| /** |
| * 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 |
| * <p/> |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * <p/> |
| * 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.hadoop.metrics2.sink.timeline.availability; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| import java.util.List; |
| |
| /** |
| * Provides sharding based on hostname |
| */ |
| public class MetricSinkWriteShardHostnameHashingStrategy implements MetricSinkWriteShardStrategy { |
| private final String hostname; |
| private final long hostnameHash; |
| private static final Log LOG = LogFactory.getLog(MetricSinkWriteShardHostnameHashingStrategy.class); |
| |
| public MetricSinkWriteShardHostnameHashingStrategy(String hostname) { |
| this.hostname = hostname; |
| this.hostnameHash = hostname != null ? computeHash(hostname) : 1000; // some constant |
| } |
| |
| @Override |
| public String findCollectorShard(List<String> collectorHosts) { |
| if (collectorHosts.isEmpty()) return null; |
| long index = hostnameHash % collectorHosts.size(); |
| index = index < 0 ? index + collectorHosts.size() : index; |
| String collectorHost = collectorHosts.get((int) index); |
| LOG.info(String.format("Calculated collector shard %s based on hostname: %s", collectorHost, hostname)); |
| return collectorHost; |
| } |
| |
| /** |
| * Compute consistent hash based on hostname which should give decently |
| * uniform distribution assuming hostname generally have a sequential |
| * numeric suffix. |
| */ |
| long computeHash(String hostname) { |
| long h = 11987L; // prime |
| int len = hostname.length(); |
| |
| for (int i = 0; i < len; i++) { |
| h = 31 * h + hostname.charAt(i); |
| } |
| return h; |
| } |
| } |