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https://issues.apache.org/jira/browse/METRON-1569?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16489883#comment-16489883
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ASF GitHub Bot commented on METRON-1569:
----------------------------------------
Github user nickwallen commented on a diff in the pull request:
https://github.com/apache/metron/pull/1022#discussion_r190742938
--- 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 --
So you're saying, hey why not just...
1. Take out the caching and just have something like a
`SimpleFieldNameConverterFactory`. This would translate the (sourceType,
WriterConfiguration) to the right `FieldNameConverter`.
2. The caching would be handled by `FieldNameConverters` in the sense that
they are effectively singletons.
I think that would work if all `FieldNameConverter` implementations are
stateless. And they all are stateless today, but I tried not to make that a
constraint. I actually tried to make this work whether they are stateless or
not.
But alas there is a bug in what I did because I need each call to
FieldNameConverters.get() to return a new instance.
I'd be open to removing the cache, if its not needed and we think
`FieldNameConverter`s would always remain stateless.
> Allow user to change field name conversion when indexing to Elasticsearch
> -------------------------------------------------------------------------
>
> Key: METRON-1569
> URL: https://issues.apache.org/jira/browse/METRON-1569
> Project: Metron
> Issue Type: Improvement
> Reporter: Nick Allen
> Assignee: Nick Allen
> Priority: Major
>
> The `ElasticsearchWriter` has a mechanism to transform the field names of a
> message before it is written to Elasticsearch. Right now this mechanism is
> hard-coded to replace all '.' dots with ':' colons.
> This mechanism was needed for Elasticsearch 2.x which did not allow dots in
> field names. Now that Metron supports Elasticsearch 5.x this is no longer a
> problem.
> A user should be able to configure the field name transformation when writing
> to Elasticsearch, as needed.
> While it might have been simpler to just remove the de-dotting mechanism,
> this would break backwards compatibility. Providing users with a means to
> configure this mechanism provides them with an upgrade path.
>
>
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