README
¶
rafty
Rafty is yet another golang library that manage to replicate log state machine.
Details about Raft protocol can be found here
Reading this documentation is recommanded before going any further.
Check out these websites will also be useful:
Why another library?
There are many libraries out there implementing the search of an understandable consensus algorithm.
Unfortunately, I mostly found them difficult to understand as there is not so much clear documentation about how to use them.
As examples, we have production ready repositories like:
So let's try to redo the wheel with more explanations.
Supported features
Here is a list of the supported features of rafty:
- PreVote election
- Leader election
- [] Logs
- Log replication
- Submit write commands
- [] Submit read commands
- [] Log compaction
- [] Membership changes
- [] Add member
- [] remove member
- [] promote member
References
- https://github.com/logcabin/logcabin
- https://github.com/funktor/distributed-hash-table/tree/raft
- https://www.cncf.io/blog/2019/11/04/building-a-large-scale-distributed-storage-system-based-on-raft/
- https://www.sofastack.tech/en/projects/sofa-jraft/consistency-raft-jraft/
- https://github.com/baidu/braft/blob/master/docs/cn/raft_protocol.md
- https://cwiki.apache.org/confluence/display/KAFKA/KIP-595%3A+A+Raft+Protocol+for+the+Metadata+Quorum
- https://towardsdatascience.com/raft-algorithm-explained-2-30db4790cdef
- https://www.alibabacloud.com/blog/raft-engineering-practices-and-the-cluster-membership-change_597742
- https://github.com/lni/dragonboat
- https://github.com/lni/dragonboat-example
- https://github.com/PlatformLab/epaxos/tree/master
- https://www.cs.princeton.edu/courses/archive/fall18/cos418/docs/p7-raft.pdf
Documentation
¶
Index ¶
Constants ¶
const ( // GRPCAddress defines the default address to run the grpc server GRPCAddress string = "127.0.0.1" // GRPCPort define the default port to run the grpc server GRPCPort uint16 = 50051 )
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Peer ¶
type Peer struct {
// Address is the address of a peer node, must be just the ip or ip:port
Address string
// contains filtered or unexported fields
}
type Rafty ¶
type Rafty struct {
// LeaderLastContactDate is the last date we heard from the leader
LeaderLastContactDate *time.Time
// Logger expose zerolog so it can be override
Logger *zerolog.Logger
Status
// PreCandidatePeers hold the list of the peers
// that will be use to elect a new leader
// if no leader has been detected
PreCandidatePeers []Peer
// Peers hold the list of the peers
Peers []Peer
// TimeMultiplier is a scaling factor that will be used during election timeout
// by electionTimeoutMin/electionTimeoutMax/leaderHeartBeatTimeout in order to avoid cluster instability
// The default value is 1 and the maximum is 10
TimeMultiplier uint
// MinimumClusterSize is the size minimum to have before starting prevote or election campain
// default is 3
// all members of the cluster will be contacted before any other tasks
MinimumClusterSize uint64
// MaxAppendEntries will hold how much append entries the leader will send to the follower at once
MaxAppendEntries uint64
// DataDir is the default data directory that will be used to store all data on the disk
// Defaults to os.TempDir()/rafty ex: /tmp/rafty
DataDir string
// PersistDataOnDisk is a boolean that allow us to persist data on disk
PersistDataOnDisk bool
// contains filtered or unexported fields
}
Rafty is a struct representing the raft requirements
func NewServer ¶
NewServer instantiate default configuration of the gRPC server and rafty to later start or stop it
func (*Rafty) SendGetLeaderRequest ¶
func (r *Rafty) SendGetLeaderRequest()
SendGetLeaderRequest allow the current node ask to other nodes who is the actual leader it also permit to get id of other nodes
func (*Rafty) Start ¶
Start permits to start the gRPC server with the provided configuration ready parameter is the channel that will be used by server to accept client requests
func (*Rafty) Stop ¶
func (r *Rafty) Stop()
Stop permits to stop the gRPC server and Rafty with the provided configuration
func (*Rafty) SubmitCommand ¶
type State ¶
type State uint32
State represent the current status of the raft server. The state can only be Leader, Candidate, Follower, ReadOnly, Down
const ( // Down state is a node that has been unreachable for a long period of time Down State = iota // ReadOnly state is a node that does not pariticipate into the voting campain // It's a passive node that issue no requests on his own but simply respond from the leader // This node can never become a follower ReadOnly // Follower state is a node that participate into the voting campain // It's a passive node that issue no requests on his own but simply respond from the leader // This node can become a Precandidate if all requirements are available Follower // Candidate state is a node that participate into the voting campain. // It can become a Leader Candidate // Leader state is a node that was previously a Candidate // It received the majority of the votes including itself and get elected as the Leader. // It will then handle all client requests // Writes requests can only be done on the leader Leader )
type Status ¶
type Status struct {
// ID of the current raft server
ID string
// Address is the current address of the raft server
Address net.TCPAddr
// State of the current raft server
// Can only be Leader, Candidate, Follower, ReadOnly, Down
State
// CurrentTerm is latest term seen during the voting campain
CurrentTerm uint64
// CurrentCommitIndex is the index of the highest log entry know to be commited
CurrentCommitIndex uint64
// LastApplied is the index of the highest log entry applied to the current raft server
LastApplied uint64
}
Status of the raft server
Source Files
Directories