kaisun2000 commented on a change in pull request #775: Add HttpRoutingDataReader URL: https://github.com/apache/helix/pull/775#discussion_r384065673
########## File path: zookeeper-api/src/main/java/org/apache/helix/zookeeper/util/HttpRoutingDataReader.java ########## @@ -0,0 +1,146 @@ +package org.apache.helix.zookeeper.util; + +/* + * 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. + */ + +import java.io.IOException; +import java.util.Collections; +import java.util.List; +import java.util.Map; +import java.util.stream.Collectors; + +import com.fasterxml.jackson.databind.ObjectMapper; +import org.apache.helix.msdcommon.constant.MetadataStoreRoutingConstants; +import org.apache.helix.msdcommon.datamodel.MetadataStoreRoutingData; +import org.apache.helix.msdcommon.datamodel.TrieRoutingData; +import org.apache.helix.msdcommon.exception.InvalidRoutingDataException; +import org.apache.http.HttpEntity; +import org.apache.http.client.config.RequestConfig; +import org.apache.http.client.methods.CloseableHttpResponse; +import org.apache.http.client.methods.HttpGet; +import org.apache.http.impl.client.CloseableHttpClient; +import org.apache.http.impl.client.DefaultBackoffStrategy; +import org.apache.http.impl.client.DefaultHttpRequestRetryHandler; +import org.apache.http.impl.client.HttpClients; +import org.apache.http.util.EntityUtils; + + +public class HttpRoutingDataReader { + private static final String MSDS_ENDPOINT = + System.getProperty(MetadataStoreRoutingConstants.MSDS_SERVER_ENDPOINT_KEY); + private static final int HTTP_TIMEOUT_IN_MS = 5000; + + /** Double-checked locking requires that the following fields be volatile */ + private static volatile Map<String, List<String>> _rawRoutingData; + private static volatile MetadataStoreRoutingData _metadataStoreRoutingData; + + /** + * This class is a Singleton. + */ + private HttpRoutingDataReader() { + } + + /** + * Fetches routing data from the data source via HTTP. + * @return a mapping from "metadata store realm addresses" to lists of + * "metadata store sharding keys", where the sharding keys in a value list all route to + * the realm address in the key disallows a meaningful mapping to be returned + */ + public static Map<String, List<String>> getRawRoutingData() throws IOException { + if (MSDS_ENDPOINT == null || MSDS_ENDPOINT.isEmpty()) { + throw new IllegalStateException( + "HttpRoutingDataReader was unable to find a valid MSDS endpoint String in System Properties!"); + } + if (_rawRoutingData == null) { + synchronized (HttpRoutingDataReader.class) { + if (_rawRoutingData == null) { + CloseableHttpResponse routingDataResponse = getAllRoutingData(); + // Update the reference if reading routingData over HTTP is successful + _rawRoutingData = parseRoutingData(routingDataResponse); + } + } + } + return _rawRoutingData; + } + + /** + * Returns the routing data read from MSDS in a MetadataStoreRoutingData format. + * @return + * @throws IOException if there is an issue connecting to MSDS + * @throws InvalidRoutingDataException if the raw routing data is not valid + */ + public static MetadataStoreRoutingData getMetadataStoreRoutingData() + throws IOException, InvalidRoutingDataException { + if (_metadataStoreRoutingData == null) { + synchronized (HttpRoutingDataReader.class) { + if (_metadataStoreRoutingData == null) { + _metadataStoreRoutingData = new TrieRoutingData(getRawRoutingData()); Review comment: I did not see the TrieRoutingData implementation. Can we make sure _metaDataStoreRoutingData will not be empty map after this line? This is important. Otherwise, with empty map, you are not going to retry getRawRoutingData. The result is disaster then. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
