perf: use faster hashing function for hashmaps (ahash)

.changeset/giant-clubs-jump.md

@@ -0,0 +1,5 @@
+---
+"eppo_core": minor
+---
+
+[ahash] Add "ahash" feature flag to use faster hash function for all hashmaps. It is changing the public interface so is disabled by default so as to not cause breakage across SDKs and allow them to update one by one.

.changeset/twenty-owls-tan.md

@@ -0,0 +1,6 @@
+---
+"python-sdk": patch
+"ruby-sdk": patch
+---
+
+perf: use faster hash function for internal hashmaps (ahash).

eppo_core/Cargo.toml

@@ -10,6 +10,9 @@ categories = ["config"]
 rust-version = "1.80.0"
 
 [features]
+# Use ahash for HashMaps. This is currently disabled by default to
+# allow SDKs adapt their usage one by one.
+ahash = ["dep:ahash"]
 # Unstable feature flag for an upcoming feature.
 event_ingestion = ["dep:uuid", "dep:exponential-backoff"]
 # Add implementation of `FromPyObject`/`ToPyObject` for some types.
@@ -24,6 +27,7 @@ rustler = ["dep:rustler"]
 vendored = []
 
 [dependencies]
+ahash = { version = "0.8.12", optional = true }
 base64 = "0.22.1"
 chrono = { version = "0.4.38", features = ["serde"] }
 derive_more = { version = "2.0.0", default-features = false, features = ["from", "into"] }

eppo_core/benches/bandit_evaluation.rs

@@ -1,9 +1,13 @@
-use std::collections::HashMap;
 use std::fs::File;
 
 use chrono::Utc;
 use criterion::{black_box, criterion_group, criterion_main, Criterion, Throughput};
 
+#[cfg(feature = "ahash")]
+use eppo_core::ahash::{HashMap, HashMapExt};
+#[cfg(not(feature = "ahash"))]
+use std::collections::HashMap;
+
 use eppo_core::ufc::UniversalFlagConfig;
 use eppo_core::{eval::get_bandit_action, Configuration, ContextAttributes, SdkMetadata, Str};
 

eppo_core/benches/evaluation_details.rs

@@ -1,8 +1,13 @@
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
 
 use chrono::Utc;
 use criterion::{black_box, criterion_group, criterion_main, Criterion, Throughput};
 
+#[cfg(feature = "ahash")]
+use eppo_core::ahash::{HashMap, HashMapExt};
+#[cfg(not(feature = "ahash"))]
+use std::collections::HashMap;
+
 use eppo_core::ufc::UniversalFlagConfig;
 use eppo_core::{
     eval::{get_assignment, get_assignment_details},
@@ -55,7 +60,11 @@ fn criterion_benchmark(c: &mut Criterion) {
     {
         let mut group = c.benchmark_group("rollout");
         group.throughput(Throughput::Elements(1));
-        let attributes = Arc::new([("country".into(), "US".into())].into());
+        let attributes = {
+            let mut map = HashMap::new();
+            map.insert("country".into(), "US".into());
+            Arc::new(map)
+        };
         group.bench_function("get_assignment", |b| {
             b.iter(|| {
                 get_assignment(
@@ -86,7 +95,7 @@ fn criterion_benchmark(c: &mut Criterion) {
     {
         let mut group = c.benchmark_group("json-config-flag");
         group.throughput(Throughput::Elements(1));
-        let attributes = Arc::new([].into());
+        let attributes = Arc::new(HashMap::new());
         group.bench_function("get_assignment", |b| {
             b.iter(|| {
                 get_assignment(
@@ -117,7 +126,11 @@ fn criterion_benchmark(c: &mut Criterion) {
     {
         let mut group = c.benchmark_group("numeric-one-of");
         group.throughput(Throughput::Elements(1));
-        let attributes = Arc::new([("number".into(), 2.0.into())].into());
+        let attributes = {
+            let mut map = HashMap::new();
+            map.insert("number".into(), 2.0.into());
+            Arc::new(map)
+        };
         group.bench_function("get_assignment", |b| {
             b.iter(|| {
                 get_assignment(
@@ -148,7 +161,11 @@ fn criterion_benchmark(c: &mut Criterion) {
     {
         let mut group = c.benchmark_group("regex-flag");
         group.throughput(Throughput::Elements(1));
-        let attributes = Arc::new([("email".into(), "test@gmail.com".into())].into());
+        let attributes = {
+            let mut map = HashMap::new();
+            map.insert("email".into(), "test@gmail.com".into());
+            Arc::new(map)
+        };
         group.bench_function("get_assignment", |b| {
             b.iter(|| {
                 get_assignment(

eppo_core/src/attributes.rs

@@ -1,8 +1,8 @@
-use std::{borrow::Cow, collections::HashMap, sync::Arc};
+use std::{borrow::Cow, sync::Arc};
 
 use serde::{Deserialize, Serialize};
 
