feat(metrics): add support for gauge metrics and include IMC metrics (#4939)

Co-authored-by: hyperswitch-bot[bot] <148525504+hyperswitch-bot[bot]@users.noreply.github.com>

crates/router/src/bin/router.rs

@@ -2,6 +2,7 @@ use router::{
     configs::settings::{CmdLineConf, Settings},
     core::errors::{ApplicationError, ApplicationResult},
     logger,
+    routes::metrics,
 };
 
 #[tokio::main]
@@ -27,6 +28,11 @@ async fn main() -> ApplicationResult<()> {
 
     logger::info!("Application started [{:?}] [{:?}]", conf.server, conf.log);
 
+    // Spawn a thread for collecting metrics at fixed intervals
+    metrics::bg_metrics_collector::spawn_metrics_collector(
+        &conf.log.telemetry.bg_metrics_collection_interval_in_secs,
+    );
+
     #[allow(clippy::expect_used)]
     let server = Box::pin(router::start_server(conf))
         .await

crates/router/src/routes/metrics.rs

@@ -1,4 +1,8 @@
-use router_env::{counter_metric, global_meter, histogram_metric, metrics_context};
+pub mod bg_metrics_collector;
+pub mod request;
+pub mod utils;
+
+use router_env::{counter_metric, gauge_metric, global_meter, histogram_metric, metrics_context};
 
 metrics_context!(CONTEXT);
 global_meter!(GLOBAL_METER, "ROUTER_API");
@@ -133,5 +137,5 @@ counter_metric!(ACCESS_TOKEN_CACHE_HIT, GLOBAL_METER);
 // A counter to indicate the access token cache miss
 counter_metric!(ACCESS_TOKEN_CACHE_MISS, GLOBAL_METER);
 
-pub mod request;
-pub mod utils;
+// Metrics for In-memory cache
+gauge_metric!(CACHE_ENTRY_COUNT, GLOBAL_METER);

crates/router/src/routes/metrics/bg_metrics_collector.rs

@@ -0,0 +1,46 @@
+use storage_impl::redis::cache;
+
+const DEFAULT_BG_METRICS_COLLECTION_INTERVAL_IN_SECS: u16 = 15;
+
+macro_rules! gauge_metrics_for_imc {
+    ($($cache:ident),*) => {
+        $(
+            {
+                cache::$cache.run_pending_tasks().await;
+
+                super::CACHE_ENTRY_COUNT.observe(
+                    &super::CONTEXT,
+                    cache::$cache.get_entry_count(),
+                    &[super::request::add_attributes(
+                        "cache_type",
+                        stringify!($cache),
+                    )],
+                );
+            }
+        )*
+    };
+}
+
+pub fn spawn_metrics_collector(metrics_collection_interval_in_secs: &Option<u16>) {
+    let metrics_collection_interval = metrics_collection_interval_in_secs
+        .unwrap_or(DEFAULT_BG_METRICS_COLLECTION_INTERVAL_IN_SECS);
+
+    tokio::spawn(async move {
+        loop {
+            gauge_metrics_for_imc!(
+                CONFIG_CACHE,
+                ACCOUNTS_CACHE,
+                ROUTING_CACHE,
+                CGRAPH_CACHE,
+                PM_FILTERS_CGRAPH_CACHE,
+                DECISION_MANAGER_CACHE,
+                SURCHARGE_CACHE
+            );
+
+            tokio::time::sleep(std::time::Duration::from_secs(
+                metrics_collection_interval.into(),
+            ))
+            .await
+        }
+    });
+}