MetaDataServer.java

/*
 * Copyright 2013-2014 the original author or authors.
 *
 * Licensed 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.springframework.cloud.aws.context;

import com.amazonaws.SDKGlobalConfiguration;
import com.amazonaws.util.EC2MetadataUtils;
import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;
import org.springframework.util.SocketUtils;

import java.io.IOException;
import java.io.OutputStream;
import java.lang.reflect.Field;
import java.net.InetSocketAddress;
import java.util.HashMap;

/**
 * @author Agim Emruli
 */
public final class MetaDataServer {

    private static final int HTTP_SERVER_TEST_PORT = SocketUtils.findAvailableTcpPort();

    @SuppressWarnings("StaticNonFinalField")
    private static HttpServer httpServer;

    private MetaDataServer() {
        // Avoid instantiation
    }

    @SuppressWarnings("NonThreadSafeLazyInitialization")
    public static HttpServer setupHttpServer() throws Exception {

        if (httpServer == null) {
            InetSocketAddress address = new InetSocketAddress(HTTP_SERVER_TEST_PORT);
            httpServer = HttpServer.create(address, -1);
            httpServer.start();
            overwriteMetadataEndpointUrl("http://" + address.getHostName() + ":" + address.getPort());
        }

        return httpServer;
    }

    public static void shutdownHttpServer() {
        if (httpServer != null) {
            httpServer.stop(10);
            httpServer = null;
        }
        resetMetadataEndpointUrlOverwrite();
        resetMetaDataCache();
    }

    private static void overwriteMetadataEndpointUrl(String localMetadataServiceEndpointUrl) {
        System.setProperty(SDKGlobalConfiguration.EC2_METADATA_SERVICE_OVERRIDE_SYSTEM_PROPERTY, localMetadataServiceEndpointUrl);
    }

    private static void resetMetadataEndpointUrlOverwrite() {
        System.clearProperty(SDKGlobalConfiguration.EC2_METADATA_SERVICE_OVERRIDE_SYSTEM_PROPERTY);
    }

    private static void resetMetaDataCache() {
        try {
            Field metadataCacheField = EC2MetadataUtils.class.getDeclaredField("cache");
            metadataCacheField.setAccessible(true);
            metadataCacheField.set(null, new HashMap<String, String>());
        } catch (Exception e) {
            throw new IllegalStateException("Unable to clear metadata cache in '" + EC2MetadataUtils.class.getName() + "'", e);
        }
    }

    public static class HttpResponseWriterHandler implements HttpHandler {

        private final String content;

        public HttpResponseWriterHandler(String content) {
            this.content = content;
        }

        @Override
        public void handle(HttpExchange httpExchange) throws IOException {
            httpExchange.sendResponseHeaders(200, this.content.getBytes().length);

            OutputStream responseBody = httpExchange.getResponseBody();
            responseBody.write(this.content.getBytes());
            responseBody.flush();
            responseBody.close();
        }
    }
}