Add option to provide URIs to monitor in addition to the config file

log4j-core-test/src/test/java/org/apache/logging/log4j/core/MonitorUriTest.java

@@ -0,0 +1,61 @@
+/*
+ * 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.logging.log4j.core;
+
+import static org.awaitility.Awaitility.waitAtMost;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collections;
+import java.util.concurrent.TimeUnit;
+import org.apache.logging.log4j.core.config.Configuration;
+import org.apache.logging.log4j.core.config.ConfigurationSource;
+import org.apache.logging.log4j.core.config.Configurator;
+import org.apache.logging.log4j.core.config.builder.api.ConfigurationBuilder;
+import org.apache.logging.log4j.core.config.builder.api.ConfigurationBuilderFactory;
+import org.apache.logging.log4j.core.config.properties.PropertiesConfiguration;
+import org.apache.logging.log4j.core.util.Source;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.CleanupMode;
+import org.junit.jupiter.api.io.TempDir;
+
+public class MonitorUriTest {
+
+    private static final int MONITOR_INTERVAL = 3;
+
+    @Test
+    void testReconfigureOnChangeInMonitorUri(@TempDir(cleanup = CleanupMode.ON_SUCCESS) final Path tempDir)
+            throws IOException {
+        ConfigurationBuilder<PropertiesConfiguration> configBuilder =
+                ConfigurationBuilderFactory.newConfigurationBuilder(PropertiesConfiguration.class);
+        Path config = tempDir.resolve("config.xml");
+        Path monitorUri = tempDir.resolve("monitorUri.xml");
+        ConfigurationSource configSource = new ConfigurationSource(new Source(config), new byte[] {}, 0);
+        Configuration configuration = configBuilder
+                .setConfigurationSource(configSource)
+                .setMonitorInterval(String.valueOf(MONITOR_INTERVAL))
+                .add(configBuilder.newMonitorUri(monitorUri.toUri().toString()))
+                .build();
+
+        try (LoggerContext loggerContext = Configurator.initialize(configuration)) {
+            Files.write(monitorUri, Collections.singletonList("a change"));
+            waitAtMost(MONITOR_INTERVAL + 2, TimeUnit.SECONDS)
+                    .until(() -> loggerContext.getConfiguration() != configuration);
+        }
+    }
+}

log4j-core/src/main/java/org/apache/logging/log4j/core/config/AbstractConfiguration.java

@@ -22,6 +22,7 @@
 import java.io.InputStream;
 import java.lang.ref.WeakReference;
 import java.net.URI;
+import java.net.URISyntaxException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -132,6 +133,7 @@ public abstract class AbstractConfiguration extends AbstractFilterable implement
     private ConcurrentMap<String, Appender> appenders = new ConcurrentHashMap<>();
     private ConcurrentMap<String, LoggerConfig> loggerConfigs = new ConcurrentHashMap<>();
     private List<CustomLevelConfig> customLevels = Collections.emptyList();
+    private List<URI> uris = Collections.emptyList();
     private final ConcurrentMap<String, String> propertyMap = new ConcurrentHashMap<>();
     private final Interpolator tempLookup = new Interpolator(propertyMap);
     private final StrSubstitutor runtimeStrSubstitutor = new RuntimeStrSubstitutor(tempLookup);
@@ -323,10 +325,19 @@ public void start() {
         LOGGER.info("Starting configuration {}...", this);
         this.setStarting();
         if (watchManager.getIntervalSeconds() >= 0) {
-            LOGGER.info(
-                    "Start watching for changes to {} every {} seconds",
-                    getConfigurationSource(),
-                    watchManager.getIntervalSeconds());
+            if (uris != null && uris.size() > 0) {
+                LOGGER.info(
+                        "Start watching for changes to {} and {} every {} seconds",
+                        getConfigurationSource(),
+                        uris,
+                        watchManager.getIntervalSeconds());
+                watchManager.addMonitorUris(configurationSource.getSource(), uris);
+            } else {
+                LOGGER.info(
+                        "Start watching for changes to {} every {} seconds",
+                        getConfigurationSource(),
+                        watchManager.getIntervalSeconds());
+            }
             watchManager.start();
         }
         if (hasAsyncLoggers()) {
@@ -729,9 +740,16 @@ protected void doConfigure() {
             } else if (child.isInstanceOf(AsyncWaitStrategyFactoryConfig.class)) {
                 final AsyncWaitStrategyFactoryConfig awsfc = child.getObject(AsyncWaitStrategyFactoryConfig.class);
                 asyncWaitStrategyFactory = awsfc.createWaitStrategyFactory();
+            } else if (child.isInstanceOf(MonitorUris.class)) {
+                uris = convertToJavaNetUris(child.getObject(MonitorUris.class).getUris());
             } else {
                 final List<String> expected = Arrays.asList(
-                        "\"Appenders\"", "\"Loggers\"", "\"Properties\"", "\"Scripts\"", "\"CustomLevels\"");
+                        "\"Appenders\"",
+                        "\"Loggers\"",
+                        "\"Properties\"",
+                        "\"Scripts\"",
+                        "\"CustomLevels\"",
+                        "\"MonitorUris\"");
                 LOGGER.error(
                         "Unknown object \"{}\" of type {} is ignored: try nesting it inside one of: {}.",
                         child.getName(),
@@ -767,6 +785,18 @@ protected void doConfigure() {
         setParents();
     }
 
