Hi Samuli, Cluster ID is allowed to start with a hyphen. But you must pass it to the kafka-storage format command line like this:
> kafka-storage.sh format --cluster-id=$MY_CLUSTER_ID ... Note the equals sign. We didn't want people to have to deal with this, which is why we made generate-uuid not create cluster IDs that started with a hyphen. best, Colin On Tue, Oct 22, 2024, at 06:44, Samuli Ruohola wrote: > Hi! > > Thank you for the Apache Kafka! We are grateful for it. > > In our root cause analysis process discussions, we were asked to share > following piece of information to the Apache Kafka community. > > Following is a known topic, in generic, it seems, already. E.g. there are > existing tickets, and Uuid.java implementation already handles the > "problem", in one way. > > Following was still asked to be raised up. > > Kafka cluster ID does not work exactly as it is defined in documentation of > Apache Kafka. > ( Those are not exactly in sync. ) > Regarding location of one character. > > In the documentation of Apache Kafka, hyphen, "-" is allowed to be in the > beginning, according to the exact definition and regexp: > > https://kafka.apache.org/documentation/ > > Quotation: > > "The cluster id ... the allowed characters are defined by the regular > expression [a-zA-Z0-9_\-]+". > > According to that, hyphen, "-", is allowed to be in the beginning of the > value of cluster ID. But that is incorrect. > > In reality, the Apache Kafka instance / cluster does not start up with > hyphen "-" in the beginning of the value of the cluster ID. > > The problem: kafka-storage could not parse command line argument ( cluster > ID ). > There comes an error: "argument --cluster-id/-t: expected one argument" > > > More: > > It seems to be a known issue in Apache kafka. Because there exists > following source codes / function: > > ... > * This will not generate a UUID equal to 0, 1, or one whose string > representation starts with a dash ("-") > */ > public static Uuid randomUuid() { > Uuid uuid = unsafeRandomUuid(); > while (RESERVED.contains(uuid) || uuid.toString().*startsWith*("*-*")) > { > uuid = unsafeRandomUuid(); > } > return uuid; > } > } > > https://fossies.org/dox/kafka-3.8.0-src/Uuid_8java_source.html > https://github.com/apache/kafka/blob/trunk/clients/src/main/java/org/apache/kafka/common/Uuid.java > https://issues.apache.org/jira/browse/KAFKA-13741 > > An other older ticket related to UUID / cluster ID starting with "hyphen": > https://issues.apache.org/jira/browse/KAFKA-15754 > > > We generated/generate the cluster ID in our own function. And that caused > trouble. > > Best Regards > Sam
