drummer

package
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 Go to latest Published: Mar 16, 2019 License: Apache-2.0 Imports: 31 Imported by: 0

README

About Drummer

Drummer is an optional component. It is provided as the reference implementation of the Master server for managing large number of distributed NodeHost instances -

  • Details about Raft clusters reported via NodeHost's IMasterClient are stored in the DrummerDB and replicated across multiple Drummer servers.
  • NodeHost and its managed Raft nodes are considered as dead when it fails to contact Drummer servers for certain amount of time.
  • A Drummer server will be elected as the leader, it monitors the the availability of known NodeHost instances and associated Raft clusters, new Raft nodes will be spawned whenever necessary to replace failed ones.
  • User applications can query Drummer servers to locate interested Raft clusters. Raft clusters can then be accessed via the NodeHost API interface.

Drummer is also used in Dragonboat's monkey testing to guard the correctness of our Raft implementation.

When to use Master servers

Do not use Master servers when -

  • you have a small and simple deployment
  • you want to use your own facilities for node failure detection and handling
  • you want to have full control of the system

Use Master servers when -

  • you have large number of NodeHost instances
  • you want to delegate node failure detection and handling to a dedicated component known as Master servers

Resources

dragonboat-drummer-cmd is a simple command line tool used to interact with Drummer.

Deployment

There are two major phases involved to deploy and operate a Dragonboat based application using Drummer.

First is the launch phase, dragonboat-drummer-cmd can be used to define what Raft clusters are required and how many replicas in each cluster. Once all required Raft clusters are defines, they can be launched. Drummer will select suitable NodeHosts and spawn Raft nodes on selected NodeHosts. This launch process typically takes less than one minute and NodeHosts are expected not to crash during the launch phase.

Once the above launch phase is successfully completed, the system enters the operation phase. Drummer then starts to monitor all connected NodeHosts and repair failed Raft nodes by spawning new ones on other available NodeHosts when necessary. Users can add more NodeHosts to expand resources available to Drummer or to replace failed NodeHost servers. The dragonboat-drummer-cmd tool can be used to query NodeHost and Raft cluster status.

Requirements

Drummer depends on Go gRPC. To get Go gRPC -

$ go get -u google.golang.org/grpc

If you are behind the GFW and always timeout on golang.org/x packages, there are easy ways to workaround.

Documentation

Overview

Package drummer implements a reference Master server and client. They can manage and monitor large number of NodeHosts distributed across the network. Raft nodes running on failed NodeHost instances can be detected and replaced automatically by Drummer servers, thus bring in high availability to the system.

Note that both Drummer servers and its IMasterClient client provided in this package are optional.

Index

Constants

View Source 
const (
	// DBUpdated indicates DB has been successfully updated
	DBUpdated uint64 = 0
	// ClusterExists means DB update has been rejected as the cluster to
	// be created already exist.
	ClusterExists uint64 = 1
	// DBBootstrapped means DB update has been rejected as the
	// DB has been bootstrapped.
	DBBootstrapped uint64 = 2
)
View Source 
const (
	// DBKVUpdated means the KV update has been successfully completed
	DBKVUpdated uint64 = 0
	// DBKVFinalized indicates that the KV update is rejected as there is
	// already a finalized record in DB with the specified key
	DBKVFinalized uint64 = 1
	// DBKVRejected indicates that the KV update is rejected
	DBKVRejected uint64 = 2
)

Variables

View Source 
var (
	// ErrDBKVUpdateRejected indicates that the update for KV has been
	// rejected.
	ErrDBKVUpdateRejected = errors.New("DB KV update rejected")
)
View Source 
var (
	// ErrInvalidRequest indicates the request can not be fulfilled as it is
	// regarded as invalid.
	ErrInvalidRequest = errors.New("invalid drummer request")
)

Functions

func AddDrummerServer 

func AddDrummerServer(ctx context.Context, client pb.DrummerClient,
	nodeID uint64, address string) (*pb.Empty, error)

AddDrummerServer adds a new drummer node with specified nodeID and address to the Drummer cluster.

func EntityFailed 

func EntityFailed(lastTick uint64, currentTick uint64) bool

EntityFailed returns whether the timeline indicates that the entity has failed.

func GRPCError 

func GRPCError(err error) error

GRPCError converts errors defined in package multiraft to gRPC errors

func GetClusterCollection 

func GetClusterCollection(ctx context.Context,
	client pb.DrummerClient) (*pb.ClusterCollection, error)

GetClusterCollection returns known clusters from the Drummer server.

func GetClusterConfig 

func GetClusterConfig() pb.Config

GetClusterConfig returns the configuration used by Raft clusters managed by the drummer server.

func GetClusterConfigFromFile 

func GetClusterConfigFromFile(fp string) pb.Config

GetClusterConfigFromFile returns the DrummerConfig read from the specified configuration file.

func GetClusterStates 

func GetClusterStates(ctx context.Context,
	client pb.DrummerClient, clusters []uint64) (*pb.ClusterStates, error)

GetClusterStates returns cluster states known to the Drummer server.

func GetNodeHostCollection 

func GetNodeHostCollection(ctx context.Context,
	client pb.DrummerClient) (*pb.NodeHostCollection, error)

