Elasticsearch backend for Spotlight

[rdmark]

Netatalk presently uses Gnome Tracker as the backend for file system indexing and search for the Spotlight feature. However, Tracker has the drawback of being explicitly designed for GUI applications, notably the Gnome desktop environment. As such, it has a few drawbacks:

• It may pull in many dependencies that aren't relevant for Netatalk or a headless server system in general
• It expects to have a Gnome desktop environment, and throws many warnings when missing

Since Netatalk introduced Spotlight support a decade ago, more light-weight and specialized indexing solutions have appeared. Notably Elasticsearch.

In fact, Samba supports Elasticsearch as a Spotlight indexing backend in addition to Tracker. It should be investigated if the same could be applied to Netatalk.

[rdmark]

Alpine Linux version 3.21 has now moved from Tracker to Localsearch (Gnome's rebranding of this technology). When installing the localsearch package, 962 MB of packages are installed on a headless Alpine system, including Weyland, the Mesa 3D graphics library, several multimedia codecs, hardware drivers, and so on.

This is yet another data point that proves Localsearch (Tracker) isn't an appropriate backend technology for a server application.