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KAFKA-20617: add validation for cluster-id in Formatter #22384

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KAFKA-20617: add validation for cluster-id in Formatter #22384

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ab0caec
KAFKA-20617: add validation for cluster-id in Formatter
gaurav-narula May 27, 2026
2a70079
Address review comments
gaurav-narula May 29, 2026
55d3e00
Stress that validating `-` would break compatibility with old cids
gaurav-narula May 29, 2026
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26 changes: 23 additions & 3 deletions metadata/src/main/java/org/apache/kafka/metadata/storage/Formatter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -229,13 +229,33 @@ public BootstrapMetadata bootstrapMetadata() {
return bootstrapMetadata;
}

/**
* Validates the correctness of the given cluster id. A valid cluster id is a base64, urlencoded, no padding
* representation of a {@link Uuid}. These checks do not validate the absence of <code>-</code> character as
* {@link Uuid#randomUuid()} avoids them only for convenience reasons.
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@fvaleri fvaleri May 29, 2026

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I would explicitly mention support for already generated CIDs. Basically it's for historical reasons.

*/
private void validateClusterId(String clusterId) {
if (clusterId == null) {
throw new FormatterException("You must specify the cluster id.");
}
if (clusterId.contains("=")) {
throw new FormatterException("The specified cluster id, " + clusterId + " is invalid: contains padding");
}
try {
Uuid uuid = Uuid.fromString(clusterId);
if (Uuid.RESERVED.contains(uuid)) {
throw new FormatterException("The specified cluster id, " + clusterId + " is reserved");
}
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@showuon showuon May 29, 2026

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Let's also validate the starting - sign.

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@gaurav-narula gaurav-narula May 29, 2026 •
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I think these are cosmetic improvemenst that've been added over time but have no bearing on correctness. Failing validation on them would hinder migration from older clusters where - was allowed.

The motivation for avoiding - in the beginning was to avoid shell escaping issues when passing cluster id in CLI tools. https://issues.apache.org/jira/browse/KAFKA-13741

Lately, https://issues.apache.org/jira/browse/KAFKA-20072 avoided - altogether to allow easier copy-pasting.

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@fvaleri fvaleri May 29, 2026 •
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Good point. Let's add a comment about this for future reference.

} catch (IllegalArgumentException e) {
throw new FormatterException("The specified cluster id, " + clusterId + " is invalid", e);
}
}

public void run() throws Exception {
if (nodeId < 0) {
throw new RuntimeException("You must specify a valid non-negative node ID.");
}
if (clusterId == null) {
throw new FormatterException("You must specify the cluster id.");
}
validateClusterId(clusterId);
if (directories.isEmpty()) {
throw new FormatterException("You must specify at least one directory to format");
}
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24 changes: 24 additions & 0 deletions metadata/src/test/java/org/apache/kafka/metadata/storage/FormatterTest.java
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Expand Up @@ -587,4 +587,28 @@ public void testFormatWithNoInitialControllers() throws Exception {
assertNotNull(logDirProps1);
}
}

@ParameterizedTest
@ValueSource(strings = {"unrvTtQISjar0JUWGU/8Pg", "igNUVIdeSPO5JCZYFhOh7Q==", "AAAAAAAAAAAAAAAAAAAAAA", "AAAAAAAAAAAAAAAAAAAAAQ"})
public void testFormatWithInvalidClusterId(String clusterId) throws Exception {
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@fvaleri fvaleri May 29, 2026

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There's no corresponding positive test showing that a valid CID passes validation. This would guard against the validation being too aggressive.

try (TestEnv testEnv = new TestEnv(2)) {
FormatterContext formatter1 = testEnv.newFormatter();
formatter1.formatter.setClusterId(clusterId);
String expectedPrefix = "The specified cluster id, " + clusterId;
assertEquals(expectedPrefix,
assertThrows(FormatterException.class,
formatter1.formatter::run).
getMessage().substring(0, expectedPrefix.length()));
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@fvaleri fvaleri May 29, 2026

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Wouldn't be easier to rewrite like:

assertTrue(message.startsWith(expectedPrefix))

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@gaurav-narula gaurav-narula May 29, 2026

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I'm indifferent here - I followed the convention used in another test in the same class

}
}

@ParameterizedTest
@ValueSource(strings = {"iIygKoNNSpGzNeAEr_QW7w", "-w_KF-snTmuEnKPqZ0RDzA", "dZMgZA7nTLqZTdzb0zbvSQ", "hxqHyN2OSSmPajVhm_DR-Q"})
public void testFormatWithValidClusterId(String clusterId) throws Exception {
try (TestEnv testEnv = new TestEnv(2)) {
FormatterContext formatter1 = testEnv.newFormatter();
formatter1.formatter.setClusterId(clusterId);
formatter1.formatter.run();
}
}
}