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role_manager.go
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/
role_manager.go
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package manager
import (
"time"
"github.com/docker/swarmkit/api"
"github.com/docker/swarmkit/log"
"github.com/docker/swarmkit/manager/state"
"github.com/docker/swarmkit/manager/state/raft"
"github.com/docker/swarmkit/manager/state/store"
"golang.org/x/net/context"
)
const roleReconcileInterval = 5 * time.Second
// roleManager reconciles the raft member list with desired role changes.
type roleManager struct {
ctx context.Context
cancel func()
store *store.MemoryStore
raft *raft.Node
doneChan chan struct{}
// pending contains changed nodes that have not yet been reconciled in
// the raft member list.
pending map[string]*api.Node
}
// newRoleManager creates a new roleManager.
func newRoleManager(store *store.MemoryStore, raftNode *raft.Node) *roleManager {
ctx, cancel := context.WithCancel(context.Background())
return &roleManager{
ctx: ctx,
cancel: cancel,
store: store,
raft: raftNode,
doneChan: make(chan struct{}),
pending: make(map[string]*api.Node),
}
}
// Run is roleManager's main loop.
func (rm *roleManager) Run() {
defer close(rm.doneChan)
var (
nodes []*api.Node
ticker *time.Ticker
tickerCh <-chan time.Time
)
watcher, cancelWatch, err := store.ViewAndWatch(rm.store,
func(readTx store.ReadTx) error {
var err error
nodes, err = store.FindNodes(readTx, store.All)
return err
},
state.EventUpdateNode{})
defer cancelWatch()
if err != nil {
log.L.WithError(err).Error("failed to check nodes for role changes")
} else {
for _, node := range nodes {
rm.pending[node.ID] = node
rm.reconcileRole(node)
}
if len(rm.pending) != 0 {
ticker = time.NewTicker(roleReconcileInterval)
tickerCh = ticker.C
}
}
for {
select {
case event := <-watcher:
node := event.(state.EventUpdateNode).Node
rm.pending[node.ID] = node
rm.reconcileRole(node)
if len(rm.pending) != 0 && ticker == nil {
ticker = time.NewTicker(roleReconcileInterval)
tickerCh = ticker.C
}
case <-tickerCh:
for _, node := range rm.pending {
rm.reconcileRole(node)
}
if len(rm.pending) == 0 {
ticker.Stop()
ticker = nil
tickerCh = nil
}
case <-rm.ctx.Done():
if ticker != nil {
ticker.Stop()
}
return
}
}
}
func (rm *roleManager) reconcileRole(node *api.Node) {
if node.Role == node.Spec.DesiredRole {
// Nothing to do.
delete(rm.pending, node.ID)
return
}
// Promotion can proceed right away.
if node.Spec.DesiredRole == api.NodeRoleManager && node.Role == api.NodeRoleWorker {
err := rm.store.Update(func(tx store.Tx) error {
updatedNode := store.GetNode(tx, node.ID)
if updatedNode == nil || updatedNode.Spec.DesiredRole != node.Spec.DesiredRole || updatedNode.Role != node.Role {
return nil
}
updatedNode.Role = api.NodeRoleManager
return store.UpdateNode(tx, updatedNode)
})
if err != nil {
log.L.WithError(err).Errorf("failed to promote node %s", node.ID)
} else {
delete(rm.pending, node.ID)
}
} else if node.Spec.DesiredRole == api.NodeRoleWorker && node.Role == api.NodeRoleManager {
// Check for node in memberlist
member := rm.raft.GetMemberByNodeID(node.ID)
if member != nil {
// Quorum safeguard
if !rm.raft.CanRemoveMember(member.RaftID) {
// TODO(aaronl): Retry later
log.L.Debugf("can't demote node %s at this time: removing member from raft would result in a loss of quorum", node.ID)
return
}
rmCtx, rmCancel := context.WithTimeout(rm.ctx, 5*time.Second)
defer rmCancel()
if err := rm.raft.RemoveMember(rmCtx, member.RaftID); err != nil {
// TODO(aaronl): Retry later
log.L.WithError(err).Debugf("can't demote node %s at this time", node.ID)
return
}
}
err := rm.store.Update(func(tx store.Tx) error {
updatedNode := store.GetNode(tx, node.ID)
if updatedNode == nil || updatedNode.Spec.DesiredRole != node.Spec.DesiredRole || updatedNode.Role != node.Role {
return nil
}
updatedNode.Role = api.NodeRoleWorker
return store.UpdateNode(tx, updatedNode)
})
if err != nil {
log.L.WithError(err).Errorf("failed to demote node %s", node.ID)
} else {
delete(rm.pending, node.ID)
}
}
}
// Stop stops the roleManager and waits for the main loop to exit.
func (rm *roleManager) Stop() {
rm.cancel()
<-rm.doneChan
}