The main class to use when interacting with a Cassandra cluster. Typically, one instance of this class will be created for each separate Cassandra cluster that your application interacts with.
Example usage:
>>> from cassandra.cluster import Cluster
>>> cluster = Cluster(['192.168.1.1', '192.168.1.2'])
>>> session = cluster.connect()
>>> session.execute("CREATE KEYSPACE ...")
>>> ...
>>> cluster.shutdown()
Any of the mutable Cluster attributes may be set as keyword arguments to the constructor.
Any of the mutable Cluster attributes may be set as keyword arguments to the constructor.
cql_version = None¶
If a specific version of CQL should be used, this may be set to that string version. Otherwise, the highest CQL version supported by the server will be automatically used.
protocol_version = 4¶
The maximum version of the native protocol to use.
The driver will automatically downgrade version based on a negotiation with the server, but it is most efficient to set this to the maximum supported by your version of Cassandra. Setting this will also prevent conflicting versions negotiated if your cluster is upgraded.
Version 2 of the native protocol adds support for lightweight transactions, batch operations, and automatic query paging. The v2 protocol is supported by Cassandra 2.0+.
Version 3 of the native protocol adds support for protocol-level client-side timestamps (see Session.use_client_timestamp), serial consistency levels for BatchStatement, and an improved connection pool.
Version 4 of the native protocol adds a number of new types, server warnings, new failure messages, and custom payloads. Details in the project docs
The following table describes the native protocol versions that are supported by each version of Cassandra:
Cassandra Version Protocol Versions 1.2 1 2.0 1, 2 2.1 1, 2, 3 2.2 1, 2, 3, 4port = 9042¶
The server-side port to open connections to. Defaults to 9042.
compression = True¶
Controls compression for communications between the driver and Cassandra. If left as the default of True, either lz4 or snappy compression may be used, depending on what is supported by both the driver and Cassandra. If both are fully supported, lz4 will be preferred.
You may also set this to ‘snappy’ or ‘lz4’ to request that specific compression type.
Setting this to False disables compression.
auth_provider¶
When protocol_version is 2 or higher, this should be an instance of a subclass of AuthProvider, such as PlainTextAuthProvider.
When protocol_version is 1, this should be a function that accepts one argument, the IP address of a node, and returns a dict of credentials for that node.
When not using authentication, this should be left as None.
load_balancing_policy = None¶
An instance of policies.LoadBalancingPolicy or one of its subclasses.
Changed in version 2.6.0.
Defaults to TokenAwarePolicy (DCAwareRoundRobinPolicy). when using CPython (where the murmur3 extension is available). DCAwareRoundRobinPolicy otherwise. Default local DC will be chosen from contact points.
Please see DCAwareRoundRobinPolicy for a discussion on default behavior with respect to DC locality and remote nodes.
reconnection_policy = <cassandra.policies.ExponentialReconnectionPolicy object>¶
An instance of policies.ReconnectionPolicy. Defaults to an instance of ExponentialReconnectionPolicy with a base delay of one second and a max delay of ten minutes.
default_retry_policy = <cassandra.policies.RetryPolicy object>¶
A default policies.RetryPolicy instance to use for all Statement objects which do not have a retry_policy explicitly set.
conviction_policy_factory = <class 'cassandra.policies.SimpleConvictionPolicy'>¶
A factory function which creates instances of policies.ConvictionPolicy. Defaults to policies.SimpleConvictionPolicy.
address_translator = <cassandra.policies.IdentityTranslator object>¶
policies.AddressTranslator instance to be used in translating server node addresses to driver connection addresses.
connection_class = <class 'cassandra.io.asyncorereactor.AsyncoreConnection'>¶
This determines what event loop system will be used for managing I/O with Cassandra. These are the current options:
cassandra.io.asyncorereactor.AsyncoreConnectioncassandra.io.libevreactor.LibevConnectioncassandra.io.eventletreactor.EventletConnection (requires monkey-patching - see doc for details)cassandra.io.geventreactor.GeventConnection (requires monkey-patching - see doc for details)cassandra.io.twistedreactor.TwistedConnectionBy default, AsyncoreConnection will be used, which uses the asyncore module in the Python standard library.
If libev is installed, LibevConnection will be used instead.
If gevent or eventlet monkey-patching is detected, the corresponding connection class will be used automatically.
metrics_enabled = False¶
Whether or not metric collection is enabled. If enabled, metrics will be an instance of Metrics.
metrics = None¶
An instance of cassandra.metrics.Metrics if metrics_enabled is True, else None.
metadata = None¶
An instance of cassandra.metadata.Metadata.
ssl_options = None¶
A optional dict which will be used as kwargs for ssl.wrap_socket() when new sockets are created. This should be used when client encryption is enabled in Cassandra.
