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KAFKA-20072 Don't generate IDs with hyphens #21313

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Merged
mimaison merged 3 commits into from
Apr 30, 2026
Merged

KAFKA-20072 Don't generate IDs with hyphens #21313

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KAFKA-20072 Don't generate IDs with hyphens
wernerdv Jan 15, 2026
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update protocol.md
wernerdv Jan 27, 2026
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update docs
wernerdv Jan 28, 2026
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6 changes: 3 additions & 3 deletions clients/src/main/java/org/apache/kafka/common/Uuid.java
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Original file line number Diff line number Diff line change
Expand Up @@ -70,12 +70,12 @@ private static Uuid unsafeRandomUuid() {

/**
* Static factory to retrieve a type 4 (pseudo randomly generated) UUID.
*
* This will not generate a UUID equal to 0, 1, or one whose string representation starts with a dash ("-")
* <p>
* This will not generate a UUID equal to 0, 1, or one whose string representation contains a dash ("-").
*/
public static Uuid randomUuid() {
Uuid uuid = unsafeRandomUuid();
while (RESERVED.contains(uuid) || uuid.toString().startsWith("-")) {
while (RESERVED.contains(uuid) || uuid.toString().contains("-")) {
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@squah-confluent squah-confluent Jan 16, 2026 •
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Note that the probability of rejecting a generated uuid rises from 1.56% (= 1/64) to 30.5% (= 1 - (63/64)**19 * 15/16, taking into account fixed bits in version 4 uuids). The new p99 number of rejections is ~3.88 (was 1.11) which I think is not too bad.

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@mumrah mumrah Jan 20, 2026

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Thanks for doing the math :)

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@ijuma ijuma Jun 1, 2026

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30% failure rate for a general utility class is really high and I don't think it makes sense. Uuids are occasionally used in cases where performance matters. Also, the reasoning for the change is unclear.

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@mumrah mumrah Jun 1, 2026 •
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Thanks, @ijuma -- that's a very good point about performance! I did check through fetch/produce paths originally, but of course that doesn't protect us from future usages (or things not caught during the review).

I'll file a patch shortly that makes this new behavior opt-in.

As to the reasoning, the original Jira I wrote was about issues with double-clicking on IDs. Really it's just meant to be a small quality of life improvement.

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@mumrah mumrah Jun 1, 2026 •
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Addressed in #22442

uuid = unsafeRandomUuid();
}
return uuid;
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2 changes: 1 addition & 1 deletion clients/src/test/java/org/apache/kafka/common/UuidTest.java
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Expand Up @@ -83,7 +83,7 @@ public void testRandomUuid() {

assertNotEquals(Uuid.ZERO_UUID, randomID);
assertNotEquals(Uuid.METADATA_TOPIC_ID, randomID);
assertFalse(randomID.toString().startsWith("-"));
assertFalse(randomID.toString().contains("-"));
}

@Test
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