There's more…

If your current Elasticsearch application depends on one or more plugins, a node can be configured to start up only if these plugins are installed and available. To achieve this behavior, you can provide the plugin.mandatory directive in the elasticsearch.yml configuration file.

For the previous example (ingest-attachment), the config line to be added is as follows:

plugin.mandatory:ingest-attachment

There are also some hints to remember while installing plugins: updating some plugins in a node environment can cause malfunctions due to different plugin versions in different nodes. If you have a big cluster for safety, it's better to check for updates in a separate environment to prevent problems (and remember to upgrade the plugin in all the nodes).

To prevent the fact updating an Elasticsearch version server which could also break your custom binary plugins due to some internal API changes, in Elasticsearch 5.x or higher, the plugins need to have the same version of Elasticsearch server in their manifest.