add basic synchronization using mutex

app/model.go

@@ -6,16 +6,15 @@ import (
 	"strings"
 )
 
-type Cluster struct {
-	pve   ProxmoxClient
-	Hosts map[string]*Host
-}
-
 func (cluster *Cluster) Init(pve ProxmoxClient) {
 	cluster.pve = pve
 }
 
-func (cluster *Cluster) Rebuild() error {
+func (cluster *Cluster) Sync() error {
+	// aquire lock on cluster, release on return
+	cluster.lock.Lock()
+	defer cluster.lock.Unlock()
+
 	cluster.Hosts = make(map[string]*Host)
 
 	// get all nodes
@@ -26,7 +25,7 @@ func (cluster *Cluster) Rebuild() error {
 	// for each node:
 	for _, hostName := range nodes {
 		// rebuild node
-		err := cluster.RebuildNode(hostName)
+		err := cluster.RebuildHost(hostName)
 		if err != nil {
 			return err
 		}
@@ -35,17 +34,51 @@ func (cluster *Cluster) Rebuild() error {
 	return nil
 }
 
-func (cluster *Cluster) RebuildNode(hostName string) error {
+// get a node in the cluster
+func (cluster *Cluster) GetHost(hostName string) (*Host, error) {
+	host_ch := make(chan *Host)
+	err_ch := make(chan error)
+
+	go func() {
+		// aquire cluster lock
+		cluster.lock.Lock()
+		defer cluster.lock.Unlock()
+		// get host
+		host, ok := cluster.Hosts[hostName]
+		if !ok {
+			host_ch <- nil
+			err_ch <- fmt.Errorf("%s not in cluster", hostName)
+		}
+		// aquire host lock to wait in case of a concurrent write
+		host.lock.Lock()
+		defer host.lock.Unlock()
+
+		host_ch <- host
+		err_ch <- nil
+	}()
+
+	host := <-host_ch
+	err := <-err_ch
+	return host, err
+}
+
+func (cluster *Cluster) RebuildHost(hostName string) error {
 	host, err := cluster.pve.Node(hostName)
 	if err != nil {
 		return err
 	}
-	cluster.Hosts[hostName] = &host
+
+	// aquire lock on host, release on return
+	host.lock.Lock()
+	defer host.lock.Unlock()
+
+	cluster.Hosts[hostName] = host
 
 	// get node's VMs
 	vms, err := host.VirtualMachines()
 	if err != nil {
 		return err
+
 	}
 	for _, vmid := range vms {
 		err := host.RebuildVM(vmid)
@@ -69,13 +102,44 @@ func (cluster *Cluster) RebuildNode(hostName string) error {
 	return nil
 }
 
+func (host *Host) GetInstance(vmid uint) (*Instance, error) {
+	instance_ch := make(chan *Instance)
+	err_ch := make(chan error)
+
+	go func() {
+		// aquire host lock
+		host.lock.Lock()
+		defer host.lock.Unlock()
+		// get instance
+		instance, ok := host.Instances[vmid]
+		if !ok {
+			instance_ch <- nil
+			err_ch <- fmt.Errorf("vmid %d not in host %s", vmid, host.Name)
+		}
+		// aquire instance lock to wait in case of a concurrent write
+		instance.lock.Lock()
+		defer instance.lock.Unlock()
+
+		instance_ch <- instance
+		err_ch <- nil
+	}()
+
+	instance := <-instance_ch
+	err := <-err_ch
+	return instance, err
+}
+
 func (host *Host) RebuildVM(vmid uint) error {
 	instance, err := host.VirtualMachine(vmid)
 	if err != nil {
 		return err
 	}
 
-	host.Instances[vmid] = &instance
+	// aquire lock on instance, release on return
+	instance.lock.Lock()
+	defer instance.lock.Unlock()
+
+	host.Instances[vmid] = instance
 
 	for volid := range instance.configDisks {
 		instance.RebuildVolume(host, volid)
@@ -86,7 +150,7 @@ func (host *Host) RebuildVM(vmid uint) error {
 	}
 
 	for deviceid := range instance.configHostPCIs {
-		instance.RebuildDevice(*host, deviceid)
+		instance.RebuildDevice(host, deviceid)
 	}
 
 	return nil
@@ -98,7 +162,11 @@ func (host *Host) RebuildCT(vmid uint) error {
 		return err
 	}
 
-	host.Instances[vmid] = &instance
+	// aquire lock on instance, release on return
+	instance.lock.Lock()
+	defer instance.lock.Unlock()
+
+	host.Instances[vmid] = instance
 
 	for volid := range instance.configDisks {
 		instance.RebuildVolume(host, volid)
@@ -114,12 +182,12 @@ func (host *Host) RebuildCT(vmid uint) error {
 func (instance *Instance) RebuildVolume(host *Host, volid string) error {
 	volumeDataString := instance.configDisks[volid]
 
-	volume, _, _, err := GetVolumeInfo(*host, volumeDataString)
+	volume, _, _, err := GetVolumeInfo(host, volumeDataString)
 	if err != nil {
 		return err
 	}
 
-	instance.Volumes[volid] = &volume
+	instance.Volumes[volid] = volume
 
 	return nil
 }
@@ -136,12 +204,12 @@ func (instance *Instance) RebuildNet(netid string) error {
 		return nil
 	}
 
-	instance.Nets[uint(idnum)] = &netinfo
+	instance.Nets[uint(idnum)] = netinfo
 
 	return nil
 }
 
-func (instance *Instance) RebuildDevice(host Host, deviceid string) error {
+func (instance *Instance) RebuildDevice(host *Host, deviceid string) error {
 	instanceDevice, ok := instance.configHostPCIs[deviceid]
 	if !ok { // if device does not exist
 		return fmt.Errorf("%s not found in devices", deviceid)