build.gradle

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */


import org.apache.tools.ant.taskdefs.condition.Os
import org.apache.tools.ant.filters.ReplaceTokens
import org.elasticsearch.gradle.BuildPlugin
import org.elasticsearch.gradle.LoggedExec
import org.elasticsearch.gradle.Version
import org.elasticsearch.gradle.VersionCollection
import org.elasticsearch.gradle.VersionProperties
import org.gradle.plugins.ide.eclipse.model.SourceFolder

import org.gradle.api.tasks.wrapper.Wrapper
import org.gradle.api.tasks.wrapper.Wrapper.DistributionType
import org.gradle.util.GradleVersion
import org.gradle.util.DistributionLocator

import java.nio.file.Files
import java.nio.file.Path
import java.security.MessageDigest

plugins {
    id 'com.gradle.build-scan' version '1.13.2'
}
if (properties.get("org.elasticsearch.acceptScanTOS", "false") == "true") {
    buildScan {
        termsOfServiceUrl = 'https://gradle.com/terms-of-service'
        termsOfServiceAgree = 'yes'
    }
}

// common maven publishing configuration
subprojects {
  group = 'org.elasticsearch'
  version = VersionProperties.elasticsearch.toString()
  description = "Elasticsearch subproject ${project.path}"
}

apply plugin: 'nebula.info-scm'
String licenseCommit
if (VersionProperties.elasticsearch.toString().endsWith('-SNAPSHOT')) {
  licenseCommit = scminfo.change ?: "master" // leniency for non git builds
} else {
  licenseCommit = "v${version}"
}
String elasticLicenseUrl = "https://raw.githubusercontent.com/elastic/elasticsearch/${licenseCommit}/licenses/ELASTIC-LICENSE.txt"

subprojects {
  // Default to the apache license
  project.ext.licenseName = 'The Apache Software License, Version 2.0'
  project.ext.licenseUrl = 'http://www.apache.org/licenses/LICENSE-2.0.txt'

  // But stick the Elastic license url in project.ext so we can get it if we need to switch to it
  project.ext.elasticLicenseUrl = elasticLicenseUrl

  // we only use maven publish to add tasks for pom generation
  plugins.withType(MavenPublishPlugin).whenPluginAdded {
    publishing {
      publications {
        // add license information to generated poms
        all {
          pom.withXml { XmlProvider xml ->
            Node node = xml.asNode()
            node.appendNode('inceptionYear', '2009')

            Node license = node.appendNode('licenses').appendNode('license')
            license.appendNode('name', project.licenseName)
            license.appendNode('url', project.licenseUrl)
            license.appendNode('distribution', 'repo')

            Node developer = node.appendNode('developers').appendNode('developer')
            developer.appendNode('name', 'Elastic')
            developer.appendNode('url', 'http://www.elastic.co')
          }
        }
      }
    }
  }
  plugins.withType(BuildPlugin).whenPluginAdded {
    project.licenseFile = project.rootProject.file('licenses/APACHE-LICENSE-2.0.txt')
    project.noticeFile = project.rootProject.file('NOTICE.txt')
  }
}

/* Introspect all versions of ES that may be tested against for backwards
 * compatibility. It is *super* important that this logic is the same as the
 * logic in VersionUtils.java, throwing out alphas because they don't have any
 * backwards compatibility guarantees and only keeping the latest beta or rc
 * in a branch if there are only betas and rcs in the branch so we have
 * *something* to test against. */
VersionCollection versions = new VersionCollection(file('server/src/main/java/org/elasticsearch/Version.java').readLines('UTF-8'))
if (versions.currentVersion != VersionProperties.elasticsearch) {
  throw new GradleException("The last version in Versions.java [${versions.currentVersion}] does not match " +
          "VersionProperties.elasticsearch [${VersionProperties.elasticsearch}]")
}

// build metadata from previous build, contains eg hashes for bwc builds
String buildMetadataValue = System.getenv('BUILD_METADATA')
if (buildMetadataValue == null) {
  buildMetadataValue = ''
}
Map<String, String> buildMetadataMap = buildMetadataValue.tokenize(';').collectEntries {
  def (String key, String value) = it.split('=')
  return [key, value]
}

