SOLR-17096: Cluster Singleton plugin support in solr.xml

solr/CHANGES.txt

@@ -23,6 +23,8 @@ Improvements
 
 * SOLR-17077: When a shard rejoins leader election, leave previous election only once to save unneeded calls to Zookeeper. (Pierre Salagnac)
 
+* SOLR-17096: solr.xml now supports declaring clusterSingleton plugins (Paul McArthur, David Smiley)
+
 Optimizations
 ---------------------
 (No changes)

solr/core/src/java/org/apache/solr/api/ClusterPluginsSource.java

@@ -0,0 +1,83 @@
+/*
+ * 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.solr.api;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.function.Function;
+import org.apache.solr.client.solrj.request.beans.PluginMeta;
+import org.apache.solr.common.util.EnvUtils;
+import org.apache.solr.core.CoreContainer;
+import org.apache.solr.core.SolrResourceLoader;
+import org.apache.solr.handler.admin.ContainerPluginsApi;
+
+/** A source for Cluster Plugin configurations */
+public interface ClusterPluginsSource {
+
+  /**
+   * Resolves the name of the class that will be used to provide cluster plugins.
+   *
+   * @return The name of the class to use as the {@link ClusterPluginsSource}
+   */
+  public static String resolveClassName() {
+    return EnvUtils.getPropAsBool(ContainerPluginsRegistry.CLUSTER_PLUGIN_EDIT_ENABLED, true)
+        ? ZkClusterPluginsSource.class.getName()
+        : NodeConfigClusterPluginsSource.class.getName();
+  }
+
+  public static ClusterPluginsSource loadClusterPluginsSource(
+      CoreContainer cc, SolrResourceLoader loader) {
+    return loader.newInstance(
+        resolveClassName(),
+        ClusterPluginsSource.class,
+        new String[0],
+        new Class<?>[] {CoreContainer.class},
+        new Object[] {cc});
+  }
+
+  /**
+   * Get the Read Api for this plugin source
+   *
+   * @return A {@link ContainerPluginsApi} Read Api for this plugin source
+   */
+  ContainerPluginsApi.Read getReadApi();
+
+  /**
+   * Get the Edit Api for this plugin source, if it supports edit operations
+   *
+   * @return A {@link ContainerPluginsApi} Edit Api for this plugin source, or null if the plugin
+   *     source does not support editing the plugin configs
+   */
+  ContainerPluginsApi.Edit getEditApi();
+
+  /**
+   * Get a map of cluster plugin configurations from this source, where keys are plugin names and
+   * values are {@link PluginMeta} plugin metadata.
+   *
+   * @return An immutable map of plugin configurations
+   */
+  Map<String, Object> plugins() throws IOException;
+
+  /**
+   * Persist the updated set of plugin configs
+   *
+   * @param modifier A function providing the map of plugin configs to be persisted
+   */
+  void persistPlugins(Function<Map<String, Object>, Map<String, Object>> modifier)
+      throws IOException;
+}

solr/core/src/java/org/apache/solr/api/ContainerPluginsRegistry.java

@@ -39,7 +39,6 @@
 import java.util.Optional;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Phaser;
-import java.util.function.Supplier;
 import org.apache.lucene.util.ResourceLoaderAware;
 import org.apache.solr.client.solrj.SolrRequest;
 import org.apache.solr.client.solrj.request.beans.PluginMeta;
@@ -55,7 +54,6 @@
 import org.apache.solr.common.util.Utils;
 import org.apache.solr.core.CoreContainer;
 import org.apache.solr.core.PluginInfo;
-import org.apache.solr.handler.admin.ContainerPluginsApi;
 import org.apache.solr.pkg.SolrPackageLoader;
 import org.apache.solr.request.SolrQueryRequest;
 import org.apache.solr.response.SolrQueryResponse;
@@ -66,7 +64,7 @@
 /**
  * This class manages the container-level plugins and their Api-s. It is responsible for adding /
  * removing / replacing the plugins according to the updated configuration obtained from {@link
- * ContainerPluginsApi#plugins(Supplier)}.
+ * ClusterPluginsSource#plugins()}.
  *
  * <p>Plugins instantiated by this class may implement zero or more {@link Api}-s, which are then
  * registered in the CoreContainer {@link ApiBag}. They may be also post-processed for additional
@@ -75,6 +73,8 @@
 public class ContainerPluginsRegistry implements ClusterPropertiesListener, MapWriter, Closeable {
   private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());
 
