feat(overflow): add overflow_forced_keys envvar

capture/src/config.rs

@@ -19,6 +19,8 @@ pub struct Config {
     #[envconfig(default = "1000")]
     pub burst_limit: NonZeroU32,
 
+    pub overflow_forced_keys: Option<String>, // Coma-delimited keys
+
     #[envconfig(nested = true)]
     pub kafka: KafkaConfig,
 

capture/src/partition_limits.rs

@@ -6,26 +6,37 @@
 /// before it causes a negative impact. In this case, instead of passing the error to the customer
 /// with a 429, we relax our ordering constraints and temporarily override the key, meaning the
 /// customers data will be spread across all partitions.
-use std::{num::NonZeroU32, sync::Arc};
+use std::collections::HashSet;
+use std::num::NonZeroU32;
+use std::sync::Arc;
 
 use governor::{clock, state::keyed::DefaultKeyedStateStore, Quota, RateLimiter};
 
 // See: https://docs.rs/governor/latest/governor/_guide/index.html#usage-in-multiple-threads
 #[derive(Clone)]
 pub struct PartitionLimiter {
     limiter: Arc<RateLimiter<String, DefaultKeyedStateStore<String>, clock::DefaultClock>>,
+    forced_keys: HashSet<String>,
 }
 
 impl PartitionLimiter {
-    pub fn new(per_second: NonZeroU32, burst: NonZeroU32) -> Self {
+    pub fn new(per_second: NonZeroU32, burst: NonZeroU32, forced_keys: Option<String>) -> Self {
         let quota = Quota::per_second(per_second).allow_burst(burst);
         let limiter = Arc::new(governor::RateLimiter::dashmap(quota));
 
-        PartitionLimiter { limiter }
+        let forced_keys: HashSet<String> = match forced_keys {
+            None => HashSet::new(),
+            Some(values) => values.split(',').map(String::from).collect(),
+        };
+
+        PartitionLimiter {
+            limiter,
+            forced_keys,
+        }
     }
 
     pub fn is_limited(&self, key: &String) -> bool {
-        self.limiter.check_key(key).is_err()
+        self.forced_keys.contains(key) || self.limiter.check_key(key).is_err()
     }
 }
 
@@ -36,8 +47,11 @@ mod tests {
 
     #[tokio::test]
     async fn low_limits() {
-        let limiter =
-            PartitionLimiter::new(NonZeroU32::new(1).unwrap(), NonZeroU32::new(1).unwrap());
+        let limiter = PartitionLimiter::new(
+            NonZeroU32::new(1).unwrap(),
+            NonZeroU32::new(1).unwrap(),
+            None,
+        );
         let token = String::from("test");
 
         assert!(!limiter.is_limited(&token));
@@ -46,13 +60,38 @@ mod tests {
 
     #[tokio::test]
     async fn bursting() {
-        let limiter =
-            PartitionLimiter::new(NonZeroU32::new(1).unwrap(), NonZeroU32::new(3).unwrap());
+        let limiter = PartitionLimiter::new(
+            NonZeroU32::new(1).unwrap(),
+            NonZeroU32::new(3).unwrap(),
+            None,
+        );
         let token = String::from("test");
 
         assert!(!limiter.is_limited(&token));
         assert!(!limiter.is_limited(&token));
         assert!(!limiter.is_limited(&token));
         assert!(limiter.is_limited(&token));
     }
+
+    #[tokio::test]
+    async fn forced_key() {
+        let key_one = String::from("one");
+        let key_two = String::from("two");
+        let key_three = String::from("three");
+        let forced_keys = Some(String::from("one,three"));
+
+        let limiter = PartitionLimiter::new(
+            NonZeroU32::new(1).unwrap(),
+            NonZeroU32::new(1).unwrap(),
+            forced_keys,
+        );
+
+        // One and three are limited from the start, two is not
+        assert!(limiter.is_limited(&key_one));
+        assert!(!limiter.is_limited(&key_two));
+        assert!(limiter.is_limited(&key_three));
+
+        // Two is limited on the second event
+        assert!(limiter.is_limited(&key_two));
+    }
 }

capture/src/server.rs

@@ -44,7 +44,11 @@ where
             .register("rdkafka".to_string(), Duration::seconds(30))
             .await;
 
-        let partition = PartitionLimiter::new(config.per_second_limit, config.burst_limit);
+        let partition = PartitionLimiter::new(
+            config.per_second_limit,
+            config.burst_limit,
+            config.overflow_forced_keys,
+        );
         let sink = sink::KafkaSink::new(config.kafka, sink_liveness, partition).unwrap();
 
         router::router(