// injecting groovy property variables into all projects
allprojects {
  project.ext {
    // for ide hacks...
    isEclipse = System.getProperty("eclipse.launcher") != null ||   // Detects gradle launched from Eclipse's IDE
            System.getProperty("eclipse.application") != null ||    // Detects gradle launched from the Eclipse compiler server
            gradle.startParameter.taskNames.contains('eclipse') ||  // Detects gradle launched from the command line to do eclipse stuff
            gradle.startParameter.taskNames.contains('cleanEclipse')
    isIdea = System.getProperty("idea.active") != null || gradle.startParameter.taskNames.contains('idea') || gradle.startParameter.taskNames.contains('cleanIdea')

    // for BWC testing
    bwcVersions = versions

    buildMetadata = buildMetadataMap
  }
}

task verifyVersions {
  doLast {
    if (gradle.startParameter.isOffline()) {
      throw new GradleException("Must run in online mode to verify versions")
    }
    // Read the list from maven central
    Node xml
    new URL('https://repo1.maven.org/maven2/org/elasticsearch/elasticsearch/maven-metadata.xml').openStream().withStream { s ->
        xml = new XmlParser().parse(s)
    }
    Set<Version> knownVersions = new TreeSet<>(xml.versioning.versions.version.collect { it.text() }.findAll { it ==~ /\d+\.\d+\.\d+/ }.collect { Version.fromString(it) })

    // Limit the known versions to those that should be index compatible, and are not future versions
    knownVersions = knownVersions.findAll { it.major >= bwcVersions.currentVersion.major - 1 && it.before(VersionProperties.elasticsearch) }

    /* Limit the listed versions to those that have been marked as released.
     * Versions not marked as released don't get the same testing and we want
     * to make sure that we flip all unreleased versions to released as soon
     * as possible after release. */
    Set<Version> actualVersions = new TreeSet<>(bwcVersions.indexCompatible.findAll { false == it.snapshot })

    // Finally, compare!
    if (knownVersions.equals(actualVersions) == false) {
      throw new GradleException("out-of-date released versions\nActual  :" + actualVersions + "\nExpected:" + knownVersions +
        "\nUpdate Version.java. Note that Version.CURRENT doesn't count because it is not released.")
    }
  }
}

/*
 * When adding backcompat behavior that spans major versions, temporarily
 * disabling the backcompat tests is necessary. This flag controls
 * the enabled state of every bwc task. It should be set back to true
 * after the backport of the backcompat code is complete.
 */
final boolean bwc_tests_enabled = true
final String bwc_tests_disabled_issue = "" /* place a PR link here when committing bwc changes */
if (bwc_tests_enabled == false) {
  if (bwc_tests_disabled_issue.isEmpty()) {
    throw new GradleException("bwc_tests_disabled_issue must be set when bwc_tests_enabled == false")
  }
  println "========================= WARNING ========================="
  println "         Backwards compatibility tests are disabled!"
  println "See ${bwc_tests_disabled_issue}"
  println "==========================================================="
}
subprojects {
  ext.bwc_tests_enabled = bwc_tests_enabled
}

task verifyBwcTestsEnabled {
  doLast {
    if (bwc_tests_enabled == false) {
      throw new GradleException('Bwc tests are disabled. They must be re-enabled after completing backcompat behavior backporting.')
    }
  }
}

task branchConsistency {
  description 'Ensures this branch is internally consistent. For example, that versions constants match released versions.'
  group 'Verification'
  dependsOn verifyVersions, verifyBwcTestsEnabled
}

subprojects {
  // ignore missing javadocs
  tasks.withType(Javadoc) { Javadoc javadoc ->
    // the -quiet here is because of a bug in gradle, in that adding a string option
    // by itself is not added to the options. By adding quiet, both this option and
    // the "value" -quiet is added, separated by a space. This is ok since the javadoc
    // command already adds -quiet, so we are just duplicating it
    // see https://discuss.gradle.org/t/add-custom-javadoc-option-that-does-not-take-an-argument/5959
    javadoc.options.encoding='UTF8'
    javadoc.options.addStringOption('Xdoclint:all,-missing', '-quiet')
  }

