arina-ielchiieva commented on a change in pull request #1886: DRILL-7273: Introduce operators for handling metadata URL: https://github.com/apache/drill/pull/1886#discussion_r344783626
########## File path: exec/java-exec/src/main/java/org/apache/drill/exec/metastore/analyze/AnalyzeInfoProviderRegistry.java ########## @@ -0,0 +1,128 @@ +/* + * 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.drill.exec.metastore.analyze; + +import org.apache.drill.common.scanner.persistence.AnnotatedClassDescriptor; +import org.apache.drill.common.scanner.persistence.ScanResult; +import org.apache.drill.exec.physical.base.GroupScan; +import org.apache.drill.metastore.exceptions.MetastoreException; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.lang.invoke.MethodHandle; +import java.lang.invoke.MethodHandles; +import java.lang.invoke.MethodType; +import java.util.Collections; +import java.util.List; +import java.util.Objects; +import java.util.stream.Collectors; + +/** + * Class is responsible for dynamic initialization of all implementations + * of {@link AnalyzeInfoProvider} annotated with {@link AnalyzeInfoProviderTemplate} and + * returning required {@link AnalyzeInfoProvider} instance for specific {@link GroupScan} implementation. + * <p> + * + * AnalyzeInfoProvider list initialization is delayed until {@link #get(GroupScan)} method is called. + * AnalyzeInfoProvider implementations must have constructor without arguments. + */ +public class AnalyzeInfoProviderRegistry { + private static final Logger logger = LoggerFactory.getLogger(AnalyzeInfoProviderRegistry.class); + + private final ScanResult classpathScan; + private volatile List<AnalyzeInfoProvider> analyzeInfoProviders; + + public AnalyzeInfoProviderRegistry(ScanResult classpathScan) { + this.classpathScan = classpathScan; + } + + /** + * Returns {@link AnalyzeInfoProvider} instance suitable for specified {@link GroupScan}. + * + * @param groupScan group scan + * @return {@link AnalyzeInfoProvider} instance + */ + public AnalyzeInfoProvider get(GroupScan groupScan) { + if (analyzeInfoProviders == null) { + synchronized (this) { + if (analyzeInfoProviders == null) { + analyzeInfoProviders = Collections.unmodifiableList(init()); + } + } + } + + List<AnalyzeInfoProvider> suitableProviders = analyzeInfoProviders.stream() + .filter(analyzeInfoProvider -> analyzeInfoProvider.supportsGroupScan(groupScan)) + .collect(Collectors.toList()); + + if (suitableProviders.isEmpty()) { + throw new MetastoreException(String.format("Unable to find AnalyzeInfoProvider implementation for GroupScan class [%s]", + groupScan.getClass().getSimpleName())); + } else if (suitableProviders.size() > 1) { + logger.warn("Found several AnalyzeInfoProvider implementations for the same GroupScan class [{}}]. " + + "Please specify only unique AnalyzeInfoProvider implementation for every group scan using [{}] annotation " + + "to prevent using arbitrary implementation.", + groupScan.getClass().getSimpleName(), AnalyzeInfoProviderTemplate.class.getName()); + } + + return suitableProviders.get(0); + } + + private List<AnalyzeInfoProvider> init() { + List<AnalyzeInfoProvider> providers; + List<AnnotatedClassDescriptor> annotatedClasses = classpathScan.getAnnotatedClasses(AnalyzeInfoProviderTemplate.class.getName()); + + providers = annotatedClasses.stream() + .map(AnnotatedClassDescriptor::getClassName) + .map(this::getAnalyzeInfoProviderInstance) + .filter(Objects::nonNull) + .map(instance -> (AnalyzeInfoProvider) instance) + .collect(Collectors.toList()); + return providers; + } + + private Object getAnalyzeInfoProviderInstance(String className) { + MethodHandles.Lookup publicLookup = MethodHandles.publicLookup(); + MethodHandle constructor; + try { + MethodType methodType = MethodType.methodType(void.class); + constructor = publicLookup.findConstructor(Class.forName(className), methodType); + } catch (ClassNotFoundException e) { + logger.error("Unable to find AnalyzeInfoProvider implementation class [{}}]", className, e); + return null; + } catch (NoSuchMethodException | IllegalAccessException e) { + logger.error("AnalyzeInfoProvider implementation class [%s] must have constructor without arguments."); + return null; + } + + Object instance; + try { + instance = constructor.invoke(); + } catch (Throwable e) { + logger.error("Unable to init AnalyzeInfoProvider class [{}}]", className, e); + return null; + } + + if (!(instance instanceof AnalyzeInfoProvider)) { + logger.error("Created instance of [{}] does not implement [{}] interface", Review comment: Same here. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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