Run core's full cluster restart tests with x-pack (elastic/x-pack-elasticsearch#2433)

This change pulls in the o.e.u.FullClusterRestartIT class from core and runs it as part of the
x-pack full cluster restart tests.

Relates elastic/x-pack-elasticsearch#1629

Original commit: elastic/x-pack-elasticsearch@87da59485f

qa/full-cluster-restart/build.gradle

@@ -3,6 +3,7 @@ import org.elasticsearch.gradle.test.RestIntegTestTask
 import org.elasticsearch.gradle.Version
 
 import java.nio.charset.StandardCharsets
+import java.nio.file.Paths
 import java.util.regex.Matcher
 
 // Apply the java plugin to this project so the sources can be edited in an IDE
@@ -59,6 +60,19 @@ Closure waitWithAuth = { NodeInfo node, AntBuilder ant ->
 
 Project mainProject = project
 
+String coreFullClusterRestartPath = project(':qa:full-cluster-restart').projectDir.toPath().resolve('src/test/java').toString()
+sourceSets {
+    test {
+        java {
+            srcDirs += [coreFullClusterRestartPath]
+        }
+    }
+}
+
+licenseHeaders {
+    approvedLicenses << 'Apache'
+}
+
 /**
  * Subdirectories of this project are test rolling upgrades with various
  * configuration options based on their name.
@@ -76,7 +90,7 @@ subprojects {
   sourceSets {
     test {
       java {
-        srcDirs = ["${mainProject.projectDir}/src/test/java"]
+        srcDirs = ["${mainProject.projectDir}/src/test/java", coreFullClusterRestartPath]
       }
       resources {
         srcDirs = ["${mainProject.projectDir}/src/test/resources"]
@@ -84,6 +98,10 @@ subprojects {
     }
   }
 
+  licenseHeaders {
+    approvedLicenses << 'Apache'
+  }
+
   String outputDir = "generated-resources/${project.name}"
 
   // This is a top level task which we will add dependencies to below.
@@ -143,6 +161,8 @@ subprojects {
     oldClusterTestRunner.configure {
       systemProperty 'tests.is_old_cluster', 'true'
       systemProperty 'tests.old_cluster_version', version.toString().minus("-SNAPSHOT")
+      systemProperty 'tests.path.repo', new File(buildDir, "cluster/shared/repo")
+      exclude 'org/elasticsearch/upgrades/FullClusterRestartIT.class'
     }
 
     Task upgradedClusterTest = tasks.create(name: "${baseName}#upgradedClusterTest", type: RestIntegTestTask)
@@ -156,6 +176,7 @@ subprojects {
       numNodes = 2
       clusterName = 'full-cluster-restart'
       dataDir = { nodeNum -> oldClusterTest.nodes[nodeNum].dataDir }
+      cleanShared = false // We want to keep snapshots made by the old cluster!
       setupCommand 'setupTestUser', 'bin/x-pack/users', 'useradd', 'test_user', '-p', 'x-pack-test-password', '-r', 'superuser'
       waitCondition = waitWithAuth
       setting 'xpack.ssl.keystore.path', 'testnode.jks'
@@ -174,6 +195,8 @@ subprojects {
     upgradedClusterTestRunner.configure {
       systemProperty 'tests.is_old_cluster', 'false'
       systemProperty 'tests.old_cluster_version', version.toString().minus("-SNAPSHOT")
+      systemProperty 'tests.path.repo', new File(buildDir, "cluster/shared/repo")
+      exclude 'org/elasticsearch/upgrades/FullClusterRestartIT.class'
     }
 
     Task versionBwcTest = tasks.create(name: "${baseName}#bwcTest") {

qa/full-cluster-restart/src/test/java/org/elasticsearch/xpack/restart/CoreFullClusterRestartIT.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+package org.elasticsearch.xpack.restart;
+
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.util.concurrent.ThreadContext;
+import org.elasticsearch.upgrades.FullClusterRestartIT;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+
+public class CoreFullClusterRestartIT extends FullClusterRestartIT {
+
+    @Override
+    protected Settings restClientSettings() {
+        String token = "Basic " + Base64.getEncoder().encodeToString("test_user:x-pack-test-password".getBytes(StandardCharsets.UTF_8));
+        return Settings.builder()
+                .put(ThreadContext.PREFIX + ".Authorization", token)
+                .build();
+    }
+}

qa/full-cluster-restart/src/test/java/org/elasticsearch/xpack/restart/FullClusterRestartIT.java

@@ -75,6 +75,16 @@ public class FullClusterRestartIT extends ESRestTestCase {
         return true;
     }
 
+    @Override
+    protected boolean preserveSnapshotsUponCompletion() {
+        return true;
+    }
+
+    @Override
+    protected boolean preserveReposUponCompletion() {
+        return true;
+    }
+
     @Override
     protected boolean preserveTemplatesUponCompletion() {
         return true;