  /* Sets up the dependencies that we build as part of this project but
    register as thought they were external to resolve internally. We register
    them as external dependencies so the build plugin that we use can be used
    to build elasticsearch plugins outside of the elasticsearch source tree. */
  ext.projectSubstitutions = [
    "org.elasticsearch.gradle:build-tools:${version}": ':build-tools',
    "org.elasticsearch:rest-api-spec:${version}": ':rest-api-spec',
    "org.elasticsearch:elasticsearch:${version}": ':server',
    "org.elasticsearch:elasticsearch-cli:${version}": ':libs:cli',
    "org.elasticsearch:elasticsearch-core:${version}": ':libs:core',
    "org.elasticsearch:elasticsearch-nio:${version}": ':libs:nio',
    "org.elasticsearch:elasticsearch-x-content:${version}": ':libs:x-content',
    "org.elasticsearch:elasticsearch-secure-sm:${version}": ':libs:secure-sm',
    "org.elasticsearch.client:elasticsearch-rest-client:${version}": ':client:rest',
    "org.elasticsearch.client:elasticsearch-rest-client-sniffer:${version}": ':client:sniffer',
    "org.elasticsearch.client:elasticsearch-rest-high-level-client:${version}": ':client:rest-high-level',
    "org.elasticsearch.client:test:${version}": ':client:test',
    "org.elasticsearch.client:transport:${version}": ':client:transport',
    "org.elasticsearch.test:framework:${version}": ':test:framework',
    "org.elasticsearch.distribution.integ-test-zip:elasticsearch:${version}": ':distribution:archives:integ-test-zip',
    "org.elasticsearch.distribution.zip:elasticsearch:${version}": ':distribution:archives:zip',
    "org.elasticsearch.distribution.zip:elasticsearch-oss:${version}": ':distribution:archives:oss-zip',
    "org.elasticsearch.distribution.tar:elasticsearch:${version}": ':distribution:archives:tar',
    "org.elasticsearch.distribution.tar:elasticsearch-oss:${version}": ':distribution:archives:oss-tar',
    "org.elasticsearch.distribution.rpm:elasticsearch:${version}": ':distribution:packages:rpm',
    "org.elasticsearch.distribution.rpm:elasticsearch-oss:${version}": ':distribution:packages:oss-rpm',
    "org.elasticsearch.distribution.deb:elasticsearch:${version}": ':distribution:packages:deb',
    "org.elasticsearch.distribution.deb:elasticsearch-oss:${version}": ':distribution:packages:oss-deb',
    "org.elasticsearch.test:logger-usage:${version}": ':test:logger-usage',
    "org.elasticsearch.xpack.test:feature-aware:${version}": ':x-pack:test:feature-aware',
    // for transport client
    "org.elasticsearch.plugin:transport-netty4-client:${version}": ':modules:transport-netty4',
    "org.elasticsearch.plugin:reindex-client:${version}": ':modules:reindex',
    "org.elasticsearch.plugin:lang-mustache-client:${version}": ':modules:lang-mustache',
    "org.elasticsearch.plugin:parent-join-client:${version}": ':modules:parent-join',
    "org.elasticsearch.plugin:aggs-matrix-stats-client:${version}": ':modules:aggs-matrix-stats',
    "org.elasticsearch.plugin:percolator-client:${version}": ':modules:percolator',
    "org.elasticsearch.plugin:rank-eval-client:${version}": ':modules:rank-eval',
  ]

  bwcVersions.snapshotProjectNames.each { snapshotName ->
    Version snapshot = bwcVersions.getSnapshotForProject(snapshotName)
    if (snapshot != null ) {
      String snapshotProject = ":distribution:bwc:${snapshotName}"
      project(snapshotProject).ext.bwcVersion = snapshot
      ext.projectSubstitutions["org.elasticsearch.distribution.deb:elasticsearch:${snapshot}"] = snapshotProject
      ext.projectSubstitutions["org.elasticsearch.distribution.rpm:elasticsearch:${snapshot}"] = snapshotProject
      ext.projectSubstitutions["org.elasticsearch.distribution.zip:elasticsearch:${snapshot}"] = snapshotProject
      if (snapshot.onOrAfter('6.3.0')) {
        ext.projectSubstitutions["org.elasticsearch.distribution.deb:elasticsearch-oss:${snapshot}"] = snapshotProject
        ext.projectSubstitutions["org.elasticsearch.distribution.rpm:elasticsearch-oss:${snapshot}"] = snapshotProject
        ext.projectSubstitutions["org.elasticsearch.distribution.zip:elasticsearch-oss:${snapshot}"] = snapshotProject
      }
    }
  }

