Dragonboat - A Multi-Group Raft library in Go / 中文版
- 2019-06-21 Dragonboat v3.0 has been released with on disk state machine and Go module support (CHANGELOG).
- 2019-02-20 Dragonboat v2.1 has been released.
Dragonboat is a high performance multi-group Raft consensus library in Go with C++11 binding support.
Consensus algorithms such as Raft provides fault-tolerance by alllowing a system continue to operate as long as the majority member servers are available. For example, a Raft cluster of 5 servers can make progress even if 2 servers fail. It also appears to clients as a single node with strong data consistency always provided. All running servers can be used to initiate read requests for aggregated read throughput.
Dragonboat handles all technical difficulties associated with Raft to allow users to just focus on their application domains. It is also very easy to use, our step-by-step examples can help new users to master it in half an hour.
- Easy to use API for building Raft based applications in Go or C++
- Feature complete and scalable multi-group Raft implementation
- Disk based and memory based state machine support
- Fully pipelined and TLS mutual authentication support, ready for high latency open environment
- Custom Raft log storage and Raft RPC support, easy to integrate with latest I/O techs
- Extensively tested including using Jepsen's Knossos linearizability checker, some results are here
Most features covered in Diego Ongaro's Raft thesis have been supported -
- leader election, log replication, snapshotting and log compaction
- membership changes
- ReadIndex protocol for read-only queries
- leadership transfer
- non-voting members
- idempotent updates transparent to applications
- batching and pipelining
- disk based state machine
Dragonboat is the fastest open source multi-group Raft implementation on Github.
For 3-nodes system using mid-range hardware (details here) and in-memory state machine, Dragonboat can sustain at 9 million writes per second when the payload is 16bytes each or 11 million mixed I/O per second at 9:1 read:write ratio. High throughput is maintained in geographically distributed environment. When the RTT between nodes is 30ms, 2 million I/O per second can still be achieved using a much larger number of clients.
The number of concurrent active Raft groups affects the overall throughput as requests become harder to be batched. On the other hand, having thousands of idle Raft groups has a much smaller impact on throughput.
Table below shows write latencies in millisecond, Dragonboat has <5ms P99 write latency when handling 8 million writes per second at 16 bytes each. Read latency is lower than writes as the ReadIndex protocol employed for linearizable reads doesn't require fsync-ed disk I/O.
| Ops | Payload Size | 99.9% percentile | 99% percentile | AVG |
|---|---|---|---|---|
| 1m | 16 | 2.24 | 1.19 | 0.79 |
| 1m | 128 | 11.11 | 1.37 | 0.92 |
| 1m | 1024 | 71.61 | 25.91 | 3.75 |
| 5m | 16 | 4.64 | 1.95 | 1.16 |
| 5m | 128 | 36.61 | 6.55 | 1.96 |
| 8m | 16 | 12.01 | 4.65 | 2.13 |
When tested on a single Raft group, Dragonboat can sustain writes at 1.25 million per second when payload is 16 bytes each, average latency is 1.3ms and the P99 latency is 2.6ms. This is achieved when using an average of 3 cores (2.8GHz) on each server.
As visualized below, Stop-the-World pauses caused by Go1.11's GC are sub-millisecond on highly loaded systems. Such very short Stop-the-World pause time is further significantly reduced in Go 1.12. Golang's runtime.ReadMemStats reports that less than 1% of the available CPU time is used by GC on highly loaded system.
- x86_64 Linux or MacOS, Go 1.12, GCC or Clang with C++11 support
- RocksDB 5.13.4 or above when using RocksDB for storing Raft logs
Master is our unstable branch for development. Please use released versions for any production purposes.
Make sure Go 1.12 or above has been installed. Instructions below require Go module support.
You need to decide whether to use RocksDB or LevelDB to store Raft logs. RocksDB is recommended.
If RocksDB 5.13.4 or above has not already been installed, follow the steps below to install it first.
To download Dragonboat to $HOME/src and install RocksDB to /usr/local/lib and /usr/local/include:
$ cd $HOME/src
$ git clone https://github.com/lni/dragonboat
$ cd $HOME/src/dragonboat
$ make install-rocksdb-ull
Run built-in tests to check the installation:
$ cd $HOME/src/dragonboat
$ GO111MODULE=on make dragonboat-test
Once completed, $HOME/src/dragonboat can be safely deleted if you just plan to use dragonboat in your application.
To use dragonboat in your application, make sure to import the package github.com/lni/dragonboat/v3 in your Go code. Also add "github.com/lni/dragonboat/v3 v3.0.0" to the require section of your go.mod file.
When building your application, you may need to tell Go where is the installed RocksDB library:
CGO_CFLAGS="-I/path/to/rocksdb/include" CGO_LDFLAGS="-L/path/to/rocksdb/lib -lrocksdb" go build -v pkgname
You can also follow our examples on how to use Dragonboat.
No extra dependency is required when choosing to use LevelDB based Raft log storage.
To use LevelDB based Raft log storage in your application, set the LogDBFactory field of your config.NodeHostConfig to the factory function leveldb.NewLogDB provided in the github.com/lni/dragonboat/v3/plugin/leveldb package.
To build the your application when you don't have RocksDB installed:
go build -v -tags="dragonboat_no_rocksdb" pkgname
FAQ, docs, step-by-step examples, DevOps doc, CHANGELOG and online chat are available.
C++ Binding info can be found here.
Dragonboat examples are here.
Dragonboat is production ready.
For reporting bugs, please open an issue. For contributing improvements or new features, please send in the pull request.
Dragonboat is licensed under the Apache License Version 2.0. See LICENSE for details.
Third party code used in Dragonboat and their licenses is summarized here.