Swarmkit notes (--manager) switch roles

This is a creation in Article, where the information may have evolved or changed.

ManagerA struct (defined in manager/manager.go ) consists of a *raft.Node member:

// Manager is the cluster manager for Swarm.// This is the high-level object holding and initializing all the manager// subsystems.type Manager struct {    ......    RaftNode   *raft.Node    ......}

and raft.Node (defined in manager/state/raft/raft.go ) contains a *events.Broadcaster member that receives a change manager role of message ( leader or a follower ):

// Node represents the Raft Node useful// configuration.type Node struct {    ......    leadershipBroadcast *events.Broadcaster    ......}   

Send change manager role The current code is located at manager/state/raft/raft.go :

Run is the main loop for a Raft node, it goes along the state machine,//acting on the messages received from other RAF T nodes in the cluster.////before running the main loop, it first starts the raft node based on saved//cluster state. If no saved state exists, it starts a single-node cluster.func (n *node) Run (CTX context.  Context) Error {.../If we cease to is the leader, we must cancel//any proposals that is Currently waiting for//a quorum to acknowledge them. It is the still//possible for these to become committed, but/or if that happens we'll apply them as            any//follower would. If Rd. Softstate! = Nil {if wasleader && Rd. Softstate.raftstate! = raft. Stateleader {Wasleader = False N.wait.cancelall () if atomic. LoadUint32 (&n.signalledleadership) = = 1 {atomic. StoreUint32 (&n.signaLledleadership, 0) n.leadershipbroadcast.write (isfollower)}} El Se if!wasleader && Rd. Softstate.raftstate = = Raft. Stateleader {Wasleader = true}} if Wasleader && atomic. LoadUint32 (&n.signalledleadership)! = 1 {//If all the entries in the log has become/                /committed, broadcast our leadership status. If N.caughtup () {Atomic.            StoreUint32 (&n.signalledleadership, 1) n.leadershipbroadcast.write (Isleader)} }    ......}

The code that receives the message is in the Manager.Run() function ( manager/manager.go ):

// Run starts all manager sub-systems and the gRPC server at the configured// address.// The call never returns unless an error occurs or `Stop()` is called.func (m *Manager) Run(parent context.Context) error {    ......    leadershipCh, cancel := m.RaftNode.SubscribeLeadership()    defer cancel()    go m.handleLeadershipEvents(ctx, leadershipCh)    ......    go func() {            err := m.RaftNode.Run(ctx)            if err != nil {                log.G(ctx).Error(err)                m.Stop(ctx)            }        }()    ......}

Node.SubscribeLeadership()And Manager.handleLeadershipEvents() the code is relatively simple, no longer repeat.