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Posted to commits@cassandra.apache.org by "Ling Mao (Jira)" <ji...@apache.org> on 2026/08/10 11:23:00 UTC
[jira] [Assigned] (CASSANDRA-21556) Add metrics about Netty memeory usage
[ https://issues.apache.org/jira/browse/CASSANDRA-21556?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Ling Mao reassigned CASSANDRA-21556:
------------------------------------
Assignee: Ling Mao
> Add metrics about Netty memeory usage
> -------------------------------------
>
> Key: CASSANDRA-21556
> URL: https://issues.apache.org/jira/browse/CASSANDRA-21556
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Observability/Metrics
> Reporter: Ling Mao
> Assignee: Ling Mao
> Priority: Normal
>
> When Netty Direct Memory leaks occur, they can be extremely difficult to diagnose and may cause serious production issues. Add metrics to monitor Netty memory usage for observability, debugging, and alerting.
> The comments in `NettyMemoryMetrics` provide a summary of what contributes to Netty Direct Memory and Java Direct Memory usage.
> Do not use `Netty allocator.metric()` for these metrics. The memory usage from individual allocators is relatively small and distributed across different components. Additionally, querying allocator metrics is not as lightweight as using `PlatformDependent::usedDirectMemory`.
> The metrics location:
>
> {code:java}
> org.apache.cassandra.metrics:type=NettyMemory,name=UsedDirectMemory
> org.apache.cassandra.metrics:type=NettyMemory,name=DirectMemoryLimit
> # promethus metrics
> # HELP cassandra_nettymemory_directmemorylimit Attribute exposed for management org.apache.cassandra.metrics:name=DirectMemoryLimit,type=NettyMemory,attribute=Value
> # TYPE cassandra_nettymemory_directmemorylimit gauge
> cassandra_nettymemory_directmemorylimit 4.294967296E9
> # HELP cassandra_nettymemory_useddirectmemory Attribute exposed for management org.apache.cassandra.metrics:name=UsedDirectMemory,type=NettyMemory,attribute=Value
> # TYPE cassandra_nettymemory_useddirectmemory gauge
> cassandra_nettymemory_useddirectmemory 1.6777216E7
> {code}
>
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