Source code for airflow.contrib.hooks.cassandra_hook

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from cassandra.cluster import Cluster
from cassandra.policies import (RoundRobinPolicy, DCAwareRoundRobinPolicy,
                                TokenAwarePolicy, WhiteListRoundRobinPolicy)
from cassandra.auth import PlainTextAuthProvider

from airflow.hooks.base_hook import BaseHook
from airflow.utils.log.logging_mixin import LoggingMixin

[docs]class CassandraHook(BaseHook, LoggingMixin): """ Hook used to interact with Cassandra Contact points can be specified as a comma-separated string in the 'hosts' field of the connection. Port can be specified in the port field of the connection. If SSL is enabled in Cassandra, pass in a dict in the extra field as kwargs for ``ssl.wrap_socket()``. For example:: { 'ssl_options' : { 'ca_certs' : PATH_TO_CA_CERTS } } Default load balancing policy is RoundRobinPolicy. To specify a different LB policy:: - DCAwareRoundRobinPolicy { 'load_balancing_policy': 'DCAwareRoundRobinPolicy', 'load_balancing_policy_args': { 'local_dc': LOCAL_DC_NAME, // optional 'used_hosts_per_remote_dc': SOME_INT_VALUE, // optional } } - WhiteListRoundRobinPolicy { 'load_balancing_policy': 'WhiteListRoundRobinPolicy', 'load_balancing_policy_args': { 'hosts': ['HOST1', 'HOST2', 'HOST3'] } } - TokenAwarePolicy { 'load_balancing_policy': 'TokenAwarePolicy', 'load_balancing_policy_args': { 'child_load_balancing_policy': CHILD_POLICY_NAME, // optional 'child_load_balancing_policy_args': { ... } // optional } } For details of the Cluster config, see cassandra.cluster. """ def __init__(self, cassandra_conn_id='cassandra_default'): conn = self.get_connection(cassandra_conn_id) conn_config = {} if conn_config['contact_points'] =',') if conn.port: conn_config['port'] = int(conn.port) if conn.login: conn_config['auth_provider'] = PlainTextAuthProvider( username=conn.login, password=conn.password) policy_name = conn.extra_dejson.get('load_balancing_policy', None) policy_args = conn.extra_dejson.get('load_balancing_policy_args', {}) lb_policy = self.get_lb_policy(policy_name, policy_args) if lb_policy: conn_config['load_balancing_policy'] = lb_policy cql_version = conn.extra_dejson.get('cql_version', None) if cql_version: conn_config['cql_version'] = cql_version ssl_options = conn.extra_dejson.get('ssl_options', None) if ssl_options: conn_config['ssl_options'] = ssl_options self.cluster = Cluster(**conn_config) self.keyspace = conn.schema self.session = None
[docs] def get_conn(self): """ Returns a cassandra Session object """ if self.session and not self.session.is_shutdown: return self.session self.session = self.cluster.connect(self.keyspace) return self.session
[docs] def get_cluster(self): return self.cluster
[docs] def shutdown_cluster(self): """ Closes all sessions and connections associated with this Cluster. """ if not self.cluster.is_shutdown: self.cluster.shutdown()
[docs] def get_lb_policy(policy_name, policy_args): policies = { 'RoundRobinPolicy': RoundRobinPolicy, 'DCAwareRoundRobinPolicy': DCAwareRoundRobinPolicy, 'WhiteListRoundRobinPolicy': WhiteListRoundRobinPolicy, 'TokenAwarePolicy': TokenAwarePolicy, } if not policies.get(policy_name) or policy_name == 'RoundRobinPolicy': return RoundRobinPolicy() if policy_name == 'DCAwareRoundRobinPolicy': local_dc = policy_args.get('local_dc', '') used_hosts_per_remote_dc = int(policy_args.get('used_hosts_per_remote_dc', 0)) return DCAwareRoundRobinPolicy(local_dc, used_hosts_per_remote_dc) if policy_name == 'WhiteListRoundRobinPolicy': hosts = policy_args.get('hosts') if not hosts: raise Exception('Hosts must be specified for WhiteListRoundRobinPolicy') return WhiteListRoundRobinPolicy(hosts) if policy_name == 'TokenAwarePolicy': allowed_child_policies = ('RoundRobinPolicy', 'DCAwareRoundRobinPolicy', 'WhiteListRoundRobinPolicy',) child_policy_name = policy_args.get('child_load_balancing_policy', 'RoundRobinPolicy') child_policy_args = policy_args.get('child_load_balancing_policy_args', {}) if child_policy_name not in allowed_child_policies: return TokenAwarePolicy(RoundRobinPolicy()) else: child_policy = CassandraHook.get_lb_policy(child_policy_name, child_policy_args) return TokenAwarePolicy(child_policy)
[docs] def table_exists(self, table): """ Checks if a table exists in Cassandra :param table: Target Cassandra table. Use dot notation to target a specific keyspace. :type table: str """ keyspace = self.keyspace if '.' in table: keyspace, table = table.split('.', 1) cluster_metadata = self.get_conn().cluster.metadata return (keyspace in cluster_metadata.keyspaces and table in cluster_metadata.keyspaces[keyspace].tables)
[docs] def record_exists(self, table, keys): """ Checks if a record exists in Cassandra :param table: Target Cassandra table. Use dot notation to target a specific keyspace. :type table: str :param keys: The keys and their values to check the existence. :type keys: dict """ keyspace = self.keyspace if '.' in table: keyspace, table = table.split('.', 1) ks = " AND ".join("{}=%({})s".format(key, key) for key in keys.keys()) cql = "SELECT * FROM {keyspace}.{table} WHERE {keys}".format( keyspace=keyspace, table=table, keys=ks) try: rs = self.get_conn().execute(cql, keys) return is not None except Exception: return False

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