ijokarumawak commented on a change in pull request #3341: NIFI-6082: Added DatabaseRecordLookupService, refactored common DB utils URL: https://github.com/apache/nifi/pull/3341#discussion_r263668911
########## File path: nifi-nar-bundles/nifi-standard-services/nifi-lookup-services-bundle/nifi-lookup-services/src/main/java/org/apache/nifi/lookup/db/SimpleDatabaseLookupService.java ########## @@ -0,0 +1,160 @@ +/* + * 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.nifi.lookup.db; + +import com.github.benmanes.caffeine.cache.Cache; +import com.github.benmanes.caffeine.cache.Caffeine; +import org.apache.commons.lang3.StringUtils; +import org.apache.nifi.annotation.lifecycle.OnEnabled; +import org.apache.nifi.components.PropertyDescriptor; +import org.apache.nifi.controller.ConfigurationContext; +import org.apache.nifi.controller.ControllerServiceInitializationContext; +import org.apache.nifi.dbcp.DBCPService; +import org.apache.nifi.expression.ExpressionLanguageScope; +import org.apache.nifi.lookup.LookupFailureException; +import org.apache.nifi.lookup.StringLookupService; +import org.apache.nifi.processor.util.StandardValidators; +import org.apache.nifi.util.Tuple; +import org.apache.nifi.util.db.JdbcCommon; + +import java.sql.Connection; +import java.sql.PreparedStatement; +import java.sql.ResultSet; +import java.sql.SQLException; +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.Map; +import java.util.Optional; +import java.util.Set; +import java.util.concurrent.locks.ReadWriteLock; +import java.util.concurrent.locks.ReentrantReadWriteLock; + +public class SimpleDatabaseLookupService extends AbstractDatabaseLookupService implements StringLookupService { + + private volatile Cache<Tuple<String, Object>, String> cache; + private final ReadWriteLock lock = new ReentrantReadWriteLock(); + + private volatile String lookupValueColumn; + + static final PropertyDescriptor LOOKUP_VALUE_COLUMN = + new PropertyDescriptor.Builder() + .name("lookup-value-column") + .displayName("Lookup Value Column") + .description("The column whose value will be returned when the Lookup value is matched") + .required(true) + .addValidator(StandardValidators.NON_EMPTY_VALIDATOR) + .expressionLanguageSupported(ExpressionLanguageScope.VARIABLE_REGISTRY) + .build(); + + @Override + protected void init(final ControllerServiceInitializationContext context) { + final List<PropertyDescriptor> properties = new ArrayList<>(); + properties.add(DBCP_SERVICE); + properties.add(TABLE_NAME); + properties.add(LOOKUP_KEY_COLUMN); + properties.add(LOOKUP_VALUE_COLUMN); + properties.add(CACHE_SIZE); + properties.add(CLEAR_CACHE_ON_ENABLED); + this.properties = Collections.unmodifiableList(properties); + } + + @OnEnabled + public void onEnabled(final ConfigurationContext context) { + this.dbcpService = context.getProperty(DBCP_SERVICE).asControllerService(DBCPService.class); + this.lookupKeyColumn = context.getProperty(LOOKUP_KEY_COLUMN).evaluateAttributeExpressions().getValue(); + this.lookupValueColumn = context.getProperty(LOOKUP_VALUE_COLUMN).evaluateAttributeExpressions().getValue(); + int cacheSize = context.getProperty(CACHE_SIZE).evaluateAttributeExpressions().asInteger(); + boolean clearCache = context.getProperty(CLEAR_CACHE_ON_ENABLED).asBoolean(); + if (this.cache == null || (cacheSize > 0 && clearCache)) { + this.cache = Caffeine.newBuilder() + .maximumSize(cacheSize) + .build(); + } + + options = JdbcCommon.AvroConversionOptions.builder() + .recordName("NiFi_DB_Record_Lookup") + // Ignore duplicates + .maxRows(1) + // Keep column names as field names + .convertNames(false) + // Get the value as a string, so logical types are irrelevant + .useLogicalTypes(false) + .build(); + } + + @Override + public Optional<String> lookup(Map<String, Object> coordinates) throws LookupFailureException { + return lookup(coordinates, null); + } + + @Override + public Optional<String> lookup(Map<String, Object> coordinates, Map<String, String> context) throws LookupFailureException { + if (coordinates == null) { + return Optional.empty(); + } + + final Object key = coordinates.get(KEY); + if (StringUtils.isBlank(key.toString())) { + return Optional.empty(); + } + + final String tableName = getProperty(TABLE_NAME).evaluateAttributeExpressions(context).getValue(); + + Tuple<String, Object> cacheLookupKey = new Tuple<>(tableName, key); + + // Not using the function param of cache.get so we can catch and handle the checked exceptions + String foundRecord = cache.get(cacheLookupKey, k -> null); + + if (foundRecord == null) { + final String selectQuery = "SELECT " + lookupValueColumn + " FROM " + tableName + " WHERE " + lookupKeyColumn + " = ?"; + try (final Connection con = dbcpService.getConnection(context); + final PreparedStatement st = con.prepareStatement(selectQuery)) { + + st.setObject(1, key); + ResultSet resultSet = st.executeQuery(); + + if (!resultSet.next()) { + return Optional.empty(); + } + + Object o = resultSet.getObject(lookupValueColumn); + if (o == null) { + return Optional.empty(); + } + foundRecord = o.toString(); + + // Populate the cache if the record is present + if (foundRecord != null) { + lock.writeLock().lock(); Review comment: Is locking required when we update the cache? Caffein cache implementation should be thread safe. And since this is only a cache for previous value, I think that's fine overwriting it if this block executed at the exactly same time. From Cache's Java doc ``` * Implementations of this interface are expected to be thread-safe, and can be safely accessed by * multiple concurrent threads. ``` ---------------------------------------------------------------- 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
