com.datastax.driver.core

Interface LatencyTracker

All Known Implementing Classes:

PerHostPercentileTracker, QueryLogger, QueryLogger.ConstantThresholdQueryLogger, QueryLogger.DynamicThresholdQueryLogger

public interface LatencyTracker

Interface for objects that are interested in tracking the latencies of the driver queries to each Cassandra nodes.

An implementation of this interface can be registered against a Cluster object trough the Cluster.register(com.datastax.driver.core.Host.StateListener) method, after which the update(Host, Statement, Exception, long) method will be called after each query of the driver to a Cassandra host with the latency/duration (in nanoseconds) of this operation.

Method Summary

Modifier and Type	Method and Description
void	onRegister(Cluster cluster) Gets invoked when the tracker is registered with a cluster, or at cluster startup if the tracker was registered at initialization with Cluster.register(LatencyTracker).
void	onUnregister(Cluster cluster) Gets invoked when the tracker is unregistered from a cluster, or at cluster shutdown if the tracker was not unregistered.
void	update(Host host, Statement statement, Exception exception, long newLatencyNanos) A method that is called after each request to a Cassandra node with the duration of that operation.

Method Detail

update

void update(Host host,
            Statement statement,
            Exception exception,
            long newLatencyNanos)

A method that is called after each request to a Cassandra node with the duration of that operation.

Note that there is no guarantee that this method won't be called concurrently by multiple threads, so implementations should synchronize internally if need be.

Parameters:

host - The Cassandra host on which a request has been performed. This parameter is never null.

statement - The Statement that has been executed. This parameter is never null.

exception - An Exception thrown when receiving the response, or null if the response was successful.

newLatencyNanos - the latency in nanoseconds of the operation. This latency corresponds to the time elapsed between when the query was sent to host and when the response was received by the driver (or the operation timed out, in which newLatencyNanos will approximately be the timeout value).

onRegister

void onRegister(Cluster cluster)

Gets invoked when the tracker is registered with a cluster, or at cluster startup if the tracker was registered at initialization with Cluster.register(LatencyTracker).

Parameters:

cluster - the cluster that this tracker is registered with.

onUnregister

void onUnregister(Cluster cluster)

Gets invoked when the tracker is unregistered from a cluster, or at cluster shutdown if the tracker was not unregistered.

Parameters:

cluster - the cluster that this tracker was registered with.