From d171db04670733120bf2c8f36b3005dcdb4ca9e7 Mon Sep 17 00:00:00 2001
From: Chenyang Ji <cyji@amazon.com>
Date: Wed, 5 Jun 2024 15:01:00 -0700
Subject: [PATCH] Refactor debugExporter into singleton

Signed-off-by: Chenyang Ji <cyji@amazon.com>
---
 .../insights/core/exporter/DebugExporter.java     | 15 ++++++++++++++-
 .../exporter/QueryInsightsExporterFactory.java    | 14 +++++---------
 .../core/exporter/DebugExporterTests.java         |  2 +-
 3 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/DebugExporter.java b/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/DebugExporter.java
index 3da057e1bb984..116bd26e1f9bc 100644
--- a/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/DebugExporter.java
+++ b/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/DebugExporter.java
@@ -26,7 +26,20 @@ public final class DebugExporter implements QueryInsightsExporter {
     /**
      * Constructor of DebugExporter
      */
-    public DebugExporter() {}
+    private DebugExporter() {}
+
+    private static class InstanceHolder {
+        private static final DebugExporter INSTANCE = new DebugExporter();
+    }
+
+    /**
+     Get the singleton instance of DebugExporter
+     *
+     @return DebugExporter instance
+     */
+    public static DebugExporter getInstance() {
+        return InstanceHolder.INSTANCE;
+    }
 
     /**
      * Write the list of SearchQueryRecord to debug log
diff --git a/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/QueryInsightsExporterFactory.java b/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/QueryInsightsExporterFactory.java
index a90b6f4ec47c9..7324590c9f582 100644
--- a/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/QueryInsightsExporterFactory.java
+++ b/plugins/query-insights/src/main/java/org/opensearch/plugin/insights/core/exporter/QueryInsightsExporterFactory.java
@@ -93,16 +93,12 @@ public void validateExporterConfig(final Settings settings) throws IllegalArgume
      * @return QueryInsightsExporter the created exporter sink
      */
     public QueryInsightsExporter createExporter(SinkType type, String indexPattern) {
-        QueryInsightsExporter exporter;
-        switch (type) {
-            case LOCAL_INDEX:
-                exporter = new LocalIndexExporter(client, DateTimeFormat.forPattern(indexPattern));
-                break;
-            default:
-                exporter = new DebugExporter();
+        if (SinkType.LOCAL_INDEX.equals(type)) {
+            QueryInsightsExporter exporter = new LocalIndexExporter(client, DateTimeFormat.forPattern(indexPattern));
+            this.exporters.add(exporter);
+            return exporter;
         }
-        this.exporters.add(exporter);
-        return exporter;
+        return DebugExporter.getInstance();
     }
 
     /**
diff --git a/plugins/query-insights/src/test/java/org/opensearch/plugin/insights/core/exporter/DebugExporterTests.java b/plugins/query-insights/src/test/java/org/opensearch/plugin/insights/core/exporter/DebugExporterTests.java
index 8bcc187115a72..736e406289b2c 100644
--- a/plugins/query-insights/src/test/java/org/opensearch/plugin/insights/core/exporter/DebugExporterTests.java
+++ b/plugins/query-insights/src/test/java/org/opensearch/plugin/insights/core/exporter/DebugExporterTests.java
@@ -23,7 +23,7 @@ public class DebugExporterTests extends OpenSearchTestCase {
 
     @Before
     public void setup() {
-        debugExporter = new DebugExporter();
+        debugExporter = DebugExporter.getInstance();
     }
 
     public void testExport() {