CAMEL-23267: Use a LinkedHashMap as inProgressRepository for file component

Author: thomas-gantenbein-tga

components/camel-file/src/main/java/org/apache/camel/component/file/GenericFileEndpoint.java

@@ -189,7 +189,7 @@ public abstract class GenericFileEndpoint<T> extends ScheduledPollEndpoint imple
                                                          + "org.apache.camel.spi.IdempotentRepository. The in-progress repository is used to account the current in "
                                                          + "progress files being consumed. By default a memory based repository is used.")
     protected IdempotentRepository inProgressRepository
-            = MemoryIdempotentRepository.memoryIdempotentRepository(DEFAULT_IN_PROGRESS_CACHE_SIZE);
+            = MemoryIdempotentRepository.memoryIdempotentRepositoryInsertionOrder(DEFAULT_IN_PROGRESS_CACHE_SIZE);
     @UriParam(label = "consumer,advanced", description = "When consuming, a local work directory can be used to "
                                                          + "store the remote file content directly in local files, to avoid loading the content into memory. This "
                                                          + "is beneficial, if you consume a very big remote file and thus can conserve memory.")
@@ -1502,7 +1502,7 @@ public IdempotentRepository getInProgressRepository() {
 
     /**
      * A pluggable in-progress repository org.apache.camel.spi.IdempotentRepository. The in-progress repository is used
-     * to account the current in progress files being consumed. By default a memory based repository is used.
+     * to account the current in progress files being consumed. By default, a memory based repository is used.
      */
     public void setInProgressRepository(IdempotentRepository inProgressRepository) {
         this.inProgressRepository = inProgressRepository;

core/camel-support/src/main/java/org/apache/camel/support/processor/idempotent/MemoryIdempotentRepository.java

@@ -16,7 +16,9 @@
  */
 package org.apache.camel.support.processor.idempotent;
 
+import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
@@ -77,6 +79,21 @@ public static IdempotentRepository memoryIdempotentRepository(int cacheSize) {
         return answer;
     }
 
+    /**
+     * Creates a new memory based repository using a {@link java.util.LinkedHashMap} as its store, with the given
+     * maximum capacity. When a new entry is added and the store has reached its maximum capacity, the oldest entry is
+     * removed.
+     */
+    public static IdempotentRepository memoryIdempotentRepositoryInsertionOrder(int cacheSize) {
+        LinkedHashMap<String, Object> map = new LinkedHashMap<>() {
+            @Override
+            protected boolean removeEldestEntry(Entry<String, Object> eldest) {
+                return size() > cacheSize;
+            }
+        };
+        return memoryIdempotentRepository(map);
+    }
+
     /**
      * Creates a new memory based repository using the given {@link Map} to use to store the processed message ids.
      * <p/>

core/camel-support/src/test/java/org/apache/camel/support/MemoryIdempotentRepositoryTest.java

@@ -0,0 +1,49 @@
+/*
+ * 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.camel.support;
+
+import java.io.IOException;
+
+import org.apache.camel.spi.IdempotentRepository;
+import org.apache.camel.support.processor.idempotent.MemoryIdempotentRepository;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class MemoryIdempotentRepositoryTest {
+
+    @Test
+    void repositoryEvictsOldestEntryWhenRepositoryIsFull() throws IOException {
+        final int cacheSize = 5;
+        final int entriesNotFittingInRepository = 4;
+        try (IdempotentRepository repository = MemoryIdempotentRepository.memoryIdempotentRepositoryInsertionOrder(
+                cacheSize)) {
+
+            for (int i = 0; i < cacheSize + entriesNotFittingInRepository; i++) {
+                repository.add(String.valueOf(i));
+            }
+
+            for (int i = entriesNotFittingInRepository; i < cacheSize + entriesNotFittingInRepository; i++) {
+                assertTrue(repository.contains(String.valueOf(i)), "Repository should contain entry " + i);
+            }
+            for (int i = 0; i < cacheSize - entriesNotFittingInRepository; i++) {
+                assertFalse(repository.contains(String.valueOf(i)), "Repository should not contain entry " + i);
+            }
+        }
+    }
+}