SOLR-16801: Reset the thread's contextClassloader after loading the C…

…oreContainer (#1645)

Co-authored-by: Thomas Wöckinger <two@silbergrau.com>
Co-authored-by: Houston Putman <houston@apache.org>
(cherry picked from commit 0a6a114)

solr/CHANGES.txt

@@ -142,6 +142,8 @@ Bug Fixes
 
 * SOLR-16765: bin/solr export tool limit property was off by 1.  Now limit results exported to the exact number. (Eric Pugh)
 
+* SOLR-16801: Reset the thread's contextClassloader after loading the CoreContainer (Thomas Wöckinger, Houston Putman)
+
 Dependency Upgrades
 ---------------------
 * PR#1494: Upgrade forbiddenapis to 3.5 (Uwe Schindler)

solr/core/src/java/org/apache/solr/core/CoreContainer.java

@@ -746,12 +746,22 @@ private void registerV2ApiIfEnabled(Class<? extends JerseyResource> clazz) {
       reason =
           "Set the thread contextClassLoader for all 3rd party dependencies that we cannot control")
   public void load() {
+    final ClassLoader originalContextClassLoader = Thread.currentThread().getContextClassLoader();
+    try {
+      // Set the thread's contextClassLoader for any plugins that are loaded via Modules or Packages
+      // and have dependencies that use the thread's contextClassLoader
+      Thread.currentThread().setContextClassLoader(loader.getClassLoader());
+      loadInternal();
+    } finally {
+      Thread.currentThread().setContextClassLoader(originalContextClassLoader);
+    }
+  }
+
+  /** Load the cores defined for this CoreContainer */
+  private void loadInternal() {
     if (log.isDebugEnabled()) {
       log.debug("Loading cores into CoreContainer [instanceDir={}]", getSolrHome());
     }
-    // Set the thread's contextClassLoader for any plugins that are loaded via Modules or Packages
-    Thread.currentThread().setContextClassLoader(loader.getClassLoader());
-
     logging = LogWatcher.newRegisteredLogWatcher(cfg.getLogWatcherConfig(), loader);
 
     ClusterEventProducerFactory clusterEventProducerFactory = new ClusterEventProducerFactory(this);