Add create network actions latency metric

Author: ndr-ds

linera-core/src/chain_worker/state.rs

@@ -47,6 +47,24 @@ use crate::{
     value_cache::ValueCache,
     worker::{NetworkActions, Notification, Reason, WorkerError},
 };
+#[cfg(with_metrics)]
+use linera_base::prometheus_util::MeasureLatency as _;
+
+#[cfg(with_metrics)]
+mod metrics {
+    use std::sync::LazyLock;
+
+    use linera_base::prometheus_util::{exponential_bucket_latencies, register_histogram};
+    use prometheus::Histogram;
+
+    pub static CREATE_NETWORK_ACTIONS_LATENCY: LazyLock<Histogram> = LazyLock::new(|| {
+        register_histogram(
+            "create_network_actions_latency",
+            "Time (ms) to create network actions",
+            exponential_bucket_latencies(10_000.0),
+        )
+    });
+}
 
 /// The state of the chain worker.
 pub(crate) struct ChainWorkerState<StorageClient>
@@ -419,6 +437,8 @@ where
         &self,
         old_round: Option<Round>,
     ) -> Result<NetworkActions, WorkerError> {
+        #[cfg(with_metrics)]
+        let _latency = metrics::CREATE_NETWORK_ACTIONS_LATENCY.measure_latency();
         let mut heights_by_recipient = BTreeMap::<_, Vec<_>>::new();
         let mut targets = self.chain.nonempty_outbox_chain_ids();
         if let Some(tracked_chains) = self.tracked_chains.as_ref() {