Segment Replication stats throwing NPE when shards are unassigned or …

…are in delayed allocation phase

Signed-off-by: Rampreeth Ethiraj <[email protected]>

CHANGELOG.md

@@ -11,6 +11,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - [Writable Warm] Add composite directory implementation and integrate it with FileCache ([12782](https://github.com/opensearch-project/OpenSearch/pull/12782))
 - Fix race condition while parsing derived fields from search definition ([14445](https://github.com/opensearch-project/OpenSearch/pull/14445))
 - Add allowlist setting for ingest-common processors ([#14439](https://github.com/opensearch-project/OpenSearch/issues/14439))
+- Fix Segment Replication stats throwing NPE when shards are unassigned or are in delayed allocation phase ([#14580](https://github.com/opensearch-project/OpenSearch/pull/14580))
 
 ### Dependencies
 - Bump `org.gradle.test-retry` from 1.5.8 to 1.5.9 ([#13442](https://github.com/opensearch-project/OpenSearch/pull/13442))

server/src/main/java/org/opensearch/index/seqno/ReplicationTracker.java

@@ -1254,6 +1254,7 @@ public ReplicationCheckpoint getLatestReplicationCheckpoint() {
     private boolean isPrimaryRelocation(String allocationId) {
         Optional<ShardRouting> shardRouting = routingTable.assignedShards()
             .stream()
+            .filter(routing -> Objects.nonNull(routing.allocationId()))
             .filter(routing -> routing.allocationId().getId().equals(allocationId))
             .findAny();
         return shardRouting.isPresent() && shardRouting.get().primary();