Speed start up by deferring post-startup ls/engine actions

[wdanilo]

Overview

Services that are being currently initialized can be divided into two categories:

• required startup to bring the necessary services up and running
• post-startup actions that could be started with low-level priority and warm up our engine

Motivation

• JGit should run its bookkeeping in the background #4116 (review) - 100ms JGit initialization can wait until first user edit
• Pre-compute Suggestion DB during build time #5068 - 1s - delivering suggestion DB isn't necessary for computing visualizations

Goal

Investigate how and if we can divide some of our existing services to provide a good compromise between accessibility of services and their performance. Mitigate at least 1s spend in SqlSuggestionRepo initialization:

Design

Let's introduce new Akka internal message - WarmUp. All actors that are interested in performing post-startup actions shall register for that message in Akka bus and start their initialization when it is delivered. Their initialization may be triggered in response to other events - the WarmUp message is there to let everyone know: Hey, all the important work is done, you have time to pre-initialize!

The language-server detects (possibly in cooperation with the IDE) when the essential part of startup is done and emits the WarmUp message then.

References

• Original issue was reported by Hubert.
• NetBeans offered following set of annotations to accommodate different initialization needs:
  • @OnStart - https://bits.netbeans.org/16/javadoc/org-openide-modules/org/openide/modules/OnStart.html
  • @OnShowing - https://bits.netbeans.org/16/javadoc/org-openide-windows/org/openide/windows/OnShowing.html
  • @OnStop - https://bits.netbeans.org/16/javadoc/org-openide-modules/org/openide/modules/OnStop.html

[4e6]

The work for delaying post-startup actions was done in #5970 #5990 and #5997