feat: add default metric prefix and metric description (#44)

* feat: add default metric prefix

* add metric description

* err message

---------

Co-authored-by: Revolution1 <[email protected]>

configs/demo_config.yml

@@ -8,12 +8,12 @@ extensions:
     stale_timeout_seconds: 180 # rotate endpoint if no new blocks for 3 minutes
     finalized_interval_seconds: 10 # get finalized head every 10 seconds
   telemetry:
-    provider: otlp
+    #provider: otlp
     #agent_endpoint: http://127.0.0.1:4317
   prometheus:
     port: 9616
     listen_address: "0.0.0.0"
-    prefix: "subway"
+    #prefix: "subway"
   cache:
     default_ttl_seconds: 60
     default_size: 500

src/extensions/prometheus/mod.rs

@@ -39,10 +39,15 @@ impl Drop for Prometheus {
 pub struct PrometheusConfig {
     pub port: u16,
     pub listen_address: String,
-    pub prefix: Option<String>,
+    #[serde(default = "default_prefix")]
+    pub prefix: String,
     pub chain_label: Option<String>,
 }
 
+fn default_prefix() -> String {
+    "subway".to_string()
+}
+
 #[async_trait]
 impl Extension for Prometheus {
     type Config = PrometheusConfig;
@@ -59,13 +64,7 @@ impl Prometheus {
             .clone()
             .map(|l| iter::once(("chain".to_string(), l.clone())).collect());
 
-        // make sure the prefix is not an Option of Some empty string
-        let prefix = match config.prefix {
-            Some(p) if p.is_empty() => Some("subway".to_string()),
-            p => p,
-        };
-        let registry = Registry::new_custom(prefix, labels)
-            .expect("It can't fail, we make sure the `prefix` is either `None` or `Some` of non-empty string");
+        let registry = Registry::new_custom(Some(config.prefix), labels).expect("prefix can not be empty string");
 
         // add subway info metric
         let info_gauge = Gauge::<U64>::with_opts(

src/extensions/prometheus/rpc_metrics.rs

@@ -64,16 +64,33 @@ pub struct InnerMetrics {
 
 impl InnerMetrics {
     fn new(registry: &Registry) -> Self {
-        let open_counter = Counter::new("open_ws_counter", "No help").unwrap();
-        let closed_counter = Counter::new("closed_ws_counter", "No help").unwrap();
-        let cache_miss_counter = CounterVec::new(Opts::new("cache_miss_counter", "No help"), &["method"]).unwrap();
-        let cache_query_counter = CounterVec::new(Opts::new("cache_query_counter", "No help"), &["method"]).unwrap();
-        let call_times =
-            HistogramVec::new(HistogramOpts::new("rpc_calls_time", "No help"), &["protocol", "method"]).unwrap();
-        let calls_started_counter =
-            CounterVec::new(Opts::new("rpc_calls_started", "No help"), &["protocol", "method"]).unwrap();
+        let open_counter = Counter::new("open_ws_counter", "Total number of opened websocket connections").unwrap();
+        let closed_counter = Counter::new("closed_ws_counter", "Total number of closed websocket connections").unwrap();
+        let cache_miss_counter = CounterVec::new(
+            Opts::new("cache_miss_counter", "Total number of cache misses of RPC requests"),
+            &["method"],
+        )
+        .unwrap();
+        let cache_query_counter = CounterVec::new(
+            Opts::new("cache_query_counter", "Total number of cache queries of RPC requests"),
+            &["method"],
+        )
+        .unwrap();
+        let call_times = HistogramVec::new(
+            HistogramOpts::new(
+                "rpc_calls_time",
+                "Time interval from the initiation to the completion of an RPC request",
+            ),
+            &["protocol", "method"],
+        )
+        .unwrap();
+        let calls_started_counter = CounterVec::new(
+            Opts::new("rpc_calls_started", "Total number of initiated RPC requests"),
+            &["protocol", "method"],
+        )
+        .unwrap();
         let calls_finished_counter = CounterVec::new(
-            Opts::new("rpc_calls_finished", "No help"),
+            Opts::new("rpc_calls_finished", "Total number of completed RPC requests"),
             &["protocol", "method", "is_error"],
         )
         .unwrap();