4 files changed, 145 insertions, 1 deletions

diff --git a/src/db/Cargo.toml b/src/db/Cargo.toml
index ef5a8659..aefbb960 100644
--- a/src/db/Cargo.toml
+++ b/src/db/Cargo.toml
@@ -15,6 +15,7 @@ path = "lib.rs"
 err-derive.workspace = true
 hexdump.workspace = true
 tracing.workspace = true
+opentelemetry.workspace = true
 
 heed = { workspace = true, optional = true }
 rusqlite = { workspace = true, optional = true, features = ["backup"] }
diff --git a/src/db/lib.rs b/src/db/lib.rs
index c8f9e13f..504f1b4c 100644
--- a/src/db/lib.rs
+++ b/src/db/lib.rs
@@ -3,6 +3,9 @@ extern crate tracing;
 
 #[cfg(feature = "lmdb")]
 pub mod lmdb_adapter;
+#[cfg(feature = "lmdb")]
+pub mod metric_proxy;
+
 #[cfg(feature = "sqlite")]
 pub mod sqlite_adapter;
 
diff --git a/src/db/lmdb_adapter.rs b/src/db/lmdb_adapter.rs
index d5066664..ecfe5e1e 100644
--- a/src/db/lmdb_adapter.rs
+++ b/src/db/lmdb_adapter.rs
@@ -226,7 +226,7 @@ impl IDb for LmdbDb {
 
 // ----
 
-struct LmdbTx<'a> {
+pub(crate) struct LmdbTx<'a> {
 	trees: &'a [Database],
 	tx: RwTxn<'a, 'a>,
 }
diff --git a/src/db/metric_proxy.rs b/src/db/metric_proxy.rs
new file mode 100644
index 00000000..e387715e
--- /dev/null
+++ b/src/db/metric_proxy.rs
@@ -0,0 +1,140 @@
+use std::path::PathBuf;
+use std::time::Instant;
+
+use crate::lmdb_adapter::{LmdbDb, LmdbTx};
+use crate::{Bound, IDb, ITx, ITxFn, OnCommit, Result, TxResult, Value, ValueIter};
+use opentelemetry::{
+	global,
+	metrics::{Counter, ValueRecorder},
+	KeyValue,
+};
+
+pub struct MetricDbProxy {
+	db: LmdbDb,
+	op_counter: Counter<u64>,
+	op_duration: ValueRecorder<f64>,
+}
+
+impl MetricDbProxy {
+	pub fn init(db: LmdbDb) -> MetricDbProxy {
+		let meter = global::meter("garage/web");
+		Self {
+			db,
+			op_counter: meter
+				.u64_counter("db.op_counter")
+				.with_description("Number of operations on the local metadata engine")
+				.init(),
+			op_duration: meter
+				.f64_value_recorder("db.op_duration")
+				.with_description("Duration of operations on the local metadata engine")
+				.init(),
+		}
+	}
+
+	fn instrument<T>(
+		&self,
+		fx: impl FnOnce() -> T,
+		op: &'static str,
+		cat: &'static str,
+		tx: &'static str,
+	) -> T {
+		let metric_tags = [
+			KeyValue::new("op", op),
+			KeyValue::new("cat", cat),
+			KeyValue::new("tx", tx),
+		];
+		self.op_counter.add(1, &metric_tags);
+
+		let request_start = Instant::now();
+		let res = fx();
+		self.op_duration.record(
+			Instant::now()
+				.saturating_duration_since(request_start)
+				.as_secs_f64(),
+			&metric_tags,
+		);
+
+		res
+	}
+}
+
+impl IDb for MetricDbProxy {
+	fn engine(&self) -> String {
+		format!("Metric Proxy on {}", self.db.engine())
+	}
+
+	fn open_tree(&self, name: &str) -> Result<usize> {
+		self.instrument(|| self.db.open_tree(name), "open_tree", "control", "no")
+	}
+
+	fn list_trees(&self) -> Result<Vec<String>> {
+		self.instrument(|| self.db.list_trees(), "list_trees", "control", "no")
+	}
+
+	fn snapshot(&self, to: &PathBuf) -> Result<()> {
+		self.instrument(|| self.db.snapshot(to), "snapshot", "control", "no")
+	}
+
+	// ---
+
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value>> {
+		self.instrument(|| self.db.get(tree, key), "get", "data", "no")
+	}
+
+	fn len(&self, tree: usize) -> Result<usize> {
+		self.instrument(|| self.db.len(tree), "len", "data", "no")
+	}
+
+	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<Option<Value>> {
+		self.instrument(|| self.db.insert(tree, key, value), "insert", "data", "no")
+	}
+
+	fn remove(&self, tree: usize, key: &[u8]) -> Result<Option<Value>> {
+		self.instrument(|| self.db.remove(tree, key), "remove", "data", "no")
+	}
+
+	fn clear(&self, tree: usize) -> Result<()> {
+		self.instrument(|| self.db.clear(tree), "clear", "data", "no")
+	}
+
+	fn iter(&self, tree: usize) -> Result<ValueIter<'_>> {
+		self.instrument(|| self.db.iter(tree), "iter", "data", "no")
+	}
+
+	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>> {
+		self.instrument(|| self.db.iter_rev(tree), "iter_rev", "data", "no")
+	}
+
+	fn range<'r>(
+		&self,
+		tree: usize,
+		low: Bound<&'r [u8]>,
+		high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		self.instrument(|| self.db.range(tree, low, high), "range", "data", "no")
+	}
+
+	fn range_rev<'r>(
+		&self,
+		tree: usize,
+		low: Bound<&'r [u8]>,
+		high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		self.instrument(
+			|| self.db.range_rev(tree, low, high),
+			"range_rev",
+			"data",
+			"no",
+		)
+	}
+
+	// ----
+
+	fn transaction(&self, f: &dyn ITxFn) -> TxResult<OnCommit, ()> {
+		self.instrument(|| self.db.transaction(f), "transaction", "control", "yes")
+	}
+}
+
+struct MetricTxProxy<'a> {
+	tx: LmdbTx<'a>,
+}