libnetwork: rewrite Network.isClusterEligible to return agent

This function was used to check if the network is a multi-host, swarm-scoped
network. Part of this check involved a check whether the cluster-agent was
present.

In all places where this function was used, the next step after checking if
the network was "cluster eligible", was to get the agent, and (again) check
if it was not nil.

This patch rewrites the isClusterEligible utility into a clusterAgent utility,
which both checks if the network is cluster-eligible, and returns the agent
(if set). For convenience, an "ok" bool is added, which callers can use to
return early (although just checking for nilness would likely have been
sufficient).

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

libnetwork/agent.go

@@ -108,8 +108,8 @@ func resolveAddr(addrOrInterface string) (net.IP, error) {
 func (c *Controller) handleKeyChange(keys []*types.EncryptionKey) error {
 	drvEnc := discoverapi.DriverEncryptionUpdate{}
 
-	a := c.getAgent()
-	if a == nil {
+	agent := c.getAgent()
+	if agent == nil {
 		log.G(context.TODO()).Debug("Skipping key change as agent is nil")
 		return nil
 	}
@@ -168,14 +168,14 @@ func (c *Controller) handleKeyChange(keys []*types.EncryptionKey) error {
 	c.mu.Unlock()
 
 	if len(added) > 0 {
-		a.networkDB.SetKey(added)
+		agent.networkDB.SetKey(added)
 	}
 
 	key, _, err := c.getPrimaryKeyTag(subsysGossip)
 	if err != nil {
 		return err
 	}
-	a.networkDB.SetPrimaryKey(key)
+	agent.networkDB.SetPrimaryKey(key)
 
 	key, tag, err := c.getPrimaryKeyTag(subsysIPSec)
 	if err != nil {
@@ -185,7 +185,7 @@ func (c *Controller) handleKeyChange(keys []*types.EncryptionKey) error {
 	drvEnc.PrimaryTag = tag
 
 	if len(deleted) > 0 {
-		a.networkDB.RemoveKey(deleted)
+		agent.networkDB.RemoveKey(deleted)
 	}
 
 	c.drvRegistry.WalkDrivers(func(name string, driver driverapi.Driver, capability driverapi.Capability) bool {
@@ -457,11 +457,8 @@ type epRecord struct {
 // Services returns a map of services keyed by the service name with the details
 // of all the tasks that belong to the service. Applicable only in swarm mode.
 func (n *Network) Services() map[string]ServiceInfo {
-	if !n.isClusterEligible() {
-		return nil
-	}
-	agent := n.getController().getAgent()
-	if agent == nil {
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return nil
 	}
 	nwID := n.ID()
@@ -532,36 +529,29 @@ func (n *Network) Services() map[string]ServiceInfo {
 	return sinfo
 }
 
-func (n *Network) isClusterEligible() bool {
+// clusterAgent returns the cluster agent if the network is a swarm-scoped,
+// multi-host network.
+func (n *Network) clusterAgent() (agent *nwAgent, ok bool) {
 	if n.scope != scope.Swarm || !n.driverIsMultihost() {
-		return false
+		return nil, false
 	}
-	return n.getController().getAgent() != nil
+	a := n.getController().getAgent()
+	return a, a != nil
 }
 
 func (n *Network) joinCluster() error {
-	if !n.isClusterEligible() {
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return nil
 	}
-
-	agent := n.getController().getAgent()
-	if agent == nil {
-		return nil
-	}
-
 	return agent.networkDB.JoinNetwork(n.ID())
 }
 
 func (n *Network) leaveCluster() error {
-	if !n.isClusterEligible() {
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return nil
 	}
-
-	agent := n.getController().getAgent()
-	if agent == nil {
-		return nil
-	}
-
 	return agent.networkDB.LeaveNetwork(n.ID())
 }
 
@@ -570,17 +560,14 @@ func (ep *Endpoint) addDriverInfoToCluster() error {
 		return nil
 	}
 	n := ep.getNetwork()
-	if !n.isClusterEligible() {
-		return nil
-	}
-
-	agent := n.getController().getAgent()
-	if agent == nil {
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return nil
 	}
 
+	nwID := n.ID()
 	for _, te := range ep.joinInfo.driverTableEntries {
-		if err := agent.networkDB.CreateEntry(te.tableName, n.ID(), te.key, te.value); err != nil {
+		if err := agent.networkDB.CreateEntry(te.tableName, nwID, te.key, te.value); err != nil {
 			return err
 		}
 	}
@@ -592,17 +579,14 @@ func (ep *Endpoint) deleteDriverInfoFromCluster() error {
 		return nil
 	}
 	n := ep.getNetwork()
-	if !n.isClusterEligible() {
-		return nil
-	}
-
-	agent := n.getController().getAgent()
-	if agent == nil {
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return nil
 	}
 
