Ling Mao created CASSANDRA-21556:
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Summary: 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
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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