[Build Tools] Custom Gradle plugin to leverage java agent

buildSrc/src/main/java/org/opensearch/gradle/agent/JavaAgent.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.gradle.agent;
+
+import org.gradle.api.Plugin;
+import org.gradle.api.Project;
+import org.gradle.api.artifacts.Configuration;
+import org.gradle.api.tasks.Copy;
+import org.gradle.api.tasks.TaskProvider;
+import org.gradle.api.tasks.testing.Test;
+
+import java.io.File;
+import java.util.Objects;
+
+/**
+ * Gradle plugin to automatically configure the OpenSearch Java agent
+ * for test tasks in OpenSearch plugin projects.
+ */
+public class JavaAgent implements Plugin<Project> {
+
+    /**
+     * Plugin implementation that sets up java agent configuration and applies it to test tasks.
+     */
+    @Override
+    public void apply(Project project) {
+        Configuration agentConfiguration = project.getConfigurations().findByName("agent");
+        if (agentConfiguration == null) {
+            agentConfiguration = project.getConfigurations().create("agent");
+        }
+
+        project.afterEvaluate(p -> {
+            String opensearchVersion = getOpensearchVersion(p);
+            p.getDependencies().add("agent", "org.opensearch:opensearch-agent-bootstrap:" + opensearchVersion);
+            p.getDependencies().add("agent", "org.opensearch:opensearch-agent:" + opensearchVersion);
+        });
+
+        Configuration finalAgentConfiguration = agentConfiguration;
+        TaskProvider<Copy> prepareJavaAgent = project.getTasks().register("prepareJavaAgent", Copy.class, task -> {
+            task.from(finalAgentConfiguration);
+            task.into(new File(project.getBuildDir(), "agent"));
+        });
+
+        project.getTasks().withType(Test.class).configureEach(testTask -> {
+            testTask.dependsOn(prepareJavaAgent);
+
+            final String opensearchVersion = getOpensearchVersion(project);
+
+            testTask.doFirst(task -> {
+                File agentJar = new File(project.getBuildDir(), "agent/opensearch-agent-" + opensearchVersion + ".jar");
+
+                testTask.jvmArgs("-javaagent:" + agentJar.getAbsolutePath());
+            });
+        });
+    }
+
+    /**
+     * Gets the OpenSearch version from project properties, with a fallback default.
+     *
+     * @param project The Gradle project
+     * @return The OpenSearch version to use
+     */
+    private String getOpensearchVersion(Project project) {
+        return Objects.requireNonNull(project.property("opensearch_version")).toString();
+    }
+}

buildSrc/src/main/resources/META-INF/gradle-plugins/opensearch.java-agent.properties

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+#
+# SPDX-License-Identifier: Apache-2.0
+#
+# The OpenSearch Contributors require contributions made to
+# this file be licensed under the Apache-2.0 license or a
+# compatible open source license.
+#
+
+implementation-class=org.opensearch.gradle.agent.JavaAgent

buildSrc/src/test/java/org/opensearch/gradle/agent/JavaAgentTests.java

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+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.gradle.agent;
+
+import org.opensearch.gradle.test.GradleUnitTestCase;
+import org.gradle.api.Project;
+import org.gradle.api.artifacts.Configuration;
+import org.gradle.api.tasks.Copy;
+import org.gradle.testfixtures.ProjectBuilder;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.io.IOException;
+
+public class JavaAgentTests extends GradleUnitTestCase {
+    private TemporaryFolder projectDir;
+    private final String PREPARE_JAVA_AGENT_TASK = "prepareJavaAgent";
+
+    @Before
+    public void setUp() throws IOException {
+        projectDir = new TemporaryFolder();
+        projectDir.create();
+    }
+
+    @After
+    public void tearDown() {
+        projectDir.delete();
+    }
+
+    /**
+     * This test is used to verify that adding the 'opensearch.java-agent' to the project
+     * creates the necessary agent configuration and tasks. This is basically
+     * a behavioral test of the {@link JavaAgent#apply(Project)} method.
+     */
+    @Test
+    public void applyJavaAgentPlugin() {
+        // Create an empty project and apply the JavaAgent plugin
+        Project project = ProjectBuilder.builder().build();
+        project.getPluginManager().apply(JavaAgent.class);
+
+        // Verify the agent configuration was created
+        Configuration agentConfig = project.getConfigurations().findByName("agent");
+        assertNotNull("Agent configuration should be created", agentConfig);
+
+        // Verify the prepareJavaAgent task was created and is of the right type
+        assertNotNull("prepareJavaAgent task should be created", project.getTasks().findByName(PREPARE_JAVA_AGENT_TASK));
+        assertTrue("prepareJavaAgent task should be of type Copy", project.getTasks().findByName(PREPARE_JAVA_AGENT_TASK) instanceof Copy);
+
+        // Verify the destination directory of the Copy task
+        Copy prepareTask = (Copy) project.getTasks().findByName(PREPARE_JAVA_AGENT_TASK);
+        assertEquals(
+            "Destination directory should be build/agent",
+            new File(project.getBuildDir(), "agent"),
+            prepareTask.getDestinationDir()
+        );
+    }
+}