set=replica_set, repl_type=host_utils.REPLICA_ROLE_SLAVE)
log.info('Slave/new master is detected as {slave}'.format(slave=slave))
if ignore_dr_slave:
log.info('Intentionally ignoring a dr_slave')
dr_slave = None
else:
dr_slave = zk.get_mysql_instance_from_replica_set(
replica_set, host_utils.REPLICA_ROLE_DR_SLAVE)
log.info(
'DR slave is detected as {dr_slave}'.format(dr_slave=dr_slave))
if dr_slave:
if dr_slave == slave:
raise Exception('Slave and dr_slave appear to be the same')
replicas = set([slave, dr_slave])
else:
replicas = set([slave])
# let's make sure that what we think is the master, actually is
confirm_replica_topology(master, replicas)
# We use master_conn as a mysql connection to the master server, if
# it is False, the master is dead
if trust_me_its_dead:
master_conn = None
else:
master_conn = is_master_alive(master, replicas)
slave_conn = mysql_lib.connect_mysql(slave)
# Test to see if the slave is setup for replication. If not, we are hosed
log.info('Testing to see if Slave/new master is setup to write '
'replication logs')
try:
mysql_lib.get_master_status(slave_conn)
except mysql_lib.ReplicationError:
log.error('New master {slave} is not setup to write replicaiton '
'logs!'.format(slave=slave))
raise
log.info('Slave/new master is setup to write replication logs')
if kill_old_master:
log.info('Killing old master, we hope you know what you are doing')
mysql_lib.shutdown_mysql(master)
master_conn = None
if master_conn:
log.info('Master is considered alive')
dead_master = False
confirm_max_replica_lag(replicas,
MAX_ALIVE_MASTER_SLAVE_LAG_SECONDS,
dead_master=dead_master)
else:
log.info('Master is considered dead')
dead_master = True
confirm_max_replica_lag(replicas,
MAX_DEAD_MASTER_SLAVE_LAG_SECONDS,
dead_master=dead_master)
if dry_run:
log.info('In dry_run mode, so exiting now')
# Using os._exit in order to not get catch in the giant try
os._exit(0)
log.info('Preliminary sanity checks complete, starting promotion')
if master_conn:
log.info('Setting read_only on master')
mysql_lib.set_global_variable(master_conn, 'read_only', True)
log.info('Confirming no writes to old master')
# If there are writes with the master in read_only mode then the
# promotion can not proceed.
# A likely reason is a client has the SUPER privilege.
confirm_no_writes(master_conn)
log.info('Waiting for replicas to be caught up')
confirm_max_replica_lag(replicas,
0,
timeout=MAX_ALIVE_MASTER_SLAVE_LAG_SECONDS,
dead_master=dead_master)
log.info('Setting up replication from old master ({master})'
'to new master ({slave})'.format(master=master,
slave=slave))
mysql_lib.setup_replication(new_master=slave, new_replica=master)
else:
log.info('Starting up a zk connection to make sure we can connect')
kazoo_client = environment_specific.get_kazoo_client()
if not kazoo_client:
raise Exception('Could not conect to zk')
log.info('Confirming replica has processed all replication '
' logs')
confirm_no_writes(slave_conn)
log.info('Looks like no writes being processed by replica via '
'replication or other means')
if len(replicas) > 1:
log.info('Confirming relpica servers in sync')
confirm_max_replica_lag(replicas,
MAX_DEAD_MASTER_SLAVE_LAG_SECONDS,
replicas_synced=True,
dead_master=dead_master)
except:
log.info('Starting rollback')
if master_conn:
log.info('Releasing read_only on old master')
mysql_lib.set_global_variable(master_conn, 'read_only', False)
log.info('Clearing replication settings on old master')
mysql_lib.reset_slave(master_conn)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Rollback complete, reraising exception')
raise
if dr_slave:
try:
mysql_lib.setup_replication(new_master=slave, new_replica=dr_slave)
except Exception as e:
log.error(e)
log.error('Setting up replication on the dr_slave failed. '
'Failing forward!')
