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perf: optimize EvaluatorBucketing #88

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acd352d
optimize EvaluatorBucketing
yuzawa-san Aug 26, 2025
59247ee
avoid intermediate copy from StringBuilder
yuzawa-san Aug 26, 2025
21716eb
Revert "avoid intermediate copy from StringBuilder"
yuzawa-san Aug 27, 2025
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38 changes: 25 additions & 13 deletions lib/sdk/server/src/main/java/com/launchdarkly/sdk/server/EvaluatorBucketing.java
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Original file line number Diff line number Diff line change
Expand Up @@ -47,30 +47,42 @@ static float computeBucketValue(
}
}

String idHash = getBucketableStringValue(contextValue);
if (idHash == null) {
StringBuilder keyBuilder = new StringBuilder();
if (seed != null) {
keyBuilder.append(seed.intValue());
} else {
keyBuilder.append(flagOrSegmentKey).append('.').append(salt);
}
keyBuilder.append('.');
if (!getBucketableStringValue(keyBuilder, contextValue)) {
return 0;
}

String prefix;
if (seed != null) {
prefix = seed.toString();
} else {
prefix = flagOrSegmentKey + "." + salt;
// turn the first 15 hex digits of this into a long
byte[] hash = DigestUtils.sha1(keyBuilder.toString());
long longVal = 0;
for (int i = 0; i < 7; i++) {
longVal <<= 8;
longVal |= (hash[i] & 0xff);
}
String hash = DigestUtils.sha1Hex(prefix + "." + idHash).substring(0, 15);
long longVal = Long.parseLong(hash, 16);
longVal <<= 4;
longVal |= ((hash[7] >> 4) & 0xf);
return (float) longVal / LONG_SCALE;
}

private static String getBucketableStringValue(LDValue userValue) {
private static boolean getBucketableStringValue(StringBuilder keyBuilder, LDValue userValue) {
switch (userValue.getType()) {
case STRING:
return userValue.stringValue();
keyBuilder.append(userValue.stringValue());
return true;
case NUMBER:
return userValue.isInt() ? String.valueOf(userValue.intValue()) : null;
if (userValue.isInt()) {
keyBuilder.append(userValue.intValue());
return true;
}
return false;
default:
return null;
return false;
}
}
}
14 changes: 14 additions & 0 deletions lib/sdk/server/src/test/java/com/launchdarkly/sdk/server/EvaluatorBucketingTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,8 @@
import com.launchdarkly.sdk.server.DataModel.RolloutKind;
import com.launchdarkly.sdk.server.DataModel.WeightedVariation;

import org.apache.commons.codec.digest.DigestUtils;

import org.junit.Test;

import java.util.Arrays;
Expand Down Expand Up @@ -132,6 +134,18 @@ public void cannotBucketByBooleanAttribute() {
assertEquals(0f, result, Float.MIN_VALUE);
}

@Test
public void optimizedHashText() {
LDContext context = LDContext.builder("key")
.set("stringattr", "33333")
.build();
float result = computeBucketValue(false, noSeed, context, null, "key", AttributeRef.fromLiteral("stringattr"), "salt");
String hash = DigestUtils.sha1Hex("key.salt.33333").substring(0, 15);
long longVal = Long.parseLong(hash, 16);
float expectedResult = longVal / (float) 0xFFFFFFFFFFFFFFFL;
assertEquals(expectedResult, result, Float.MIN_VALUE);
}

private static void assertVariationIndexFromRollout(
int expectedVariation,
Rollout rollout,
Expand Down