+  public static final String CLUSTER_PLUGIN_EDIT_ENABLED = "solr.cluster.plugin.edit.enabled";
+
   private static final ObjectMapper mapper =
       SolrJacksonAnnotationInspector.createObjectMapper()
           .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
@@ -85,6 +85,8 @@ public class ContainerPluginsRegistry implements ClusterPropertiesListener, MapW
   private final CoreContainer coreContainer;
   private final ApiBag containerApiBag;
 
+  private final ClusterPluginsSource pluginsSource;
+
   private final Map<String, ApiInfo> currentPlugins = new HashMap<>();
 
   private Phaser phaser;
@@ -117,9 +119,11 @@ public void unregisterListener(PluginRegistryListener listener) {
     listeners.remove(listener);
   }
 
-  public ContainerPluginsRegistry(CoreContainer coreContainer, ApiBag apiBag) {
+  public ContainerPluginsRegistry(
+      CoreContainer coreContainer, ApiBag apiBag, ClusterPluginsSource pluginsSource) {
     this.coreContainer = coreContainer;
     this.containerApiBag = apiBag;
+    this.pluginsSource = pluginsSource;
   }
 
   @Override
@@ -171,7 +175,7 @@ public int hashCode() {
   public synchronized void refresh() {
     Map<String, Object> pluginInfos;
     try {
-      pluginInfos = ContainerPluginsApi.plugins(coreContainer.zkClientSupplier);
+      pluginInfos = pluginsSource.plugins();
     } catch (IOException e) {
       log.error("Could not read plugins data", e);
       return;

solr/core/src/java/org/apache/solr/api/NodeConfigClusterPluginsSource.java

@@ -0,0 +1,106 @@
+/*
+ * 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.solr.api;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+import org.apache.solr.cluster.placement.PlacementPluginFactory;
+import org.apache.solr.core.CoreContainer;
+import org.apache.solr.core.NodeConfig;
+import org.apache.solr.core.PluginInfo;
+import org.apache.solr.handler.admin.ContainerPluginsApi;
+
+/**
+ * Plugin configurations that are defined in solr.xml. This supports immutable deployments, and the
+ * /cluster/plugin Edit APIs are not available
+ */
+public class NodeConfigClusterPluginsSource implements ClusterPluginsSource {
+
+  private final Map<String, Object> plugins;
+
+  private final ContainerPluginsApi api;
+
+  public NodeConfigClusterPluginsSource(final CoreContainer cc) {
+    api = new ContainerPluginsApi(cc, this);
+    plugins = Map.copyOf(readPlugins(cc.getNodeConfig()));
+  }
+
+  @Override
+  public ContainerPluginsApi.Read getReadApi() {
+    return api.readAPI;
+  }
+
+  @Override
+  public ContainerPluginsApi.Edit getEditApi() {
+    return null;
+  }
+
+  @Override
+  public Map<String, Object> plugins() throws IOException {
+    return plugins;
+  }
+
+  /**
+   * This method should never be invoked because the Edit Apis are not made available by the plugin
+   *
+   * @throws UnsupportedOperationException always
+   */
+  @Override
+  public void persistPlugins(Function<Map<String, Object>, Map<String, Object>> modifier) {
+    throw new UnsupportedOperationException(
+        "The NodeConfigContainerPluginsSource does not support updates to plugin configurations");
+  }
+
+  private static Map<String, Object> readPlugins(final NodeConfig cfg) {
+    Map<String, Object> pluginInfos = new HashMap<>();
+    PluginInfo[] clusterPlugins = cfg.getClusterPlugins();
+    if (clusterPlugins != null) {
+      for (PluginInfo p : clusterPlugins) {
+        Map<String, Object> pluginMap = new HashMap<>();
+        final String pluginName = getPluginName(p);
+        pluginMap.put("name", pluginName);
+        pluginMap.put("class", p.className);
+
+        if (p.initArgs.size() > 0) {
+          Map<String, Object> config = p.initArgs.toMap(new HashMap<>());
+          pluginMap.put("config", config);
+        }
+
+        pluginInfos.put(pluginName, pluginMap);
+      }
+    }
+    return pluginInfos;
+  }
+
+  /**
+   * Get the correct name for a plugin. Custom plugins must have a name set already, but built-in
+   * plugins may omit the name in solr.xml and require inference here
+   */
+  private static String getPluginName(final PluginInfo pluginInfo) {
+
+    if (pluginInfo.name == null) {
+      if (pluginInfo.type.equals("replicaPlacementFactory")) {
+        return PlacementPluginFactory.PLUGIN_NAME;
+      }
+    }
+
+    return pluginInfo.name;
+  }
+}

