Fixed testPluginInstalled test

build.gradle

@@ -162,15 +162,44 @@ task integTest(type: RestIntegTestTask) {
 }
 tasks.named("check").configure { dependsOn(integTest) }
 
+def _numNodes = findProperty('numNodes') as Integer ?: 1
+
 integTest {
+
+    doFirst {
+        // Tell the test JVM if the cluster JVM is running under a debugger so that tests can
+        // use longer timeouts for requests.
+        def isDebuggingCluster = getDebug() || System.getProperty("test.debug") != null
+        systemProperty 'cluster.debug', isDebuggingCluster
+        // Set number of nodes system property to be used in tests
+        systemProperty 'cluster.number_of_nodes', "${_numNodes}"
+        // There seems to be an issue when running multi node run or integ tasks with unicast_hosts
+        // not being written, the waitForAllConditions ensures it's written
+        getClusters().forEach { cluster ->
+            cluster.waitForAllConditions()
+        }
+    }
+
     // The --debug-jvm command-line option makes the cluster debuggable; this makes the tests debuggable
     if (System.getProperty("test.debug") != null) {
         jvmArgs '-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=*:5005'
     }
 }
 
 testClusters.integTest {
-    testDistribution = "INTEG_TEST"
+    testDistribution = "ARCHIVE"
+    // Cluster shrink exception thrown if we try to set numberOfNodes to 1, so only apply if > 1
+    if (_numNodes > 1) numberOfNodes = _numNodes
+    // When running integration tests it doesn't forward the --debug-jvm to the cluster anymore
+    // i.e. we have to use a custom property to flag when we want to debug OpenSearch JVM
+    // since we also support multi node integration tests we increase debugPort per node
+    if (System.getProperty("opensearch.debug") != null) {
+        def debugPort = 5005
+        nodes.forEach { node ->
+            node.jvmArgs("-agentlib:jdwp=transport=dt_socket,server=n,suspend=y,address=*:${debugPort}")
+            debugPort += 1
+        }
+    }
 
     // This installs our plugin into the testClusters
     plugin(project.tasks.bundlePlugin.archiveFile)