Change WeakConcurrentMap's cleaner thread's CCL centrally (#804)

Author: eyalkoren

apm-agent-core/src/main/java/co/elastic/apm/agent/util/DataStructures.java

@@ -0,0 +1,48 @@
+/*-
+ * #%L
+ * Elastic APM Java agent
+ * %%
+ * Copyright (C) 2018 - 2019 Elastic and contributors
+ * %%
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ * #L%
+ */
+package co.elastic.apm.agent.util;
+
+import com.blogspot.mydailyjava.weaklockfree.WeakConcurrentMap;
+
+public class DataStructures {
+
+    /**
+     * Use this utility method for WeakConcurrentMap creation if it is created in the context of a request processing
+     * thread whose context class loader is the web application ClassLoader.
+     * This leaks the web application ClassLoader when the application is undeployed/redeployed.
+     * <p>
+     * Tomcat will then stop the thread because it thinks it was created by the web application.
+     * That means that the map will never be cleared, creating a severe memory leak.
+     *
+     * @param <K> map key type
+     * @param <V> map value type
+     * @return a new WeakConcurrentMap with a cleaner thread who's context class loader is the system/bootstrap class loader
+     */
+    public static <K, V> WeakConcurrentMap<K, V> createWeakConcurrentMapWithCleanerThread() {
+        WeakConcurrentMap<K, V> map = new WeakConcurrentMap<>(true);
+        map.getCleanerThread().setContextClassLoader(null);
+        return map;
+    }
+}

apm-agent-plugins/apm-jdbc-plugin/src/main/java/co/elastic/apm/agent/jdbc/helper/JdbcHelper.java

@@ -27,6 +27,7 @@
 import co.elastic.apm.agent.bci.VisibleForAdvice;
 import co.elastic.apm.agent.impl.transaction.Span;
 import co.elastic.apm.agent.impl.transaction.TraceContextHolder;
+import co.elastic.apm.agent.util.DataStructures;
 import com.blogspot.mydailyjava.weaklockfree.WeakConcurrentMap;
 
 import javax.annotation.Nullable;
@@ -35,17 +36,7 @@
 public abstract class JdbcHelper {
     @SuppressWarnings("WeakerAccess")
     @VisibleForAdvice
-    public static final WeakConcurrentMap<Object, String> statementSqlMap;
-
-    static {
-        statementSqlMap = new WeakConcurrentMap<>(true);
-        // This class will probably be loaded in the context of a request processing thread
-        // whose context class loader is the web application ClassLoader.
-        // This leaks the web application ClassLoader when the application is undeployed/redeployed.
-        // Tomcat will then stop the thread because it thinks it was created by the web application.
-        // That means that the map will never be cleared, creating a severe memory leak.
-        statementSqlMap.getCleanerThread().setContextClassLoader(null);
-    }
+    public static final WeakConcurrentMap<Object, String> statementSqlMap = DataStructures.createWeakConcurrentMapWithCleanerThread();
 
     /**
      * Maps the provided sql to the provided Statement object

apm-agent-plugins/apm-jdbc-plugin/src/main/java/co/elastic/apm/agent/jdbc/helper/JdbcHelperImpl.java

@@ -29,6 +29,7 @@
 import co.elastic.apm.agent.impl.transaction.Span;
 import co.elastic.apm.agent.impl.transaction.TraceContextHolder;
 import co.elastic.apm.agent.jdbc.signature.SignatureParser;
+import co.elastic.apm.agent.util.DataStructures;
 import com.blogspot.mydailyjava.weaklockfree.WeakConcurrentMap;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -43,7 +44,7 @@ public class JdbcHelperImpl extends JdbcHelper {
     public static final String DB_SPAN_ACTION = "query";
 
     private static final Logger logger = LoggerFactory.getLogger(JdbcHelperImpl.class);
-    private static final WeakConcurrentMap<Connection, ConnectionMetaData> metaDataMap = new WeakConcurrentMap<Connection, ConnectionMetaData>(true);
+    private static final WeakConcurrentMap<Connection, ConnectionMetaData> metaDataMap = DataStructures.createWeakConcurrentMapWithCleanerThread();
 
     @VisibleForAdvice
     public static final ThreadLocal<SignatureParser> SIGNATURE_PARSER_THREAD_LOCAL = new ThreadLocal<SignatureParser>() {

apm-agent-plugins/apm-urlconnection-plugin/src/main/java/co/elastic/apm/agent/urlconnection/HttpUrlConnectionInstrumentation.java

@@ -29,6 +29,7 @@
 import co.elastic.apm.agent.http.client.HttpClientHelper;
 import co.elastic.apm.agent.impl.transaction.Span;
 import co.elastic.apm.agent.impl.transaction.TraceContext;
+import co.elastic.apm.agent.util.DataStructures;
 import com.blogspot.mydailyjava.weaklockfree.WeakConcurrentMap;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.NamedElement;
@@ -51,7 +52,7 @@
 public abstract class HttpUrlConnectionInstrumentation extends ElasticApmInstrumentation {
 
     @VisibleForAdvice
-    public static final WeakConcurrentMap<HttpURLConnection, Span> inFlightSpans = new WeakConcurrentMap<HttpURLConnection, Span>(true);
+    public static final WeakConcurrentMap<HttpURLConnection, Span> inFlightSpans = DataStructures.createWeakConcurrentMapWithCleanerThread();
 
     @Override
     public Collection<String> getInstrumentationGroupNames() {