  /*
   * Gradle only resolve project substitutions during dependency resolution but
   * we sometimes want to do the resolution at other times. This creates a
   * convenient method we can call to do it.
   */
  ext.dependencyToProject = { Dependency dep ->
    if (dep instanceof ProjectDependency) {
      return dep.dependencyProject
    } else {
      String substitution = projectSubstitutions.get("${dep.group}:${dep.name}:${dep.version}")
      if (substitution != null) {
        return findProject(substitution)
      }
      return null
    }
  }

  project.afterEvaluate {
    configurations.all {
      resolutionStrategy.dependencySubstitution { DependencySubstitutions subs ->
        projectSubstitutions.each { k,v ->
          subs.substitute(subs.module(k)).with(subs.project(v))
        }
      }
    }

    // Handle javadoc dependencies across projects. Order matters: the linksOffline for
    // org.elasticsearch:elasticsearch must be the last one or all the links for the
    // other packages (e.g org.elasticsearch.client) will point to server rather than
    // their own artifacts.
    if (project.plugins.hasPlugin(BuildPlugin)) {
      String artifactsHost = VersionProperties.elasticsearch.isSnapshot() ? "https://snapshots.elastic.co" : "https://artifacts.elastic.co"
      Closure sortClosure = { a, b -> b.group <=> a.group }
      Closure depJavadocClosure = { dep ->
        if (dep.group != null && dep.group.startsWith('org.elasticsearch')) {
          Project upstreamProject = dependencyToProject(dep)
          if (upstreamProject != null) {
            project.javadoc.dependsOn "${upstreamProject.path}:javadoc"
            String artifactPath = dep.group.replaceAll('\\.', '/') + '/' + dep.name.replaceAll('\\.', '/') + '/' + dep.version
            project.javadoc.options.linksOffline artifactsHost + "/javadoc/" + artifactPath, "${upstreamProject.buildDir}/docs/javadoc/"
          }
        }
      }
      project.configurations.compile.dependencies.findAll().toSorted(sortClosure).each(depJavadocClosure)
      project.configurations.compileOnly.dependencies.findAll().toSorted(sortClosure).each(depJavadocClosure)
    }
  }
}

// Ensure similar tasks in dependent projects run first. The projectsEvaluated here is
// important because, while dependencies.all will pickup future dependencies,
// it is not necessarily true that the task exists in both projects at the time
// the dependency is added.
gradle.projectsEvaluated {
  allprojects {
    if (project.path == ':test:framework') {
      // :test:framework:test cannot run before and after :server:test
      return
    }
    if (tasks.findByPath('test') != null && tasks.findByPath('integTest') != null) {
      integTest.mustRunAfter test
    }
    configurations.all { Configuration configuration ->
      /*
       * The featureAwarePlugin configuration has a dependency on x-pack:plugin:core and x-pack:plugin:core has a dependency on the
       * featureAwarePlugin configuration. The below task ordering logic would force :x-pack:plugin:core:test
       * :x-pack:test:feature-aware:test to depend on each other circularly. We break that cycle here.
       */
      if (configuration.name == "featureAwarePlugin") {
        return
      }
      dependencies.all { Dependency dep ->
        Project upstreamProject = dependencyToProject(dep)
        if (upstreamProject != null) {
          if (project.path == upstreamProject.path) {
            // TODO: distribution integ tests depend on themselves (!), fix that
            return
          }
          for (String taskName : ['test', 'integTest']) {
            Task task = project.tasks.findByName(taskName)
            Task upstreamTask = upstreamProject.tasks.findByName(taskName)
            if (task != null && upstreamTask != null) {
              task.mustRunAfter(upstreamTask)
            }
          }
        }
      }
    }
  }
}

// intellij configuration
allprojects {
  apply plugin: 'idea'

  if (isIdea) {
    project.buildDir = file('build-idea')
  }
  idea {
    module {
      inheritOutputDirs = false
      outputDir = file('build-idea/classes/main')
      testOutputDir = file('build-idea/classes/test')

