Add support for JSON and YAML configurations

.java-version

@@ -0,0 +1 @@
+17.0

flume-ng-node/pom.xml

@@ -35,6 +35,7 @@
     <pmd.maxAllowedViolations>5</pmd.maxAllowedViolations>
     <module.name>org.apache.flume.node</module.name>
     <junit-jupiter.version>6.1.3</junit-jupiter.version>
+    <snake-yaml.version>3.2</snake-yaml.version>
   </properties>
 
   <dependencies>
@@ -100,6 +101,13 @@
       <groupId>org.apache.commons</groupId>
       <artifactId>commons-text</artifactId>
     </dependency>
+
+    <dependency>
+      <groupId>org.snakeyaml</groupId>
+      <artifactId>snakeyaml-engine</artifactId>
+      <version>${snake-yaml.version}</version>
+      <optional>true</optional>
+    </dependency>
     <!-- For ThreadSafe and GuardedBy annotations -->
     <dependency>
       <groupId>com.google.code.findbugs</groupId>

flume-ng-node/src/main/java/org/apache/flume/node/Application.java

@@ -106,7 +106,6 @@ public void handleConfigurationEvent(MaterializedConfiguration conf) {
             startAllComponents(conf);
         } catch (InterruptedException e) {
             logger.info("Interrupted while trying to handle configuration event");
-            return;
         } finally {
             // If interrupted while trying to lock, we don't own the lock, so must not attempt to unlock
             if (lifecycleLock.isHeldByCurrentThread()) {

flume-ng-node/src/main/java/org/apache/flume/node/ConfigurationSource.java

@@ -23,10 +23,11 @@
  */
 public interface ConfigurationSource {
 
-    static final String PROPERTIES = "properties";
-    static final String JSON = "json";
-    static final String YAML = "yaml";
-    static final String XML = "xml";
+    String PROPERTIES = "properties";
+    String JSON = "json";
+    String YAML = "yaml";
+    String YML = "yml";
+    String XML = "xml";
 
     /**
      * Returns the InputStream if it hasn't already been processed.

flume-ng-node/src/main/java/org/apache/flume/node/UriConfigurationProvider.java

@@ -36,6 +36,7 @@
 import org.apache.flume.conf.FlumeConfiguration;
 import org.apache.flume.lifecycle.LifecycleAware;
 import org.apache.flume.lifecycle.LifecycleState;
+import org.apache.flume.node.internal.YamlConfigConverter;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
@@ -186,6 +187,7 @@ public class UriConfigurationProvider extends AbstractConfigurationProvider impl
     private final EventBus eventBus;
     private final int interval;
     private final CounterGroup counterGroup;
+    private final boolean isYamlSupported;
     private LifecycleState lifecycleState = LifecycleState.IDLE;
     private ScheduledExecutorService executorService;
 
@@ -201,6 +203,14 @@ public UriConfigurationProvider(
         this.eventBus = eventBus;
         this.interval = pollInterval;
         counterGroup = new CounterGroup();
+        boolean isYaml;
+        try {
+            Class.forName("org.snakeyaml.engine.v2.api.Load");
+            isYaml = true;
+        } catch (Exception exception) {
+            isYaml = false;
+        }
+        isYamlSupported = isYaml;
     }
 
     @Override
@@ -256,6 +266,15 @@ public FlumeConfiguration getFlumeConfiguration() {
                     switch (configurationSource.getExtension()) {
                         case ConfigurationSource.JSON:
                         case ConfigurationSource.YAML:
+                        case ConfigurationSource.YML: {
+                            if (isYamlSupported) {
+                                properties = YamlConfigConverter.convertYamlToProperties(is);
+                            } else {
+                                logger.warn(
+                                        "File extension type {} is unsupported", configurationSource.getExtension());
+                            }
+                            break;
+                        }
                         case ConfigurationSource.XML: {
                             logger.warn("File extension type {} is unsupported", configurationSource.getExtension());
                             break;

flume-ng-node/src/main/java/org/apache/flume/node/internal/YamlConfigConverter.java

