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Posted to commits@rocketmq.apache.org by "qianye1001 (via GitHub)" <gi...@apache.org> on 2026/06/10 09:35:11 UTC
[I] [Enhancement] Set initial capacity for ProxyContext internal HashMap to avoid resize [rocketmq]
qianye1001 opened a new issue, #10460:
URL: https://github.com/apache/rocketmq/issues/10460
### Before Creating the Enhancement Request
- [x] I have confirmed that this should be classified as an enhancement rather than a bug/feature.
### Summary
`ProxyContext` (in `org.apache.rocketmq.proxy.common`) uses a `HashMap` with the default initial capacity (16) and default load factor (0.75) to hold context entries. The resize threshold is therefore `12`.
In typical request paths, the context is populated with the 10 standard keys defined in `ContextVariable` (`remote-address`, `local-address`, `client-id`, `channel`, `language`, `client-version`, `remaining-ms`, `action`, `protocol-type`, `namespace`) plus additional entries injected via `withVal(...)` from various processors / interceptors. As soon as the entry count exceeds 12, the underlying `HashMap` triggers a rehash/resize on the hot request path, which is unnecessary overhead given that the upper bound of entries is well-known.
### Motivation
`ProxyContext` is created on every inbound request (gRPC / Remoting), so this resize cost is paid per RPC. Pre-sizing the map eliminates a guaranteed reallocation + rehash on a hot path with effectively zero downside (the extra memory footprint is negligible, ~256 bytes per context).
### Describe the Solution You'd Like
Initialize the internal map with an explicit initial capacity (suggest `64`) so that under the default load factor the threshold (`48`) comfortably exceeds the realistic upper bound of context entries, and no resize will happen on the request path.
```java
// proxy/src/main/java/org/apache/rocketmq/proxy/common/ProxyContext.java
private static final int DEFAULT_INITIAL_CAPACITY = 64;
private final Map<String, Object> value = new HashMap<>(DEFAULT_INITIAL_CAPACITY);
```
### Describe Alternatives You've Considered
- Keep using the default capacity — rejected, incurs a deterministic resize on every request once entries cross 12.
- Use a smaller capacity such as 32 — works for most cases but still risks resize when interceptors/plugins push more values; 64 leaves comfortable headroom while staying small.
- Switch to a different map implementation (e.g. `IdentityHashMap`, array-backed) — out of scope; preserving `HashMap` semantics with a tuned initial capacity is the minimal change.
### Additional Context
File: `proxy/src/main/java/org/apache/rocketmq/proxy/common/ProxyContext.java`
Related code:
- `ProxyContext#value` field — the map being resized.
- `ContextVariable` — defines 10 well-known keys, all of which are usually set during a single request lifecycle.
Happy to send a PR.
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Re: [I] [Enhancement] Set initial capacity for ProxyContext internal HashMap to avoid resize [rocketmq]
Posted by "tiagoejoaquim110717-hash (via GitHub)" <gi...@apache.org>.
tiagoejoaquim110717-hash commented on issue #10460:
URL: https://github.com/apache/rocketmq/issues/10460#issuecomment-4700972497
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Re: [I] [Enhancement] Set initial capacity for ProxyContext internal HashMap to avoid resize [rocketmq]
Posted by "oss-sentinel-ai (via GitHub)" <gi...@apache.org>.
oss-sentinel-ai commented on issue #10460:
URL: https://github.com/apache/rocketmq/issues/10460#issuecomment-4668695366
loongsuite-site-bootstrap: started successfully (OpenTelemetry auto-instrumentation initialized).
"**Issue Evaluation**\n\nCategory: `type/enhancement` | Status: **Confirmed**\n\nVerified against the current codebase on `develop` branch.\n\n**Analysis:**\n- `ProxyContext#value` is initialized as `new HashMap<>()` (default capacity 16, resize threshold 12 at 0.75 load factor).\n- `ContextVariable` defines 10 well-known keys, all typically populated per request.\n- With interceptors/plugins adding more entries, the map reliably crosses the threshold of 12 on every request, triggering a resize on the hot path.\n\n**Assessment:**\n- **Feasibility:** Straightforward \u2014 single-line change with no behavioral impact.\n- **Scope:** `proxy/src/main/java/org/apache/rocketmq/proxy/common/ProxyContext.java` only.\n- **Compatibility:** No breaking changes. The proposed capacity of 64 (threshold 48) provides comfortable headroom.\n- **Impact:** Eliminates a deterministic rehash on every gRPC/Remoting request. Negligible memory overhead (~256 bytes per context).\n\nThis is a valid and wel
l-motivated optimization. The suggested approach (initial capacity = 64) is reasonable.\n\n---\n*Automated evaluation by oss-sentinel-ai*\n"
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Re: [I] [Enhancement] Set initial capacity for ProxyContext internal HashMap to avoid resize [rocketmq]
Posted by "oss-sentinel-ai (via GitHub)" <gi...@apache.org>.
oss-sentinel-ai commented on issue #10460:
URL: https://github.com/apache/rocketmq/issues/10460#issuecomment-4668712910
**Issue Evaluation**
Category: `type/enhancement` | Status: **Confirmed**
Verified against the current codebase on `develop` branch.
**Analysis:**
- `ProxyContext#value` is initialized as `new HashMap<>()` (default capacity 16, resize threshold 12 at 0.75 load factor).
- `ContextVariable` defines 10 well-known keys, all typically populated per request.
- With interceptors/plugins adding more entries, the map reliably crosses the threshold of 12 on every request, triggering a resize on the hot path.
**Assessment:**
- **Feasibility:** Straightforward — single-line change with no behavioral impact.
- **Scope:** `proxy/src/main/java/org/apache/rocketmq/proxy/common/ProxyContext.java` only.
- **Compatibility:** No breaking changes. The proposed capacity of 64 (threshold 48) provides comfortable headroom.
- **Impact:** Eliminates a deterministic rehash on every gRPC/Remoting request. Negligible memory overhead (~256 bytes per context).
This is a valid and well-motivated optimization. The suggested approach (initial capacity = 64) is reasonable.
---
*Automated evaluation by oss-sentinel-ai*
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Re: [I] [Enhancement] Set initial capacity for ProxyContext internal HashMap to avoid resize [rocketmq]
Posted by "tiagoejoaquim110717-hash (via GitHub)" <gi...@apache.org>.
tiagoejoaquim110717-hash commented on issue #10460:
URL: https://github.com/apache/rocketmq/issues/10460#issuecomment-4700975256
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Re: [I] [Enhancement] Set initial capacity for ProxyContext internal HashMap to avoid resize [rocketmq]
Posted by "RongtongJin (via GitHub)" <gi...@apache.org>.
RongtongJin closed issue #10460: [Enhancement] Set initial capacity for ProxyContext internal HashMap to avoid resize
URL: https://github.com/apache/rocketmq/issues/10460
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