belugabehr commented on a change in pull request #884: HBASE-23347 Allowable custom authentication methods for RPCs URL: https://github.com/apache/hbase/pull/884#discussion_r356750081
########## File path: hbase-server/src/main/java/org/apache/hadoop/hbase/security/provider/SaslServerAuthenticationProviders.java ########## @@ -0,0 +1,179 @@ +/** + * 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 org.apache.hadoop.hbase.security.provider; + +import java.util.HashMap; +import java.util.Optional; +import java.util.ServiceLoader; +import java.util.concurrent.atomic.AtomicReference; +import java.util.stream.Collectors; + +import org.apache.hadoop.conf.Configuration; +import org.apache.yetus.audience.InterfaceAudience; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + [email protected] +public final class SaslServerAuthenticationProviders { + private static final Logger LOG = LoggerFactory.getLogger( + SaslClientAuthenticationProviders.class); + + public static final String EXTRA_PROVIDERS_KEY = "hbase.server.sasl.provider.extras"; + private static final AtomicReference<SaslServerAuthenticationProviders> holder = + new AtomicReference<>(); + + private final Configuration conf; + private final HashMap<Byte, SaslServerAuthenticationProvider> providers; + + private SaslServerAuthenticationProviders(Configuration conf, + HashMap<Byte, SaslServerAuthenticationProvider> providers) { + this.conf = conf; + this.providers = providers; + } + + /** + * Returns the number of registered providers. + */ + public int getNumRegisteredProviders() { + return providers.size(); + } + + /** + * Returns a singleton instance of {@link SaslServerAuthenticationProviders}. + */ + public static SaslServerAuthenticationProviders getInstance(Configuration conf) { + SaslServerAuthenticationProviders providers = holder.get(); + if (null == providers) { + synchronized (holder) { + // Someone else beat us here + providers = holder.get(); + if (null != providers) { + return providers; + } + + providers = createProviders(conf); + holder.set(providers); + } + } + return providers; + } Review comment: There used to be a problem with this kind of synchronization in the JDK. I'm not sure if it's still the case, but I would KISS. Just synchronize the entire method and not have to worry about any race conditions later. ---------------------------------------------------------------- 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
