Added datastore latency histogram to prometheus metrics

limitador/Cargo.toml

@@ -35,6 +35,7 @@ cfg-if = "1"
 prometheus = "0.13"
 lazy_static = "1"
 tracing = "0.1.40"
+tracing-subscriber = "0.3.18"
 
 # Optional dependencies
 rocksdb = { version = "0.21.0", optional = true, features = ["multi-threaded-cf"] }
@@ -53,6 +54,7 @@ tokio = { version = "1", optional = true, features = [
 infinispan = { version = "0.3", optional = true }
 reqwest = { version = "0.11", optional = true }
 base64 = { version = "0.21.0", optional = true }
+log = "0.4.20"
 
 [dev-dependencies]
 serial_test = "2.0.0"

limitador/src/lib.rs

@@ -323,6 +323,10 @@ impl RateLimiter {
         }
     }
 
+    pub fn metrics(&self) -> &PrometheusMetrics {
+        &self.prometheus_metrics
+    }
+
     pub fn get_namespaces(&self) -> HashSet<Namespace> {
         self.storage.get_namespaces()
     }
@@ -508,6 +512,10 @@ impl AsyncRateLimiter {
         }
     }
 
+    pub fn metrics(&self) -> &PrometheusMetrics {
+        &self.prometheus_metrics
+    }
+
     pub fn get_namespaces(&self) -> HashSet<Namespace> {
         self.storage.get_namespaces()
     }

limitador/src/prometheus_metrics.rs

@@ -1,5 +1,8 @@
 use crate::limit::Namespace;
-use prometheus::{Encoder, IntCounterVec, IntGauge, Opts, Registry, TextEncoder};
+use prometheus::{
+    Encoder, Histogram, HistogramOpts, IntCounterVec, IntGauge, Opts, Registry, TextEncoder,
+};
+use std::time::Duration;
 
 const NAMESPACE_LABEL: &str = "limitador_namespace";
 const LIMIT_NAME_LABEL: &str = "limit_name";
@@ -22,15 +25,26 @@ lazy_static! {
         name: "limitador_up".into(),
         description: "Limitador is running".into(),
     };
+    static ref DATASTORE_LATENCY: Metric = Metric {
+        name: "counter_latency".into(),
+        description: "Latency to the underlying counter datastore".into(),
+    };
 }
 
 pub struct PrometheusMetrics {
     registry: Registry,
     authorized_calls: IntCounterVec,
     limited_calls: IntCounterVec,
+    counter_latency: Histogram,
     use_limit_name_label: bool,
 }
 
+impl Default for PrometheusMetrics {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl PrometheusMetrics {
     pub fn new() -> Self {
         Self::new_with_options(false)
@@ -65,6 +79,10 @@ impl PrometheusMetrics {
         self.limited_calls.with_label_values(&labels).inc();
     }
 
+    pub fn counter_access(&self, duration: Duration) {
+        self.counter_latency.observe(duration.as_secs_f64());
+    }
+
     pub fn gather_metrics(&self) -> String {
         let mut buffer = Vec::new();
 
@@ -79,6 +97,7 @@ impl PrometheusMetrics {
         let authorized_calls_counter = Self::authorized_calls_counter();
         let limited_calls_counter = Self::limited_calls_counter(use_limit_name_label);
         let limitador_up_gauge = Self::limitador_up_gauge();
+        let counter_latency = Self::counter_latency();
 
         let registry = Registry::new();
 
@@ -94,12 +113,17 @@ impl PrometheusMetrics {
             .register(Box::new(limitador_up_gauge.clone()))
             .unwrap();
 
+        registry
+            .register(Box::new(counter_latency.clone()))
+            .unwrap();
+
         limitador_up_gauge.set(1);
 
         Self {
             registry,
             authorized_calls: authorized_calls_counter,
             limited_calls: limited_calls_counter,
+            counter_latency,
             use_limit_name_label,
         }
     }
@@ -129,6 +153,14 @@ impl PrometheusMetrics {
     fn limitador_up_gauge() -> IntGauge {
         IntGauge::new(&LIMITADOR_UP.name, &LIMITADOR_UP.description).unwrap()
     }
+
+    fn counter_latency() -> Histogram {
+        Histogram::with_opts(HistogramOpts::new(
+            &DATASTORE_LATENCY.name,
+            &DATASTORE_LATENCY.description,
+        ))
+        .unwrap()
+    }
 }
 
 #[cfg(test)]