Github user nickwallen commented on a diff in the pull request:
https://github.com/apache/metron/pull/1022#discussion_r190702283
--- 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 --
Maybe I am misunderstanding you, but the ConfigurationsUpdater ensures that
our configuration classes stay in-sync with Zk. That's now what this class
does.
This maintains a `FieldNameConverter` instance for each source type that is
then used by the `ElasticsearchWriter` to do the field name conversion. Are
you proposing a different way to do this?
---