+	nwID := n.ID()
 	for _, te := range ep.joinInfo.driverTableEntries {
-		if err := agent.networkDB.DeleteEntry(te.tableName, n.ID(), te.key); err != nil {
+		if err := agent.networkDB.DeleteEntry(te.tableName, nwID, te.key); err != nil {
 			return err
 		}
 	}
@@ -615,15 +599,8 @@ func (ep *Endpoint) addServiceInfoToCluster(sb *Sandbox) error {
 	}
 
 	n := ep.getNetwork()
-	if !n.isClusterEligible() {
-		return nil
-	}
-	c := n.getController()
-	agent := c.getAgent()
-	if agent == nil {
-		// this should not happen normally, as the network is not considered
-		// "ClusterEligible" if the agent is nil (in which case we wouldn't
-		// reach this code).
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return nil
 	}
 
@@ -659,12 +636,12 @@ func (ep *Endpoint) addServiceInfoToCluster(sb *Sandbox) error {
 		if n.ingress {
 			ingressPorts = ep.ingressPorts
 		}
-		if err := c.addServiceBinding(ep.svcName, ep.svcID, n.ID(), ep.ID(), name, ep.virtualIP, ingressPorts, ep.svcAliases, ep.myAliases, ep.Iface().Address().IP, "addServiceInfoToCluster"); err != nil {
+		if err := n.getController().addServiceBinding(ep.svcName, ep.svcID, n.ID(), ep.ID(), name, ep.virtualIP, ingressPorts, ep.svcAliases, ep.myAliases, ep.Iface().Address().IP, "addServiceInfoToCluster"); err != nil {
 			return err
 		}
 	} else {
 		// This is a container simply attached to an attachable network
-		if err := c.addContainerNameResolution(n.ID(), ep.ID(), name, ep.myAliases, ep.Iface().Address().IP, "addServiceInfoToCluster"); err != nil {
+		if err := n.getController().addContainerNameResolution(n.ID(), ep.ID(), name, ep.myAliases, ep.Iface().Address().IP, "addServiceInfoToCluster"); err != nil {
 			return err
 		}
 	}
@@ -700,15 +677,8 @@ func (ep *Endpoint) deleteServiceInfoFromCluster(sb *Sandbox, fullRemove bool, m
 	}
 
 	n := ep.getNetwork()
-	if !n.isClusterEligible() {
-		return nil
-	}
-	c := n.getController()
-	agent := c.getAgent()
-	if agent == nil {
-		// this should not happen normally, as the network is not considered
-		// "ClusterEligible" if the agent is nil (in which case we wouldn't
-		// reach this code).
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return nil
 	}
 
@@ -746,12 +716,12 @@ func (ep *Endpoint) deleteServiceInfoFromCluster(sb *Sandbox, fullRemove bool, m
 			if n.ingress {
 				ingressPorts = ep.ingressPorts
 			}
-			if err := c.rmServiceBinding(ep.svcName, ep.svcID, n.ID(), ep.ID(), name, ep.virtualIP, ingressPorts, ep.svcAliases, ep.myAliases, ep.Iface().Address().IP, "deleteServiceInfoFromCluster", true, fullRemove); err != nil {
+			if err := n.getController().rmServiceBinding(ep.svcName, ep.svcID, n.ID(), ep.ID(), name, ep.virtualIP, ingressPorts, ep.svcAliases, ep.myAliases, ep.Iface().Address().IP, "deleteServiceInfoFromCluster", true, fullRemove); err != nil {
 				return err
 			}
 		} else {
 			// This is a container simply attached to an attachable network
-			if err := c.delContainerNameResolution(n.ID(), ep.ID(), name, ep.myAliases, ep.Iface().Address().IP, "deleteServiceInfoFromCluster"); err != nil {
+			if err := n.getController().delContainerNameResolution(n.ID(), ep.ID(), name, ep.myAliases, ep.Iface().Address().IP, "deleteServiceInfoFromCluster"); err != nil {
 				return err
 			}
 		}
@@ -795,15 +765,12 @@ func (n *Network) addDriverWatches() {
 	if len(n.driverTables) == 0 {
 		return
 	}
-	if !n.isClusterEligible() {
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return
 	}
 
 	c := n.getController()
-	agent := c.getAgent()
-	if agent == nil {
-		return
-	}
 	for _, table := range n.driverTables {
 		ch, cancel := agent.networkDB.Watch(table.name, n.ID())
 		agent.Lock()
@@ -831,12 +798,8 @@ func (n *Network) addDriverWatches() {
 }
 
 func (n *Network) cancelDriverWatches() {
-	if !n.isClusterEligible() {
-		return
-	}
-
-	agent := n.getController().getAgent()
-	if agent == nil {
+	agent, ok := n.clusterAgent()
+	if !ok {
 		return
 	}