Detect duplicate settings keys on startup

This commit changes the startup behavior of Elasticsearch to throw an
exception if duplicate settings keys are detected in the Elasticsearch
configuration file.

Closes #13079

core/src/main/java/org/elasticsearch/common/settings/loader/PropertiesSettingsLoader.java

@@ -20,6 +20,7 @@
 package org.elasticsearch.common.settings.loader;
 
 import org.apache.lucene.util.IOUtils;
+import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.common.io.FastStringReader;
 import org.elasticsearch.common.io.stream.StreamInput;
 
@@ -36,7 +37,7 @@ public class PropertiesSettingsLoader implements SettingsLoader {
 
     @Override
     public Map<String, String> load(String source) throws IOException {
-        Properties props = new Properties();
+        Properties props = new NoDuplicatesProperties();
         FastStringReader reader = new FastStringReader(source);
         try {
             props.load(reader);
@@ -52,7 +53,7 @@ public class PropertiesSettingsLoader implements SettingsLoader {
 
     @Override
     public Map<String, String> load(byte[] source) throws IOException {
-        Properties props = new Properties();
+        Properties props = new NoDuplicatesProperties();
         StreamInput stream = StreamInput.wrap(source);
         try {
             props.load(stream);
@@ -65,4 +66,15 @@ public class PropertiesSettingsLoader implements SettingsLoader {
             IOUtils.closeWhileHandlingException(stream);
         }
     }
+
+    class NoDuplicatesProperties extends Properties {
+        @Override
+        public synchronized Object put(Object key, Object value) {
+            Object previousValue = super.put(key, value);
+            if (previousValue != null) {
+                throw new ElasticsearchParseException("duplicate settings key [{}] found, previous value [{}], current value [{}]", key, previousValue, value);
+            }
+            return previousValue;
+        }
+    }
 }

core/src/main/java/org/elasticsearch/common/settings/loader/XContentSettingsLoader.java

@@ -20,7 +20,6 @@
 package org.elasticsearch.common.settings.loader;
 
 import org.elasticsearch.ElasticsearchParseException;
-import org.elasticsearch.common.xcontent.XContent;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.common.xcontent.XContentType;
@@ -141,7 +140,18 @@ public abstract class XContentSettingsLoader implements SettingsLoader {
             sb.append(pathEle).append('.');
         }
         sb.append(fieldName);
-        settings.put(sb.toString(), parser.text());
+        String key = sb.toString();
+        String currentValue = parser.text();
+        String previousValue = settings.put(key, currentValue);
+        if (previousValue != null) {
+            throw new ElasticsearchParseException(
+                    "duplicate settings key [{}] found at line number [{}], column number [{}], previous value [{}], current value [{}]",
+                    key,
+                    parser.getTokenLocation().lineNumber,
+                    parser.getTokenLocation().columnNumber,
+                    previousValue,
+                    currentValue
+            );
+        }
     }
-
 }

core/src/test/java/org/elasticsearch/common/settings/loader/JsonSettingsLoaderTests.java

@@ -19,19 +19,19 @@
 
 package org.elasticsearch.common.settings.loader;
 
+import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.common.settings.SettingsException;
 import org.elasticsearch.test.ESTestCase;
 import org.junit.Test;
 
 import static org.elasticsearch.common.settings.Settings.settingsBuilder;
-import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.equalTo;
 
 /**
  *
  */
 public class JsonSettingsLoaderTests extends ESTestCase {
-
     @Test
     public void testSimpleJsonSettings() throws Exception {
         String json = "/org/elasticsearch/common/settings/loader/test-settings.json";
@@ -50,4 +50,17 @@ public class JsonSettingsLoaderTests extends ESTestCase {
         assertThat(settings.getAsArray("test1.test3")[0], equalTo("test3-1"));
         assertThat(settings.getAsArray("test1.test3")[1], equalTo("test3-2"));
     }
+
+    public void testDuplicateKeysThrowsException() {
+        String json = "{\"foo\":\"bar\",\"foo\":\"baz\"}";
+        try {
+            settingsBuilder()
+                    .loadFromSource(json)
+                    .build();
+            fail("expected exception");
+        } catch (SettingsException e) {
+            assertEquals(e.getCause().getClass(), ElasticsearchParseException.class);
+            assertTrue(e.toString().contains("duplicate settings key [foo] found at line number [1], column number [13], previous value [bar], current value [baz]"));
+        }
+    }
 }

core/src/test/java/org/elasticsearch/common/settings/loader/PropertiesSettingsLoaderTests.java

@@ -0,0 +1,47 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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.elasticsearch.common.settings.loader;
+
+import org.elasticsearch.ElasticsearchParseException;
+import org.elasticsearch.test.ESTestCase;
+
+import java.io.IOException;
+import java.nio.charset.Charset;
+
+public class PropertiesSettingsLoaderTests extends ESTestCase {
+    public void testDuplicateKeyFromStringThrowsException() throws IOException {
+        PropertiesSettingsLoader loader = new PropertiesSettingsLoader();
+        try {
+            loader.load("foo=bar\nfoo=baz");
+            fail("expected exception");
+        } catch (ElasticsearchParseException e) {
+            assertEquals(e.getMessage(), "duplicate settings key [foo] found, previous value [bar], current value [baz]");
+        }
+    }
+
+    public void testDuplicateKeysFromBytesThrowsException() throws IOException {
+        PropertiesSettingsLoader loader = new PropertiesSettingsLoader();
+        try {
+            loader.load("foo=bar\nfoo=baz".getBytes(Charset.defaultCharset()));
+        } catch (ElasticsearchParseException e) {
+            assertEquals(e.getMessage(), "duplicate settings key [foo] found, previous value [bar], current value [baz]");
+        }
+    }
+}

core/src/test/java/org/elasticsearch/common/settings/loader/YamlSettingsLoaderTests.java

@@ -19,6 +19,7 @@
 
 package org.elasticsearch.common.settings.loader;
 
+import org.elasticsearch.ElasticsearchParseException;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.settings.SettingsException;
 import org.elasticsearch.test.ESTestCase;
@@ -31,7 +32,6 @@ import static org.hamcrest.Matchers.equalTo;
  *
  */
 public class YamlSettingsLoaderTests extends ESTestCase {
-
     @Test
     public void testSimpleYamlSettings() throws Exception {
         String yaml = "/org/elasticsearch/common/settings/loader/test-settings.yml";
@@ -66,4 +66,17 @@ public class YamlSettingsLoaderTests extends ESTestCase {
                 .loadFromStream(yaml, getClass().getResourceAsStream(yaml))
                 .build();
     }
-}
+
+    public void testDuplicateKeysThrowsException() {
+        String yaml = "foo: bar\nfoo: baz";
+        try {
+            settingsBuilder()
+                    .loadFromSource(yaml)
+                    .build();
+            fail("expected exception");
+        } catch (SettingsException e) {
+            assertEquals(e.getCause().getClass(), ElasticsearchParseException.class);
+            assertTrue(e.toString().contains("duplicate settings key [foo] found at line number [2], column number [6], previous value [bar], current value [baz]"));
+        }
+    }
+}