      // also ignore other possible build dirs
      excludeDirs += file('build')
      excludeDirs += file('build-eclipse')

      iml {
        // fix so that Gradle idea plugin properly generates support for resource folders
        // see also https://issues.gradle.org/browse/GRADLE-2975
        withXml {
          it.asNode().component.content.sourceFolder.findAll { it.@url == 'file://$MODULE_DIR$/src/main/resources' }.each {
            it.attributes().remove('isTestSource')
            it.attributes().put('type', 'java-resource')
          }
          it.asNode().component.content.sourceFolder.findAll { it.@url == 'file://$MODULE_DIR$/src/test/resources' }.each {
            it.attributes().remove('isTestSource')
            it.attributes().put('type', 'java-test-resource')
          }
        }
      }
    }
  }

  task cleanIdeaBuildDir(type: Delete) {
    delete 'build-idea'
  }
  cleanIdeaBuildDir.setGroup("ide")
  cleanIdeaBuildDir.setDescription("Deletes the IDEA build directory.")

  tasks.cleanIdea.dependsOn(cleanIdeaBuildDir)
}

idea {
  project {
    vcs = 'Git'
  }
}
// Make sure gradle idea was run before running anything in intellij (including import).
File ideaMarker = new File(projectDir, '.local-idea-is-configured')
tasks.idea.doLast {
  ideaMarker.setText('', 'UTF-8')
}
if (System.getProperty('idea.active') != null && ideaMarker.exists() == false) {
  throw new GradleException('You must run gradle idea from the root of elasticsearch before importing into IntelliJ')
}

// eclipse configuration
allprojects {
  apply plugin: 'eclipse'
  // Name all the non-root projects after their path so that paths get grouped together when imported into eclipse.
  if (path != ':') {
    eclipse.project.name = path
    if (Os.isFamily(Os.FAMILY_WINDOWS)) {
      eclipse.project.name = eclipse.project.name.replace(':', '_')
    }
  }

  plugins.withType(JavaBasePlugin) {
    File eclipseBuild = project.file('build-eclipse')
    eclipse.classpath.defaultOutputDir = eclipseBuild
    if (isEclipse) {
      // set this so generated dirs will be relative to eclipse build
      project.buildDir = eclipseBuild
    }
    eclipse.classpath.file.whenMerged { classpath ->
      // give each source folder a unique corresponding output folder
      int i = 0;
      classpath.entries.findAll { it instanceof SourceFolder }.each { folder ->
        i++;
        // this is *NOT* a path or a file.
        folder.output = "build-eclipse/" + i
      }
    }
  }

  File licenseHeaderFile;
  String prefix = ':x-pack';

  if (Os.isFamily(Os.FAMILY_WINDOWS)) {
    prefix = prefix.replace(':', '_')
  }
  if (eclipse.project.name.startsWith(prefix)) {
      licenseHeaderFile = new File(project.rootDir, 'buildSrc/src/main/resources/license-headers/elastic-license-header.txt')
  } else {
      licenseHeaderFile = new File(project.rootDir, 'buildSrc/src/main/resources/license-headers/oss-license-header.txt')
  }

  String lineSeparator = Os.isFamily(Os.FAMILY_WINDOWS) ? '\\\\r\\\\n' : '\\\\n'
  String licenseHeader = licenseHeaderFile.getText('UTF-8').replace(System.lineSeparator(), lineSeparator)
  task copyEclipseSettings(type: Copy) {
    // TODO: "package this up" for external builds
    from new File(project.rootDir, 'buildSrc/src/main/resources/eclipse.settings')
    into '.settings'
    filter{ it.replaceAll('@@LICENSE_HEADER_TEXT@@', licenseHeader)}
  }
  // otherwise .settings is not nuked entirely
  task wipeEclipseSettings(type: Delete) {
    delete '.settings'
  }
  tasks.cleanEclipse.dependsOn(wipeEclipseSettings)
  // otherwise the eclipse merging is *super confusing*
  tasks.eclipse.dependsOn(cleanEclipse, copyEclipseSettings)
}

// we need to add the same --debug-jvm option as
// the real RunTask has, so we can pass it through
class Run extends DefaultTask {
  boolean debug = false