+    private List<URI> convertToJavaNetUris(final List<Uri> uris) {
+        final List<URI> javaNetUris = new ArrayList<>();
+        for (Uri uri : uris) {
+            try {
+                javaNetUris.add(new URI(uri.getUri()));
+            } catch (URISyntaxException e) {
+                LOGGER.error("Error parsing monitor URI: " + uri, e);
+            }
+        }
+        return javaNetUris;
+    }
+
     public static Level getDefaultLevel() {
         final String levelName = PropertiesUtil.getProperties()
                 .getStringProperty(DefaultConfiguration.DEFAULT_LEVEL, Level.ERROR.name());

log4j-core/src/main/java/org/apache/logging/log4j/core/config/ConfigurationFileWatcher.java

@@ -17,7 +17,10 @@
 package org.apache.logging.log4j.core.config;
 
 import java.io.File;
+import java.net.URI;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import org.apache.logging.log4j.core.util.AbstractWatcher;
 import org.apache.logging.log4j.core.util.FileWatcher;
 import org.apache.logging.log4j.core.util.Source;
@@ -28,38 +31,57 @@
  */
 public class ConfigurationFileWatcher extends AbstractWatcher implements FileWatcher {
 
-    private File file;
-    private long lastModifiedMillis;
+    private Map<File, Long> monitoredFiles = new HashMap<>();
 
     public ConfigurationFileWatcher(
             final Configuration configuration,
             final Reconfigurable reconfigurable,
             final List<ConfigurationListener> configurationListeners,
             long lastModifiedMillis) {
         super(configuration, reconfigurable, configurationListeners);
-        this.lastModifiedMillis = lastModifiedMillis;
     }
 
     @Override
     public long getLastModified() {
-        return file != null ? file.lastModified() : 0;
+        Long lastModifiedMillis = 0L;
+        for (final File monitoredFile : monitoredFiles.keySet()) {
+            if (monitoredFile.lastModified() > lastModifiedMillis) {
+                lastModifiedMillis = monitoredFile.lastModified();
+            }
+        }
+        return lastModifiedMillis;
     }
 
     @Override
     public void fileModified(final File file) {
-        lastModifiedMillis = file.lastModified();
+        monitoredFiles.entrySet().stream()
+                .forEach(monitoredFile ->
+                        monitoredFile.setValue(monitoredFile.getKey().lastModified()));
     }
 
     @Override
     public void watching(final Source source) {
-        file = source.getFile();
-        lastModifiedMillis = file.lastModified();
+        File file = source.getFile();
+        monitoredFiles.put(file, file.lastModified());
         super.watching(source);
     }
 
