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Documentation
  • About TiDB
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      • The TiDB System Variables
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      • The TiDB Server Logs
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      • Use Encrypted Connections
    • SQL Optimization
      • Understand the Query Execution Plan
      • Introduction to Statistics
    • Language Structure
      • Literal Values
      • Schema Object Names
      • Keywords and Reserved Words
      • User-Defined Variables
      • Expression Syntax
      • Comment Syntax
    • Globalization
      • Character Set Support
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      • Time Zone Support
    • Data Types
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      • The ENUM data type
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      • Aggregate (GROUP BY) Functions
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      • Precision Math
    • SQL Statement Syntax
      • Data Definition Statements
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      • Transactions
      • Database Administration Statements
      • Prepared SQL Statement Syntax
      • Utility Statements
      • TiDB SQL Syntax Diagram
    • JSON Functions and Generated Column
    • Connectors and APIs
    • TiDB Transaction Isolation Levels
    • Error Codes and Troubleshooting
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      • Garbage Collection (GC)
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    • Hardware and Software Requirements
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      • Ansible Deployment (Recommended)
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      • Docker Deployment
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      • Cross-Region Deployment
      • Kubernetes Deployment
    • Configure
      • Configuration Flags
      • Configuration File Description
      • Modify Component Configuration Using Ansible
      • Enable TLS Authentication
      • Generate Self-signed Certificates
    • Monitor
      • Overview of the Monitoring Framework
      • Key Metrics
      • Monitor a TiDB Cluster
    • Scale
      • Scale a TiDB Cluster
      • Scale Using Ansible
    • Upgrade
      • Upgrade the Component Version
      • TiDB 2.0 Upgrade Guide
    • Tune Performance
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      • Backup and Restore
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        • Migrate All the Data
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    • TiDB-Ansible Common Operations
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    • Syncer
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TiDB Architecture

The TiDB platform is comprised of three key components: the TiDB server, the PD server, and the TiKV server. In addition, TiDB also provides the TiSpark component for the complex OLAP requirements.

image alt text

TiDB server

The TiDB server is in charge of the following operations:

  1. Receiving the SQL requests

  2. Processing the SQL related logics

  3. Locating the TiKV address for storing and computing data through Placement Driver (PD)

  4. Exchanging data with TiKV

  5. Returning the result

The TiDB server is stateless. It does not store data and it is for computing only. TiDB is horizontally scalable and provides the unified interface to the outside through the load balancing components such as Linux Virtual Server (LVS), HAProxy, or F5.

Placement Driver server

The Placement Driver (PD) server is the managing component of the entire cluster and is in charge of the following three operations:

  1. Storing the metadata of the cluster such as the region location of a specific key.

  2. Scheduling and load balancing regions in the TiKV cluster, including but not limited to data migration and Raft group leader transfer.

  3. Allocating the transaction ID that is globally unique and monotonic increasing.

As a cluster, PD needs to be deployed to an odd number of nodes. Usually it is recommended to deploy to 3 online nodes at least.

TiKV server

The TiKV server is responsible for storing data. From an external view, TiKV is a distributed transactional Key-Value storage engine. Region is the basic unit to store data. Each Region stores the data for a particular Key Range which is a left-closed and right-open interval from StartKey to EndKey. There are multiple Regions in each TiKV node. TiKV uses the Raft protocol for replication to ensure the data consistency and disaster recovery. The replicas of the same Region on different nodes compose a Raft Group. The load balancing of the data among different TiKV nodes are scheduled by PD. Region is also the basic unit for scheduling the load balance.

TiSpark

TiSpark deals with the complex OLAP requirements. TiSpark makes Spark SQL directly run on the storage layer of the TiDB cluster, combines the advantages of the distributed TiKV cluster, and integrates into the big data ecosystem. With TiSpark, TiDB can support both OLTP and OLAP scenarios in one cluster, so the users never need to worry about data synchronization.

"TiDB Architecture" was last updated Oct 11 2018: architecture, features: Improve Overview (#649) (1c1df5d)
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