GetNodeHostCollection returns nodehosts known to the Drummer.

func NewDB 

func NewDB(clusterID uint64, nodeID uint64) statemachine.IStateMachine

NewDB creates a new DB instance.

func RemoveDrummerServer 

func RemoveDrummerServer(ctx context.Context, client pb.DrummerClient,
	nodeID uint64) (*pb.Empty, error)

RemoveDrummerServer removes the specified node from the Drummer cluster.

func SubmitBootstrappped 

func SubmitBootstrappped(ctx context.Context,
	client pb.DrummerClient) error

SubmitBootstrappped sets the bootstrapped flag on Drummer server.

func SubmitCreateDrummerChange 

func SubmitCreateDrummerChange(ctx context.Context, client pb.DrummerClient,
	clusterID uint64, members []uint64, appName string) error

SubmitCreateDrummerChange submits Drummer change used for defining clusters.

func SubmitRegions 

func SubmitRegions(ctx context.Context,
	client pb.DrummerClient, region pb.Regions) error

SubmitRegions submits regions info to the Drummer server.

Types

type DB 

type DB struct {
	ClusterID      uint64 `json:"-"`
	NodeID         uint64 `json:"-"`
	Version        uint64
	Tick           uint64
	LaunchDeadline uint64
	Failed         bool
	Clusters       map[uint64]*pb.Cluster
	KVMap          map[string][]byte
	ClusterImage   *multiCluster
	NodeHostImage  *multiNodeHost
	NodeHostInfo   map[string]pb.NodeHostInfo
	Requests       map[string][]pb.NodeHostRequest
	Outgoing       map[string][]pb.NodeHostRequest
}

DB is the struct used to maintain the raft-backed Drummer DB

func (*DB) Close 

func (d *DB) Close()

Close closes the DB instance.

func (*DB) GetHash 

func (d *DB) GetHash() uint64

GetHash returns the state machine hash.

func (*DB) Lookup 

func (d *DB) Lookup(key []byte) []byte

Lookup performances local data lookup on the DB.

func (*DB) RecoverFromSnapshot 

func (d *DB) RecoverFromSnapshot(r io.Reader, files []statemachine.SnapshotFile,
	done <-chan struct{}) error

RecoverFromSnapshot recovers DB state from a snapshot.

func (*DB) SaveSnapshot 

func (d *DB) SaveSnapshot(w io.Writer, fc statemachine.ISnapshotFileCollection,
	done <-chan struct{}) (uint64, error)

SaveSnapshot generates a snapshot of the DB

func (*DB) Update 

func (d *DB) Update(data []byte) uint64

Update updates the DB instance.

type Drummer 

type Drummer struct {
	// contains filtered or unexported fields
}

Drummer is the main struct used by the Drummer server

func NewDrummer 

func NewDrummer(nh *dragonboat.NodeHost, grpcHost string) *Drummer

NewDrummer creates a new Drummer instance.

func (*Drummer) Start 

func (d *Drummer) Start()

Start starts the Drummer server.

func (*Drummer) Stop 

func (d *Drummer) Stop()

Stop gracefully stops the Drummer server.

type NodehostAPI 

type NodehostAPI struct {
	// contains filtered or unexported fields
}

NodehostAPI implements the grpc server used for making raft IO requests.

func NewNodehostAPI 

func NewNodehostAPI(address string, nh *dragonboat.NodeHost) *NodehostAPI

NewNodehostAPI creates a new NodehostAPI server instance.

func (*NodehostAPI) CloseSession 

func (api *NodehostAPI) CloseSession(ctx context.Context,
	cs *client.Session) (*pb.SessionResponse, error)

CloseSession closes the specified client session instance.

func (*NodehostAPI) GetSession 

func (api *NodehostAPI) GetSession(ctx context.Context,
	req *pb.SessionRequest) (*client.Session, error)

GetSession gets a new client session instance.

func (*NodehostAPI) Propose 

func (api *NodehostAPI) Propose(ctx context.Context,
	req *pb.RaftProposal) (*pb.RaftResponse, error)

Propose makes a propose.

func (*NodehostAPI) Read 

func (api *NodehostAPI) Read(ctx context.Context,
	req *pb.RaftReadIndex) (*pb.RaftResponse, error)

Read makes a linearizable read operation.

func (*NodehostAPI) Stop 

func (api *NodehostAPI) Stop()

Stop stops the NodehostAPI instance.

Source Files

View all Source files

Directories

Path Synopsis
Package client contains RPC client functions and structs.
 Package client contains RPC client functions and structs.
Package drummerpb is a generated protocol buffer package.
 Package drummerpb is a generated protocol buffer package.
Package multiraftpb is a generated protocol buffer package.
 Package multiraftpb is a generated protocol buffer package.
Package server contains server programs used by the drummer package.
 Package server contains server programs used by the drummer package.
drummer
Drummer is dragonboat's drummer server program.
 Drummer is dragonboat's drummer server program.
drummercmd
Drummercmd is a drummer client program.
 Drummercmd is a drummer client program.
nodehost
Nodehost is dragonboat's nodehost server program.
 Nodehost is dragonboat's nodehost server program.

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