| /* |
| * 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.geode.cache.server; |
| |
| import org.apache.geode.cache.CacheCallback; |
| |
| |
| /** |
| * A load probe is installed in a cache server to measure the load on the cache server for balancing |
| * load between multiple cache servers. |
| * |
| * <p> |
| * The getLoad method will be called once per poll interval see |
| * {@link CacheServer#setLoadPollInterval(long)} The {@link ServerLoad} object returned by the |
| * getLoad method will be sent to the locator every time the load for this server changes. To |
| * conserve bandwidth, it's a good idea to round the load calculations so that the load will not be |
| * sent too frequently. |
| * </p> |
| * <p> |
| * The {@link ServerLoad} object contains two floating point numbers indicating the load on the |
| * server due to client to server connections and due to subscription connections. When routing a |
| * connection, the locator will choose the server that has the lowest load. |
| * </p> |
| * <p> |
| * It is generally a good idea to pick a load function where 0 connections corresponds to 0 load. |
| * The default gemfire load probes return a fraction between 0 and 1, where 0 indicates no load, and |
| * 1 indicates the server is completely loaded. |
| * </p> |
| * <p> |
| * Because cache servers can be stopped, reconfigured, and restarted, the open and close methods on |
| * this callback can be called several times. If the same callback object is installed on multiple |
| * cache servers, open and close will be called once for each cache server. |
| * </p> |
| * |
| * @since GemFire 5.7 |
| * |
| */ |
| public interface ServerLoadProbe extends CacheCallback { |
| /** |
| * Get the load on this server. This method will be called once every pool interval. |
| * |
| * @return The current load on this server. |
| */ |
| ServerLoad getLoad(ServerMetrics metrics); |
| |
| /** |
| * Signals that a cache server using this load probe has been started. |
| */ |
| void open(); |
| |
| /** |
| * Signals that a cache server using this load probe has been closed. |
| */ |
| @Override |
| void close(); |
| } |