From 5dbff1d1c1d5a1ebf91df58df7daa59a26394c7d Mon Sep 17 00:00:00 2001
From: Alan Woodward <romseygeek@apache.org>
Date: Tue, 25 Nov 2014 11:49:36 +0000
Subject: [PATCH] SOLR-6763: Shard leader elections should not persist across
 ZK session expiry

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1641590 13f79535-47bb-0310-9956-ffa450edef68
---
 solr/CHANGES.txt                              |  3 +++
 .../apache/solr/cloud/ElectionContext.java    | 20 ++++++++++---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index baead9f1770..bbe20c8a13e 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -299,6 +299,9 @@ Bug Fixes
 * SOLR-3774: Solr adds RequestHandler SolrInfoMBeans twice to the JMX server.
   (Tomás Fernández Löbbe, hossman, Mark Miller)
 
+* SOLR-6763: Shard leader elections should not persist across session expiry
+  (Alan Woodward, Mark Miller)
+
 Optimizations
 ----------------------
 
diff --git a/solr/core/src/java/org/apache/solr/cloud/ElectionContext.java b/solr/core/src/java/org/apache/solr/cloud/ElectionContext.java
index 41913438c0e..8a4278d360d 100644
--- a/solr/core/src/java/org/apache/solr/cloud/ElectionContext.java
+++ b/solr/core/src/java/org/apache/solr/cloud/ElectionContext.java
@@ -1,9 +1,5 @@
 package org.apache.solr.cloud;
 
-import java.io.Closeable;
-import java.io.IOException;
-import java.util.concurrent.TimeUnit;
-
 import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.solr.common.SolrException;
 import org.apache.solr.common.SolrException.ErrorCode;
@@ -28,6 +24,7 @@ import org.apache.zookeeper.KeeperException.NodeExistsException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.io.Closeable;
 import java.io.IOException;
 import java.util.List;
 import java.util.concurrent.ExecutorService;
@@ -136,13 +133,12 @@ class ShardLeaderElectionContextBase extends ElectionContext {
     try {
       RetryUtil.retryOnThrowable(NodeExistsException.class, 15000, 1000,
           new RetryCmd() {
-            
             @Override
             public void execute() throws Throwable {
-              zkClient.makePath(leaderPath, ZkStateReader.toJSON(leaderProps),
-                  CreateMode.EPHEMERAL, true);
+              zkClient.makePath(leaderPath, ZkStateReader.toJSON(leaderProps), CreateMode.EPHEMERAL, true);
             }
-          });
+          }
+      );
     } catch (Throwable t) {
       if (t instanceof OutOfMemoryError) {
         throw (OutOfMemoryError) t;
@@ -407,13 +403,19 @@ final class ShardLeaderElectionContext extends ShardLeaderElectionContextBase {
     
     Slice slices = zkController.getClusterState().getSlice(collection, shardId);
     int cnt = 0;
-    while (true && !isClosed && !cc.isShutDown()) {
+    while (!isClosed && !cc.isShutDown()) {
       // wait for everyone to be up
       if (slices != null) {
         int found = 0;
         try {
           found = zkClient.getChildren(shardsElectZkPath, null, true).size();
         } catch (KeeperException e) {
+          if (e instanceof KeeperException.SessionExpiredException) {
+            // if the session has expired, then another election will be launched, so
+            // quit here
+            throw new SolrException(ErrorCode.SERVER_ERROR,
+                                    "ZK session expired - cancelling election for " + collection + " " + shardId);
+          }
           SolrException.log(log,
               "Error checking for the number of election participants", e);
         }