Metrics refresh full-scans okapi_outbox (COUNT(*) GROUP BY status incl. 7 days of DELIVERED) every 15s per instance

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Issue 类型
重构
描述清晰度
基本清楚
活跃度
活跃
技术栈
kotlin, mysql, postgresql
领域
databases, observability

调研方向

Start in MicrometerOutboxMetrics, where the refresh runs the two queries, and in OutboxStore.countByStatuses and findOldestCreatedAt, which hold the GROUP BY status SQL. Decide which statuses the metrics need, then rewrite the oldest-per-status lookup as an index-ordered LIMIT 1 query per status. Done when the queries no longer scan DELIVERED rows and the metrics tests still pass on both PostgreSQL and MySQL.

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描述

enhancement

Severity: Medium (performance) · Area: okapi-micrometer MicrometerOutboxMetrics, OutboxStore.countByStatuses/findOldestCreatedAt · Found in: code review of main @ e5630a1

Problem

Every metrics refresh runs two queries per instance, every 15 s by default:

SELECT status, COUNT(*) FROM okapi_outbox GROUP BY status;
SELECT status, MIN(created_at) FROM okapi_outbox WHERE status IN (?,?,?) GROUP BY status;
  • COUNT(*) ... GROUP BY status has to visit every row. The table keeps 7 days of DELIVERED rows by default (purger retention), which is ~60 M rows at 100 msg/s. N application instances each run this full scan every 15 s.
  • The MIN(created_at) query is index-friendly on MySQL (loose index scan), but Postgres before v18 has no skip scan. GROUP BY status with IN can scan the whole (status, created_at) index, again dominated by DELIVERED rows nobody alerts on.

Load grows with retention × throughput × instance count, on the same primary that serves the application's writes.

Suggested fix

  • Restrict both queries to the statuses that matter operationally (PENDING, FAILED). DELIVERED count/lag is rarely useful, and when it is, it can come from the counters.
  • Compute oldest-per-status with per-status index-ordered lookups, e.g. (SELECT created_at FROM okapi_outbox WHERE status='PENDING' ORDER BY created_at LIMIT 1), which costs O(log n) on both databases.
  • Optionally report DELIVERED from planner estimates or drop it.
主要语言
Kotlin
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14
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0
平均合并
9 小时 54 分钟
30 天内合并 PR
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