add support for tokio-console & make deps opt-in via feature

libs/utils/Cargo.toml

@@ -10,6 +10,10 @@ default = []
 # which adds some runtime cost to run tests on outage conditions
 testing = ["fail/failpoints"]
 
+# Enables debugging functionality that's based on the `tracing` crate,
+# e.g., tokio-console or tracing-chrome.
+tracing-based-debugging = [ "console-subscriber", "tracing-chrome", "tracing-flame", "tokio/tracing" ]
+
 [dependencies]
 arc-swap.workspace = true
 sentry.workspace = true
@@ -20,6 +24,7 @@ bincode.workspace = true
 bytes.workspace = true
 camino.workspace = true
 chrono.workspace = true
+console-subscriber = {workspace = true, optional = true}
 diatomic-waker.workspace = true
 flate2.workspace = true
 git-version.workspace = true
@@ -47,7 +52,9 @@ tokio-tar.workspace = true
 tokio-util.workspace = true
 toml_edit = { workspace = true, features = ["serde"] }
 tracing.workspace = true
+tracing-chrome = { workspace = true, optional = true }
 tracing-error.workspace = true
+tracing-flame = { workspace = true, optional = true }
 tracing-subscriber = { workspace = true, features = ["json", "registry"] }
 rand.workspace = true
 scopeguard.workspace = true
@@ -66,8 +73,6 @@ const_format.workspace = true
 # to use tokio channels as streams, this is faster to compile than async_stream
 # why is it only here? no other crate should use it, streams are rarely needed.
 tokio-stream = { version = "0.1.14" }
-tracing-chrome = "0.7.1"
-tracing-flame = "0.2.0"
 
 serde_path_to_error.workspace = true
 
@@ -80,6 +85,9 @@ camino-tempfile.workspace = true
 serde_assert.workspace = true
 tokio = { workspace = true, features = ["test-util"] }
 
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(tokio_unstable)'] }
+
 [[bench]]
 name = "benchmarks"
 harness = false

libs/utils/src/logging.rs

@@ -1,5 +1,6 @@
 use std::{
     io::BufWriter,
+    num::NonZeroUsize,
     str::FromStr,
     sync::{Arc, Mutex},
 };
@@ -189,6 +190,36 @@ pub fn init(
         },
     );
 
+    let r = {
+        let varname = "NEON_UTILS_LOGGING_ENABLE_TOKIO_CONSOLE";
+        let console_subscriber_config: Option<NonZeroUsize> = crate::env::var(varname);
+        #[cfg(tokio_unstable)]
+        {
+            r.with(match console_subscriber_config {
+                Some(n) => {
+                    use console_subscriber::ConsoleLayer;
+                    Some(
+                        console_subscriber::Builder::default()
+                            .event_buffer_capacity(
+                                n.get() * ConsoleLayer::DEFAULT_EVENT_BUFFER_CAPACITY,
+                            )
+                            .client_buffer_capacity(
+                                n.get() * ConsoleLayer::DEFAULT_CLIENT_BUFFER_CAPACITY,
+                            )
+                            .spawn(),
+                    )
+                }
+                None => None,
+            })
+        }
+        #[cfg(not(tokio_unstable))]
+        if console_subscriber_config.is_some() {
+            panic!("recompile with --cfg tokio_unstable to enable {varname}");
+        } else {
+            r
+        }
+    };
+
     let r = r.with(match tracing_error_layer_enablement {
         TracingErrorLayerEnablement::EnableWithRustLogFilter => {
             Some(tracing_error::ErrorLayer::default().with_filter(rust_log_env_filter()))