How do I troubleshoot a lock timeout that blocks synchronization for 1 cloud account or resource?

Issue/Introduction

This article describes how to troubleshoot a cloud account or individual resource whose synchronization does not run, is skipped, or continuously reports a lock acquisition timeout even though Redis is generally available. This scenario indicates distributed-lock contention or a leftover lock and is not the same as a Redis connection failure.

Symptoms

• Only 1 cloud account or a small number of resources fail to synchronize, while other accounts work.
• A manual synchronization API returns success, but the target service does not enter the actual synchronization flow.
• The log contains resource sync get lock timeout!, one resource in cloud sync get lock timeout!, or Failed to acquire lock during resource sync.
• Redis PING succeeds, and login and other caching functions have no obvious issue.
• Synchronization was repeatedly submitted for the same account, or the issue began after the previous synchronization process exited unexpectedly.

Environment

• Product: ZCenter
• Version: 5.1.0
• Component: VM, RDS, OSS, Container, and Security resource synchronization, and Redis/Redisson

Possible causes

• The same account is being synchronized, and a new request exits after failing to acquire the account lock within 1 second.