com.datastax.driver.core

Class PerHostPercentileTracker.Builder

java.lang.Object

com.datastax.driver.core.PerHostPercentileTracker.Builder

Enclosing class:

PerHostPercentileTracker

public static class PerHostPercentileTracker.Builder
extends Object

Helper class to builder PerHostPercentileTracker instances with a fluent interface.

Method Summary

Modifier and Type	Method and Description
PerHostPercentileTracker	build() Builds the PerHostPercentileTracker instance configured with this builder.
PerHostPercentileTracker.Builder	withInterval(long interval, TimeUnit unit) Sets the time interval over which samples are recorded.
PerHostPercentileTracker.Builder	withMinRecordedValues(int minRecordedValues) Sets the minimum number of values that must be recorded for a host before we consider the sample size significant.
PerHostPercentileTracker.Builder	withNumberOfHosts(int numberOfHosts) Sets the number of distinct hosts that the driver will ever connect to.
PerHostPercentileTracker.Builder	withNumberOfSignificantValueDigits(int numberOfSignificantValueDigits) Sets the number of significant decimal digits to which histograms will maintain value resolution and separation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

withNumberOfSignificantValueDigits

public PerHostPercentileTracker.Builder withNumberOfSignificantValueDigits(int numberOfSignificantValueDigits)

Sets the number of significant decimal digits to which histograms will maintain value resolution and separation. This must be an integer between 0 and 5.

If not set explicitly, this value defaults to 3.

See the HdrHistogram Javadocs for a more detailed explanation on how this parameter affects the resolution of recorded samples.

Parameters:

numberOfSignificantValueDigits - the new value.

Returns:

this builder.

withMinRecordedValues

public PerHostPercentileTracker.Builder withMinRecordedValues(int minRecordedValues)

Sets the minimum number of values that must be recorded for a host before we consider the sample size significant.

If this count is not reached during a given interval, PerHostPercentileTracker.getLatencyAtPercentile(Host, double) will return a negative value, indicating that statistics are not available. In particular, this is true during the first interval.

If not set explicitly, this value default to 1000.

Parameters:

minRecordedValues - the new value.

Returns:

this builder.

withNumberOfHosts

public PerHostPercentileTracker.Builder withNumberOfHosts(int numberOfHosts)

Sets the number of distinct hosts that the driver will ever connect to.

This parameter is only used to pre-size internal maps in order to avoid unnecessary rehashing.

If not set explicitly, this value defaults to 16.

Parameters:

numberOfHosts - the new value.

Returns:

this builder.

withInterval

public PerHostPercentileTracker.Builder withInterval(long interval,
                                                     TimeUnit unit)

Sets the time interval over which samples are recorded.

For each host, there is a "live" histogram where current latencies are recorded, and a "cached", read-only histogram that is used when clients call PerHostPercentileTracker.getLatencyAtPercentile(Host, double). Each time the cached histogram becomes older than the interval, the two histograms are switched. Note that statistics will not be available during the first interval at cluster startup, since we don't have a cached histogram yet.

If not set explicitly, this value defaults to 5 minutes.

Parameters:

interval - the new interval.

unit - the unit that the interval is expressed in.

Returns:

this builder.

build

public PerHostPercentileTracker build()

Builds the PerHostPercentileTracker instance configured with this builder.

Returns:

the instance.