From a7dfbb8d182c43834a352a75d5f4b3e6c0912925 Mon Sep 17 00:00:00 2001
From: Rishikesh1159 <rishireddy1159@gmail.com>
Date: Wed, 10 Aug 2022 05:09:18 +0000
Subject: [PATCH] Adding logic and tests for rejecting checkpoints if shard is
 in PrimaryMode.

Signed-off-by: Rishikesh1159 <rishireddy1159@gmail.com>
---
 .../org/opensearch/index/shard/IndexShard.java  |  8 ++++++++
 .../SegmentReplicationTargetServiceTests.java   | 17 +++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/server/src/main/java/org/opensearch/index/shard/IndexShard.java b/server/src/main/java/org/opensearch/index/shard/IndexShard.java
index b05eec4304cd5..c90129b4d1cca 100644
--- a/server/src/main/java/org/opensearch/index/shard/IndexShard.java
+++ b/server/src/main/java/org/opensearch/index/shard/IndexShard.java
@@ -1431,6 +1431,14 @@ public final boolean shouldProcessCheckpoint(ReplicationCheckpoint requestCheckp
             logger.trace(() -> new ParameterizedMessage("Ignoring new replication checkpoint - shard is not started {}", state()));
             return false;
         }
+        if (getReplicationTracker().isPrimaryMode()) {
+            logger.trace(
+                () -> new ParameterizedMessage(
+                    "Ignoring new replication checkpoint - shard is in primaryMode and cannot receive any checkpoints."
+                )
+            );
+            return false;
+        }
         ReplicationCheckpoint localCheckpoint = getLatestReplicationCheckpoint();
         if (localCheckpoint.isAheadOf(requestCheckpoint)) {
             logger.trace(
diff --git a/server/src/test/java/org/opensearch/indices/replication/SegmentReplicationTargetServiceTests.java b/server/src/test/java/org/opensearch/indices/replication/SegmentReplicationTargetServiceTests.java
index 8b4bda7de50ad..3c3a09ce4df12 100644
--- a/server/src/test/java/org/opensearch/indices/replication/SegmentReplicationTargetServiceTests.java
+++ b/server/src/test/java/org/opensearch/indices/replication/SegmentReplicationTargetServiceTests.java
@@ -204,6 +204,23 @@ public void testNewCheckpoint_validationPassesAndReplicationFails() throws IOExc
         closeShard(indexShard, false);
     }
 
+    /**
+     * here we are starting a new shard in PrimaryMode and testing that we don't process a checkpoint on shard when it is in PrimaryMode.
+     */
+    public void testRejectCheckpointOnShardPrimaryMode() throws IOException {
+        SegmentReplicationTargetService spy = spy(sut);
+
+        // Starting a new shard in PrimaryMode.
+        IndexShard primaryShard = newStartedShard(true);
+        IndexShard spyShard = spy(primaryShard);
+        doNothing().when(spy).startReplication(any(), any(), any());
+        spy.onNewCheckpoint(aheadCheckpoint, spyShard);
+
+        // Verify that checkpoint is not processed as shard is in PrimaryMode.
+        verify(spy, times(0)).startReplication(any(), any(), any());
+        closeShards(primaryShard);
+    }
+
     public void testReplicationOnDone() throws IOException {
         SegmentReplicationTargetService spy = spy(sut);
         IndexShard spyShard = spy(indexShard);