org.elasticsearch.common

Class Randomness

java.lang.Object

org.elasticsearch.common.Randomness

public final class Randomness
extends java.lang.Object

Provides factory methods for producing reproducible sources of randomness. Reproducible sources of randomness contribute to reproducible tests. When running the Elasticsearch test suite, the test runner will establish a global random seed accessible via the system property "tests.seed". By seeding a random number generator with this global seed, we ensure that instances of Random produced with this class produce reproducible sources of randomness under when running under the Elasticsearch test suite. Alternatively, a reproducible source of randomness can be produced by providing a setting a reproducible seed. When running the Elasticsearch server process, non-reproducible sources of randomness are provided (unless a setting is provided for a module that exposes a seed setting (e.g., DiscoveryService#NODE_ID_SEED_SETTING)).

Method Summary

Modifier and Type	Method and Description
static java.util.Random	get() Provides a source of randomness that is reproducible when running under the Elasticsearch test suite, and otherwise produces a non-reproducible source of randomness.
static java.util.Random	get(Settings settings, Setting<java.lang.Long> setting) Provides a reproducible source of randomness seeded by a long seed in the settings with the key setting.
static void	shuffle(java.util.List<?> list)

Methods inherited from class java.lang.Object

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

Method Detail

get

public static java.util.Random get(Settings settings,
                                   Setting<java.lang.Long> setting)

Provides a reproducible source of randomness seeded by a long seed in the settings with the key setting.

Parameters:

settings - the settings containing the seed

setting - the setting to access the seed

Returns:

a reproducible source of randomness

get

public static java.util.Random get()

Provides a source of randomness that is reproducible when running under the Elasticsearch test suite, and otherwise produces a non-reproducible source of randomness. Reproducible sources of randomness are created when the system property "tests.seed" is set and the security policy allows reading this system property. Otherwise, non-reproducible sources of randomness are created.

Returns:

a source of randomness

Throws:

java.lang.IllegalStateException - if running tests but was not able to acquire an instance of Random from RandomizedContext or tests are running but tests.seed is not set

shuffle

public static void shuffle(java.util.List<?> list)