sim-lib: Allows amount and interval ranges in manual activity definition

Amounts and intervals in activities can now be fixed values (e.g. 1000) or ranges (e.g.
[500, 1000]). If a range is provided, the value will be sampled uniformly at
random from it.

sim-lib/src/lib.rs

@@ -4,6 +4,7 @@ use bitcoin::Network;
 use csv::WriterBuilder;
 use lightning::ln::features::NodeFeatures;
 use lightning::ln::PaymentHash;
+use rand::Rng;
 use serde::{Deserialize, Serialize};
 use std::collections::HashSet;
 use std::fmt::{Display, Formatter};
@@ -86,6 +87,52 @@ pub struct SimParams {
     pub activity: Vec<ActivityParser>,
 }
 
+/// Either a value or a range parsed from the simulation file.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum ValueOrRange<T> {
+    Value(T),
+    Range(T, T),
+}
+
+impl<T> ValueOrRange<T>
+where
+    T: std::cmp::PartialOrd + rand_distr::uniform::SampleUniform + Copy,
+{
+    /// Get the enclosed value. If value is defined aa a range, sample from it uniformly at random.
+    pub fn value(&self) -> T {
+        match self {
+            ValueOrRange::Value(x) => *x,
+            ValueOrRange::Range(x, y) => {
+                let mut rng = rand::thread_rng();
+                rng.gen_range(*x..*y)
+            }
+        }
+    }
+
+    /// Whether this is a range or not
+    pub fn is_range(&self) -> bool {
+        matches!(self, ValueOrRange::Range(..))
+    }
+}
+
+impl<T> Display for ValueOrRange<T>
+where
+    T: Display,
+{
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ValueOrRange::Value(x) => write!(f, "{x}"),
+            ValueOrRange::Range(x, y) => write!(f, "({x}-{y})"),
+        }
+    }
+}
+
+/// The payment amount in msat. Either a value or a range.
+type Amount = ValueOrRange<u64>;
+/// The interval of seconds between payments. Either a value or a range.
+type Interval = ValueOrRange<u16>;
+
 /// Data structure used to parse information from the simulation file. It allows source and destination to be
 /// [NodeId], which enables the use of public keys and aliases in the simulation description.
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -97,9 +144,10 @@ pub struct ActivityParser {
     #[serde(with = "serializers::serde_node_id")]
     pub destination: NodeId,
     // The interval of the event, as in every how many seconds the payment is performed.
-    pub interval_secs: u16,
+    pub interval_secs: Interval,
     // The amount of m_sat to used in this payment.
-    pub amount_msat: u64,
+    #[serde(with = "serializers::serde_value_or_range")]
+    pub amount_msat: Amount,
 }
 
 /// Data structure used internally by the simulator. Both source and destination are represented as [PublicKey] here.
@@ -111,9 +159,9 @@ pub struct ActivityDefinition {
     // The destination of the payment.
     pub destination: NodeInfo,
     // The interval of the event, as in every how many seconds the payment is performed.
-    pub interval_secs: u16,
+    pub interval_secs: Interval,
     // The amount of m_sat to used in this payment.
-    pub amount_msat: u64,
+    pub amount_msat: Amount,
 }
 
 #[derive(Debug, Error)]
@@ -762,7 +810,8 @@ async fn produce_events(
     shutdown: Trigger,
     listener: Listener,
 ) {
-    let interval = time::Duration::from_secs(act.interval_secs as u64);
+    let mut interval = time::Duration::from_secs(act.interval_secs.value() as u64);
+    let mut amt = act.amount_msat.value();
 
     log::debug!(
         "Started producer for {} every {}s: {} -> {}.",
@@ -776,8 +825,17 @@ async fn produce_events(
         tokio::select! {
         biased;
         _ = time::sleep(interval) => {
-            // Consumer was dropped
-            if sender.send(SimulationEvent::SendPayment(act.destination.clone(), act.amount_msat)).await.is_err() {
+            // Resample if needed
+            if act.interval_secs.is_range() {
+                interval = time::Duration::from_secs(act.interval_secs.value() as u64);
+                log::debug!("Resampling interval. New value: {}", interval.as_secs());
+            }
+            if act.amount_msat.is_range() {
+                amt = act.amount_msat.value();
+                log::debug!("Resampling payment amount. New value: {}", amt);
+            }
+            if sender.send(SimulationEvent::SendPayment(act.destination.clone(), amt)).await.is_err() {
+                // Consumer was dropped
                 log::debug!(
                     "Stopped producer for {}: {} -> {}. Consumer cannot be reached.",
                     act.amount_msat,

sim-lib/src/serializers.rs

@@ -45,6 +45,42 @@ pub mod serde_node_id {
     }
 }
 
+pub mod serde_value_or_range {
+    use super::*;
+    use serde::de::Error;
+
+    use crate::ValueOrRange;
+
+    pub fn serialize<S, T>(x: &ValueOrRange<T>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+        T: std::fmt::Display,
+    {
+        serializer.serialize_str(&match x {
+            ValueOrRange::Value(p) => p.to_string(),
+            ValueOrRange::Range(x, y) => format!("[{}, {}]", x, y),
+        })
+    }
+
+    pub fn deserialize<'de, D, T>(deserializer: D) -> Result<ValueOrRange<T>, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+        T: serde::Deserialize<'de> + std::cmp::PartialOrd + std::fmt::Display + Copy,
+    {
+        let a = ValueOrRange::deserialize(deserializer)?;
+        if let ValueOrRange::Range(x, y) = a {
+            if x >= y {
+                return Err(D::Error::custom(format!(
+                    "Cannot parse range. Ranges must be strictly increasing (i.e. [x, y] with x > y). Received [{}, {}]",
+                    x, y
+                )));
+            }
+        }
+
+        Ok(a)
+    }
+}
+
 pub fn deserialize_path<'de, D>(deserializer: D) -> Result<String, D::Error>
 where
     D: serde::Deserializer<'de>,