[ISSUE #10441] Reduce per-RPC allocation in metrics by caching static AttributeKey instances

[wang-jiahua]

Summary

Reduce per-RPC allocation by replacing reflective AttributeKey.stringKey(name) / AttributeKey.booleanKey(name) calls with pre-built static AttributeKey<T> singletons.

Problem

JFR heap dump showed 38,182 InternalAttributeKeyImpl instances for only 6 distinct key names. Every AttributesBuilder.put(String, T) call internally creates a fresh AttributeKey — a stateless immutable object that should be a singleton.

Fix

Define static final AttributeKey<T> LABEL_*_KEY constants in BrokerMetricsConstant and RemotingMetricsConstant, then migrate all put(String, T) callsites to put(AttributeKey<T>, T).

Files

File	Change
BrokerMetricsConstant.java	+19: 14 typed AttributeKey<> constants
BrokerMetricsManager.java	Migrate put calls to typed keys
PopMetricsManager.java	Migrate put calls to typed keys
RemotingMetricsConstant.java	+10: 5 typed AttributeKey<> constants
RemotingMetricsManager.java	Migrate put calls + .equals() comparison

Split Note

Three misc optimizations previously bundled here (NopStatusListener, TopicMessageType.metricsValue cache, RemotingHelper eager eval fix) have been split into PR #10491.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR focuses on reducing allocation/CPU overhead on metrics and remoting hot paths by introducing AttributeKey singletons and adding small caches for frequently repeated attribute/metric lookups.

Changes:

• Added fast-path caching for remoting request/response code distribution counting.
• Introduced typed OpenTelemetry AttributeKey constants and attribute caching/build helpers in remoting and broker metrics.
• Reduced repeated string allocations (e.g., cached lowercase metrics value, avoided Map.getOrDefault boxing paths).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
remoting/src/main/java/org/apache/rocketmq/remoting/netty/RemotingCodeDistributionHandler.java	Adds “last code” fast path to reduce map lookups for hot request/response codes.
remoting/src/main/java/org/apache/rocketmq/remoting/metrics/RemotingMetricsManager.java	Adds attribute caching and typed label keys to reduce OpenTelemetry attribute overhead.
remoting/src/main/java/org/apache/rocketmq/remoting/metrics/RemotingMetricsConstant.java	Introduces typed AttributeKey singletons for labels.
remoting/src/main/java/org/apache/rocketmq/remoting/common/RemotingHelper.java	Minor optimization to avoid getOrDefault overhead for code descriptions.
common/src/main/java/org/apache/rocketmq/common/attribute/TopicMessageType.java	Caches lowercase metrics value to avoid repeated conversions.
broker/src/main/resources/rmq.broker.logback.xml	Suppresses Logback status output via NopStatusListener.
broker/src/main/java/org/apache/rocketmq/broker/metrics/PopMetricsManager.java	Switches to typed label keys for attributes.
broker/src/main/java/org/apache/rocketmq/broker/metrics/BrokerMetricsManager.java	Adds topic attributes cache and switches to typed label keys.
broker/src/main/java/org/apache/rocketmq/broker/metrics/BrokerMetricsConstant.java	Introduces typed AttributeKey singletons for broker metrics labels.

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[codecov-commenter]

Codecov Report

❌ Patch coverage is 31.37255% with 35 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.04%. Comparing base (82a6a78) to head (f8e69a4).
⚠️ Report is 19 commits behind head on develop.

Files with missing lines	Patch %	Lines
.../rocketmq/broker/metrics/BrokerMetricsManager.java	0.00%	25 Missing ⚠️
...etmq/remoting/metrics/RemotingMetricsConstant.java	0.00%	5 Missing ⚠️
...che/rocketmq/broker/metrics/PopMetricsManager.java	33.33%	4 Missing ⚠️
...ketmq/remoting/metrics/RemotingMetricsManager.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #10443      +/-   ##
=============================================
- Coverage      48.06%   48.04%   -0.03%     
- Complexity     13313    13321       +8     
=============================================
  Files           1377     1377              
  Lines         100632   100726      +94     
  Branches       12995    13010      +15     
=============================================
+ Hits           48369    48392      +23     
- Misses         46344    46383      +39     
- Partials        5919     5951      +32     

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[oss-sentinel-ai]

Review by github-manager-bot

Summary

This PR caches OpenTelemetry AttributeKey instances as static finals to avoid per-RPC allocation, optimizes TopicMessageType lookup, adds a volatile inline cache for RemotingCodeDistributionHandler, and adds Logback NopStatusListener to suppress startup log noise.

Findings

• [Good] BrokerMetricsConstant.java:69-86 — Pre-built typed AttributeKey singletons eliminate per-call allocation on the metrics hot path.
• [Good] BrokerMetricsManager.java:105-120 — Import changes correctly reference the new cached keys.
• [Good] RemotingCodeDistributionHandler.java:35-68 — Volatile inline cache pattern correctly avoids ConcurrentHashMap.computeIfAbsent() on repeated request codes.
• [Good] TopicMessageType.java — Enum-based lookup is more efficient than string comparison.
• [Good] rmq.broker.logback.xml — NopStatusListener suppresses Logback startup noise in production.

Suggestions

1. The volatile inline cache pattern in RemotingCodeDistributionHandler is effective for sequential workloads. Consider documenting that this optimization assumes temporal locality in request codes.
2. Consider adding a microbenchmark to quantify the allocation reduction.

Verdict

✅ Approved — Solid performance optimization with clean implementation.

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Automated review by github-manager-bot

[RockteMQ-AI]

Review by github-manager-bot

Summary

Pre-builds AttributeKey singletons as static constants in BrokerMetricsConstant and updates all call sites to use them, eliminating per-RPC allocation of InternalAttributeKeyImpl objects.

Findings

• [Critical] BrokerMetricsConstant.java:69-83 — All 15 AttributeKey singletons are correctly typed (stringKey for String labels, booleanKey for boolean labels). Each call to AttributeKey.stringKey("name") creates a new object; caching eliminates this per-RPC allocation.
• [Critical] BrokerMetricsManager.java, PopMetricsManager.java, RemotingMetricsManager.java — All call sites consistently updated to use the cached keys. No remaining AttributeKey.stringKey() calls on hot paths.
• [Info] RemotingMetricsManager.java:125-135 — The newAttributes() helper now uses cached keys. This is called on every RPC completion, so the savings are proportional to RPC throughput.

Suggestions

No concerns. This is a straightforward, low-risk optimization with clear benefits on high-throughput brokers.

Verdict: LGTM. Clean optimization with consistent application across all metrics call sites.

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Automated review by github-manager-bot