log.info('Updating zk')
zk_write_attempt = 0
while True:
try:
modify_mysql_zk.swap_master_and_slave(slave, dry_run=False)
break
except:
if zk_write_attempt > MAX_ZK_WRITE_ATTEMPTS:
log.info('Final failure writing to zk, bailing')
raise
else:
log.info('Write to zk failed, trying again')
zk_write_attempt = zk_write_attempt + 1
log.info('Removing read_only from new master')
mysql_lib.set_global_variable(slave_conn, 'read_only', False)
log.info('Removing replication configuration from new master')
mysql_lib.reset_slave(slave_conn)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Failover complete')
if not master_conn:
log.info('As master is dead, will try to launch a replacement. Will '
'sleep 20 seconds first to let things settle')
time.sleep(20)
launch_replacement_db_host.launch_replacement_db_host(master)
def mysql_failover(master, dry_run, skip_lock,
ignore_dr_slave, trust_me_its_dead, kill_old_master):
""" Promote a new MySQL master
Args:
master - Hostaddr object of the master instance to be demoted
dry_run - Do not change state, just do sanity testing and exit
skip_lock - Do not take a promotion lock
ignore_dr_slave - Ignore the existance of a dr_slave
trust_me_its_dead - Do not test to see if the master is dead
kill_old_master - Send a mysqladmin kill command to the old master
Returns:
new_master - The new master server
"""
log.info('Master to demote is {master}'.format(master=master))
zk = host_utils.MysqlZookeeper()
(replica_set, _) = zk.get_replica_set_from_instance(master, rtypes=['master'])
log.info('Replica set is detected as '
'{replica_set}'.format(replica_set=replica_set))
# take a lock here to make sure nothing changes underneath us
if not skip_lock and not dry_run:
log.info('Taking promotion lock on replica set')
lock_identifier = get_promotion_lock(replica_set)
else:
lock_identifier = None
# giant try. If there any problems we roll back from the except
try:
master_conn = False
slave = zk.get_mysql_instance_from_replica_set(replica_set=replica_set,
repl_type=host_utils.REPLICA_ROLE_SLAVE)
log.info('Slave/new master is detected as {slave}'.format(slave=slave))
if ignore_dr_slave:
log.info('Intentionally ignoring a dr_slave')
dr_slave = None
else:
dr_slave = zk.get_mysql_instance_from_replica_set(replica_set,
host_utils.REPLICA_ROLE_DR_SLAVE)
log.info('DR slave is detected as {dr_slave}'.format(dr_slave=dr_slave))
if dr_slave:
if dr_slave == slave:
raise Exception('Slave and dr_slave appear to be the same')
replicas = set([slave, dr_slave])
else:
replicas = set([slave])
# We use master_conn as a mysql connection to the master server, if
# it is False, the master is dead
if trust_me_its_dead:
master_conn = None
else:
master_conn = is_master_alive(master, replicas)
# Test to see if the slave is setup for replication. If not, we are hosed
log.info('Testing to see if Slave/new master is setup to write '
'replication logs')
mysql_lib.get_master_status(slave)
if kill_old_master and not dry_run:
log.info('Killing old master, we hope you know what you are doing')
mysql_lib.shutdown_mysql(master)
master_conn = None
if master_conn:
log.info('Master is considered alive')
dead_master = False
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_NORMAL,
dead_master)
else:
log.info('Master is considered dead')
dead_master = True
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_LOOSE,
dead_master)
if dry_run:
log.info('In dry_run mode, so exiting now')
# Using os._exit in order to not get catch in the giant try
os._exit(environment_specific.DRY_RUN_EXIT_CODE)
log.info('Preliminary sanity checks complete, starting promotion')
if master_conn:
log.info('Setting read_only on master')
mysql_lib.set_global_variable(master, 'read_only', True)
log.info('Confirming no writes to old master')
# If there are writes with the master in read_only mode then the
# promotion can not proceed.
# A likely reason is a client has the SUPER privilege.
confirm_no_writes(master)
log.info('Waiting for replicas to be caught up')
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_NONE,
dead_master,
True,
mysql_lib.NORMAL_HEARTBEAT_LAG)
log.info('Setting up replication from old master ({master}) '
'to new master ({slave})'.format(master=master,
slave=slave))
mysql_lib.setup_replication(new_master=slave, new_replica=master)
else:
log.info('Starting up a zk connection to make sure we can connect')
kazoo_client = environment_specific.get_kazoo_client()
if not kazoo_client:
raise Exception('Could not conect to zk')
log.info('Confirming replica has processed all replication '
' logs')
confirm_no_writes(slave)
log.info('Looks like no writes being processed by replica via '
'replication or other means')
if len(replicas) > 1:
log.info('Confirming replica servers are synced')
confirm_max_replica_lag(replicas,
mysql_lib.REPLICATION_TOLERANCE_LOOSE,
dead_master,
True)
except:
log.info('Starting rollback')
if master_conn:
log.info('Releasing read_only on old master')
mysql_lib.set_global_variable(master, 'read_only', False)
log.info('Clearing replication settings on old master')
mysql_lib.reset_slave(master)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Rollback complete, reraising exception')
raise
if dr_slave:
try:
mysql_lib.setup_replication(new_master=slave, new_replica=dr_slave)
except Exception as e:
log.error(e)
log.error('Setting up replication on the dr_slave failed. '
'Failing forward!')
log.info('Updating zk')
zk_write_attempt = 0
while True:
try:
modify_mysql_zk.swap_master_and_slave(slave, dry_run=False)
break
except:
if zk_write_attempt > MAX_ZK_WRITE_ATTEMPTS:
log.info('Final failure writing to zk, bailing')
raise
else:
log.info('Write to zk failed, trying again')
zk_write_attempt = zk_write_attempt+1
log.info('Removing read_only from new master')
mysql_lib.set_global_variable(slave, 'read_only', False)
log.info('Removing replication configuration from new master')
mysql_lib.reset_slave(slave)
if lock_identifier:
log.info('Releasing promotion lock')
release_promotion_lock(lock_identifier)
log.info('Failover complete')
# we don't really care if this fails, but we'll print a message anyway.
try:
environment_specific.generic_json_post(
environment_specific.CHANGE_FEED_URL,
{'type': 'MySQL Failover',
'environment': replica_set,
'description': "Failover from {m} to {s}".format(m=master, s=slave),
'author': host_utils.get_user(),
'automation': False,
'source': "mysql_failover.py on {}".format(host_utils.HOSTNAME)})
except Exception as e:
log.warning("Failover completed, but change feed "
"not updated: {}".format(e))
if not master_conn:
log.info('As master is dead, will try to launch a replacement. Will '
'sleep 20 seconds first to let things settle')
time.sleep(20)
launch_replacement_db_host.launch_replacement_db_host(master)