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package raft
import (
"io"
"time"
)
// RPCResponse captures both a response and a potential error.
type RPCResponse struct {
Response interface{}
Error error
}
// RPC has a command, and provides a response mechanism.
type RPC struct {
Command interface{}
Reader io.Reader // Set only for InstallSnapshot
RespChan chan<- RPCResponse
}
// Respond is used to respond with a response, error or both
func (r *RPC) Respond(resp interface{}, err error) {
r.RespChan <- RPCResponse{resp, err}
}
// Transport provides an interface for network transports
// to allow Raft to communicate with other nodes.
type Transport interface {
// Consumer returns a channel that can be used to
// consume and respond to RPC requests.
Consumer() <-chan RPC
// LocalAddr is used to return our local address to distinguish from our peers.
LocalAddr() ServerAddress
// AppendEntriesPipeline returns an interface that can be used to pipeline
// AppendEntries requests.
AppendEntriesPipeline(id ServerID, target ServerAddress) (AppendPipeline, error)
// AppendEntries sends the appropriate RPC to the target node.
AppendEntries(id ServerID, target ServerAddress, args *AppendEntriesRequest, resp *AppendEntriesResponse) error
// RequestVote sends the appropriate RPC to the target node.
RequestVote(id ServerID, target ServerAddress, args *RequestVoteRequest, resp *RequestVoteResponse) error
// InstallSnapshot is used to push a snapshot down to a follower. The data is read from
// the ReadCloser and streamed to the client.
InstallSnapshot(id ServerID, target ServerAddress, args *InstallSnapshotRequest, resp *InstallSnapshotResponse, data io.Reader) error
// EncodePeer is used to serialize a peer's address.
EncodePeer(id ServerID, addr ServerAddress) []byte
// DecodePeer is used to deserialize a peer's address.
DecodePeer([]byte) ServerAddress
// SetHeartbeatHandler is used to setup a heartbeat handler
// as a fast-pass. This is to avoid head-of-line blocking from
// disk IO. If a Transport does not support this, it can simply
// ignore the call, and push the heartbeat onto the Consumer channel.
SetHeartbeatHandler(cb func(rpc RPC))
// TimeoutNow is used to start a leadership transfer to the target node.
TimeoutNow(id ServerID, target ServerAddress, args *TimeoutNowRequest, resp *TimeoutNowResponse) error
}
// WithClose is an interface that a transport may provide which
// allows a transport to be shut down cleanly when a Raft instance
// shuts down.
//
// It is defined separately from Transport as unfortunately it wasn't in the
// original interface specification.
type WithClose interface {
// Close permanently closes a transport, stopping
// any associated goroutines and freeing other resources.
Close() error
}
// LoopbackTransport is an interface that provides a loopback transport suitable for testing
// e.g. InmemTransport. It's there so we don't have to rewrite tests.
type LoopbackTransport interface {
Transport // Embedded transport reference
WithPeers // Embedded peer management
WithClose // with a close routine
}
// WithPeers is an interface that a transport may provide which allows for connection and
// disconnection. Unless the transport is a loopback transport, the transport specified to
// "Connect" is likely to be nil.
type WithPeers interface {
Connect(peer ServerAddress, t Transport) // Connect a peer
Disconnect(peer ServerAddress) // Disconnect a given peer
DisconnectAll() // Disconnect all peers, possibly to reconnect them later
}
// AppendPipeline is used for pipelining AppendEntries requests. It is used
// to increase the replication throughput by masking latency and better
// utilizing bandwidth.
type AppendPipeline interface {
// AppendEntries is used to add another request to the pipeline.
// The send may block which is an effective form of back-pressure.
AppendEntries(args *AppendEntriesRequest, resp *AppendEntriesResponse) (AppendFuture, error)
// Consumer returns a channel that can be used to consume
// response futures when they are ready.
Consumer() <-chan AppendFuture
// Close closes the pipeline and cancels all inflight RPCs
Close() error
}
// AppendFuture is used to return information about a pipelined AppendEntries request.
type AppendFuture interface {
Future
// Start returns the time that the append request was started.
// It is always OK to call this method.
Start() time.Time
// Request holds the parameters of the AppendEntries call.
// It is always OK to call this method.
Request() *AppendEntriesRequest
// Response holds the results of the AppendEntries call.
// This method must only be called after the Error
// method returns, and will only be valid on success.
Response() *AppendEntriesResponse
}
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