feat(tvix/tracing): introduce common tvix-tracing crate

Introduce a new common crate that contains tracing boilerplate which then
can be used in the cli, tvix-store and tvix-build crates.
It has otlp as an optional feature, which is currently only used by
tvix-store.

Change-Id: I41468ac4d9c65174515d721513b96fea463d6ed2
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11758
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: Simon Hauser <simon.hauser@helsinki-systems.de>

tvix/cli/Cargo.toml

@@ -14,6 +14,7 @@ tvix-castore = { path = "../castore" }
 tvix-store = { path = "../store", default-features = false, features = []}
 tvix-eval = { path = "../eval" }
 tvix-glue = { path = "../glue" }
+tvix-tracing = { path = "../tracing" }
 bytes = "1.4.0"
 clap = { version = "4.0", features = ["derive", "env"] }
 dirs = "4.0.0"
@@ -21,8 +22,7 @@ rustyline = "10.0.0"
 rnix = "0.11.0"
 thiserror = "1.0.38"
 tokio = "1.28.0"
-tracing = { version = "0.1.37", features = ["max_level_trace", "release_max_level_info"] }
-tracing-subscriber = "0.3.16"
+tracing = "0.1.40"
 
 [dependencies.wu-manber]
 git = "https://github.com/tvlfyi/wu-manber.git"

tvix/cli/src/main.rs

@@ -5,9 +5,6 @@ use repl::Repl;
 use std::rc::Rc;
 use std::{fs, path::PathBuf};
 use tracing::Level;
-use tracing_subscriber::fmt::writer::MakeWriterExt;
-use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
-use tracing_subscriber::{EnvFilter, Layer};
 use tvix_build::buildservice;
 use tvix_eval::builtins::impure_builtins;
 use tvix_eval::observer::{DisassemblingObserver, TracingObserver};
@@ -27,8 +24,12 @@ static GLOBAL: Jemalloc = Jemalloc;
 
 #[derive(Parser, Clone)]
 struct Args {
-    #[arg(long)]
-    log_level: Option<Level>,
+    /// A global log level to use when printing logs.
+    /// It's also possible to set `RUST_LOG` according to
+    /// `tracing_subscriber::filter::EnvFilter`, which will always have
+    /// priority.
+    #[arg(long, default_value_t=Level::INFO)]
+    log_level: Level,
 
     /// Path to a script to evaluate
     script: Option<PathBuf>,
@@ -270,24 +271,7 @@ fn lint(code: &str, path: Option<PathBuf>, args: &Args) -> bool {
 fn main() {
     let args = Args::parse();
 
-    // configure log settings
-    let level = args.log_level.unwrap_or(Level::INFO);
-
-    let subscriber = tracing_subscriber::registry().with(
-        tracing_subscriber::fmt::Layer::new()
-            .with_writer(std::io::stderr.with_max_level(level))
-            .compact()
-            .with_filter(
-                EnvFilter::builder()
-                    .with_default_directive(level.into())
-                    .from_env()
-                    .expect("invalid RUST_LOG"),
-            ),
-    );
-    subscriber
-        .try_init()
-        .expect("unable to set up tracing subscriber");
-
+    tvix_tracing::init(args.log_level).expect("unable to set up tracing subscriber");
     let tokio_runtime = tokio::runtime::Runtime::new().expect("failed to setup tokio runtime");
 
     let io_handle = init_io_handle(&tokio_runtime, &args);