solr/core/src/java/org/apache/solr/cluster/placement/AttributeFetcher.java

/*
 * 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.cluster.placement;

import org.apache.solr.cluster.Node;

import java.util.Set;

/**
 * <p>Instances of this interface are used to fetch various attributes from nodes (and other sources) in the cluster.</p>
 */
public interface AttributeFetcher {
  /** Request the number of cores on each node. To get the value use {@link AttributeValues#getCoresCount(Node)} */
  AttributeFetcher requestNodeCoreCount();

  /** Request the disk hardware type on each node. To get the value use {@link AttributeValues#getDiskType(Node)} */
  AttributeFetcher requestNodeDiskType();

  /** Request the free disk size on each node. To get the value use {@link AttributeValues#getFreeDisk(Node)} */
  AttributeFetcher requestNodeFreeDisk();

  /** Request the total disk size on each node. To get the value use {@link AttributeValues#getTotalDisk(Node)} */
  AttributeFetcher requestNodeTotalDisk();

  /** Request the heap usage on each node. To get the value use {@link AttributeValues#getHeapUsage(Node)} */
  AttributeFetcher requestNodeHeapUsage();

  /** Request the system load average on each node. To get the value use {@link AttributeValues#getSystemLoadAverage(Node)} */
  AttributeFetcher requestNodeSystemLoadAverage();

  /** Request a given system property on each node. To get the value use {@link AttributeValues#getSystemProperty(Node, String)} */
  AttributeFetcher requestNodeSystemProperty(String name);

  /** Request an environment variable on each node. To get the value use {@link AttributeValues#getEnvironmentVariable(Node, String)} */
  AttributeFetcher requestNodeEnvironmentVariable(String name);

  /** Request a node metric from each node. To get the value use {@link AttributeValues#getMetric(Node, String, NodeMetricRegistry)} */
  AttributeFetcher requestNodeMetric(String metricName, NodeMetricRegistry registry);


  /**
   * The set of nodes from which to fetch all node related attributes. Calling this method is mandatory if any of the {@code requestNode*}
   * methods got called.
   */
  AttributeFetcher fetchFrom(Set<Node> nodes);

  /** Requests a (non node) metric of a given scope and name. To get the value use {@link AttributeValues#getMetric(String, String)} */
  AttributeFetcher requestMetric(String scope, String metricName);

  /**
   * Fetches all requested node attributes from all nodes passed to {@link #fetchFrom(Set)} as well as non node attributes
   * (those requested for example using {@link #requestMetric(String, String)}.
   * @return An instance allowing retrieval of all attributed that could be fetched.
   */
  AttributeValues fetchAttributes();

  /**
   * Registry options for {@link Node} metrics.
   */
  enum NodeMetricRegistry {
    /** corresponds to solr.node */
    SOLR_NODE,
    /** corresponds to solr.jvm */
    SOLR_JVM
  }

  enum DiskHardwareType {
    SSD, ROTATIONAL
  }
}