Elasticsearch and Guice

Elastic Stack Elasticsearch
1

Hi,

Just wanted to know if elasticsearch is moving away from using Guice to wire dependencies? If yes, are there any discussion posts where I can read more about the reasons behind it?

Thanks.

2

For some developer comments about dependency injection modules in ES, see

Please note that ES has always used an older (and somewhat optimized) shadowed version of Guice 2 while Guice is now at 4.1. This brought some challenges concerning the tracing and backporting of fixed bugs, see https://github.com/elastic/elasticsearch/issues/283 and https://github.com/elastic/elasticsearch/pull/17921

3

Thanks Jörg, that was helpful.

Is the plan to completely remove Guice from the elasticsearch codebase in favour of constructor injection by hand, or to have a small set of modules for top level services (e.g. SearchModule, TransportModule) that has a flat structure and then use Guice to wire only these top level modules and use @Inject for their discovery?

If you are completely removing Guice, then what approach are you taking to lookup (inject) a specific service from a different service?

4

I can not speak for the ES developers but what I can read between the lines is that Guice shall completely disappear in 5.0

From ES plugin developer perspective, I'm bound to that decision and I hope I can navigate through the labyrinth of factories, registries, modules and services that would have to be wired by hand into the code - kind of a struggle, like back in the old days of Java 2 and J2EE. But, I understand that because Guice ignores plugin isolation and collides with classloading as long as the software around Guice is not providing classloader separated dependency injection aka "everything is a plugin" design pattern, which ES never tried consequently enough. I mean, initiate plugin code first, then create separate Guice injectors each with all ES modules for each plugin. Instead, all plugins were considered a module within the Guice hierarchy.

From the perspective as a great fan of the magic of Guice (and Guava), I would have to follow my own code base in order to use Guice again, which means, wrap my own code base around Elasticsearch, including a web app platform with plugins, custom bootstrapping (aka embedding Elasticsearch) - yes, reinventing the wheel. I doubt this could be a satisfying solution for everyone.

I haven't tried ES 5.0 - it is moving too fast and it collides with several other projects in my timeline - so I am still confident all will work out well in the end.