From 06aa34cd1038f69b708c32ed4e7a530170291a1b Mon Sep 17 00:00:00 2001 From: Aleksey Kladov Date: Thu, 4 Feb 2021 13:27:34 +0300 Subject: More architecture.md --- docs/dev/architecture.md | 44 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 42 insertions(+), 2 deletions(-) (limited to 'docs') diff --git a/docs/dev/architecture.md b/docs/dev/architecture.md index 2ba8b7967..56ebaa3df 100644 --- a/docs/dev/architecture.md +++ b/docs/dev/architecture.md @@ -373,8 +373,48 @@ There's no additional checks in CI, formatting and tidy tests are run with `carg **Architecture Invariant:** tests do not depend on any kind of external resources, they are perfectly reproducible. +### Error Handling + +**Architecture Invariant:** core parts of rust-analyzer (`ide`/`hir`) don't interact with the outside world and thus can't fail. +Only parts touching LSP are allowed to do IO. + +Internals of rust-analyzer need to deal with broken code, but this is not an error condition. +rust-analyzer is robust: various analysis compute `(T, Vec)` rather than `Result`. + +rust-analyzer is a complex long-running process. +It will always have bugs and panics. +But a panic in an isolated feature should not bring down the whole process. +Each LSP-request is protected by a `catch_unwind`. +We use `always` and `never` macros instead of `assert` to gracefully recover from impossible conditions. + ### Observability -I've run out of steam here :) rust-analyzer is a long-running process, so its important to understand what's going on inside. -We have hierarchical profiler (`RA_PROFILER=1`) and object counting (`RA_COUNT=1`). +We have several instruments for that. + +The event loop that runs rust-analyzer is very explicit. +Rather than spawning futures or scheduling callbacks (open), the event loop accepts an `enum` of possible events (closed). +It's easy to see all the things that trigger rust-analyzer processing, together with their performance + +rust-analyzer includes a simple hierarchical profiler (`hprof`). +It is enabled with `RA_PROFILE='*>50` env var (log all (`*`) actions which take more than `50` ms) and produces output like: + +``` +85ms - handle_completion + 68ms - import_on_the_fly + 67ms - import_assets::search_for_relative_paths + 0ms - crate_def_map:wait (804 calls) + 0ms - find_path (16 calls) + 2ms - find_similar_imports (1 calls) + 0ms - generic_params_query (334 calls) + 59ms - trait_solve_query (186 calls) + 0ms - Semantics::analyze_impl (1 calls) + 1ms - render_resolution (8 calls) + 0ms - Semantics::analyze_impl (5 calls) +``` + +This is cheap enough to enable in production. + + +Similarly, we save live object counting (`RA_COUNT=1`). +It is not cheap enough to enable in prod, and this is a bug which should be fixed. -- cgit v1.2.3