| /** |
| * 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 com.twitter.distributedlog.net; |
| |
| /** |
| * Resolve the dns by rows. |
| * <p> |
| * It resolves domain name like `(region)-(row)xx-xxx-xxx.*` to network location |
| * `/(region)/(row)`. If resolution failed, it returns `/default-region/default-row`. |
| * <p> |
| * region could be override in <code>hostRegionOverrides</code>. for example, if the |
| * host name is <i>regionA-row1-xx-yyy</i>, it would be resolved to `/regionA/row1` |
| * without any overrides. If the specified overrides is <i>regionA-row1-xx-yyy:regionB</i>, |
| * the resolved network location would be <i>/regionB/row1</i>. |
| * <p> |
| * Region overrides provide optimization hits to bookkeeper if two `logical` regions are |
| * in same or close locations. |
| * |
| * @see DNSResolver#DNSResolver(String) |
| */ |
| public class DNSResolverForRows extends DNSResolver { |
| static final String DEFAULT_ROW = "/default-region/default-row"; |
| |
| public DNSResolverForRows() { |
| } |
| |
| public DNSResolverForRows(String hostRegionOverrides) { |
| super(hostRegionOverrides); |
| } |
| |
| @Override |
| protected String resolveToNetworkLocation(String domainName) { |
| String[] parts = domainName.split("\\."); |
| if (parts.length <= 0) { |
| return DEFAULT_ROW; |
| } |
| String hostName = parts[0]; |
| String[] labels = hostName.split("-"); |
| if (labels.length != 4) { |
| return DEFAULT_ROW; |
| } |
| |
| String region = hostNameToRegion.get(hostName); |
| if (null == region) { |
| region = labels[0]; |
| } |
| |
| final String rack = labels[1]; |
| |
| if (rack.length() < 2) { |
| // Default to rack name if the rack name format cannot be recognized |
| return String.format("/%s/%s", region, rack); |
| } else { |
| return String.format("/%s/%s", region, rack.substring(0, 2)); |
| } |
| } |
| } |