Geo-Distributed Deployment Topology

This document takes the typical architecture of three data centers (DC) in two cities as an example, and introduces the geo-distributed deployment architecture and the key configuration.

Topology information

Topology templates

• The geo-distributed topology template

Key parameters

This section describes the key parameter configuration of the TiDB geo-distributed deployment.

TiKV parameters

• The gRPC compression format (none by default):

  To increase the transmission speed of gRPC packages between geo-distributed target nodes, set this parameter to gzip.

  server.grpc-compression-type: gzip

• The label configuration:

  Since TiKV is deployed across different data centers, if the physical machines go down, the Region Group might lose three of the default five replicas, which causes the cluster unavailability. To address this issue, you can configure the labels to enable the smart scheduling of PD, which ensures that the Region Group does not allow three replicas to be located in TiKV instances on the same machine in the same cabinet of the same data center.

• The TiKV configuration:

  The same host-level label information is configured for the same physical machine.

  config:
    server.labels:
      zone: bj
      dc: bja
      rack: rack1
      host: host2

• To prevent remote TiKV nodes from launching unnecessary Raft elections, it is required to increase the minimum and maximum number of ticks that the remote TiKV nodes need to launch an election. The two parameters are set to 0 by default.

  raftstore.raft-min-election-timeout-ticks: 1000
  raftstore.raft-max-election-timeout-ticks: 1020

PD parameters

• The PD metadata information records the topology of the TiKV cluster. PD schedules the Raft Group replicas on the following four dimensions:

  replication.location-labels: ["zone","dc","rack","host"]

• To ensure high availability of the cluster, adjust the number of Raft Group replicas to be 5:

  replication.max-replicas: 5

• Forbid the remote TiKV Raft replica being elected as Leader:

  label-property:
        reject-leader:
          - key: "dc"
            value: "sha"

Note:

• You do not need to manually create the tidb user in the configuration file. The TiUP cluster component automatically creates the tidb user on the target machines. You can customize the user, or keep the user consistent with the control machine.
• If you configure the deployment directory as a relative path, the cluster will be deployed in the home directory of the user.