fix: set SlaveNode to DBSync status before commit bgsave task

[cheniujh]

这个PR修复了 Issue #2795 。
具体地，调换了两行代码的执行顺序。确保在Master端的SlaveNode会在提交bgsave任务开始前就进入DBSync状态（暂停BInlog的Purge），以确保bgsave执行时所基于的binlog(增量续传的起始点)不会在某些极端情况下被purge掉。

This PR fixes Issue #2795.
Specifically, it changes the execution order of two lines of code to ensure that the SlaveNode on the Master side enters the DBSync state (pausing Binlog purge) before the bgsave task begins. This ensures that the binlog, which serves as the starting point for incremental replication, is not purged in extreme cases during the execution of bgsave.

[coderabbitai]

Walkthrough

The primary change involves simplifying the PikaReplServerConn::HandleDBSyncRequest method by removing a duplicate call to the TryDBSync function. This change addresses potential redundancy and ensures the correct handling of the database synchronization logic.

Changes

Files	Change Summary
src/pika_repl_server_conn.cc	Removed a duplicate call to g_pika_server->TryDBSync in the HandleDBSyncRequest method.

Poem

In the code where syncs align,
We trimmed the extra, just in time.
With cleaner flow, our job’s now neat,
The server hums a sync so sweet.
🎵✨🐇

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[coderabbitai]

Actionable comments posted: 0

Review details

Configuration used: CodeRabbit UI
Review profile: CHILL

Commits

Files that changed from the base of the PR and between 1de6598 and 720224f.

Files selected for processing (1)

• src/pika_repl_server_conn.cc (1 hunks)

Additional comments not posted (1)

src/pika_repl_server_conn.cc (1)

288-290: LGTM! Ensure the synchronization logic is unaffected.

The removal of the redundant call to TryDBSync is correct as it eliminates potential inefficiencies. Verify that this change does not impact the synchronization behavior.

Verification successful

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The removal of the redundant TryDBSync call in HandleDBSyncRequest is correct.

The remaining call to TryDBSync should be sufficient to handle the synchronization logic, as it ensures the database synchronization process is initiated correctly. The change eliminates unnecessary redundancy, which can improve efficiency.

• Ensure the synchronization logic is validated through testing to confirm no side effects.

Scripts executed

The following scripts were executed for the analysis:

Script:

#!/bin/bash
# Description: Verify the behavior of HandleDBSyncRequest after removing redundant TryDBSync call.

# Test: Search for the function usage to understand the impact of the change.
rg --type cpp -A 10 'HandleDBSyncRequest'

Length of output: 2231

---

Script:

#!/bin/bash
# Description: Gather context around the TryDBSync function and its usage within the repository.

# Find the definition of TryDBSync function
rg --type cpp -A 10 'TryDBSync'

# Find all calls to TryDBSync in the repository
rg --type cpp 'TryDBSync'

Length of output: 8223