def start_cassandra(db_ips, db_master, keyname):
""" Creates a monit configuration file and prompts Monit to start Cassandra.
Args:
db_ips: A list of database node IPs to start Cassandra on.
db_master: The IP address of the DB master.
keyname: A string containing the deployment's keyname.
Raises:
AppScaleDBError if unable to start Cassandra.
"""
logging.info("Starting Cassandra...")
for ip in db_ips:
init_config = '{script} --local-ip {ip} --master-ip {db_master}'.format(
script=SETUP_CASSANDRA_SCRIPT, ip=ip, db_master=db_master)
try:
utils.ssh(ip, keyname, init_config)
except subprocess.CalledProcessError:
message = 'Unable to configure Cassandra on {}'.format(ip)
logging.exception(message)
raise dbconstants.AppScaleDBError(message)
try:
start_service_cmd = START_SERVICE_SCRIPT + CASSANDRA_WATCH_NAME
utils.ssh(ip, keyname, start_service_cmd)
except subprocess.CalledProcessError:
message = 'Unable to start Cassandra on {}'.format(ip)
logging.exception(message)
raise dbconstants.AppScaleDBError(message)
logging.info('Waiting for Cassandra to be ready')
status_cmd = '{} status'.format(cassandra_interface.NODE_TOOL)
while (utils.ssh(db_master, keyname, status_cmd,
method=subprocess.call) != 0):
time.sleep(5)
logging.info("Successfully started Cassandra.")
def wait_for_quorum(keyname, db_nodes, replication):
""" Waits until enough Cassandra nodes are up for a quorum.
Args:
keyname: A string containing the deployment's keyname.
db_nodes: An integer specifying the total number of DB nodes.
replication: An integer specifying the keyspace replication factor.
"""
command = cassandra_interface.NODE_TOOL + " " + 'status'
key_file = '{}/{}.key'.format(utils.KEY_DIRECTORY, keyname)
ssh_cmd = ['ssh', '-i', key_file, appscale_info.get_db_master_ip(), command]
# Determine the number of nodes needed for a quorum.
if db_nodes < 1 or replication < 1:
raise dbconstants.AppScaleDBError('At least 1 database machine is needed.')
if replication > db_nodes:
raise dbconstants.AppScaleDBError(
'The replication factor cannot exceed the number of database machines.')
can_fail = math.ceil(replication/2.0 - 1)
needed = int(db_nodes - can_fail)
while True:
output = subprocess.check_output(ssh_cmd)
nodes_ready = len(
[line for line in output.splitlines() if line.startswith('UN')])
logging.info('{} nodes are up. {} are needed.'.format(nodes_ready, needed))
if nodes_ready >= needed:
break
time.sleep(1)
def estimate_total_entities(session, db_master, keyname):
""" Estimate the total number of entities.
Args:
session: A cassandra-driver session.
db_master: A string containing the IP address of the primary DB node.
keyname: A string containing the deployment keyname.
Returns:
A string containing an entity count.
Raises:
AppScaleDBError if unable to get a count.
"""
query = SimpleStatement(
'SELECT COUNT(*) FROM "{}"'.format(dbconstants.APP_ENTITY_TABLE),
consistency_level=ConsistencyLevel.ONE
)
try:
rows = session.execute(query)[0].count
return str(rows / len(dbconstants.APP_ENTITY_SCHEMA))
except dbconstants.TRANSIENT_CASSANDRA_ERRORS:
stats_cmd = '{nodetool} cfstats {keyspace}.{table}'.format(
nodetool=cassandra_interface.NODE_TOOL,
keyspace=cassandra_interface.KEYSPACE,
table=dbconstants.APP_ENTITY_TABLE)
stats = utils.ssh(db_master, keyname, stats_cmd,
method=subprocess.check_output)
for line in stats.splitlines():
if 'Number of keys (estimate)' in line:
return '{} (estimate)'.format(line.split()[-1])
raise dbconstants.AppScaleDBError('Unable to estimate total entities.')