Ensure global test seed is used for all random testing tasks

[mark-vieira]

Recently it was noticed that the global generated test seed reported at the beginning of every Gradle build was not always used for subsequent test tasks. For example:

=======================================
Elasticsearch Build Hamster says Hello!
  Gradle Version        : 5.2.1
  OS Info               : Mac OS X 10.14.3 (x86_64)
  JDK Version           : 11 (Oracle Corporation 11.0.2 [OpenJDK 64-Bit Server VM 11.0.2+9])
  JAVA_HOME             : /Users/mark/.sdkman/candidates/java/11.0.2-open
  Random Testing Seed   : DA01B1B09A1CDA37
=======================================

> Task :server:integTest
==> Test Info: seed=4804DC280933D0C4; jvms=6; suites=319

As you can see, the global seed DA01B1B09A1CDA37 is not the same as the seed 4804DC280933D0C4 used by the :server:integTest Task.

It turns out the reason for this is an implementation detail in how the Ant junit4 task works.

// Initialize random if not already provided.
    if (random == null) {
      this.random = MoreObjects.firstNonNull( 
          Strings.emptyToNull(getProject().getProperty(SYSPROP_RANDOM_SEED())),
          SeedUtils.formatSeed(new Random().nextLong()));
    }

In this case it looks for an Ant project property, and if not defined, falls back to generating a new seed.

We currently rely on explicitly setting the test.seed system property on the test task here but this actually gets ignored when the forked test VMs are created and the randomly generated seed (created above) is used instead.

// Pass the random seed property.
    createJvmarg().setValue("-D" + SYSPROP_PREFIX() + "=" + CURRENT_PREFIX());
    createJvmarg().setValue("-D" + SYSPROP_RANDOM_SEED() + "=" + random);

While investigating it was noticed that invoking the build with an explicit seed (ex: ./gradlew -Dtest.seed=foo) does result in the behavior we want, which is that all random test tasks in the build use the global seed. The reason for this is that all build system properties are inherited by Ant as project properties.

This PR simply unifies these behaviors such that when the global seed is generated as part of the build (not specified on the commandline) we explicitly set the appropriate Ant project property to ensure this propagates to any and all Ant tasks.

[elasticmachine]

Pinging @elastic/es-core-infra

[mark-vieira]

@elasticmachine retest this please

[rjernst]

LGTM, one nit

[rjernst]

we try to use concrete types, as it makes it easier to port these classes to java (which we have slowly been doing).

[mark-vieira]

Then when we port from Java -> Kotlin we'll have to change back to val 😉

[mark-vieira]

☝️ joking about porting to Kotlin FYI 😆