By default, a ca_certs value should be supplied (the value should be a string pointing to the location of the CA certs file), and you probably want to specify ssl_version as ssl.PROTOCOL_TLSv1 to match Cassandra’s default protocol.
sockopts = None¶
An optional list of tuples which will be used as arguments to socket.setsockopt() for all created sockets.
Note: some drivers find setting TCPNODELAY beneficial in the context of their execution model. It was not found generally beneficial for this driver. To try with your own workload, set sockopts = [(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)]
max_schema_agreement_wait = 10¶
The maximum duration (in seconds) that the driver will wait for schema agreement across the cluster. Defaults to ten seconds. If set <= 0, the driver will bypass schema agreement waits altogether.
control_connection_timeout = 2.0¶
A timeout, in seconds, for queries made by the control connection, such as querying the current schema and information about nodes in the cluster. If set to None, there will be no timeout for these queries.
idle_heartbeat_interval = 30¶
Interval, in seconds, on which to heartbeat idle connections. This helps keep connections open through network devices that expire idle connections. It also helps discover bad connections early in low-traffic scenarios. Setting to zero disables heartbeats.
schema_event_refresh_window = 2¶
Window, in seconds, within which a schema component will be refreshed after receiving a schema_change event.
The driver delays a random amount of time in the range [0.0, window) before executing the refresh. This serves two purposes:
1.) Spread the refresh for deployments with large fanout from C* to client tier, preventing a ‘thundering herd’ problem with many clients refreshing simultaneously.
2.) Remove redundant refreshes. Redundant events arriving within the delay period are discarded, and only one refresh is executed.
Setting this to zero will execute refreshes immediately.
Setting this negative will disable schema refreshes in response to push events (refreshes will still occur in response to schema change responses to DDL statements executed by Sessions of this Cluster).
topology_event_refresh_window = 10¶
Window, in seconds, within which the node and token list will be refreshed after receiving a topology_change event.
Setting this to zero will execute refreshes immediately.
Setting this negative will disable node refreshes in response to push events (refreshes will still occur in response to new nodes observed on “UP” events).
See schema_event_refresh_window for discussion of rationale
connect_timeout = 5¶
Timeout, in seconds, for creating new connections.
This timeout covers the entire connection negotiation, including TCP establishment, options passing, and authentication.
schema_metadata_enabled = True¶
Flag indicating whether internal schema metadata is updated.
When disabled, the driver does not populate Cluster.metadata.keyspaces on connect, or on schema change events. This can be used to speed initial connection, and reduce load on client and server during operation. Turning this off gives away token aware request routing, and programmatic inspection of the metadata model.
token_metadata_enabled = True¶
Flag indicating whether internal token metadata is updated.
When disabled, the driver does not query node token information on connect, or on topology change events. This can be used to speed initial connection, and reduce load on client and server during operation. It is most useful in large clusters using vnodes, where the token map can be expensive to compute. Turning this off gives away token aware request routing, and programmatic inspection of the token ring.
connect(keyspace=None)[source]¶
Creates and returns a new Session object. If keyspace is specified, that keyspace will be the default keyspace for operations on the Session.
shutdown()[source]¶
Closes all sessions and connection associated with this Cluster. To ensure all connections are properly closed, you should always call shutdown() on a Cluster instance when you are done with it.
Once shutdown, a Cluster should not be used for any purpose.
register_user_type(keyspace, user_type, klass)[source]¶
Registers a class to use to represent a particular user-defined type. Query parameters for this user-defined type will be assumed to be instances of klass. Result sets for this user-defined type will be instances of klass. If no class is registered for a user-defined type, a namedtuple will be used for result sets, and non-prepared statements may not encode parameters for this type correctly.
keyspace is the name of the keyspace that the UDT is defined in.
user_type is the string name of the UDT to register the mapping for.
klass should be a class with attributes whose names match the fields of the user-defined type. The constructor must accepts kwargs for each of the fields in the UDT.
This method should only be called after the type has been created within Cassandra.
Example:
cluster = Cluster(protocol_version=3)
session = cluster.connect()
session.set_keyspace('mykeyspace')
session.execute("CREATE TYPE address (street text, zipcode int)")
session.execute("CREATE TABLE users (id int PRIMARY KEY, location address)")
# create a class to map to the "address" UDT
class Address(object):
def __init__(self, street, zipcode):
self.street = street
self.zipcode = zipcode
cluster.register_user_type('mykeyspace', 'address', Address)
# insert a row using an instance of Address
session.execute("INSERT INTO users (id, location) VALUES (%s, %s)",
(0, Address("123 Main St.", 78723)))
# results will include Address instances
results = session.execute("SELECT * FROM users")
row = results[0]
print row.id, row.location.street, row.location.zipcode
register_listener(listener)[source]¶
Adds a cassandra.policies.HostStateListener subclass instance to the list of listeners to be notified when a host is added, removed, marked up, or marked down.
unregister_listener(listener)[source]¶
Removes a registered listener.
set_max_requests_per_connection(host_distance, max_requests)[source]¶
Sets a threshold for concurrent requests per connection, above which new connections will be created to a host (up to max connections; see set_max_connections_per_host()).