-use crate::Str;
+use crate::{hashmap::HashMap, Str};
 
 mod context_attributes;
 

eppo_core/src/attributes/context_attributes.rs

@@ -1,8 +1,8 @@
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
 
 use serde::{Deserialize, Serialize};
 
-use crate::Str;
+use crate::{hashmap::*, Str};
 
 use super::{
     AttributeValue, AttributeValueImpl, Attributes, CategoricalAttribute, NumericAttribute,
@@ -81,11 +81,11 @@ impl ContextAttributes {
 
 #[cfg(feature = "pyo3")]
 mod pyo3_impl {
-    use std::{collections::HashMap, sync::Arc};
+    use std::sync::Arc;
 
     use pyo3::{prelude::*, types::PyDict};
 
-    use crate::{Attributes, CategoricalAttribute, NumericAttribute, Str};
+    use crate::{hashmap::*, Attributes, CategoricalAttribute, NumericAttribute, Str};
 
     use super::ContextAttributes;
 

eppo_core/src/bandits.rs

@@ -1,6 +1,6 @@
 #![allow(missing_docs)]
 
-use std::collections::HashMap;
+use crate::hashmap::HashMap;
 
 use serde::{Deserialize, Serialize};
 

eppo_core/src/configuration_store.rs

@@ -46,8 +46,9 @@ impl ConfigurationStore {
 
 #[cfg(test)]
 mod tests {
-    use std::{collections::HashMap, sync::Arc};
+    use std::sync::Arc;
 
+    use crate::hashmap::*;
     use chrono::Utc;
 
     use super::ConfigurationStore;

eppo_core/src/eval/eval_bandits.rs

@@ -1,6 +1,7 @@
-use std::collections::HashMap;
 use std::sync::Arc;
 
+use crate::hashmap::HashMap;
+
 use chrono::{DateTime, Utc};
 use serde::Serialize;
 

eppo_core/src/eval/eval_details_builder.rs

@@ -1,4 +1,6 @@
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
+
+use crate::hashmap::*;
 
 use chrono::{DateTime, Utc};
 

eppo_core/src/eval/eval_precomputed.rs

@@ -1,6 +1,7 @@
-use std::collections::HashMap;
 use std::sync::Arc;
 
+use crate::hashmap::*;
+
 use chrono::{DateTime, Utc};
 
 use crate::eval::get_assignment;
@@ -58,7 +59,7 @@ pub fn get_precomputed_configuration(
                 );
                 None
             })
-            .map(|assignment| ((flag_key.clone(), PrecomputedAssignment::from(assignment))))
+            .map(|assignment| (flag_key.clone(), PrecomputedAssignment::from(assignment)))
         })
         .collect::<HashMap<_, _>>();
 
@@ -137,14 +138,15 @@ pub fn get_precomputed_configuration(
 mod tests {
     use crate::Str;
     use chrono::Utc;
-    use std::collections::HashMap;
 
     use crate::{
         eval::get_precomputed_configuration, ufc::UniversalFlagConfig, Configuration,
         ContextAttributes, SdkMetadata,
     };
     use std::{fs, sync::Arc};
 
+    use crate::hashmap::*;
+
     #[test]
     fn test_precomputed_assignment_basic() {
         let _ = env_logger::builder().is_test(true).try_init();

eppo_core/src/eval/eval_rules.rs

@@ -81,7 +81,9 @@ impl ConditionCheck {
 
 #[cfg(test)]
 mod tests {
-    use std::{collections::HashMap, sync::Arc};
+    use std::sync::Arc;
+
+    use crate::hashmap::*;
 
