From 12bf217970917ca1c600dc49db2073468b9bb598 Mon Sep 17 00:00:00 2001
From: Marc Handalian <handalm@amazon.com>
Date: Tue, 15 Feb 2022 10:27:29 -0800
Subject: [PATCH] Remove bypass of fsync on primaries and force fsync on
 replicas.

This change will force an fsync on replicas when a new commit point is received.

Signed-off-by: Marc Handalian <handalm@amazon.com>
---
 .../opensearch/index/engine/InternalEngine.java    |  3 +++
 .../java/org/opensearch/index/store/Store.java     | 14 +++++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/server/src/main/java/org/opensearch/index/engine/InternalEngine.java b/server/src/main/java/org/opensearch/index/engine/InternalEngine.java
index 1fc998164ac12..4076162f949c4 100644
--- a/server/src/main/java/org/opensearch/index/engine/InternalEngine.java
+++ b/server/src/main/java/org/opensearch/index/engine/InternalEngine.java
@@ -352,6 +352,9 @@ public void updateCurrentInfos(byte[] infosBytes, long gen) throws IOException {
             toIndexInput(infosBytes),
             gen);
         assert gen == infos.getGeneration();
+        if (gen > getLatestSegmentInfos().getGeneration()) {
+            this.store.syncDirectory();
+        }
         externalReaderManager.internalReaderManager.setCurrentInfos(infos);
         externalReaderManager.maybeRefresh();
     }
diff --git a/server/src/main/java/org/opensearch/index/store/Store.java b/server/src/main/java/org/opensearch/index/store/Store.java
index 04825ea701fe9..6176e06e243a6 100644
--- a/server/src/main/java/org/opensearch/index/store/Store.java
+++ b/server/src/main/java/org/opensearch/index/store/Store.java
@@ -104,6 +104,7 @@
 import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
@@ -208,6 +209,14 @@ public Directory directory() {
         return directory;
     }
 
+    /**
+     * Forces an fsync on the directory - to be called by replicas after receiving a new commit point.
+     * @throws IOException if we are unable to list current directory contents.
+     */
+    public void syncDirectory() throws IOException {
+        this.directory.sync(Arrays.asList(this.directory.listAll()));
+    }
+
     /**
      * Returns the last committed segments info for this store
      *
@@ -785,11 +794,6 @@ public Set<String> getPendingDeletions() throws IOException {
             // to be removed once fixed in FilterDirectory.
             return unwrap(this).getPendingDeletions();
         }
-
-        @Override
-        public void sync(Collection<String> names) throws IOException {
-            // Do nothing.
-        }
     }
 
     /**