TiKV

TiKV ("Ti" stands for Titanium) is a distributed transactional key-value database, originally created to complement TiDB, a distributed HTAP database compatible with the MySQL protocol. TiKV is built in Rust and powered by Raft, and was inspired by the design of Google Spanner and HBase, but without dependency on any specific distributed file system.

With the implementation of the Raft consensus algorithm in Rust and consensus state stored in RocksDB, TiKV guarantees data consistency. Placement Driver (PD), which is introduced to implement auto-sharding, enables automatic data migration. The transaction model is similar to Google's Percolator with some performance improvements. TiKV also provides snapshot isolation (SI), snapshot isolation with lock (SQL: SELECT ... FOR UPDATE), and externally consistent reads and writes in distributed transactions.

TiKV has the following key features:

• Geo-Replication

  TiKV uses Raft and the Placement Driver to support Geo-Replication.

• Horizontal scalability

  With PD and carefully designed Raft groups, TiKV excels in horizontal scalability and can easily scale to 100+ TBs of data.

• Consistent distributed transactions

  Similar to Google's Spanner, TiKV supports externally-consistent distributed transactions.

• Coprocessor support

  Similar to Hbase, TiKV implements a coprocessor framework to support distributed computing.

• Cooperates with TiDB

  Thanks to the internal optimization, TiKV and TiDB can work together to be a compelling database solution with high horizontal scalability, externally-consistent transactions, support for RDBMS, and NoSQL design patterns.

TiKV Adopters

You can view the list of TiKV Adopters.

TiKV Roadmap

You can see the TiKV Roadmap.

TiKV software stack

• Placement Driver: PD is the cluster manager of TiKV, which periodically checks replication constraints to balance load and data automatically.
• Store: There is a RocksDB within each Store and it stores data into the local disk.
• Region: Region is the basic unit of Key-Value data movement. Each Region is replicated to multiple Nodes. These multiple replicas form a Raft group.
• Node: A physical node in the cluster. Within each node, there are one or more Stores. Within each Store, there are many Regions.

When a node starts, the metadata of the Node, Store and Region are recorded into PD. The status of each Region and Store is reported to PD regularly.

Try TiKV

TiKV was originally a component of TiDB. To run TiKV you must build and run it with PD, which is used to manage a TiKV cluster. You can use TiKV together with TiDB or separately on its own.

We provide multiple deployment methods, but it is recommended to use our Ansible deployment for production environment. The TiKV documentation is available on TiKV's wiki page.

Testing deployment

• Try TiKV and TiDB

  You can use tidb-docker-compose to quickly test TiKV and TiDB on a single machine. This is the easiest way. For other ways, see TiDB documentation.

• Try TiKV separately

  • Deploy TiKV Using Docker Compose: To quickly test TiKV separately without TiDB using tidb-docker-compose on a single machine
  • Deploy TiKV Using Docker: To deploy a multi-node TiKV testing cluster using Docker
  • Deploy TiKV Using Binary Files: To deploy a TiKV cluster using binary files on a single node or on multiple nodes

Production deployment

For the production environment, use Ansible to deploy the cluster.

• Deploy TiDB Using Ansible
• Deploy TiKV separately Using Ansible

Client drivers

Currently, the only interface to TiKV is the TiDB Go client and the TiSpark Java client.

If you want to try the Go client, see Try Two Types of APIs.

Setting up a development workspace

The TiKV codebase is primarily written in Rust, but has components written in C++ (RocksDB) and Go (gRPC). To provide consistency and avoid opinion-based arguments, we make extensive use of linters and automated formatting tools. Additionally, due to Rust's youth we are currently utilizing nightly builds which provide access to many useful features.

Checking your prerequisites

To build TiKV you'll need to at least have the following installed:

• git - Version control
• rustup - Rust toolchain manager
• awk - Pattern scanning/processing language
• cmake - Build tool (required for gRPC)
• go - Programming language (required for gRPC)
• make - Build tool (run common workflows)
• clang or gcc - C compiler toolchain

Getting the repository

git clone https://github.com/tikv/tikv.git
cd tikv
# Future instructions assume you are in this repository

Configuring your Rust toolchain

rustup is an official toolchain manager for Rust, similar to rvm or rbenv from the Ruby world.

TiKV uses the version of the Rust toolchain specified in rust-toolchain. rustup and cargo will automatically utilize this file. We also make use of the rustfmt and clippy components.

rustup component add rustfmt-preview

Building & testing

While TiKV includes a Makefile with common workflows, you are also able to use cargo as you would in a normal Rust project.

At this point, you can build TiKV:

make build

During interactive development, you may prefer using cargo check, which will do parse, borrow check, and lint run on your code, but not actually compile it. It is particularly handy alongside cargo-watch which will run a command each time you change a file.

cargo install cargo-watch
cargo watch -s "cargo check"

When you're ready to test out your changes, use the dev task. It will format your codebase, build with clippy enabled, and run tests. This should run without failure before you create a PR.

make dev

You can run the full test suite locally, or just run a specific test:

# Run the full suite
make test
# Run a specific test
cargo test $TESTNAME

Our CI systems automatically test all the pull requests, so making sure the full suite passes the test before creating your PR is not strictly required. All merged PRs must have passed CI test.

Getting the rest of the system working

To get other components (TiDB and PD) working, we suggest you follow the development guide, because you need the pd-server at least to work alongside tikv-server for integration level testing.

Configuration

Read our configuration guide to learn about various configuration options.

Contributing

Contributions are welcome! See CONTRIBUTING for details on submitting patches and the contribution workflow.

For beginners, we have prepared many suitable tasks for you. Checkout our Help Wanted issues for a list, in which we have also marked the difficulty level.

If you are planning something big, for example, relates to multiple components or changes current behaviors, make sure to open an issue to discuss with us before going on.

The TiKV team actively develops and maintains a bunch of dependencies used in TiKV, which you may be also interested in:

• rust-prometheus: The Prometheus client for Rust, our metrics collecting and reporting library
• rust-rocksdb: Our RocksDB binding and wrapper for Rust
• raft-rs: The Raft distributed consensus algorithm implemented in Rust
• grpc-rs: The gRPC library for Rust built on the gRPC C Core library and Rust Futures
• fail-rs: Fail points for Rust

License

TiKV is under the Apache 2.0 license. See the LICENSE file for details.

Acknowledgments

• Thanks etcd for providing some great open source tools.
• Thanks RocksDB for their powerful storage engines.
• Thanks mio for providing metal I/O library for Rust.
• Thanks rust-clippy. We do love the great project.