     use crate::{
         eval::{eval_visitor::NoopEvalVisitor, subject::Subject},
@@ -361,7 +363,11 @@ mod tests {
             &mut NoopEvalVisitor,
             &Subject::new(
                 "key".into(),
-                Arc::new(HashMap::from([("age".into(), 11.0.into())]))
+                Arc::new({
+                    let mut map = HashMap::new();
+                    map.insert("age".into(), 11.0.into());
+                    map
+                })
             )
         ));
     }
@@ -392,21 +398,33 @@ mod tests {
             &mut NoopEvalVisitor,
             &Subject::new(
                 "key".into(),
-                Arc::new(HashMap::from([("age".into(), 20.0.into())]))
+                Arc::new({
+                    let mut map = HashMap::new();
+                    map.insert("age".into(), 20.0.into());
+                    map
+                })
             )
         ));
         assert!(!rule.eval(
             &mut NoopEvalVisitor,
             &Subject::new(
                 "key".into(),
-                Arc::new(HashMap::from([("age".into(), 17.0.into())]))
+                Arc::new({
+                    let mut map = HashMap::new();
+                    map.insert("age".into(), 17.0.into());
+                    map
+                })
             )
         ));
         assert!(!rule.eval(
             &mut NoopEvalVisitor,
             &Subject::new(
                 "key".into(),
-                Arc::new(HashMap::from([("age".into(), 110.0.into())]))
+                Arc::new({
+                    let mut map = HashMap::new();
+                    map.insert("age".into(), 110.0.into());
+                    map
+                })
             )
         ));
     }
@@ -427,7 +445,11 @@ mod tests {
             &mut NoopEvalVisitor,
             &Subject::new(
                 "key".into(),
-                Arc::new(HashMap::from([("name".into(), "alice".into())]))
+                Arc::new({
+                    let mut map = HashMap::new();
+                    map.insert("name".into(), "alice".into());
+                    map
+                })
             )
         ));
     }

eppo_core/src/eval/evaluator.rs

@@ -1,4 +1,6 @@
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
+
+use crate::hashmap::HashMap;
 
 use chrono::Utc;
 

eppo_core/src/events.rs

@@ -1,4 +1,6 @@
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
+
+use crate::hashmap::HashMap;
 
 use serde::Serialize;
 

eppo_core/src/hashmap.rs

@@ -0,0 +1,5 @@
+#[cfg(feature = "ahash")]
+pub use ahash::{HashMap, HashMapExt};
+
+#[cfg(not(feature = "ahash"))]
+pub use std::collections::HashMap;

eppo_core/src/lib.rs

@@ -49,6 +49,10 @@
 
 #![warn(rustdoc::missing_crate_level_docs)]
 
+// Re-export public dependencies.
+#[cfg(feature = "ahash")]
+pub use ahash;
+
 pub mod attributes;
 pub mod background;
 pub mod bandits;
@@ -67,6 +71,7 @@ pub mod ufc;
 
 mod configuration;
 mod error;
+mod hashmap;
 mod obfuscation;
 mod precomputed;
 mod sdk_key;

eppo_core/src/precomputed.rs

@@ -1,6 +1,6 @@
-use std::collections::HashMap;
 use std::sync::Arc;
 
+use crate::hashmap::HashMap;
 use base64::Engine;
 use rand::Rng;
 use serde::{Deserialize, Serialize};
@@ -198,6 +198,8 @@ impl From<PrecomputedBandit> for ObfuscatedPrecomputedBandit {
 
 #[cfg(test)]
 mod tests {
+    use crate::hashmap::*;
+
     use super::*;
 
     #[test]

eppo_core/src/ufc/compiled_flag_config.rs

@@ -1,4 +1,6 @@
-use std::{collections::HashMap, sync::Arc};
+use std::sync::Arc;
+
+use crate::hashmap::*;
 
 use serde::Serialize;
 

eppo_core/src/ufc/models.rs

@@ -1,5 +1,4 @@
-use std::collections::HashMap;
-
+use crate::hashmap::HashMap;
 use derive_more::From;
 use regex::Regex;
 use semver::Version;

python-sdk/Cargo.toml

@@ -8,7 +8,7 @@ publish = false
 crate-type = ["cdylib"]
 
 [dependencies]
-eppo_core = { version = "=9.3.0", path = "../eppo_core", features = ["pyo3"] }
+eppo_core = { version = "=9.3.0", path = "../eppo_core", features = ["pyo3", "ahash"] }
 log = "0.4.22"
 pyo3 = "0.27.2"
 pyo3-log = "0.13.2"

python-sdk/src/client.rs

@@ -1,5 +1,4 @@
 use std::{
-    collections::HashMap,
     ops::Deref,
     sync::{
         atomic::{AtomicBool, Ordering},
@@ -17,6 +16,7 @@ use pyo3::{
 };
 
 use eppo_core::{
+    ahash::HashMap,
     background::BackgroundThread,
     configuration_fetcher::ConfigurationFetcher,
     configuration_poller::{