[jira] [Created] (KAFKA-5987) Kafka metrics templates used in document generation should maintain order of tags

["Randall Hauch (JIRA)" <ji...@apache.org>]

Randall Hauch created KAFKA-5987:
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             Summary: Kafka metrics templates used in document generation should maintain order of tags
                 Key: KAFKA-5987
                 URL: https://issues.apache.org/jira/browse/KAFKA-5987
             Project: Kafka
          Issue Type: Improvement
          Components: clients
    Affects Versions: 1.0.0
            Reporter: Randall Hauch
            Assignee: Randall Hauch
             Fix For: 1.0.0


KAFKA-5191 recently added a new {{MetricNameTemplate}} that is used to create the {{MetricName}} objects in the producer and consumer, as we as in the newly-added generation of metric documentation. The {{MetricNameTemplate}} and the {{Metric.toHtmlTable}} do not maintain the order of the tags, which means the resulting HTML documentation will order the table of MBean attributes based upon the lexicographical ordering of the MBeans, each of which uses the lexicographical ordering of its tags. This can result in the following order:

{noformat}
kafka.connect:type=sink-task-metrics,connector={connector},partition={partition},task={task},topic={topic}
kafka.connect:type=sink-task-metrics,connector={connector},task={task}
{noformat}

However, if the MBeans maintained the order of the tags then the documentation would use the following order:

{noformat}
kafka.connect:type=sink-task-metrics,connector={connector},task={task}
kafka.connect:type=sink-task-metrics,connector={connector},task={task},topic={topic},partition={partition}
{noformat}

This would be more readable, and the code that is creating the templates would have control over the order of the tags. 

To maintain order, {{MetricNameTemplate}} should used a {{LinkedHashSet}} for the tags, and the {{Metrics.toHtmlTable}} method should also use a {{LinkedHashMap}} when building up the tags used in the MBean name.

Note that JMX MBean names use {{ObjectName}} that does not maintain order, so this change should have no impact on JMX MBean names.



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