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main.go: Remove sleep during shutdown #777

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merged 1 commit into from
Jul 21, 2017
Merged

main.go: Remove sleep during shutdown #777

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89 changes: 58 additions & 31 deletions main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,8 @@ import (

"github.com/joho/godotenv"

"sync"

// Backends need to be imported for their init() to get executed and them to register
"github.com/coreos/flannel/backend"
_ "github.com/coreos/flannel/backend/alivpc"
Expand Down Expand Up @@ -230,31 +232,48 @@ func main() {
sigs := make(chan os.Signal, 1)
signal.Notify(sigs, os.Interrupt, syscall.SIGTERM)

// This is the main context that everything should run in.
// All spawned goroutines should exit when cancel is called on this context.
// Go routines spawned from main.go coordinate using a WaitGroup. This provides a mechanism to allow the shutdownHandler goroutine
// to block until all the goroutines return . If those goroutines spawn other goroutines then they are responsible for
// blocking and returning only when cancel() is called.
ctx, cancel := context.WithCancel(context.Background())
go shutdown(sigs, cancel)
wg := sync.WaitGroup{}

wg.Add(1)
go func() {
shutdownHandler(ctx, sigs, cancel)
wg.Done()
}()

if opts.healthzPort > 0 {
// It's not super easy to shutdown the HTTP server so don't attempt to stop it cleanly
go mustRunHealthz()
}

// Fetch the network config (i.e. what backend to use etc..).
config, err := getConfig(ctx, sm)
if err == errCanceled {
exit()
wg.Wait()
os.Exit(0)
}

// Create a backend manager then use it to create the backend and register the network with it.
bm := backend.NewManager(ctx, sm, extIface)
be, err := bm.GetBackend(config.BackendType)
if err != nil {
log.Errorf("Error fetching backend: %s", err)
exit()
cancel()
wg.Wait()
os.Exit(1)
}

bn, err := be.RegisterNetwork(ctx, config)
if err != nil {
log.Errorf("Error registering network: %s", err)
exit()
cancel()
wg.Wait()
os.Exit(1)
}

// Set up ipMasq if needed
Expand All @@ -280,42 +299,44 @@ func main() {
}

// Start "Running" the backend network. This will block until the context is done so run in another goroutine.
go bn.Run(ctx)
log.Infof("Finished starting backend.")
log.Info("Running backend.")
wg.Add(1)
go func() {
bn.Run(ctx)
wg.Done()
}()

daemon.SdNotify(false, "READY=1")

// Kube subnet mgr doesn't lease the subnet for this node - it just uses the podCidr that's already assigned.
if opts.kubeSubnetMgr {
// Wait for the shutdown to be signalled
<-ctx.Done()
} else {
// Block waiting to renew the lease
_ = MonitorLease(ctx, sm, bn)
if !opts.kubeSubnetMgr {
err = MonitorLease(ctx, sm, bn, &wg)
if err == errInterrupted {
// The lease was "revoked" - shut everything down
cancel()
}
}

// To get to here, the Cancel signal must have been received or the lease has been revoked.
exit()
}

func exit() {
// Wait just a second for the cancel signal to propagate everywhere, then just exit cleanly.
log.Info("Waiting for cancel to propagate...")
time.Sleep(time.Second)
log.Info("Exiting...")
log.Info("Waiting for all goroutines to exit")
// Block waiting for all the goroutines to finish.
wg.Wait()
log.Info("Exiting cleanly...")
os.Exit(0)
}

func shutdown(sigs chan os.Signal, cancel context.CancelFunc) {
// Wait for the shutdown signal.
<-sigs
func shutdownHandler(ctx context.Context, sigs chan os.Signal, cancel context.CancelFunc) {
// Wait for the context do be Done or for the signal to come in to shutdown.
select {
case <-ctx.Done():
log.Info("Stopping shutdownHandler...")
case <-sigs:
// Call cancel on the context to close everything down.
cancel()
log.Info("shutdownHandler sent cancel signal...")
}

// Unregister to get default OS nuke behaviour in case we don't exit cleanly
signal.Stop(sigs)
log.Info("Starting shutdown...")

// Call cancel on the context to close everything down.
cancel()
log.Info("Sent cancel signal...")
}

func getConfig(ctx context.Context, sm subnet.Manager) (*subnet.Config, error) {
Expand All @@ -339,10 +360,16 @@ func getConfig(ctx context.Context, sm subnet.Manager) (*subnet.Config, error) {
}
}

func MonitorLease(ctx context.Context, sm subnet.Manager, bn backend.Network) error {
func MonitorLease(ctx context.Context, sm subnet.Manager, bn backend.Network, wg *sync.WaitGroup) error {
// Use the subnet manager to start watching leases.
evts := make(chan subnet.Event)
go subnet.WatchLease(ctx, sm, bn.Lease().Subnet, evts)

wg.Add(1)
go func() {
subnet.WatchLease(ctx, sm, bn.Lease().Subnet, evts)
wg.Done()
}()

renewMargin := time.Duration(opts.subnetLeaseRenewMargin) * time.Minute
dur := bn.Lease().Expiration.Sub(time.Now()) - renewMargin

Expand Down