SOLR-15953: remove unused LTRThreadModule.preClose CloseHook logic (#562)

Author: cpoerschke

solr/CHANGES.txt

@@ -522,6 +522,8 @@ Other Changes
 
 * SOLR-15934: CloseHook is now an interface with default method implementations instead of an abstract class. (Mike Drob)
 
+* SOLR-15953: Remove unused LTRThreadModule.preClose CloseHook logic. (Christine Poerschke)
+
 * SOLR-15916: Remove dist/ from the binary release. The solr-core and solrj jars will be included in the server WEB-INF/lib directory,
 and each individual module's jar will be included in its directory's lib/ folder. (Houston Putman)
 

solr/modules/ltr/src/java/org/apache/solr/ltr/LTRThreadModule.java

@@ -20,10 +20,7 @@
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Semaphore;
 
-import org.apache.solr.common.util.ExecutorUtil;
 import org.apache.solr.common.util.NamedList;
-import org.apache.solr.core.CloseHook;
-import org.apache.solr.core.SolrCore;
 import org.apache.solr.util.SolrPluginUtils;
 import org.apache.solr.util.plugin.NamedListInitializedPlugin;
 
@@ -56,7 +53,7 @@
  * <code>totalPoolThreads</code> imposes a contention between the queries if
  * <code>(totalPoolThreads &lt; numThreadsPerRequest * total parallel queries)</code>.
  */
-public final class LTRThreadModule implements CloseHook, NamedListInitializedPlugin  {
+public final class LTRThreadModule implements NamedListInitializedPlugin  {
 
   public static LTRThreadModule getInstance(NamedList<?> args) {
 
@@ -163,13 +160,6 @@ public void execute(Runnable command) {
     createWeightScoreExecutor.execute(command);
   }
 
-  @Override
-  public void preClose(SolrCore core) {
-    // TODO: Investigate...
-    //   All uses of setExecutor use the core container's update executor, which could impact other cores?
-    ExecutorUtil.shutdownAndAwaitTermination(createWeightScoreExecutor);
-  }
-
   public void setExecutor(ExecutorService sharedExecutor) {
     this.createWeightScoreExecutor = sharedExecutor;
   }