Reduce Redis blocking replay pressure by bootjp · Pull Request #1140 · bootjp/elastickv

bootjp · 2026-07-22T12:53:22Z

Author: bootjp

Summary

stop replaying read-only XREAD BLOCK calls to the secondary backend
keep bounded replay for mutating blocking commands such as BZPOP/XREADGROUP
add coverage for blocking replay behavior

Risk

changes secondary replay behavior for XREAD BLOCK only; mutating blocking commands continue to replay to preserve secondary consumption state

Tests

go test ./proxy -run 'TestDualWriter_Blocking|TestBlockingCommandTimeout|TestClassifyCommand' -count=1\n- go test ./proxy -count=1\n- go test ./cmd/redis-proxy -count=1\n- golangci-lint run ./proxy ./cmd/redis-proxy --timeout=5m

coderabbitai · 2026-07-22T12:53:30Z

📝 Walkthrough

Walkthrough

BZPOPMIN と BZPOPMAX の結果を ZREM としてセカンダリへ非同期リプレイする処理を追加し、XREAD などのブロッキング読み取りはリプレイしないよう変更した。対応するデュアルライターのテストも追加した。

Changes

ブロッキング操作のリプレイ

Layer / File(s)	Summary
リプレイコマンド生成 `proxy/blocking.go`	`BZPOPMIN` と `BZPOPMAX` のレスポンスからキーとメンバーを抽出し、`ZREM` の再実行データを生成する。
Blocking への統合と検証 `proxy/dualwrite.go`, `proxy/proxy_test.go`	`DualWriter.Blocking` が生成可能なリプレイだけをセカンダリへ非同期投入し、`BZPOPMIN` の `ZREM` 変換と `XREAD` のリプレイなしをテストする。

Estimated code review effort: 3 (Moderate) | ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	Redis のブロッキング処理のセカンダリ再生負荷を下げる変更内容を端的に表しており、主旨と一致しています。

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bootjp · 2026-07-22T12:53:39Z

@codex review

gemini-code-assist · 2026-07-22T12:53:41Z

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Reviewed commit: 8603f83157

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chatgpt-codex-connector · 2026-07-22T13:03:10Z

+
+func secondaryBlockingReplay(cmd string, resp any) (string, []any, bool) {
+	switch strings.ToUpper(cmd) {
+	case "BZPOPMIN", "BZPOPMAX":


Replay all mutating blocking commands

ClassifyCommand still routes mutating blocking commands such as BLPOP/BRPOP/BRPOPLPUSH/BLMOVE/BLMPOP and XREADGROUP ... BLOCK into Blocking, but this helper now returns ok only for BZPOPMIN/BZPOPMAX. Redis documents BLPOP as removing the returned element (https://redis.io/docs/latest/commands/blpop/) and XREADGROUP as @write with delivered messages tracked in the PEL (https://redis.io/docs/latest/commands/xreadgroup/), so in dual-write modes a successful primary call for these commands now queues no secondary mutation and can leave consumed jobs or consumer-group state behind on the secondary after failover/migration. Please either keep replaying these write-like blocking commands or translate them deterministically as well.

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chatgpt-codex-connector · 2026-07-22T13:03:10Z

+		if !ok {
+			return "", nil, false
+		}
+		return "ZREM", []any{"ZREM", key, member}, true


Preserve ordering for BZPOP removals

When a producer ZADD is followed by a consumer BZPOPMIN on the primary before the secondary has applied the ZADD, this replayed ZREM can run first and remove 0 rows; dispatchAsyncQueue starts queued writes in separate goroutines (proxy/async_queue.go:74-76), so an earlier enqueued ZADD is not guaranteed to reach the secondary before this new removal. If the ZADD then applies later, the item that was already popped on the primary is resurrected on the secondary after failover/migration. The previous bounded blocking replay would wait for the secondary item instead of no-oping, so this deterministic replay needs ordering with prior writes or a retry/conditional path when the removal observes no member.

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bootjp · 2026-07-22T13:04:29Z

@coderabbitai review

coderabbitai · 2026-07-22T13:04:37Z

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bootjp · 2026-07-22T13:06:23Z

@codex review

coderabbitai

🧹 Nitpick comments (1)

proxy/proxy_test.go (1)
639-665: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

BZPOPMAX も同じ再生契約で検証してください。

このテストは BZPOPMIN のみを検証しています。BZPOPMAX についても、返却された key/member が ZREM に変換されるケースを追加してください。両者はセットアップと期待値が同じなので、表駆動テストにまとめると契約を明確に維持できます。

As per coding guidelines, “Unit tests must be co-located with packages in *_test.go files; prefer table-driven test cases.”
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@proxy/proxy_test.go` around lines 639 - 665, The test currently covers only
BZPOPMIN replay behavior; extend it to verify the same contract for BZPOPMAX.
Refactor TestDualWriter_Blocking_ReplaysBZPopMinAsZRem into a table-driven test
covering both commands, using the returned key/member to assert the secondary
call is ZREM with the expected arguments.
Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@proxy/proxy_test.go`:
- Around line 639-665: The test currently covers only BZPOPMIN replay behavior;
extend it to verify the same contract for BZPOPMAX. Refactor
TestDualWriter_Blocking_ReplaysBZPopMinAsZRem into a table-driven test covering
both commands, using the returned key/member to assert the secondary call is
ZREM with the expected arguments.

ℹ️ Review info

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Run ID: b272418a-0d33-4c28-b027-dc9e9a5681ec

📥 Commits

Reviewing files that changed from the base of the PR and between 9c5d497 and 8603f83.

📒 Files selected for processing (3)

proxy/blocking.go
proxy/dualwrite.go
proxy/proxy_test.go

chatgpt-codex-connector · 2026-07-22T13:11:57Z

Codex Review: Didn't find any major issues. Already looking forward to the next diff.

Reviewed commit: da952d66e4

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chatgpt-codex-connector Bot reviewed Jul 22, 2026

View reviewed changes

Reduce blocking replay pressure in Redis proxy

da952d6

bootjp force-pushed the feature/redis-blocking-secondary-replay branch from 8603f83 to da952d6 Compare July 22, 2026 13:06

coderabbitai Bot reviewed Jul 22, 2026

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bootjp merged commit 43eb009 into main Jul 22, 2026
11 checks passed

bootjp deleted the feature/redis-blocking-secondary-replay branch July 22, 2026 13:20

This was referenced Jul 23, 2026

redis-proxy: raise ElasticKV connection budget #1154

Merged

Reduce Redis proxy replay backpressure #1146

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Reduce Redis blocking replay pressure - #1140

Reduce Redis blocking replay pressure#1140
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