From 3bbf8aaa8a9f57c43d64e9c361184c379d90b9c9 Mon Sep 17 00:00:00 2001
From: David Smiley <dsmiley@apache.org>
Date: Tue, 5 Apr 2016 14:15:31 -0400
Subject: [PATCH] SOLR-8875: Fix null clusterState from ZkStateWriter. Revert
 my sanity check asserts in Overseer.

---
 solr/CHANGES.txt                                              | 3 +++
 solr/core/src/java/org/apache/solr/cloud/Overseer.java        | 1 +
 .../java/org/apache/solr/cloud/overseer/ZkStateWriter.java    | 4 ++--
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index 5ab52b29542..9e6da65d9ce 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -101,6 +101,9 @@ Bug Fixes
 * SOLR-8902: Make sure ReturnFields only returns the requested fields from (fl=) evn when 
   DocumentTransformers ask for getExtraRequestFields()  (ryan)
 
+* SOLR-8875: SolrCloud Overseer clusterState could unexpectedly be null resulting in NPE.
+  (Scott Blum via David Smiley)
+
 Optimizations
 ----------------------
 * SOLR-8722: Don't force a full ZkStateReader refresh on every Overseer operation.
diff --git a/solr/core/src/java/org/apache/solr/cloud/Overseer.java b/solr/core/src/java/org/apache/solr/cloud/Overseer.java
index 0e5bded5f3f..f25cab7b670 100644
--- a/solr/core/src/java/org/apache/solr/cloud/Overseer.java
+++ b/solr/core/src/java/org/apache/solr/cloud/Overseer.java
@@ -151,6 +151,7 @@ public class Overseer implements Closeable {
             continue; // not a no, not a yes, try ask again
           }
 
+          //TODO consider removing 'refreshClusterState' and simply check if clusterState is null
           if (refreshClusterState) {
             try {
               reader.updateClusterState();
diff --git a/solr/core/src/java/org/apache/solr/cloud/overseer/ZkStateWriter.java b/solr/core/src/java/org/apache/solr/cloud/overseer/ZkStateWriter.java
index 9fb3ada40c6..ec67ed7dbc4 100644
--- a/solr/core/src/java/org/apache/solr/cloud/overseer/ZkStateWriter.java
+++ b/solr/core/src/java/org/apache/solr/cloud/overseer/ZkStateWriter.java
@@ -16,6 +16,7 @@
  */
 package org.apache.solr.cloud.overseer;
 
+import java.lang.invoke.MethodHandles;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
@@ -35,8 +36,6 @@ import org.slf4j.LoggerFactory;
 
 import static java.util.Collections.singletonMap;
 
-import java.lang.invoke.MethodHandles;
-
 /**
  * ZkStateWriter is responsible for writing updates to the cluster state stored in ZooKeeper for
  * both stateFormat=1 collection (stored in shared /clusterstate.json in ZK) and stateFormat=2 collections
@@ -84,6 +83,7 @@ public class ZkStateWriter {
 
     this.reader = zkStateReader;
     this.stats = stats;
+    this.clusterState = zkStateReader.getClusterState();
   }
 
   /**