+    /**
+     * Add the given URIs to be watched.
+     *
+     * @param monitorUris URIs to also watch
+     */
+    public void addMonitorUris(final List<URI> monitorUris) {
+        monitorUris.forEach(uri -> {
+            File additionalFile = new Source(uri).getFile();
+            monitoredFiles.put(additionalFile, additionalFile.lastModified());
+        });
+    }
+
     @Override
     public boolean isModified() {
-        return lastModifiedMillis != file.lastModified();
+        return monitoredFiles.entrySet().stream()
+                .anyMatch(file -> file.getValue() != file.getKey().lastModified());
     }
 
     @Override

log4j-core/src/main/java/org/apache/logging/log4j/core/config/ConfigurationSource.java

@@ -382,4 +382,8 @@ public String toString() {
             return null;
         }
     }
+
+    Source getSource() {
+        return this.source;
+    }
 }

log4j-core/src/main/java/org/apache/logging/log4j/core/config/MonitorUris.java

@@ -0,0 +1,58 @@
+/*
+ * 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.logging.log4j.core.config;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.apache.logging.log4j.core.Core;
+import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.config.plugins.PluginElement;
+import org.apache.logging.log4j.core.config.plugins.PluginFactory;
+
+/**
+ * Container for MonitorUri objects.
+ */
+@Plugin(name = "MonitorUris", category = Core.CATEGORY_NAME, printObject = true)
+public final class MonitorUris {
+
+    private final List<Uri> uris;
+
+    private MonitorUris(final Uri[] uris) {
+        this.uris = new ArrayList<>(Arrays.asList(uris));
+    }
+
+    /**
+     * Create a MonitorUris object to contain all the URIs to be monitored.
+     *
+     * @param uris An array of URIs.
+     * @return A MonitorUris object.
+     */
+    @PluginFactory
+    public static MonitorUris createMonitorUris( //
+            @PluginElement("Uris") final Uri[] uris) {
+        return new MonitorUris(uris == null ? Uri.EMPTY_ARRAY : uris);
+    }
+
+    /**
+     * Returns a list of the {@code Uri} objects created during configuration.
+     * @return the URIs to be monitored
+     */
+    public List<Uri> getUris() {
+        return uris;
+    }
+}

log4j-core/src/main/java/org/apache/logging/log4j/core/config/Uri.java

@@ -0,0 +1,88 @@
+/*
+ * 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.logging.log4j.core.config;
+
+import java.util.Objects;
+import org.apache.logging.log4j.core.Core;
+import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.config.plugins.PluginFactory;
+import org.apache.logging.log4j.core.config.plugins.PluginValue;
+import org.apache.logging.log4j.status.StatusLogger;
+
+/**
+ * Descriptor of a URI object that is created via configuration.
+ */
+@Plugin(name = "Uri", category = Core.CATEGORY_NAME, printObject = true)
+public final class Uri {
+
+    /**
+     * The empty array.
+     */
+    static final Uri[] EMPTY_ARRAY = {};
+
+    private final String uri;
+
+    private Uri(final String uri) {
+        this.uri = Objects.requireNonNull(uri, "uri is null");
+    }
+
+    /**
+     * Creates a Uri object.
+     *
+     * @param uri the URI.
+     * @return A Uri object.
+     */
+    @PluginFactory
+    public static Uri createUri( // @formatter:off
+            @PluginValue("uri") final String uri) {
+        // @formatter:on
+
+        StatusLogger.getLogger().debug("Creating Uri('{}')", uri);
+        return new Uri(uri);
+    }
+
+    /**
+     * Returns the URI.
+     *
+     * @return the URI
+     */
+    public String getUri() {
+        return uri;
+    }
+
+    @Override
+    public int hashCode() {
+        return uri.hashCode();
+    }
+
+    @Override
+    public boolean equals(final Object object) {
+        if (this == object) {
+            return true;
+        }
+        if (!(object instanceof Uri)) {
+            return false;
+        }
+        final Uri other = (Uri) object;
+        return this.uri == other.uri;
+    }
+
+    @Override
+    public String toString() {
+        return "Uri[" + uri + "]";
+    }
+}