add macros.rs; conditional logging macros

database/Cargo.toml

@@ -9,6 +9,7 @@ repository  = "https://github.com/Cuprate/cuprate/tree/main/database"
 keywords    = ["cuprate", "database"]
 
 [features]
+# default   = ["heed", "redb", "service", "tracing"]
 default   = ["heed", "redb", "service"]
 # default   = ["redb", "service"]
 # default   = ["redb-memory", "service"]
@@ -33,7 +34,6 @@ monero-serai     = { workspace = true, features = ["std"] }
 paste            = { workspace = true }
 page_size        = { version = "0.6.0" } # Needed for database resizes, they must be a multiple of the OS page size.
 thiserror        = { workspace = true }
-tracing          = { workspace = true }
 
 # `service` feature.
 crossbeam    = { workspace = true, features = ["std"], optional = true }
@@ -45,9 +45,10 @@ thread_local = { workspace = true }
 rayon        = { workspace = true, optional = true }
 
 # Optional features.
-heed  = { version = "0.20.0", features = ["read-txn-no-tls"], optional = true }
-redb  = { version = "2.1.0", optional = true }
-serde = { workspace = true, optional = true }
+heed    = { version = "0.20.0", features = ["read-txn-no-tls"], optional = true }
+redb    = { version = "2.1.0", optional = true }
+serde   = { workspace = true, optional = true }
+tracing = { workspace = true, optional = true }
 
 [dev-dependencies]
 bytemuck = { version = "1.14.3", features = ["must_cast", "derive", "min_const_generics", "extern_crate_alloc"] }

database/src/lib.rs

@@ -58,6 +58,7 @@
 //!
 //! `ConcreteEnv` invariants you can rely on:
 //! - It implements [`Env`]
+//! - It implements [`Debug`]
 //! - Upon [`Drop::drop`], all database data will sync to disk
 //!
 //! Note that `ConcreteEnv` itself is not a clonable type,
@@ -78,8 +79,9 @@
 //!
 //! The default is `heed`.
 //!
-//! `tracing` is always enabled and cannot be disabled via feature-flag.
-//! <!-- FIXME: tracing should be behind a feature flag -->
+//! Logging with [`tracing`](https://docs.rs/tracing)
+//! can be enabled with the `tracing` feature flag,
+//! this is disabled by default.
 //!
 //! # Invariants when not using `service`
 //! `cuprate_database` can be used without the `service` feature enabled but
@@ -274,6 +276,8 @@ pub mod resize;
 mod key;
 pub use key::Key;
 
+mod macros;
+
 mod storable;
 pub use storable::{Storable, StorableBytes, StorableVec};
 

database/src/macros.rs

@@ -0,0 +1,155 @@
+//! General macros.
+
+//---------------------------------------------------------------------------------------------------- Logging
+// The below macros/types/functions allow for conditional
+// logging with `tracing` depending on if the feature flag
+// is enabled or not.
+//
+// These macros (e.g. [`info2`]) are used instead of the tracing macro directly.
+// #[tracing::instrument] will still need to be handled by us by using `#[cfg_attr]`.
+
+/// Dummy structure with methods that copy the ones on [`tracing::Span`].
+///
+/// This is used when "tracing" is disabled such that span functions:
+/// ```rust,ignore
+/// let span: DummySpan = info_span2!("span");
+/// let _guard = span.enter();
+/// ```
+/// will still work as this struct will just be returned, then
+/// [`DummySpan::enter`] will be called instead, which is just a dummy method.
+pub(crate) struct DummySpan;
+
+impl DummySpan {
+    /// Emulates [`tracing::Span::enter`].
+    #[inline]
+    pub(crate) const fn enter(&self) -> &Self {
+        self
+    }
+}
+
+/// Drop impl is needed to satisfy clippy.
+impl Drop for DummySpan {
+    #[inline]
+    fn drop(&mut self) {}
+}
+
+/// [`tracing::warn_span`].
+macro_rules! warn_span2 {
+    ($($token:tt)*) => {{
+        cfg_if::cfg_if! {
+            if #[cfg(feature = "tracing")] {
+                tracing::warn_span!($($token)*)
+            } else {
+                $crate::macros::DummySpan
+            }
+        }
+    }};
+}
+pub(crate) use warn_span2;
+
+/// [`tracing::warn`].
+macro_rules! warn2 {
+    ($($token:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::warn!($($token)*)
+    };
+}
+pub(crate) use warn2;
+
+/// [`tracing::trace_span`].
+macro_rules! trace_span2 {
+    ($($token:tt)*) => {{
+        cfg_if::cfg_if! {
+            if #[cfg(feature = "tracing")] {
+                tracing::trace_span!($($token)*)
+            } else {
+                $crate::macros::DummySpan
+            }
+        }
+    }};
+}
+pub(crate) use trace_span2;
+
+/// [`tracing::trace`].
+macro_rules! trace2 {
+    ($($token:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::trace!($($token)*)
+    };
+}
+pub(crate) use trace2;
+
+/// [`tracing::info_span`].
+macro_rules! info_span2 {
+    ($($token:tt)*) => {{
+        cfg_if::cfg_if! {
+            if #[cfg(feature = "tracing")] {
+                tracing::info_span!($($token)*)
+            } else {
+                $crate::macros::DummySpan
+            }
+        }
+    }};
+}
+pub(crate) use info_span2;
+
+/// [`tracing::info`].
+macro_rules! info2 {
+    ($($token:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::info!($($token)*)
+    };
+}
+pub(crate) use info2;
+
+/// [`tracing::error_span`].
+macro_rules! error_span2 {
+    ($($token:tt)*) => {{
+        cfg_if::cfg_if! {
+            if #[cfg(feature = "tracing")] {
+                tracing::error_span!($($token)*)
+            } else {
+                $crate::macros::DummySpan
+            }
+        }
+    }};
+}
+pub(crate) use error_span2;
+
+/// [`tracing::error`].
+macro_rules! error2 {
+    ($($token:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::error!($($token)*)
+    };
+}
+pub(crate) use error2;
+
+/// [`tracing::debug_span`].
+macro_rules! debug_span2 {
+    ($($token:tt)*) => {{
+        cfg_if::cfg_if! {
+            if #[cfg(feature = "tracing")] {
+                tracing::debug_span!($($token)*)
+            } else {
+                $crate::macros::DummySpan
+            }
+        }
+    }};
+}
+pub(crate) use debug_span2;
+
+/// [`tracing::debug`].
+macro_rules! debug2 {
+    ($($token:tt)*) => {
+        #[cfg(feature = "tracing")]
+        tracing::debug!($($token)*)
+    };
+}
+pub(crate) use debug2;
+
+//---------------------------------------------------------------------------------------------------- Tests
+#[cfg(test)]
+mod test {
+    // use super::*;
+}