From e8c4d64f6251260f9c2f7cbdbf2e532166965639 Mon Sep 17 00:00:00 2001
From: Tom Willemsen <tom.willemsen@stfc.ac.uk>
Date: Fri, 15 May 2026 13:15:58 +0100
Subject: [PATCH 1/2] Emit some frames as vetoed

---
 src/howl.rs | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/howl.rs b/src/howl.rs
index 76589cd..2b1cd45 100644
--- a/src/howl.rs
+++ b/src/howl.rs
@@ -133,7 +133,7 @@ fn produce_messages(
     match producer.send(
         BaseRecord::to(conf.event_topic)
             .key("")
-            .payload(generate_fake_metadata(fbb, now_nanos))
+            .payload(generate_fake_metadata(rng, fbb, now_nanos))
             .timestamp(now_nanos / 1_000_000),
     ) {
         Ok(_) => {}
@@ -238,14 +238,19 @@ fn generate_fake_events<'a>(
     fbb.finished_data()
 }
 
-fn generate_fake_metadata<'a>(fbb: &'a mut FlatBufferBuilder<'_>, timestamp_ns: i64) -> &'a [u8] {
+fn generate_fake_metadata<'a>(
+    rng: &mut ThreadRng,
+    fbb: &'a mut FlatBufferBuilder<'_>,
+    timestamp_ns: i64
+) -> &'a [u8] {
     fbb.reset();
+    let vetos = rng.random_range(0..=1);
     let args = Pu00MessageArgs {
         reference_time: timestamp_ns,
         message_id: 0,
         source_name: Some(fbb.create_string("saluki")),
         period_number: Some(0),
-        vetos: Some(0),
+        vetos: Some(vetos),
         proton_charge: Some(0.1),
     };
     let pu00 = Pu00Message::create(fbb, &args);
@@ -281,7 +286,7 @@ pub fn howl(conf: &HowlConfig) {
             as u32;
     debug!("ev44 size is {ev44_size} bytes");
 
-    let pu00_size = generate_fake_metadata(&mut fbb, now_nanos).len() as u32;
+    let pu00_size = generate_fake_metadata(&mut rng, &mut fbb, now_nanos).len() as u32;
     debug!("pu00 size is {pu00_size} bytes");
 
     // calculate overall rate (with both ev44 and pu00)

From b61d4cd510e038d29441c789accef0fd6cbb96d3 Mon Sep 17 00:00:00 2001
From: Tom Willemsen <tom.willemsen@stfc.ac.uk>
Date: Fri, 15 May 2026 13:31:42 +0100
Subject: [PATCH 2/2] do it properly

---
 src/howl.rs | 18 +++++++++++++-----
 src/main.rs |  5 +++++
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/howl.rs b/src/howl.rs
index 2b1cd45..d4a9cff 100644
--- a/src/howl.rs
+++ b/src/howl.rs
@@ -133,7 +133,12 @@ fn produce_messages(
     match producer.send(
         BaseRecord::to(conf.event_topic)
             .key("")
-            .payload(generate_fake_metadata(rng, fbb, now_nanos))
+            .payload(generate_fake_metadata(
+                rng,
+                fbb,
+                now_nanos,
+                conf.veto_probability,
+            ))
             .timestamp(now_nanos / 1_000_000),
     ) {
         Ok(_) => {}
@@ -241,16 +246,17 @@ fn generate_fake_events<'a>(
 fn generate_fake_metadata<'a>(
     rng: &mut ThreadRng,
     fbb: &'a mut FlatBufferBuilder<'_>,
-    timestamp_ns: i64
+    timestamp_ns: i64,
+    veto_probability: f64,
 ) -> &'a [u8] {
     fbb.reset();
-    let vetos = rng.random_range(0..=1);
+    let is_vetoed = rng.random_range(0.0..1.0) < veto_probability;
     let args = Pu00MessageArgs {
         reference_time: timestamp_ns,
         message_id: 0,
         source_name: Some(fbb.create_string("saluki")),
         period_number: Some(0),
-        vetos: Some(vetos),
+        vetos: Some(if is_vetoed { 1 } else { 0 }),
         proton_charge: Some(0.1),
     };
     let pu00 = Pu00Message::create(fbb, &args);
@@ -265,6 +271,7 @@ pub struct HowlConfig<'a> {
     pub messages_per_frame: u32,
     pub frames_per_second: u32,
     pub frames_per_run: u32,
+    pub veto_probability: f64, // 1 = always vetoed, 0 = never vetoed
     pub event_message_config: &'a EventMessageConfig,
     pub kafka_config: Option<Vec<KafkaOption>>,
 }
@@ -286,7 +293,8 @@ pub fn howl(conf: &HowlConfig) {
             as u32;
     debug!("ev44 size is {ev44_size} bytes");
 
-    let pu00_size = generate_fake_metadata(&mut rng, &mut fbb, now_nanos).len() as u32;
+    let pu00_size =
+        generate_fake_metadata(&mut rng, &mut fbb, now_nanos, conf.veto_probability).len() as u32;
     debug!("pu00 size is {pu00_size} bytes");
 
     // calculate overall rate (with both ev44 and pu00)
diff --git a/src/main.rs b/src/main.rs
index a79973c..9d30b17 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -87,6 +87,9 @@ enum Commands {
         /// Maximum detector ID
         #[arg(long, default_value = "1000")]
         det_max: i32,
+        /// Veto probability (0 = never vetoed; 1 = always vetoed)
+        #[arg(long, default_value = "0.0")]
+        veto_probability: f64,
         // Additonal command line arguments
         #[arg(short = 'X', long)]
         kafka_config: Option<Vec<KafkaOption>>,
@@ -147,6 +150,7 @@ async fn main() {
             tof_sigma,
             det_min,
             det_max,
+            veto_probability,
             kafka_config,
         } => howl(&HowlConfig {
             kafka_config,
@@ -163,6 +167,7 @@ async fn main() {
                 det_min,
                 det_max,
             },
+            veto_probability,
         }),
         Commands::Count {
             topic,