com.twitter.distributedlog.net.DNSResolverForRows Maven / Gradle / Ivy
/**
* 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.
*
* It resolves domain name like `(region)-(row)xx-xxx-xxx.*` to network location
* `/(region)/(row)`. If resolution failed, it returns `/default-region/default-row`.
*
* region could be override in hostRegionOverrides. for example, if the
* host name is regionA-row1-xx-yyy, it would be resolved to `/regionA/row1`
* without any overrides. If the specified overrides is regionA-row1-xx-yyy:regionB,
* the resolved network location would be /regionB/row1.
*
* 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));
}
}
}