  @org.gradle.api.internal.tasks.options.Option(
        option = "debug-jvm",
        description = "Enable debugging configuration, to allow attaching a debugger to elasticsearch."
  )
  public void setDebug(boolean enabled) {
    project.project(':distribution').run.clusterConfig.debug = enabled
  }
}
task run(type: Run) {
  dependsOn ':distribution:run'
  description = 'Runs elasticsearch in the foreground'
  group = 'Verification'
  impliesSubProjects = true
}

wrapper {
    distributionType = DistributionType.ALL
    doLast {
        final DistributionLocator locator = new DistributionLocator()
        final GradleVersion version = GradleVersion.version(wrapper.gradleVersion)
        final URI distributionUri = locator.getDistributionFor(version, wrapper.distributionType.name().toLowerCase(Locale.ENGLISH))
        final URI sha256Uri = new URI(distributionUri.toString() + ".sha256")
        final String sha256Sum = new String(sha256Uri.toURL().bytes)
        wrapper.getPropertiesFile() << "distributionSha256Sum=${sha256Sum}\n"
        println "Added checksum to wrapper properties"
    }
}

static void assertLinesInFile(final Path path, final List<String> expectedLines) {
  final List<String> actualLines = Files.readAllLines(path)
  int line = 0
  for (final String expectedLine : expectedLines) {
    final String actualLine = actualLines.get(line)
    if (expectedLine != actualLine) {
      throw new GradleException("expected line [${line + 1}] in [${path}] to be [${expectedLine}] but was [${actualLine}]")
    }
    line++
  }
}

/*
 * Check that all generated JARs have our NOTICE.txt and an appropriate
 * LICENSE.txt in them. We configurate this in gradle but we'd like to
 * be extra paranoid.
 */
subprojects { project ->
  project.tasks.withType(Jar).whenTaskAdded { jarTask ->
    final Task extract = project.task("extract${jarTask.name.capitalize()}", type: LoggedExec) {
      dependsOn jarTask
      ext.destination = project.buildDir.toPath().resolve("jar-extracted/${jarTask.name}")
      commandLine "${->new File(rootProject.compilerJavaHome, 'bin/jar')}",
          'xf', "${-> jarTask.outputs.files.singleFile}", 'META-INF/LICENSE.txt', 'META-INF/NOTICE.txt'
      workingDir destination
      doFirst {
        project.delete(destination)
        Files.createDirectories(destination)
      }
    }

    final Task checkNotice = project.task("verify${jarTask.name.capitalize()}Notice") {
      dependsOn extract
      doLast {
        final List<String> noticeLines = Files.readAllLines(project.noticeFile.toPath())
        final Path noticePath = extract.destination.resolve('META-INF/NOTICE.txt')
        assertLinesInFile(noticePath, noticeLines)
      }
    }
    project.check.dependsOn checkNotice

    final Task checkLicense = project.task("verify${jarTask.name.capitalize()}License") {
      dependsOn extract
      doLast {
        final List<String> licenseLines = Files.readAllLines(project.licenseFile.toPath())
        final Path licensePath = extract.destination.resolve('META-INF/LICENSE.txt')
        assertLinesInFile(licensePath, licenseLines)
      }
    }
    project.check.dependsOn checkLicense
  }
}

/* Remove assemble/dependenciesInfo on all qa projects because we don't need to publish
 * artifacts for them. */
gradle.projectsEvaluated {
  subprojects {
    if (project.path.startsWith(':qa')) {
      Task assemble = project.tasks.findByName('assemble')
      if (assemble) {
        project.tasks.remove(assemble)
        project.build.dependsOn.remove('assemble')
      }
      Task dependenciesInfo = project.tasks.findByName('dependenciesInfo')
      if (dependenciesInfo) {
        project.tasks.remove(dependenciesInfo)
        project.precommit.dependsOn.remove('dependenciesInfo')
      }
    }
  }
}

if (System.properties.get("build.compare") != null) {
  apply plugin: 'compare-gradle-builds'
  compareGradleBuilds {
    ext.referenceProject = System.properties.get("build.compare")
    doFirst {
      if (file(referenceProject).exists() == false) {
        throw new GradleException(
                "Use git worktree to check out a version to compare against to ../elasticsearch_build_reference"
        )
      }
    }
    sourceBuild {
      gradleVersion = "4.8.1" // does not default to gradle weapper of project dir, but current version
      projectDir = referenceProject
      tasks = ["clean", "assemble"]
      arguments = ["-Dbuild.compare_friendly=true"]
    }
    targetBuild {
      tasks = ["clean", "assemble"]
      // use -Dorg.gradle.java.home= to alter jdk versions
      arguments = ["-Dbuild.compare_friendly=true"]
    }
  }
}