add basic metrics of multilevel task queue

Cargo.toml

@@ -14,6 +14,12 @@ parking_lot_core = "0.7"
 crossbeam-deque = "0.7"
 dashmap = "1.2.0"
 rand = "0.7"
+lazy_static = "1"
+
+[dependencies.prometheus]
+# FIXME: Use crates-io version when rust-prometheus 0.8 is released
+git = "https://github.com/tikv/rust-prometheus.git"
+rev = "d919ccd35976b9b84b8d03c07138c1cc05a36087"
 
 [dev-dependencies]
 criterion = "0.3"
@@ -38,4 +44,4 @@ name = "ping_pong"
 harness = false
 
 [profile.bench]
-codegen-units = 1
+codegen-units = 1

src/lib.rs

@@ -4,6 +4,7 @@
 
 //! Yatp is a thread pool that tries to be adaptive, responsive and generic.
 
+pub mod metrics;
 pub mod pool;
 pub mod queue;
 pub mod task;

src/metrics.rs

@@ -0,0 +1,47 @@
+// Copyright 2020 TiKV Project Authors. Licensed under Apache-2.0.
+
+//! Metrics of the thread pool.
+
+use lazy_static::lazy_static;
+use prometheus::*;
+use std::sync::Mutex;
+
+lazy_static! {
+    /// Elapsed time of each level in the multilevel task queue.
+    pub static ref MULTILEVEL_LEVEL_ELAPSED: IntCounterVec = IntCounterVec::new(
+        new_opts(
+            "multilevel_level_elapsed",
+            "elapsed time of each level in the multilevel task queue"
+        ),
+        &["name", "level"]
+    )
+    .unwrap();
+
+    /// The chance that a level 0 task is scheduled to run.
+    pub static ref MULTILEVEL_LEVEL0_CHANCE: GaugeVec = GaugeVec::new(
+        new_opts(
+            "multilevel_level0_chance",
+            "the chance that a level 0 task is scheduled to run"
+        ),
+        &["name"]
+    )
+    .unwrap();
+
+    static ref NAMESPACE: Mutex<Option<String>> = Mutex::new(None);
+}
+
+/// Sets the namespace used in the metrics. This function should be called before
+/// the metrics are used or any thread pool is created.
+///
+/// The namespace is missing by default.
+pub fn set_namespace(s: Option<impl Into<String>>) {
+    *NAMESPACE.lock().unwrap() = s.map(Into::into)
+}
+
+fn new_opts(name: &str, help: &str) -> Opts {
+    let mut opts = Opts::new(name, help);
+    if let Some(ref namespace) = *NAMESPACE.lock().unwrap() {
+        opts = opts.namespace(namespace);
+    }
+    opts
+}