Ec2NameResolver.java

/*
 * Licensed to ElasticSearch and Shay Banon under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. ElasticSearch 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.
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package org.elasticsearch.cloud.aws.network;

import com.google.common.io.Closeables;
import org.elasticsearch.ExceptionsHelper;
import org.elasticsearch.cloud.aws.AwsEc2Service;
import org.elasticsearch.common.component.AbstractComponent;
import org.elasticsearch.common.network.NetworkService.CustomNameResolver;
import org.elasticsearch.common.settings.Settings;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.URL;
import java.net.URLConnection;

/**
 * Resolves certain ec2 related 'meta' hostnames into an actual hostname
 * obtained from ec2 meta-data.
 * <p/>
 * Valid config values for {@link Ec2HostnameType}s are -
 * <ul>
 * <li>_ec2_ - maps to privateIpv4</li>
 * <li>_ec2:privateIp_ - maps to privateIpv4</li>
 * <li>_ec2:privateIpv4_</li>
 * <li>_ec2:privateDns_</li>
 * <li>_ec2:publicIp_ - maps to publicIpv4</li>
 * <li>_ec2:publicIpv4_</li>
 * <li>_ec2:publicDns_</li>
 * </ul>
 *
 * @author Paul_Loy (keteracel)
 */
public class Ec2NameResolver extends AbstractComponent implements CustomNameResolver {

    /**
     * enum that can be added to over time with more meta-data types (such as ipv6 when this is available)
     *
     * @author Paul_Loy
     */
    private static enum Ec2HostnameType {

        PRIVATE_IPv4("ec2:privateIpv4", "local-ipv4"),
        PRIVATE_DNS("ec2:privateDns", "local-hostname"),
        PUBLIC_IPv4("ec2:publicIpv4", "public-ipv4"),
        PUBLIC_DNS("ec2:publicDns", "public-hostname"),

        // some less verbose defaults
        PUBLIC_IP("ec2:publicIp", PUBLIC_IPv4.ec2Name),
        PRIVATE_IP("ec2:privateIp", PRIVATE_IPv4.ec2Name),
        EC2("ec2", PRIVATE_IPv4.ec2Name);

        final String configName;
        final String ec2Name;

        private Ec2HostnameType(String configName, String ec2Name) {
            this.configName = configName;
            this.ec2Name = ec2Name;
        }
    }

    /**
     * Construct a {@link CustomNameResolver}.
     */
    public Ec2NameResolver(Settings settings) {
        super(settings);
    }

    /**
     * @param type the ec2 hostname type to discover.
     * @return the appropriate host resolved from ec2 meta-data.
     * @throws IOException if ec2 meta-data cannot be obtained.
     * @see CustomNameResolver#resolveIfPossible(String)
     */
    public InetAddress resolve(Ec2HostnameType type, boolean warnOnFailure) {
        URLConnection urlConnection = null;
        InputStream in = null;
        try {
            URL url = new URL(AwsEc2Service.EC2_METADATA_URL + type.ec2Name);
            logger.debug("obtaining ec2 hostname from ec2 meta-data url {}", url);
            urlConnection = url.openConnection();
            urlConnection.setConnectTimeout(2000);
            in = urlConnection.getInputStream();
            BufferedReader urlReader = new BufferedReader(new InputStreamReader(in));

            String metadataResult = urlReader.readLine();
            if (metadataResult == null || metadataResult.length() == 0) {
                logger.error("no ec2 metadata returned from {}", url);
                return null;
            }
            return InetAddress.getByName(metadataResult);
        } catch (IOException e) {
            if (warnOnFailure) {
                logger.warn("failed to get metadata for [" + type.configName + "]: " + ExceptionsHelper.detailedMessage(e));
            } else {
                logger.debug("failed to get metadata for [" + type.configName + "]: " + ExceptionsHelper.detailedMessage(e));
            }
            return null;
        } finally {
            Closeables.closeQuietly(in);
        }
    }

    @Override
    public InetAddress resolveDefault() {
        return null; // using this, one has to explicitly specify _ec2_ in network setting
//        return resolve(Ec2HostnameType.DEFAULT, false);
    }

    @Override
    public InetAddress resolveIfPossible(String value) {
        for (Ec2HostnameType type : Ec2HostnameType.values()) {
            if (type.configName.equals(value)) {
                return resolve(type, true);
            }
        }
        return null;
    }

}