* If plugin does not provide `lucene` property, we consider that the plugin is compatible.
* If plugin provides `lucene` property, we try to load related Enum org.apache.lucene.util.Version. If this fails, it means that the node is too "old" comparing to the Lucene version the plugin was built for.
* We compare then two first digits of current node lucene version against two first digits of plugin Lucene version. If not equal, it means that the plugin is too "old" for the current node.
Plugin developers who wants to launch plugin check only have to add a `lucene` property in `es-plugin.properties` file. If you are using maven to build your plugin, you can do it like this:
In `pom.xml`:
```xml
<properties>
<lucene.version>4.6.0</lucene.version>
</properties>
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<filtering>true</filtering>
</resource>
</resources>
</build>
```
In `es-plugin.properties`, add:
```properties
lucene=${lucene.version}
```
BTW, if you don't already have it, you can add the plugin version as well:
```properties
version=${project.version}
```
You can disable that check using `plugins.check_lucene: false`.
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