From 0d9e606f9ddaabe1a0ea5d8060b987a759251098 Mon Sep 17 00:00:00 2001
From: Finn Carroll <carrofin@amazon.com>
Date: Thu, 31 Oct 2024 11:10:54 -0700
Subject: [PATCH] Feature flag GRPC_ENABLE_SETTING

Signed-off-by: Finn Carroll <carrofin@amazon.com>
---
 .../org/opensearch/common/util/FeatureFlags.java    | 13 ++++++++++++-
 .../grpc/AbstractGrpcServerTransport.java           |  3 +--
 server/src/main/java/org/opensearch/node/Node.java  | 13 +++++++++----
 3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/server/src/main/java/org/opensearch/common/util/FeatureFlags.java b/server/src/main/java/org/opensearch/common/util/FeatureFlags.java
index 6df68013a8119..bd5cbb81c47e0 100644
--- a/server/src/main/java/org/opensearch/common/util/FeatureFlags.java
+++ b/server/src/main/java/org/opensearch/common/util/FeatureFlags.java
@@ -128,6 +128,16 @@ public class FeatureFlags {
         Property.NodeScope
     );
 
+    /**
+     * Gates the functionality of the Netty4 gRPC server.
+     */
+    public static final String GRPC_EXPERIMENTAL = "opensearch.experimental.feature.grpc.enabled";
+    public static final Setting<Boolean> GRPC_ENABLE_SETTING = Setting.boolSetting(
+        GRPC_EXPERIMENTAL,
+        false,
+        Property.NodeScope
+    );
+
     private static final List<Setting<Boolean>> ALL_FEATURE_FLAG_SETTINGS = List.of(
         REMOTE_STORE_MIGRATION_EXPERIMENTAL_SETTING,
         EXTENSIONS_SETTING,
@@ -138,7 +148,8 @@ public class FeatureFlags {
         STAR_TREE_INDEX_SETTING,
         APPLICATION_BASED_CONFIGURATION_TEMPLATES_SETTING,
         READER_WRITER_SPLIT_EXPERIMENTAL_SETTING,
-        TERM_VERSION_PRECOMMIT_ENABLE_SETTING
+        TERM_VERSION_PRECOMMIT_ENABLE_SETTING,
+        GRPC_ENABLE_SETTING
     );
 
     /**
diff --git a/server/src/main/java/org/opensearch/grpc/AbstractGrpcServerTransport.java b/server/src/main/java/org/opensearch/grpc/AbstractGrpcServerTransport.java
index 03d997aff3f6e..cd56b02d0413b 100644
--- a/server/src/main/java/org/opensearch/grpc/AbstractGrpcServerTransport.java
+++ b/server/src/main/java/org/opensearch/grpc/AbstractGrpcServerTransport.java
@@ -119,9 +119,8 @@ public GrpcStats stats() {
     // gRPC service definitions provided at bind
     abstract protected TransportAddress bindAddress(InetAddress hostAddress, PortsRange portRange);
 
-    // TODO: IDENTICAL TO - HTTP SERVER TRANSPORT
     protected void bindServer() {
-        InetAddress hostAddresses[];
+        InetAddress[] hostAddresses;
         try {
             hostAddresses = networkService.resolveBindHostAddresses(bindHosts);
         } catch (IOException e) {
diff --git a/server/src/main/java/org/opensearch/node/Node.java b/server/src/main/java/org/opensearch/node/Node.java
index 7ddfc28d0a888..f8e7ba750b504 100644
--- a/server/src/main/java/org/opensearch/node/Node.java
+++ b/server/src/main/java/org/opensearch/node/Node.java
@@ -313,7 +313,9 @@
 
 import static java.util.stream.Collectors.toList;
 import static org.opensearch.common.util.FeatureFlags.BACKGROUND_TASK_EXECUTION_EXPERIMENTAL;
+import static org.opensearch.common.util.FeatureFlags.GRPC_ENABLE_SETTING;
 import static org.opensearch.common.util.FeatureFlags.TELEMETRY;
+import static org.opensearch.common.util.FeatureFlags.initializeFeatureFlags;
 import static org.opensearch.env.NodeEnvironment.collectFileCacheDataPath;
 import static org.opensearch.index.ShardIndexingPressureSettings.SHARD_INDEXING_PRESSURE_ENABLED_ATTRIBUTE_KEY;
 import static org.opensearch.indices.RemoteStoreSettings.CLUSTER_REMOTE_STORE_PINNED_TIMESTAMP_ENABLED;
@@ -1753,16 +1755,19 @@ public void onTimeout(TimeValue timeout) {
 
         injector.getInstance(HttpServerTransport.class).start();
 
-        // TODO: FEATURE FLAG HERE?
-        injector.getInstance(GrpcServerTransport.class).start();
+        if (FeatureFlags.isEnabled(GRPC_ENABLE_SETTING)) {
+            injector.getInstance(GrpcServerTransport.class).start();
+        }
 
         if (WRITE_PORTS_FILE_SETTING.get(settings())) {
             TransportService transport = injector.getInstance(TransportService.class);
             writePortsFile("transport", transport.boundAddress());
             HttpServerTransport http = injector.getInstance(HttpServerTransport.class);
             writePortsFile("http", http.boundAddress());
-            GrpcServerTransport grpc = injector.getInstance(GrpcServerTransport.class);
-            writePortsFile("grpc", grpc.boundAddress());
+            if (FeatureFlags.isEnabled(GRPC_ENABLE_SETTING)) {
+                GrpcServerTransport grpc = injector.getInstance(GrpcServerTransport.class);
+                writePortsFile("grpc", grpc.boundAddress());
+            }
         }
 
         logger.info("started");