Supports generic metrics for rpc (#298)

Cargo.lock

@@ -6594,6 +6594,7 @@ dependencies = [
  "metrics",
  "miner",
  "network",
+ "parking_lot 0.12.3",
  "serde",
  "serde_json",
  "shared_types",

node/rpc/Cargo.toml

@@ -27,3 +27,4 @@ merkle_light = { path = "../../common/merkle_light" }
 merkle_tree = { path = "../../common/merkle_tree"}
 futures-channel = "^0.3"
 metrics = { workspace = true }
+parking_lot = "0.12.3"

node/rpc/src/lib.rs

@@ -6,6 +6,7 @@ extern crate miner as zgs_miner;
 mod admin;
 mod config;
 mod error;
+mod middleware;
 mod miner;
 pub mod types;
 mod zgs;
@@ -77,8 +78,10 @@ pub async fn run_server(
     Ok(handles)
 }
 
-fn server_builder(ctx: Context) -> HttpServerBuilder {
-    HttpServerBuilder::default().max_request_body_size(ctx.config.max_request_body_size)
+fn server_builder(ctx: Context) -> HttpServerBuilder<middleware::Metrics> {
+    HttpServerBuilder::default()
+        .max_request_body_size(ctx.config.max_request_body_size)
+        .set_middleware(middleware::Metrics::default())
 }
 
 /// Run a single RPC server for all namespace RPCs.

node/rpc/src/middleware.rs

@@ -0,0 +1,50 @@
+use std::{collections::HashMap, sync::Arc, time::Instant};
+
+use jsonrpsee::core::middleware::Middleware;
+use metrics::{register_meter_with_group, Histogram, Meter, Sample};
+use parking_lot::RwLock;
+
+struct RpcMetric {
+    qps: Arc<dyn Meter>,
+    latency: Arc<dyn Histogram>,
+}
+
+impl RpcMetric {
+    fn new(method_name: &String) -> Self {
+        let group = format!("rpc_{}", method_name);
+
+        Self {
+            qps: register_meter_with_group(group.as_str(), "qps"),
+            latency: Sample::ExpDecay(0.015).register_with_group(group.as_str(), "latency", 1024),
+        }
+    }
+}
+
+#[derive(Clone, Default)]
+pub struct Metrics {
+    metrics_by_method: Arc<RwLock<HashMap<String, RpcMetric>>>,
+}
+
+impl Middleware for Metrics {
+    type Instant = Instant;
+
+    fn on_request(&self) -> Self::Instant {
+        Instant::now()
+    }
+
+    fn on_call(&self, name: &str) {
+        let mut metrics_by_method = self.metrics_by_method.write();
+        let entry = metrics_by_method
+            .entry(name.to_string())
+            .or_insert_with_key(RpcMetric::new);
+        entry.qps.mark(1);
+    }
+
+    fn on_result(&self, name: &str, _success: bool, started_at: Self::Instant) {
+        let mut metrics_by_method = self.metrics_by_method.write();
+        let entry = metrics_by_method
+            .entry(name.to_string())
+            .or_insert_with_key(RpcMetric::new);
+        entry.latency.update_since(started_at);
+    }
+}