The cluster planned in tidb includes 6 dB, 3 PD and 3 kV. When the application is disconnected, which address is it connected to?

Access through load balancing tidbserver

TiDB The cluster is mainly divided into three components ：

TiDB Server

TiDB Server Responsible for receiving SQL request , Handle SQL Related logic , And pass PD Find the... That stores the data needed for the calculation TiKV Address , And TiKV Get data interactively , The final result . TiDB Server It's stateless , It doesn't store data in itself , Only responsible for calculation , It can expand infinitely , You can use load balancing components （ Such as LVS、HAProxy or F5） Provide a unified access address to the outside world .

PD Server

Placement Driver ( abbreviation PD) It is the management module of the whole cluster , There are three main tasks ： One is to store the meta information of the cluster （ Some Key Where to store it TiKV node ）; The second is right TiKV Cluster scheduling and load balancing （ Such as data migration 、Raft group leader And so on ）; Third, allocate globally unique and incremental transactions ID.

PD It's a cluster , You need to deploy an odd number of nodes , Generally, it is recommended to deploy at least 3 Nodes .

TiKV Server

TiKV Server Responsible for storing data , Looking from the outside TiKV It's a distributed transaction provider Key-Value Storage engine . The basic unit of data storage is Region, Every Region Responsible for storing one Key Range （ from StartKey To EndKey Left closed right open interval of ） The data of , Every TiKV Nodes will be responsible for multiple Region .TiKV Use Raft Make a copy of the agreement , Keep data consistent and disaster tolerant . Copy with Region Manage for the unit , Multiple... On different nodes Region Constitute a Raft Group, Make copies of each other . Data in multiple TiKV The load balance between PD Dispatch , Here, too Region Scheduling for units .
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Include 6 individual DB, Refer to 6 individual tidb server? Application link tidb server The address and port of , such as ip:4000

Connect tidb Server The address of

any tidb server Of IP： Ports can be connected

It's usually a link tidb server, If there are more than one server, Connect any one , If you want to use high availability , We have to get a load to provide vip.