From 8ac4fdd6bb84b225919d30f6073e7dad02aeb0a1 Mon Sep 17 00:00:00 2001
From: markrmiller <markrmiller@apache.org>
Date: Tue, 23 Feb 2016 13:59:04 -0500
Subject: [PATCH] SOLR-8696: Start the Overseer before actions that need the
 overseer on init and when reconnecting after zk expiration and improve init
 logic.

---
 solr/CHANGES.txt                              |  3 ++
 .../org/apache/solr/cloud/ZkController.java   | 36 ++++++++-----------
 2 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index 3afc961a99b..bf548ae67e2 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -215,6 +215,9 @@ Bug Fixes
 * SOLR-8497: Merge index does not mark the Directory objects it creates as 'done' and they are retained in the 
   Directory cache. (Sivlio Sanchez, Mark Miller)
 
+* SOLR-8696: Start the Overseer before actions that need the overseer on init and when reconnecting after 
+  zk expiration and improve init logic. (Scott Blum, Mark Miller)
+
 Optimizations
 ----------------------
 * SOLR-7876: Speed up queries and operations that use many terms when timeAllowed has not been
diff --git a/solr/core/src/java/org/apache/solr/cloud/ZkController.java b/solr/core/src/java/org/apache/solr/cloud/ZkController.java
index 7874e2b0167..391f69a927c 100644
--- a/solr/core/src/java/org/apache/solr/cloud/ZkController.java
+++ b/solr/core/src/java/org/apache/solr/cloud/ZkController.java
@@ -266,11 +266,8 @@ public final class ZkController {
 
               // seems we dont need to do this again...
               // Overseer.createClientNodes(zkClient, getNodeName());
-
-              cc.cancelCoreRecoveries();
-
-              registerAllCoresAsDown(registerOnReconnect, false);
-
+              
+              // start the overseer first as following code may need it's processing
               if (!zkRunOnly) {
                 ElectionContext context = new OverseerElectionContext(zkClient,
                     overseer, getNodeName());
@@ -284,6 +281,10 @@ public final class ZkController {
                 overseerElector.joinElection(context, true);
               }
 
+              cc.cancelCoreRecoveries();
+
+              registerAllCoresAsDown(registerOnReconnect, false);
+
               zkStateReader.createClusterStateWatchersAndUpdate();
 
               // we have to register as live first to pick up docs in the buffer
@@ -620,26 +621,12 @@ public final class ZkController {
   private void init(CurrentCoreDescriptorProvider registerOnReconnect) {
 
     try {
-      boolean createdWatchesAndUpdated = false;
-      Stat stat = zkClient.exists(ZkStateReader.LIVE_NODES_ZKNODE, null, true);
-      if (stat != null && stat.getNumChildren() > 0) {
-        zkStateReader.createClusterStateWatchersAndUpdate();
-        createdWatchesAndUpdated = true;
-        publishAndWaitForDownStates();
-      }
-
       createClusterZkNodes(zkClient);
 
-      createEphemeralLiveNode();
-
-      ShardHandler shardHandler;
-      UpdateShardHandler updateShardHandler;
-      shardHandler = cc.getShardHandlerFactory().getShardHandler();
-      updateShardHandler = cc.getUpdateShardHandler();
-
+      // start the overseer first as following code may need it's processing
       if (!zkRunOnly) {
         overseerElector = new LeaderElector(zkClient);
-        this.overseer = new Overseer(shardHandler, updateShardHandler,
+        this.overseer = new Overseer(cc.getShardHandlerFactory().getShardHandler(), cc.getUpdateShardHandler(),
             CommonParams.CORES_HANDLER_PATH, zkStateReader, this, cloudConfig);
         ElectionContext context = new OverseerElectionContext(zkClient,
             overseer, getNodeName());
@@ -647,10 +634,15 @@ public final class ZkController {
         overseerElector.joinElection(context, false);
       }
 
-      if (!createdWatchesAndUpdated) {
+      zkStateReader.createClusterStateWatchersAndUpdate();
+      Stat stat = zkClient.exists(ZkStateReader.LIVE_NODES_ZKNODE, null, true);
+      if (stat != null && stat.getNumChildren() > 0) {
         zkStateReader.createClusterStateWatchersAndUpdate();
+        publishAndWaitForDownStates();
       }
 
+      // Do this last to signal we're up.
+      createEphemeralLiveNode();
     } catch (IOException e) {
       log.error("", e);
       throw new SolrException(SolrException.ErrorCode.SERVER_ERROR,