kaisun2000 commented on a change in pull request #775: Add HttpRoutingDataReader URL: https://github.com/apache/helix/pull/775#discussion_r383490911
########## File path: zookeeper-api/src/main/java/org/apache/helix/zookeeper/util/HttpRoutingDataReader.java ########## @@ -0,0 +1,134 @@ +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.concurrent.TimeUnit; +import java.util.stream.Collectors; + +import com.jcabi.aspects.RetryOnFailure; +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.methods.CloseableHttpResponse; +import org.apache.http.client.methods.HttpGet; +import org.apache.http.impl.client.CloseableHttpClient; +import org.apache.http.impl.client.HttpClients; +import org.apache.http.util.EntityUtils; +import org.codehaus.jackson.map.ObjectMapper; + + +public class HttpRoutingDataReader { + private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper(); + 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 + */ + @RetryOnFailure(attempts = 3, delay = 1, unit = TimeUnit.SECONDS) + public static Map<String, List<String>> getRawRoutingData() + throws IOException { + if (_rawRoutingData == null) { + synchronized (HttpRoutingDataReader.class) { + if (_rawRoutingData == null) { + String msdsEndpoint = + System.getProperty(MetadataStoreRoutingConstants.MSDS_SERVER_ENDPOINT_KEY); + if (msdsEndpoint == null || msdsEndpoint.isEmpty()) { + throw new IllegalStateException( + "HttpRoutingDataReader was unable to find a valid MSDS endpoint String in System Properties!"); + } + + // Note: HttpClient's timeout settings are system timeout settings by default + CloseableHttpClient httpClient = HttpClients.createDefault(); + // Update the reference + _rawRoutingData = getAllRoutingData(httpClient, msdsEndpoint); + // Close any open resources + httpClient.close(); + } + } + } + return _rawRoutingData; + } + + /** + * Returns the routing data read from MSDS in a MetadataStoreRoutingData format. + * @return + * @throws IOException + * @throws InvalidRoutingDataException + */ + public static MetadataStoreRoutingData getMetadataStoreRoutingData() + throws IOException, InvalidRoutingDataException { + if (_metadataStoreRoutingData == null) { + synchronized (HttpRoutingDataReader.class) { + if (_metadataStoreRoutingData == null) { + _metadataStoreRoutingData = new TrieRoutingData(getRawRoutingData()); + } + } + } + return _metadataStoreRoutingData; + } + + /** + * Makes an HTTP call to fetch all routing data. + * @param httpClient + * @param msdsEndpoint + * @return + * @throws IOException + */ + private static Map<String, List<String>> getAllRoutingData(CloseableHttpClient httpClient, + String msdsEndpoint) + throws IOException { + HttpGet requestAllData = new HttpGet( + msdsEndpoint + MetadataStoreRoutingConstants.MSDS_GET_ALL_ROUTING_DATA_ENDPOINT); + CloseableHttpResponse response = httpClient.execute(requestAllData); Review comment: Either I did not get what you mean by VIP or you did not get what I mean here. What really concerns me is that some rest servers may not be available for whatever reason, say network partition. Then we should retry for another rest server. Otherwise, mission critical application may not be able to start. So the retry logic is very critical. We don't have this retry logic. You can think of this retry logic similar to Zookeeper native client retry different quorum node. ---------------------------------------------------------------- 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]
