Fix: gradual rollout

src/strategy.rs

@@ -107,7 +107,7 @@ pub fn partial_rollout(group: &str, variable: Option<&String>, rollout: u32) ->
         100 => true,
         rollout => {
             if let Ok(normalised) = normalised_hash(group, variable, 100) {
-                rollout > normalised
+                rollout >= normalised
             } else {
                 false
             }
@@ -119,7 +119,7 @@ pub fn partial_rollout(group: &str, variable: Option<&String>, rollout: u32) ->
 /// required for extension strategies, but reusing this is probably a good idea
 /// for consistency across implementations.
 pub fn normalised_hash(group: &str, identifier: &str, modulus: u32) -> std::io::Result<u32> {
-    normalised_hash_internal(group, identifier, modulus, 0, 0)
+    normalised_hash_internal(group, identifier, modulus, 0)
 }
 
 const VARIANT_NORMALIZATION_SEED: u32 = 86028157;
@@ -133,23 +133,22 @@ pub fn normalised_variant_hash(
     identifier: &str,
     modulus: u32,
 ) -> std::io::Result<u32> {
-    normalised_hash_internal(group, identifier, modulus, VARIANT_NORMALIZATION_SEED, 1)
+    normalised_hash_internal(group, identifier, modulus, VARIANT_NORMALIZATION_SEED)
 }
 
 fn normalised_hash_internal(
     group: &str,
     identifier: &str,
     modulus: u32,
     seed: u32,
-    additional: u32,
 ) -> std::io::Result<u32> {
     // See https://github.com/stusmall/murmur3/pull/16 : .chain may avoid
     // copying in the general case, and may be faster (though perhaps
     // benchmarking would be useful - small datasizes here could make the best
     // path non-obvious) - but until murmur3 is fixed, we need to provide it
     // with a single string no matter what.
     let mut reader = Cursor::new(format!("{}:{}", &group, &identifier));
-    murmur3_32(&mut reader, seed).map(|hash_result| (hash_result % modulus) + additional)
+    murmur3_32(&mut reader, seed).map(|hash_result| hash_result % modulus + 1)
 }
 
 // Build a closure to handle session id rollouts, parameterised by groupId and a