Support Region/Global Linearizability Consistency

[scsldb]

Description

In order to adapt to the scenario of cross data center deployments (#18273), we expect to solve two problems:

• When reading local data, allocate timestamps from local to avoid high latency
• When need to read remote data, allocate global timestamps to ensure linearizability consistency

The basic idea is to allow PD to allocate local timestamps and global timestamps. Local timestamps are allocated from the same data center and can only ensure consistency within the data center. Global timestamps are allocated by the collaboration of PDs in different data centers and can ensure consistency globally.

Category

Feature

Task List

• Allocate timestamps from different data centers (PD)
• Allocate global timestamps (PD)
• Allocate timestamps with specified data centers Local/Global Transaction Txn Allocator in Cross-DC Deployment Roadmap tikv/pd#2759 (PD)
• Bind table/partition to data center (TiDB)
• Begin transactions with specified data centers Local/Global Transaction in Cross-DC Deployment Tasklist #20448 (TiDB)
• Check if transactions' read set is within specified data centers (TiDB)

Value

• Reduce the latency of reading and writing data when deploying across data centers

[nolouch]

/assign @disksing

[shenli]

Is there a design doc?

[JmPotato]

Is there a design doc?

You can check this doc, but only in Chinese now.