fix ThreadLocal leaks in webapp (#2585)

* remove ThreadLocal data at the end of request processing
fixes #1761

Author: Vladimir Kotal

opengrok-indexer/src/main/java/org/opengrok/indexer/analysis/AnalyzerGuru.java

@@ -506,6 +506,15 @@ public static FileAnalyzer getAnalyzer(InputStream in, String file) throws IOExc
         return factory.getAnalyzer();
     }
 
+    /**
+     * Free resources associated with all registered analyzers.
+     */
+    public static void returnAnalyzers() {
+        for (FileAnalyzerFactory analyzer : factories) {
+            analyzer.returnAnalyzer();
+        }
+    }
+
     /**
      * Populate a Lucene document with the required fields.
      *

opengrok-indexer/src/main/java/org/opengrok/indexer/analysis/FileAnalyzerFactory.java

@@ -205,6 +205,13 @@ public final FileAnalyzer getAnalyzer() {
         return fa;
     }
 
+    /**
+     * Free thread-local data.
+     */
+    public void returnAnalyzer() {
+        cachedAnalyzer.remove();
+    }
+
     /**
      * Create a new analyzer.
      * @return an analyzer

opengrok-web/src/main/java/org/opengrok/web/WebappListener.java

@@ -22,24 +22,26 @@
  */
 package org.opengrok.web;
 
-import java.io.File;
-import java.io.IOException;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-import javax.servlet.ServletContext;
-import javax.servlet.ServletContextEvent;
-import javax.servlet.ServletContextListener;
-import javax.servlet.ServletRequestEvent;
-import javax.servlet.ServletRequestListener;
 import org.json.simple.parser.ParseException;
 import org.opengrok.indexer.Info;
+import org.opengrok.indexer.analysis.AnalyzerGuru;
 import org.opengrok.indexer.authorization.AuthorizationFramework;
 import org.opengrok.indexer.configuration.RuntimeEnvironment;
 import org.opengrok.indexer.logger.LoggerFactory;
 import org.opengrok.indexer.web.PageConfig;
 import org.opengrok.indexer.web.SearchHelper;
 import org.opengrok.web.api.v1.suggester.provider.service.SuggesterServiceFactory;
 
+import javax.servlet.ServletContext;
+import javax.servlet.ServletContextEvent;
+import javax.servlet.ServletContextListener;
+import javax.servlet.ServletRequestEvent;
+import javax.servlet.ServletRequestListener;
+import java.io.File;
+import java.io.IOException;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
 import static org.opengrok.indexer.util.StatisticsUtils.loadStatistics;
 import static org.opengrok.indexer.util.StatisticsUtils.saveStatistics;
 
@@ -135,6 +137,8 @@ public void requestDestroyed(ServletRequestEvent e) {
         if (sh != null) {
             sh.destroy();
         }
+
+        AnalyzerGuru.returnAnalyzers();
     }
 
     /**

opengrok-web/src/test/java/org/opengrok/web/WebappListenerTest.java

@@ -0,0 +1,27 @@
+package org.opengrok.web;
+
+import org.junit.Test;
+
+import javax.servlet.ServletContext;
+import javax.servlet.ServletRequestEvent;
+import javax.servlet.http.HttpServletRequest;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class WebappListenerTest {
+    /**
+     * simple smoke test for WebappListener request handling
+     */
+    @Test
+    public void testRequest() {
+        WebappListener wl = new WebappListener();
+        final HttpServletRequest req = mock(HttpServletRequest.class);
+        final ServletContext servletContext = mock(ServletContext.class);
+        when(req.getServletContext()).thenReturn(servletContext);
+        ServletRequestEvent event = new ServletRequestEvent(servletContext, req);
+
+        wl.requestInitialized(event);
+        wl.requestDestroyed(event);
+    }
+}