Fixes #237 - Upgrade to elasticsearch 7.3.1

[iagodvsantos]

• Rebuild gradle wrapper
• Upgrade ES to 7.3.1

Note: Since there is an error on build-tools es plugin in the version 7.3.1 as stated here -> elastic/elasticsearch#45891 (comment) a workaround was necessary

Closes:. #237

[nomoa]

Left one comment on build.gradle, everything else looks very good.
Thanks!

[jillesvangurp]

7.3.1 is out by now.

[nomoa]

Thanks!

@softwaredoug I could merge as is but since it requires uploading a new build I think that it makes sense that you merge it once you have time to prepare a new release.

[jillesvangurp]

It would help us if we could upgrade this to 7.3.1. I think this should not introduce additional api changes.

[softwaredoug]

Thanks @iagodvsantos @nomoa @jillesvangurp

All looks good, but when rebuilding locally I got the following, which I'm hopeful is innocuous:

> Task :test
Exception in thread "Thread-3" java.lang.ClassCastException: class org.apache.logging.log4j.simple.SimpleLoggerContext cannot be cast to class org.apache.logging.log4j.core.LoggerContext (org.apache.logging.log4j.simple.SimpleLoggerContext and org.apache.logging.log4j.core.LoggerContext are in unnamed module of loader 'app')
        at org.elasticsearch.test.ESTestCase.lambda$static$0(ESTestCase.java:236)
        at java.base/java.lang.Thread.run(Thread.java:835)
        Suppressed: java.lang.IllegalStateException: No context information for thread: Thread[id=26, name=Thread-3, state=RUNNABLE, group=TGRP-ValidatingLtrQueryBuilderTests]. Is this thread running under a class com.carrotsearch.randomizedtesting.RandomizedRunner runner context? Add @RunWith(class com.carrotsearch.randomizedtesting.RandomizedRunner.class) to your test class. Make sure your code accesses random contexts within @BeforeClass and @AfterClass boundary (for example, static test class initializers are not permitted to access random contexts).
                at com.carrotsearch.randomizedtesting.RandomizedContext.context(RandomizedContext.java:249)
                at com.carrotsearch.randomizedtesting.RandomizedContext.current(RandomizedContext.java:134)
                at com.carrotsearch.randomizedtesting.RandomizedRunner.augmentStackTrace(RandomizedRunner.java:1885)
                at com.carrotsearch.randomizedtesting.RunnerThreadGroup.uncaughtException(RunnerThreadGroup.java:20)
                at java.base/java.lang.Thread.dispatchUncaughtException(Thread.java:1997)

BUILD SUCCESSFUL in 1m 23s

[jillesvangurp]

I've been running with the 7.3.1 build today and did not notice this issue. But there may be some issue with the test classpath dependencies for log4j. It may be pulling in different versions for log4j-core and log4j-api transitively. I've seen similar issues on other plugin projects. I think the api dependency might be coming along with elasticsearch.

In any case, the solution is adding matching versions of both as test dependencies.

[jillesvangurp]

I can take a look at this tomorrow if needed; but it would be great if you can update the PR directly.

[jillesvangurp]

I was not able to reproduce the log related exception. It produces no output during gradle test. But if this comes back; try adding these dependencies.

testCompile 'org.apache.logging.log4j:log4j-core:2.12.1'
testCompile 'org.apache.logging.log4j:log4j-api:2.12.1'