Runtime interface to add support for tracing from wasm (#6381)

* Add span recording to tracing implementation

* Add tracing proxy

* switch to rustc_hash::FxHashMap

* Replace lazy_static and hashmap with thread_local and vec.

* fix marking valid span as invalid while removing invalid spans

* refactor, add wasm_tracing module in `support`

* update registered spans

* tidy up

* typos

* refactor

* update flag name to signal lost trace - `is_valid_trace`

* update flag name to signal lost trace - `is_valid_trace`

* update docs

* update docs

* Use tracing Field recording to store the actual `name` and `target`
from wasm traces.

* fix debug log in subscriber + small refactor

* add tests

* handle misuse in case trying to exit span not held

* Implement filter for wasm traces, simplify field recording for primitive types

* remove superfluous warning

* update docs

* Update primitives/tracing/src/proxy.rs

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* update docs, apply suggestions

* move Proxy from thread_local to `Extension`, rename macro

* fix test

* unify native & wasm span macro calls

* implement wasm tracing control facility in primitives and frame

* add cli flag `--wasm-tracing`

* fix

* switch to `Option<u4>` (possible performance degradation), switch
to static mut bool

* performance improvement using u64 vs Option<u64>

* performance improvement moving concat to client

* update docs

* Update client/cli/src/params/import_params.rs

Co-authored-by: Cecile Tonglet <cecile@parity.io>

* performance improvement

* Revert "performance improvement"

This reverts commit 55ff8817a86302cd93bb6197eb4ca5bc7f4fb524.

* small refactor

* formatting

* bump impl_version

* Update client/cli/src/config.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* update docs

* small fixes, remove pub static

* nit

* add integration tests and refactor Subscriber

* tests

* revert formatting

* try fix test that works locally but not in CI

* try fix test that works locally but not in CI

* debug test that works locally but not in CI

* fix test that works locally but not in CI

* remove pub visibility from bool in runtime

* make TracingSpanGuard #[cfg(not(feature = "std"))], update docs, comments

* make TracingProxy drop implementation conditional on !empty state

* add docs for TraceHandler

* remove blank line

* update expect message

* update tests

* rename cli option to tracing_enable_wasm

* rename cli option to tracing_enable_wasm

* fix

* ensure wasm-tracing features are wasm only

* bump impl_version

* bump impl_version

* add `"pallet-scheduler/std"` to `[features]` `std` in node/runtime

* refactor service to remove sp_tracing dependency

* refactor: line width, trait bounds

* improve LogTraceHandler output

* fix test

* improve tracing log output

* Apply suggestions from code review

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* swap wasm indication from trace name to a separate value

* Update client/tracing/src/lib.rs

* add docs

* remove runtime features

remove wasm_tracing option from CLI

remove wasm_tracing flag from ProfilingSubscriber

Co-authored-by: Matt Rutherford <mattrutherford@users.noreply.github.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Cecile Tonglet <cecile@parity.io>

substrate/primitives/tracing/src/lib.rs

@@ -19,13 +19,35 @@
 //!
 //! To trace functions or invidual code in Substrate, this crate provides [`tracing_span`]
 //! and [`enter_span`]. See the individual docs for how to use these macros.
-
+//!
+//! Note that to allow traces from wasm execution environment there are
+//! 2 reserved identifiers for tracing `Field` recording, stored in the consts:
+//! `WASM_TARGET_KEY` and `WASM_NAME_KEY` - if you choose to record fields, you
+//! must ensure that your identifiers do not clash with either of these.
+//!
+//! Additionally, we have a const: `WASM_TRACE_IDENTIFIER`, which holds a span name used
+//! to signal that the 'actual' span name and target should be retrieved instead from
+//! the associated Fields mentioned above.
 #![cfg_attr(not(feature = "std"), no_std)]
 
+#[cfg(feature = "std")]
+#[macro_use]
+extern crate rental;
+
 #[cfg(feature = "std")]
 #[doc(hidden)]
 pub use tracing;
 
+#[cfg(feature = "std")]
+pub mod proxy;
+
+#[cfg(feature = "std")]
+use std::sync::atomic::{AtomicBool, Ordering};
+
+/// Flag to signal whether to run wasm tracing
+#[cfg(feature = "std")]
+static WASM_TRACING_ENABLED: AtomicBool = AtomicBool::new(false);
+
 /// Runs given code within a tracing span, measuring it's execution time.
 ///
 /// If tracing is not enabled, the code is still executed.
@@ -83,3 +105,13 @@ macro_rules! if_tracing {
 macro_rules! if_tracing {
 	( $if:expr ) => {{}}
 }
+
+#[cfg(feature = "std")]
+pub fn wasm_tracing_enabled() -> bool {
+	WASM_TRACING_ENABLED.load(Ordering::Relaxed)
+}
+
+#[cfg(feature = "std")]
+pub fn set_wasm_tracing(b: bool) {
+	WASM_TRACING_ENABLED.store(b, Ordering::Relaxed)
+}