(“This Week in Glean” is a series of blog posts that the Glean Team at Mozilla is using to try to communicate better about our work. They could be release notes, documentation, hopes, dreams, or whatever: so long as it is inspired by Glean.)
All "This Week in Glean" blog posts are listed in the [TWiG index](https://mozilla.github.io/glean/book/appendix/twig.html)
(and on the [Mozilla Data blog](https://blog.mozilla.org/data/category/glean/)).
The top layer of the Glean SDK are the different [language implementations](https://mozilla.github.io/glean/book/dev/core/internal/implementations.html).
Language implementations expose a nice ergonomic API to initialize Glean and record metrics in the respective language.
Additionally each implementation handles some special cases for the platform they are running on, like gathering application and platform data or hooking into system events.
The nice API calls into the Glean SDK using the exposed FFI functions of `glean-ffi`.
Unfortunately at the moment different language implementations carry different amounts of actual logic in them.
Sometimes metric implementations require this (e.g. we rely on the clock source of Kotlin for timing metrics),
in other parts we just didn't move the logic out of the implementations yet.
We're actively working on [moving logic into the Rust part where we can](https://bugzilla.mozilla.org/show_bug.cgi?id=1651382) and might eventually use some code generation to unify the other parts.
