From 3a4b4310b48c8c79ad686a535ab8dc849102ada5 Mon Sep 17 00:00:00 2001
From: Shalin Shekhar Mangar <shalin@apache.org>
Date: Fri, 23 Oct 2015 14:03:49 +0000
Subject: [PATCH] SOLR-8189: eTag calculation during HTTP Cache Validation uses
 unsynchronized WeakHashMap causing threads to be stuck in runnable state

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1710218 13f79535-47bb-0310-9956-ffa450edef68
---
 solr/CHANGES.txt                                               | 3 +++
 .../org/apache/solr/servlet/cache/HttpCacheHeaderUtil.java     | 3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index 602e4fa8b75..8d129a9d99d 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -288,6 +288,9 @@ Bug Fixes
 
 * SOLR-7843: DataImportHandler's delta imports leak memory because the delta keys are kept in memory
   and not cleared after the process is finished. (Pablo Lozano via shalin)
+
+* SOLR-8189: eTag calculation during HTTP Cache Validation uses unsynchronized WeakHashMap causing
+  threads to be stuck in runnable state. (shalin)
   
 Optimizations
 ----------------------
diff --git a/solr/core/src/java/org/apache/solr/servlet/cache/HttpCacheHeaderUtil.java b/solr/core/src/java/org/apache/solr/servlet/cache/HttpCacheHeaderUtil.java
index 7785f1aa757..228a169a474 100644
--- a/solr/core/src/java/org/apache/solr/servlet/cache/HttpCacheHeaderUtil.java
+++ b/solr/core/src/java/org/apache/solr/servlet/cache/HttpCacheHeaderUtil.java
@@ -56,8 +56,7 @@ public final class HttpCacheHeaderUtil {
    *
    * @see #calcEtag
    */
-  private static Map<SolrCore, EtagCacheVal> etagCoreCache
-    = new WeakHashMap<>();
+  private static Map<SolrCore, EtagCacheVal> etagCoreCache = Collections.synchronizedMap(new WeakHashMap<>());
 
   /** @see #etagCoreCache */
   private static class EtagCacheVal {