PoolingOptions Class

Represents the options related to connection pooling.

For each host selected by the load balancing policy, the driver keeps a core amount of connections open at all times (GetCoreConnectionsPerHost(HostDistance)). If the use of those connections reaches a configurable threshold (GetMaxSimultaneousRequestsPerConnectionTreshold(HostDistance)), more connections are created up to the configurable maximum number of connections (GetMaxConnectionPerHost(HostDistance)).

The driver uses connections in an asynchronous manner and multiple requests can be submitted on the same connection at the same time without waiting for a response. This means that the driver only needs to maintain a relatively small number of connections to each Cassandra host. The PoolingOptions allows you to to control how many connections are kept per host.

Each of these parameters can be separately set for Local and Remote hosts. For Ignored hosts, the default for all those settings is 0 and cannot be changed.

The default amount of connections depend on the Cassandra version of the Cluster, as newer versions of Cassandra (2.1 and above) support a higher number of in-flight requests.

For Cassandra 2.1 and above, the default amount of connections per host are:

Local datacenter: 1 core connection per host, with 2 connections as maximum when the simultaneous requests threshold is reached.
Remote datacenter: 1 core connection per host (being 1 also max).

For older Cassandra versions (1.2 and 2.0), the default amount of connections per host are:

Local datacenter: 2 core connection per host, with 8 connections as maximum when the simultaneous requests threshold is reached.
Remote datacenter: 1 core connection per host (being 2 the maximum).

Inheritance Hierarchy

SystemObject
DsePoolingOptions

Namespace: Dse
Assembly: Dse (in Dse.dll) Version: 2.9.0

Syntax

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public class PoolingOptions

The PoolingOptions type exposes the following members.

Constructors

	Name	Description
	PoolingOptions	DEPRECATED: It will be removed in future versions. Use Create(ProtocolVersion) instead. Creates a new instance of PoolingOptions using defaults suitable for old server versions (Apache Cassandra 2.0 and below) for compatibility reasons. It's recommended that you use Create(ProtocolVersion) providing the server protocol version.

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Methods

	Name	Description
	Create	Creates a new instance of PoolingOptions using the default amount of connections and settings based on the protocol version. For modern server versions (Apache Cassandra 2.1+) the amount of core connections are set to 1, setting 2 for max local connections.
	GetCoreConnectionsPerHost	The core number of connections per host. For the provided HostDistance, this correspond to the number of connections initially created and kept open to each host of that distance.
	GetHeartBeatInterval	Gets the amount of idle time in milliseconds that has to pass before the driver issues a request on an active connection to avoid idle time disconnections. Remarks A value of 0 or null means that the heartbeat functionality at connection level is disabled.
	GetMaxConnectionPerHost	The maximum number of connections per host. For the provided distance, this correspond to the maximum number of connections that can be created per host at that distance.
	GetMaxRequestsPerConnection	Gets the maximum amount of requests that can be in-flight on a single connection at the same time. This setting acts as a fixed maximum, once this value is reached for a host the pool will start rejecting requests, throwing BusyPoolException instances. This setting should not be mistaken with GetMaxSimultaneousRequestsPerConnectionTreshold(HostDistance).
	GetMaxSimultaneousRequestsPerConnectionTreshold	Number of simultaneous requests on each connections to a host after which more connections are created. If all the connections opened to a host are handling more than this number of simultaneous requests and there is less than GetMaxConnectionPerHost(HostDistance) connections open to this host, a new connection is open.
	GetMinSimultaneousRequestsPerConnectionTreshold	Number of simultaneous requests on a connection below which connections in excess are reclaimed. If an opened connection to an host at distance distance handles less than this number of simultaneous requests and there is more than #GetCoreConnectionsPerHost connections open to this host, the connection is closed. The default value for this option is 25 for Local and Remote hosts.
	GetWarmup	Gets whether all connections to hosts in the local datacenter must be opened on connect. Default: true.
	SetCoreConnectionsPerHost	Sets the core number of connections per host.
	SetHeartBeatInterval	Sets the amount of idle time in milliseconds that has to pass before the driver issues a request on an active connection to avoid idle time disconnections. Remarks When set to 0 the heartbeat functionality at connection level is disabled.
	SetMaxConnectionsPerHost	Sets the maximum number of connections per host.
	SetMaxRequestsPerConnection	Sets the maximum amount of requests that can be in-flight on a single connection at the same time. This setting acts as a fixed maximum, once this value is reached for a host the pool will start rejecting requests, throwing BusyPoolException instances. This setting should not be mistaken with SetMaxSimultaneousRequestsPerConnectionTreshold(HostDistance, Int32).
	SetMaxSimultaneousRequestsPerConnectionTreshold	Sets number of simultaneous requests on all connections to an host after which more connections are created.
	SetMinSimultaneousRequestsPerConnectionTreshold	Sets the number of simultaneous requests on a connection below which connections in excess are reclaimed.
	SetWarmup	Sets whether all connections to hosts in the local datacenter must be opened on connect. Default: true.

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Fields

	Name	Description
	DefaultHeartBeatInterval	The default heartbeat interval in milliseconds: 30000.
	DefaultMaxRequestsPerConnection	Default maximum amount of requests that can be in-flight on a single connection at the same time after which the connection will start rejecting requests: 2048.

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Reference

Dse Namespace