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https://issues.apache.org/jira/browse/JENA-1122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15136988#comment-15136988
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ASF GitHub Bot commented on JENA-1122:
--------------------------------------
Github user ajs6f commented on a diff in the pull request:
https://github.com/apache/jena/pull/123#discussion_r52173358
--- Diff:
jena-fuseki2/jena-fuseki-core/src/main/java/org/apache/jena/fuseki/build/RefCountingMap.java
---
@@ -0,0 +1,187 @@
+/**
+ * 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.jena.fuseki.build;
+
+import java.util.Collection;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * A key -> value 'map' which reference counts entries.
+ *
+ * <p>
+ * The same (key,value) pair can be added to the map several times and
then
+ * removed several times. A reference count is incremented for each
addition
+ * and, provided the count is greater than 0, decremented on removal.
+ * <p>
+ *
+ * <p>
+ * The pair is removed from the map when a remove decrements the
reference count to 0.
+ * </p>
+ *
+ * <p>
+ * This class is thread safe.
+ * </p>
+ *
+ * @param <K>
+ * @param <T>
+ */
+public class RefCountingMap<K, T> {
--- End diff --
There's, understandably, a lot of methods here that just pass-through to
`ConcurrentHashMap`. Maybe it would be worth doing `extends
ConcurrentHashMap<K, CountedRef<T>>` and just overriding the methods that need
overriding?
> Fuseki fails to start if configured with two services that share the same
> dataset with a lucene index.
> ------------------------------------------------------------------------------------------------------
>
> Key: JENA-1122
> URL: https://issues.apache.org/jira/browse/JENA-1122
> Project: Apache Jena
> Issue Type: Bug
> Components: Text
> Affects Versions: Jena 3.0.0, Fuseki 2.3.0
> Reporter: Brian McBride
>
> This problem arises when the assemblers for the two services run. For each
> service, a separate TextIndexLucene object is created. Both of those objects
> try to lock the same Lucene index directory and one fails.
> A proposed fix is to modify the TextDatasetFactory to only create one
> TextIndexLucene object per on disk directory.
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