@@ -0,0 +1,116 @@
+/*
+ * 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.flume.node.internal;
+
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+import org.snakeyaml.engine.v2.api.Load;
+import org.snakeyaml.engine.v2.api.LoadSettings;
+
+/**
+ * Converts YAML and/or JSON files into Java properties that can be consumed by the UriConfigurationProvider.
+ * This uses version 3.x of SnakeYaml that is hosted at https://codeberg.org/snakeyaml/snakeyaml-engine
+ * and supports YAML 1.2.
+ */
+public class YamlConfigConverter {
+
+    public static Properties convertYamlToProperties(InputStream yamlInputStream) {
+        Properties properties = new Properties();
+
+        LoadSettings settings = LoadSettings.builder().build();
+        Load load = new Load(settings);
+
+        // 2. Load the YAML content into basic Java structures
+        Object yamlData = load.loadFromInputStream(yamlInputStream);
+
+        // 3. Recursively flatten the data structure
+        if (yamlData instanceof Map) {
+            flattenMap("", (Map<?, ?>) yamlData, properties);
+        } else if (yamlData != null) {
+            throw new IllegalArgumentException("Root YAML element must be a mapping object.");
+        }
+
+        return properties;
+    }
+
+    private static void flattenMap(String prefix, Map<?, ?> map, Properties properties) {
+        map.forEach((key, value) -> {
+            String currentKey = prefix.isEmpty() ? String.valueOf(key) : prefix + "." + key;
+
+            if (value instanceof Map) {
+                Map<?, ?> childMap = (Map<?, ?>) value;
+                if (!prefix.isEmpty() && isComponentMap(childMap)) {
+                    properties.setProperty(currentKey, String.join(" ", keyNames(childMap)));
+                }
+                flattenMap(currentKey, childMap, properties);
+            } else if (value instanceof List) {
+                flattenList(currentKey, (List<?>) value, properties);
+            } else if (value != null) {
+                properties.setProperty(currentKey, String.valueOf(value));
+            }
+        });
+    }
+
+    /**
+     * Determines whether a Map represents a set of named components, such as the sources, channels
+     * or sinks of an agent. This is the case when every key is a String and every value is a Map.
+     */
+    private static boolean isComponentMap(Map<?, ?> map) {
+        if (map.isEmpty()) {
+            return false;
+        }
+        for (Map.Entry<?, ?> entry : map.entrySet()) {
+            if (!(entry.getKey() instanceof String) || !(entry.getValue() instanceof Map)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private static List<String> keyNames(Map<?, ?> map) {
+        List<String> names = new ArrayList<>(map.size());
+        map.keySet().forEach(key -> names.add((String) key));
+        return names;
+    }
+
+    private static void flattenList(String prefix, List<?> list, Properties properties) {
+        // Flume expects a list of simple values, such as channel names, as a space separated value.
+        if (list.stream().noneMatch(value -> value instanceof Map || value instanceof List)) {
+            List<String> values = new ArrayList<>(list.size());
+            list.stream().filter(value -> value != null).forEach(value -> values.add(String.valueOf(value)));
+            if (!values.isEmpty()) {
+                properties.setProperty(prefix, String.join(" ", values));
+            }
+            return;
+        }
+        for (int i = 0; i < list.size(); i++) {
+            Object value = list.get(i);
+            String currentKey = prefix + "[" + i + "]";
+
+            if (value instanceof Map) {
+                flattenMap(currentKey, (Map<?, ?>) value, properties);
+            } else if (value instanceof List) {
+                flattenList(currentKey, (List<?>) value, properties);
+            } else if (value != null) {
+                properties.setProperty(currentKey, String.valueOf(value));
+            }
+        }
+    }
+}

flume-ng-node/src/test/java/org/apache/flume/node/TestApplication.java

@@ -212,13 +212,15 @@ public Void answer(InvocationOnMock invocation) throws Throwable {
 
