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https://issues.apache.org/jira/browse/CASSANDRA-16938?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17412663#comment-17412663
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Brandon Williams commented on CASSANDRA-16938:
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I don't see how it matters in a serialized format like json.
> Missed wait latencies in the output of `nodetool tpstats -F`
> ------------------------------------------------------------
>
> Key: CASSANDRA-16938
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16938
> Project: Cassandra
> Issue Type: Bug
> Components: Tool/nodetool
> Reporter: Andres de la Peña
> Assignee: Andres de la Peña
> Priority: Normal
> Fix For: 4.1, 4.0.x
>
> Attachments: json-after.txt, json-before.txt
>
>
> The output of {{nodetool tpstats -F json}} always prints an empty map for
> {{WaitLatencies}}:
> {code:java}
> $ nodetool tpstats -F json
> (...)"WaitLatencies":{},(...)
> {code}
> The same happens with yaml output:
> {code:java}
> $ nodetool tpstats -F yaml
> (...)
> WaitLatencies: {}
> (...)
> {code}
> This happens because [this
> cast|https://github.com/apache/cassandra/blob/cassandra-4.0.1/src/java/org/apache/cassandra/tools/nodetool/stats/TpStatsHolder.java#L61-L63]
> silently fails inside a try-catch with an empty catch block:
> {code:java}
> String[] strValues = (String[])
> Arrays.stream(probe.metricPercentilesAsArray(probe.getMessagingQueueWaitMetrics(entry.getKey())))
> .map(D -> D.toString())
> .toArray();
> {code}
> When we would need something like:
> {code:java}
> String[] strValues =
> Arrays.stream(probe.metricPercentilesAsArray(probe.getMessagingQueueWaitMetrics(entry.getKey())))
> .map(Object::toString)
> .toArray(String[]::new);
> {code}
> This conversion from {{Double[]}} to {{String[]}} was introduced during
> CASSANDRA-16230. My guess is that the conversion was done trying to work
> around a malformed JSON output detected in [the new
> tests|https://github.com/apache/cassandra/blob/cassandra-4.0.1/test/unit/org/apache/cassandra/tools/NodeToolTPStatsTest.java#L158]
> added by that ticket. Without the conversion the output would be something
> like:
> {code:java}
> $ nodetool tpstats -F json
> (...)"WaitLatencies":{"READ_RSP":[Ljava.lang.Double;@398dada8,(...)
> {code}
> That's because {{json-simple}} doesn't handle well arrays. I think that
> instead of converting the array of doubles to an array of strings we can
> simply use {{jackson-mapper-asl}} to print the proper array.
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