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new 474798afbed KAFKA-20072: Don't generate IDs with hyphens (#21313)
474798afbed is described below
commit 474798afbed318c7ff316b2ca38e559aa1a136ad
Author: Dmitry Werner <[email protected]>
AuthorDate: Thu Apr 30 17:21:43 2026 +0500
KAFKA-20072: Don't generate IDs with hyphens (#21313)
The `Uuid#randomUuid` method has been modified to avoid generating UUIDs
containing hyphens.
Reviewers: Mickael Maison <[email protected]>, David Arthur
<[email protected]>, Sean Quah <[email protected]>
---
clients/src/main/java/org/apache/kafka/common/Uuid.java | 6 +++---
.../src/test/java/org/apache/kafka/common/UuidTest.java | 2 +-
docs/design/protocol.md | 16 ++++++++++++++++
3 files changed, 20 insertions(+), 4 deletions(-)
diff --git a/clients/src/main/java/org/apache/kafka/common/Uuid.java
b/clients/src/main/java/org/apache/kafka/common/Uuid.java
index 6f7f09537f1..5463f7e4a7f 100644
--- a/clients/src/main/java/org/apache/kafka/common/Uuid.java
+++ b/clients/src/main/java/org/apache/kafka/common/Uuid.java
@@ -70,12 +70,12 @@ public class Uuid implements Comparable<Uuid> {
/**
* 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("-")) {
uuid = unsafeRandomUuid();
}
return uuid;
diff --git a/clients/src/test/java/org/apache/kafka/common/UuidTest.java
b/clients/src/test/java/org/apache/kafka/common/UuidTest.java
index 9acc8145be8..8b440d48491 100644
--- a/clients/src/test/java/org/apache/kafka/common/UuidTest.java
+++ b/clients/src/test/java/org/apache/kafka/common/UuidTest.java
@@ -83,7 +83,7 @@ public class UuidTest {
assertNotEquals(Uuid.ZERO_UUID, randomID);
assertNotEquals(Uuid.METADATA_TOPIC_ID, randomID);
- assertFalse(randomID.toString().startsWith("-"));
+ assertFalse(randomID.toString().contains("-"));
}
@Test
diff --git a/docs/design/protocol.md b/docs/design/protocol.md
index 87966feee10..35144739059 100644
--- a/docs/design/protocol.md
+++ b/docs/design/protocol.md
@@ -215,3 +215,19 @@ Others have asked if maybe we shouldn't support many
different protocols. Prior
Another question is why we don't adopt XMPP, STOMP, AMQP or an existing
protocol. The answer to this varies by protocol, but in general the problem is
that the protocol does determine large parts of the implementation and we
couldn't do what we are doing if we didn't have control over the protocol. Our
belief is that it is possible to do better than existing messaging systems have
in providing a truly distributed messaging system, and to do this we need to
build something that works diff [...]
A final question is why we don't use a system like Protocol Buffers or Thrift
to define our request messages. These packages excel at helping you to managing
lots and lots of serialized messages. However we have only a few messages.
Support across languages is somewhat spotty (depending on the package). Finally
the mapping between binary log format and wire protocol is something we manage
somewhat carefully and this would not be possible with these systems. Finally
we prefer the style of [...]
+
+## Recommendations for 3rd‑party Clients: Member ID Format
+
+When a Kafka client participates in group protocols (e.g.,
`ConsumerGroupHeartbeat` RPC), it must generate a **member ID** to identify
itself to the broker. While the protocol does not strictly enforce the format
of this ID, we strongly recommend the following:
+
+1. **Use a base64‑encoded UUID** as the member ID.
+2. **Encode the UUID using URL‑safe base64** (without `+` or `/` characters).
+3. **Omit hyphens** — the resulting string should be a continuous sequence of
alphanumeric characters (e.g., `abc123def456`).
+
+**Example**
+A standard UUID (`00000000-0000-0000-0000-000000000000`) should be transformed
into a URL‑safe base64 string like:
`YzYxNjQ4OTItZDE1Mi00Y2E4LWIyNzUtYmIwMzAwMDAwMDAw`
+
+*(Note: This is illustrative; actual encoding depends on the UUID bytes.)*
+
+**Important**
+While this is a strong recommendation, the protocol does **not** reject member
IDs that deviate from this format.
