The Plugin interface currently contains 6 different methods for
adding modules. Elasticsearch has 3 different levels of injectors,
and for each of those, there are two methods. The first takes no
arguments and returns a collection of class objects to construct. The
second takes a Settings object and returns a collection of module
objects already constructed. The settings argument is unecessary because
the plugin can already get the settings from its constructor. Removing
that, the only difference between the two versions is returning an
already constructed Module, or a module Class, and there is no reason
the plugin can't construct all their modules themselves.
This change reduces the plugin api down to just 3 methods for adding
modules. Each returns a Collection<Module>. It also removes the
processModule method, which was unnecessary since onModule
implementations fullfill the same requirement. And finally, it renames
the modules() method to nodeModules() so it is clear these are created
once for each node.
This is one of our esoteric metadata mappers so I think we should distribute
it in a plugin rather than in elasticsearch core.
This introduces one limitation: the value of the `_size` parameter is not
retrievable for documents that are only in the transaction log.
Ryan Ernst
Adrien Grand