Pertains to connection pool management in protocol versions {1,2}.
get_max_requests_per_connection(host_distance)[source]¶
set_min_requests_per_connection(host_distance, min_requests)[source]¶
Sets a threshold for concurrent requests per connection, below which connections will be considered for disposal (down to core connections; see set_core_connections_per_host()).
Pertains to connection pool management in protocol versions {1,2}.
get_min_requests_per_connection(host_distance)[source]¶
get_core_connections_per_host(host_distance)[source]¶
Gets the minimum number of connections per Session that will be opened for each host with HostDistance equal to host_distance. The default is 2 for LOCAL and 1 for REMOTE.
This property is ignored if protocol_version is 3 or higher.
set_core_connections_per_host(host_distance, core_connections)[source]¶
Sets the minimum number of connections per Session that will be opened for each host with HostDistance equal to host_distance. The default is 2 for LOCAL and 1 for REMOTE.
Protocol version 1 and 2 are limited in the number of concurrent requests they can send per connection. The driver implements connection pooling to support higher levels of concurrency.
If protocol_version is set to 3 or higher, this is not supported (there is always one connection per host, unless the host is remote and connect_to_remote_hosts is False) and using this will result in an UnsupporteOperation.
get_max_connections_per_host(host_distance)[source]¶
Gets the maximum number of connections per Session that will be opened for each host with HostDistance equal to host_distance. The default is 8 for LOCAL and 2 for REMOTE.
This property is ignored if protocol_version is 3 or higher.
set_max_connections_per_host(host_distance, max_connections)[source]¶
Sets the maximum number of connections per Session that will be opened for each host with HostDistance equal to host_distance. The default is 2 for LOCAL and 1 for REMOTE.
If protocol_version is set to 3 or higher, this is not supported (there is always one connection per host, unless the host is remote and connect_to_remote_hosts is False) and using this will result in an UnsupporteOperation.
refresh_schema_metadata(max_schema_agreement_wait=None)[source]¶
Synchronously refresh all schema metadata.
By default, the timeout for this operation is governed by max_schema_agreement_wait and control_connection_timeout.
Passing max_schema_agreement_wait here overrides max_schema_agreement_wait.
Setting max_schema_agreement_wait <= 0 will bypass schema agreement and refresh schema immediately.
An Exception is raised if schema refresh fails for any reason.
refresh_keyspace_metadata(keyspace, max_schema_agreement_wait=None)[source]¶
Synchronously refresh keyspace metadata. This applies to keyspace-level information such as replication and durability settings. It does not refresh tables, types, etc. contained in the keyspace.
See refresh_schema_metadata() for description of max_schema_agreement_wait behavior
refresh_table_metadata(keyspace, table, max_schema_agreement_wait=None)[source]¶
Synchronously refresh table metadata. This applies to a table, and any triggers or indexes attached to the table.
See refresh_schema_metadata() for description of max_schema_agreement_wait behavior
refresh_user_type_metadata(keyspace, user_type, max_schema_agreement_wait=None)[source]¶
Synchronously refresh user defined type metadata.
See refresh_schema_metadata() for description of max_schema_agreement_wait behavior
refresh_user_function_metadata(keyspace, function, max_schema_agreement_wait=None)[source]¶
Synchronously refresh user defined function metadata.
function is a cassandra.UserFunctionDescriptor.
See refresh_schema_metadata() for description of max_schema_agreement_wait behavior
refresh_user_aggregate_metadata(keyspace, aggregate, max_schema_agreement_wait=None)[source]¶
Synchronously refresh user defined aggregate metadata.
aggregate is a cassandra.UserAggregateDescriptor.
See refresh_schema_metadata() for description of max_schema_agreement_wait behavior
refresh_nodes()[source]¶
Synchronously refresh the node list and token metadata
An Exception is raised if node refresh fails for any reason.
set_meta_refresh_enabled(enabled)[source]¶
Deprecated: set schema_metadata_enabled token_metadata_enabled instead
Sets a flag to enable (True) or disable (False) all metadata refresh queries. This applies to both schema and node topology.
Disabling this is useful to minimize refreshes during multiple changes.
Meta refresh must be enabled for the driver to become aware of any cluster topology changes or schema updates.
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