     @Test
     public void testFlumeInit() throws Exception {
-        File configFile = new File(baseDir, "flume-conf-init.properties");
-        Files.copy(
-                new File(getClass()
-                        .getClassLoader()
-                        .getResource("flume-conf-init.properties")
-                        .getFile()),
-                configFile);
+        for (String fileName :
+                new String[] {"flume-conf-init.properties", "flume-conf-init.yml", "flume-conf-init.json"}) {
+            runFlumeInit(fileName);
+        }
+    }
+
+    private void runFlumeInit(String fileName) throws Exception {
+        File configFile = new File(baseDir, fileName);
+        Files.copy(new File(getClass().getClassLoader().getResource(fileName).getFile()), configFile);
         ConfigurationSource source = new FileConfigurationSource(configFile.toURI());
         List<ConfigurationSource> sourceList = new ArrayList<>();
         sourceList.add(source);
@@ -227,12 +229,12 @@ public void testFlumeInit() throws Exception {
         List<LifecycleAware> components = Lists.newArrayList();
         Application application = new Application(components);
         MaterializedConfiguration configuration = configurationProvider.getConfiguration();
-        Assert.assertNotNull("Unable to create configuration", configuration);
+        Assert.assertNotNull("Unable to create configuration from " + fileName, configuration);
         application.handleConfigurationEvent(configuration);
         application.start();
         Map<String, Channel> channels = configuration.getChannels();
         Channel channel = channels.get("processedChannel");
-        Assert.assertNotNull("Channel not found", channel);
+        Assert.assertNotNull("Channel not found using " + fileName, channel);
         Map<String, SourceRunner> sourceRunners = configuration.getSourceRunners();
         Assert.assertNotNull("No source runners", sourceRunners);
         SourceRunner runner = sourceRunners.get("source1");

flume-ng-node/src/test/java/org/apache/flume/node/internal/YamlConfigConverterTest.java

@@ -0,0 +1,64 @@
+/*
+ * 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.flume.node.internal;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.fail;
+
+import java.io.FileInputStream;
+import java.util.Properties;
+import org.junit.jupiter.api.Test;
+
+public class YamlConfigConverterTest {
+
+    @Test
+    public void testYaml() {
+        try {
+            FileInputStream is = new FileInputStream("target/test-classes/flume-conf-init.yml");
+            Properties props = YamlConfigConverter.convertYamlToProperties(is);
+            assertNotNull(props);
+            is = new FileInputStream("target/test-classes/flume-conf-init.properties");
+            Properties properties = new Properties();
+            properties.load(is);
+            System.out.println(props.size() + " properties");
+            for (String name : props.stringPropertyNames()) {
+                System.out.println(name + ": " + props.get(name));
+            }
+            assertEquals(properties, props);
+            assertNull(props.getProperty("host1"));
+        } catch (Exception ex) {
+            fail("Unable to convert YAML to properties: " + ex.getMessage());
+        }
+    }
+
+    @Test
+    public void testJson() {
+        try {
+            FileInputStream is = new FileInputStream("target/test-classes/flume-conf-init.json");
+            Properties props = YamlConfigConverter.convertYamlToProperties(is);
+            assertNotNull(props);
+            is = new FileInputStream("target/test-classes/flume-conf-init.properties");
+            Properties properties = new Properties();
+            properties.load(is);
+            assertEquals(properties, props);
+        } catch (Exception ex) {
+            fail("Unable to convert JSON to properties: " + ex.getMessage());
+        }
+    }
+}

flume-ng-node/src/test/resources/flume-conf-init.json

@@ -0,0 +1,38 @@
+{
+  "host1": {
+    "sources": {
+      "source1": {
+        "type": "org.apache.flume.source.LocalSource",
+        "channels": [
+          "channel1"
+        ],
+        "totalEvents": 5,
+        "backoffSleepIncrement": 50
+      },
+      "processedSource": {
+        "type": "org.apache.flume.source.LocalSource",
+        "channels": [
+          "processedChannel"
+        ]
+      }
+    },
+    "channels": {
+      "channel1": {
+        "type": "memory",
+        "capacity": 10000
+      },
+      "processedChannel": {
+        "type": "memory",
+        "capacity": 10000
+      }
+    },
+    "sinks": {
+      "sink1": {
+        "type": "org.apache.flume.sink.NullInitSink",
+        "batchSize": 1,
+        "targetSource": "processedSource",
+        "channel": "channel1"
+      }
+    }
+  }
+}