Github user mmiklavc commented on a diff in the pull request: https://github.com/apache/metron/pull/1022#discussion_r190915687 --- Diff: metron-platform/metron-elasticsearch/src/main/java/org/apache/metron/elasticsearch/writer/CachedFieldNameConverterFactory.java --- @@ -0,0 +1,155 @@ +/** + * 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.metron.elasticsearch.writer; + +import com.github.benmanes.caffeine.cache.Cache; +import com.github.benmanes.caffeine.cache.Caffeine; +import org.apache.commons.lang.ClassUtils; +import org.apache.commons.lang3.StringUtils; +import org.apache.commons.lang3.exception.ExceptionUtils; +import org.apache.metron.common.configuration.writer.WriterConfiguration; +import org.apache.metron.common.field.DeDotFieldNameConverter; +import org.apache.metron.common.field.FieldNameConverter; +import org.apache.metron.common.field.FieldNameConverters; +import org.apache.metron.common.field.NoopFieldNameConverter; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.lang.invoke.MethodHandles; +import java.util.concurrent.TimeUnit; + +/** + * A {@link FieldNameConverterFactory} that is backed by a cache. + * + * <p>Each sensor type can use a different {@link FieldNameConverter} implementation. + * + * <p>The {@link WriterConfiguration} allows a user to define the {@link FieldNameConverter} + * that should be used for a given sensor type. + * + * <p>The {@link FieldNameConverter}s are maintained in a cache for a fixed period of time + * after they are created. Once they expire, the {@link WriterConfiguration} is used to + * reload the {@link FieldNameConverter}. + * + * <p>The user can change the {@link FieldNameConverter} in use at runtime. A change --- End diff -- I definitely appreciate the thinking around state though I think we can safely leave that out for now. This isn't client-facing, so refactoring later would have less consequence than something we expose via config or the UI. I think you could probably use the enum as a factory directly and use FieldNameConverter converter = FieldNameConverters.valueOf(converterName).get() in ElasticsearchWriter line 80 directly. We do this a number of places as a combination strategy/factory pattern. https://github.com/apache/metron/blob/master/metron-platform/metron-common/src/main/java/org/apache/metron/common/utils/CompressionStrategies.java https://github.com/apache/metron/blob/master/metron-platform/metron-enrichment/src/main/java/org/apache/metron/enrichment/bolt/UnifiedEnrichmentBolt.java#L194 I definitely get wanting to provide a factory, and I think you effectively get that with the enum you already created.
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