[ISSUE #14981] Fix concurrent publishConfig race condition for PostgreSQL

[wushiyuanmaimob]

Fixes

• Fixes [Bug] PostgreSQL: Concurrent publishConfig calls lead to UniqueIndexConflict instead of idempotent update #14981

Description

In a Nacos cluster using PostgreSQL as the database backend, concurrent calls to the publishConfig API for the same dataId, group, and tenant occasionally result in a 500 Internal Server Error due to UniqueIndexConflict.

Root Cause

ExternalConfigInfoPersistServiceImpl.insertOrUpdate() uses a check-then-act pattern:

1. SELECT to check if the config exists
2. If not exists → INSERT
3. If exists → UPDATE

Under high concurrency, two threads can both find "not exists" and both attempt INSERT. The second one hits the unique constraint (uk_configinfo_datagrouptenant) and throws DataIntegrityViolationException.

For MySQL, this is typically handled by ON DUPLICATE KEY UPDATE or automatic retry in some deployments. PostgreSQL has no such fallback.

Fix

Catch DataIntegrityViolationException on INSERT and fall back to UPDATE, making the operation idempotent across all database backends (MySQL, PostgreSQL, Oracle, etc.).

Before:

check → INSERT → throw exception ❌

After:

check → INSERT → unique constraint violated → UPDATE ✓

Changes

File	Description
ExternalConfigInfoPersistServiceImpl.java	Add fallback to UPDATE on INSERT duplicate key violation (+25/-5 lines)

Testing

• Checkstyle: 0 violations
• Compile: PASS

This fix makes insertOrUpdate and insertOrUpdateCas idempotent under concurrent access without requiring application-level retries.

[github-actions]

Thanks for your this PR. 🙏
Please check again for your PR changes whether contains any usage/api/configuration change such as Add new API , Add new configuration, Change default value of configuration.
If so, please add or update documents(markdown type) in docs/next/ for repository nacos-group/nacos-group.github.io

---

感谢您提交的PR。 🙏
请再次查看您的PR内容，确认是否包含任何使用方式/API/配置参数的变更，如：新增API、新增配置参数、修改默认配置等操作。
如果是，请确保在提交之前，在仓库nacos-group/nacos-group.github.io中的docs/next/目录下添加或更新文档（markdown格式）。

[github-actions]

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