[GitHub] [sling-org-apache-sling-jcr-resource] rombert commented on a diff in pull request #38: SLING-11654 implement AccessMetrics

[GitBox <gi...@apache.org>]

rombert commented on code in PR #38:
URL: https://github.com/apache/sling-org-apache-sling-jcr-resource/pull/38#discussion_r1016614651


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src/main/java/org/apache/sling/jcr/resource/internal/helper/AccessLogger.java:
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@@ -0,0 +1,129 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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.
+ */
+package org.apache.sling.jcr.resource.internal.helper;
+
+import java.io.Closeable;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicLong;
+import java.util.stream.Collectors;
+
+import org.apache.sling.api.resource.Resource;
+import org.apache.sling.api.resource.ResourceResolver;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ *  Helper class to report on repository access.
+ *  
+ *  The focus is to have a less overhead as possible if it is not used; in case it is enabled and access
+ *  is logged, the performance overhead does not matter.
+ *  
+ *  In the current implementation it has 2 features:
+ *  * Write a stacktrace on every recorded operation; this comes with a massive overhead and it is definitely
+ *    not recommended to turn this on on production, since it can easily create 100s of megabytes of log and will slow
+ *    down processing massively. To use this turn on TRACE logging on 'org.apache.sling.jcr.resource.AccessLogger.operation'
+ *  * When a resource resolver is closed, dump a single log statement about the number of recorded operations. The overhead is
+ *    very small and it can be turned on for a longer period of time also in production. To use it enable DEBUG logging on
+ *    'org.apache.sling.jcr.resource.AccessLogger.statistics'.
+ *  
+ *
+ */
+public class AccessLogger implements Closeable {
+    
+    
+    Map<String,AtomicLong> metrics = new HashMap<>();

Review Comment:
   @joerghoh  - this `HashMap` is not suitable for concurrent access, even though keys and values are thread-safe. It is possible to enter an endless loop while working with the map under certain circumstances.



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