solr/core/src/java/org/apache/solr/api/ZkClusterPluginsSource.java

@@ -0,0 +1,114 @@
+/*
+ * 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.solr.api;
+
+import java.io.IOException;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import org.apache.solr.client.solrj.request.beans.PluginMeta;
+import org.apache.solr.common.cloud.SolrZkClient;
+import org.apache.solr.common.cloud.ZkStateReader;
+import org.apache.solr.common.util.Utils;
+import org.apache.solr.core.CoreContainer;
+import org.apache.solr.handler.admin.ContainerPluginsApi;
+import org.apache.zookeeper.KeeperException;
+import org.apache.zookeeper.data.Stat;
+
+/**
+ * The plugin configurations are stored and retrieved from the ZooKeeper cluster properties, stored
+ * at the {@link ZkStateReader#CONTAINER_PLUGINS} location This supports mutable configurations, and
+ * management via the /cluster/plugin APIs
+ */
+public class ZkClusterPluginsSource implements ClusterPluginsSource {
+
+  private final Supplier<SolrZkClient> zkClientSupplier;
+
+  private final ContainerPluginsApi api;
+
+  public ZkClusterPluginsSource(CoreContainer coreContainer) {
+    this.zkClientSupplier = coreContainer.zkClientSupplier;
+    this.api = new ContainerPluginsApi(coreContainer, this);
+  }
+
+  @Override
+  public ContainerPluginsApi.Read getReadApi() {
+    return api.readAPI;
+  }
+
+  @Override
+  public ContainerPluginsApi.Edit getEditApi() {
+    return api.editAPI;
+  }
+
+  /**
+   * Retrieve the current plugin configurations.
+   *
+   * @return current plugin configurations, where keys are plugin names and values are {@link
+   *     PluginMeta} plugin metadata.
+   * @throws IOException on IO errors
+   */
+  @Override
+  @SuppressWarnings("unchecked")
+  public Map<String, Object> plugins() throws IOException {
+    SolrZkClient zkClient = zkClientSupplier.get();
+    try {
+      Map<String, Object> clusterPropsJson =
+          (Map<String, Object>)
+              Utils.fromJSON(zkClient.getData(ZkStateReader.CLUSTER_PROPS, null, new Stat(), true));
+      return Map.copyOf(
+          (Map<String, Object>)
+              clusterPropsJson.computeIfAbsent(
+                  ZkStateReader.CONTAINER_PLUGINS, o -> new LinkedHashMap<>()));
+    } catch (KeeperException.NoNodeException e) {
+      return new LinkedHashMap<>();
+    } catch (KeeperException | InterruptedException e) {
+      throw new IOException("Error reading cluster property", SolrZkClient.checkInterrupted(e));
+    }
+  }
+
+  @Override
+  public void persistPlugins(Function<Map<String, Object>, Map<String, Object>> modifier)
+      throws IOException {
+    try {
+      zkClientSupplier
+          .get()
+          .atomicUpdate(
+              ZkStateReader.CLUSTER_PROPS,
+              bytes -> {
+                @SuppressWarnings("unchecked")
+                Map<String, Object> rawJson =
+                    bytes == null
+                        ? new LinkedHashMap<>()
+                        : (Map<String, Object>) Utils.fromJSON(bytes);
+                @SuppressWarnings("unchecked")
+                Map<String, Object> pluginsModified =
+                    modifier.apply(
+                        (Map<String, Object>)
+                            rawJson.computeIfAbsent(
+                                ZkStateReader.CONTAINER_PLUGINS, o -> new LinkedHashMap<>()));
+                if (pluginsModified == null) return null;
+                rawJson.put(ZkStateReader.CONTAINER_PLUGINS, pluginsModified);
+                return Utils.toJSON(rawJson);
+              });
+    } catch (KeeperException | InterruptedException e) {
+      throw new IOException("Error reading cluster property", SolrZkClient.checkInterrupted(e));
+    }
+  }
+}