Implement basic metrics in table

src/table/Cargo.toml

@@ -17,6 +17,8 @@ path = "lib.rs"
 garage_rpc = { version = "0.6.0", path = "../rpc" }
 garage_util = { version = "0.6.0", path = "../util" }
 
+opentelemetry = "0.17"
+
 async-trait = "0.1.7"
 bytes = "1.0"
 hexdump = "0.1"

src/table/data.rs

@@ -13,6 +13,7 @@ use garage_rpc::system::System;
 
 use crate::crdt::Crdt;
 use crate::gc::GcTodoEntry;
+use crate::metrics::*;
 use crate::replication::*;
 use crate::schema::*;
 
@@ -28,6 +29,8 @@ pub struct TableData<F: TableSchema, R: TableReplication> {
 	pub(crate) merkle_todo: sled::Tree,
 	pub(crate) merkle_todo_notify: Notify,
 	pub(crate) gc_todo: sled::Tree,
+
+	pub(crate) metrics: TableMetrics,
 }
 
 impl<F, R> TableData<F, R>
@@ -51,6 +54,8 @@ where
 			.open_tree(&format!("{}:gc_todo_v2", F::TABLE_NAME))
 			.expect("Unable to open DB tree");
 
+		let metrics = TableMetrics::new(F::TABLE_NAME, merkle_todo.clone());
+
 		Arc::new(Self {
 			system,
 			instance,
@@ -60,6 +65,7 @@ where
 			merkle_todo,
 			merkle_todo_notify: Notify::new(),
 			gc_todo,
+			metrics,
 		})
 	}
 

src/table/lib.rs

@@ -4,6 +4,7 @@
 #[macro_use]
 extern crate log;
 
+mod metrics;
 pub mod schema;
 pub mod util;
 

src/table/metrics.rs

@@ -0,0 +1,25 @@
+use opentelemetry::{global, metrics::*, KeyValue};
+
+/// TableMetrics reference all counter used for metrics
+pub struct TableMetrics {
+	merkle_updater_todo_queue_length: ValueObserver<u64>,
+}
+impl TableMetrics {
+	pub fn new(table_name: &'static str, merkle_todo: sled::Tree) -> Self {
+		let meter = global::meter(table_name);
+		TableMetrics {
+			merkle_updater_todo_queue_length: meter
+				.u64_value_observer(
+					format!("merkle_updater_todo_queue_length"),
+					move |observer| {
+						observer.observe(
+							merkle_todo.len() as u64,
+							&[KeyValue::new("table_name", table_name)],
+						)
+					},
+				)
+				.with_description("Bucket merkle updater TODO queue length")
+				.init(),
+		}
+	}
+}