Merge pull request #23914 from tonistiigi/upadate-manager-error-message

Add better error messages for unavailable swarm commands

daemon/cluster/cluster.go

@@ -39,9 +39,6 @@ const (
 	maxReconnectDelay     = 30 * time.Second
 )
 
-// ErrNoManager is returned then a manager-only function is called on non-manager
-var ErrNoManager = fmt.Errorf("This node is not participating as a Swarm manager")
-
 // ErrNoSwarm is returned on leaving a cluster that was never initialized
 var ErrNoSwarm = fmt.Errorf("This node is not part of Swarm")
 
@@ -476,7 +473,7 @@ func (c *Cluster) Inspect() (types.Swarm, error) {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return types.Swarm{}, ErrNoManager
+		return types.Swarm{}, c.errNoManager()
 	}
 
 	swarm, err := getSwarm(c.getRequestContext(), c.client)
@@ -497,7 +494,7 @@ func (c *Cluster) Update(version uint64, spec types.Spec) error {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return ErrNoManager
+		return c.errNoManager()
 	}
 
 	swarm, err := getSwarm(c.getRequestContext(), c.client)
@@ -629,13 +626,25 @@ func (c *Cluster) isActiveManager() bool {
 	return c.conn != nil
 }
 
+// errNoManager returns error describing why manager commands can't be used.
+// Call with read lock.
+func (c *Cluster) errNoManager() error {
+	if c.node == nil {
+		return fmt.Errorf("This node is not a Swarm manager. Use \"docker swarm init\" or \"docker swarm join --manager\" to connect this node to Swarm and try again.")
+	}
+	if c.node.Manager() != nil {
+		return fmt.Errorf("This node is not a Swarm manager. Manager is being prepared or has trouble connecting to the cluster.")
+	}
+	return fmt.Errorf("This node is not a Swarm manager. Worker nodes can't be used to view or modify cluster state. Please run this command on a manager node or promote the current node to a manager.")
+}
+
 // GetServices returns all services of a managed swarm cluster.
 func (c *Cluster) GetServices(options apitypes.ServiceListOptions) ([]types.Service, error) {
 	c.RLock()
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return nil, ErrNoManager
+		return nil, c.errNoManager()
 	}
 
 	filters, err := newListServicesFilters(options.Filter)
@@ -664,7 +673,7 @@ func (c *Cluster) CreateService(s types.ServiceSpec) (string, error) {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return "", ErrNoManager
+		return "", c.errNoManager()
 	}
 
 	ctx := c.getRequestContext()
@@ -692,7 +701,7 @@ func (c *Cluster) GetService(input string) (types.Service, error) {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return types.Service{}, ErrNoManager
+		return types.Service{}, c.errNoManager()
 	}
 
 	service, err := getService(c.getRequestContext(), c.client, input)
@@ -708,7 +717,7 @@ func (c *Cluster) UpdateService(serviceID string, version uint64, spec types.Ser
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return ErrNoManager
+		return c.errNoManager()
 	}
 
 	serviceSpec, err := convert.ServiceSpecToGRPC(spec)
@@ -735,7 +744,7 @@ func (c *Cluster) RemoveService(input string) error {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return ErrNoManager
+		return c.errNoManager()
 	}
 
 	service, err := getService(c.getRequestContext(), c.client, input)
@@ -755,7 +764,7 @@ func (c *Cluster) GetNodes(options apitypes.NodeListOptions) ([]types.Node, erro
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return nil, ErrNoManager
+		return nil, c.errNoManager()
 	}
 
 	filters, err := newListNodesFilters(options.Filter)
@@ -783,7 +792,7 @@ func (c *Cluster) GetNode(input string) (types.Node, error) {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return types.Node{}, ErrNoManager
+		return types.Node{}, c.errNoManager()
 	}
 
 	node, err := getNode(c.getRequestContext(), c.client, input)
@@ -799,7 +808,7 @@ func (c *Cluster) UpdateNode(nodeID string, version uint64, spec types.NodeSpec)
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return ErrNoManager
+		return c.errNoManager()
 	}
 
 	nodeSpec, err := convert.NodeSpecToGRPC(spec)
@@ -826,7 +835,7 @@ func (c *Cluster) RemoveNode(input string) error {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return ErrNoManager
+		return c.errNoManager()
 	}
 
 	ctx := c.getRequestContext()
@@ -848,7 +857,7 @@ func (c *Cluster) GetTasks(options apitypes.TaskListOptions) ([]types.Task, erro
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return nil, ErrNoManager
+		return nil, c.errNoManager()
 	}
 
 	filters, err := newListTasksFilters(options.Filter)
@@ -876,7 +885,7 @@ func (c *Cluster) GetTask(input string) (types.Task, error) {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return types.Task{}, ErrNoManager
+		return types.Task{}, c.errNoManager()
 	}
 
 	task, err := getTask(c.getRequestContext(), c.client, input)
@@ -892,7 +901,7 @@ func (c *Cluster) GetNetwork(input string) (apitypes.NetworkResource, error) {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return apitypes.NetworkResource{}, ErrNoManager
+		return apitypes.NetworkResource{}, c.errNoManager()
 	}
 
 	network, err := getNetwork(c.getRequestContext(), c.client, input)
@@ -908,7 +917,7 @@ func (c *Cluster) GetNetworks() ([]apitypes.NetworkResource, error) {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return nil, ErrNoManager
+		return nil, c.errNoManager()
 	}
 
 	r, err := c.client.ListNetworks(c.getRequestContext(), &swarmapi.ListNetworksRequest{})
@@ -931,7 +940,7 @@ func (c *Cluster) CreateNetwork(s apitypes.NetworkCreateRequest) (string, error)
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return "", ErrNoManager
+		return "", c.errNoManager()
 	}
 
 	if runconfig.IsPreDefinedNetwork(s.Name) {
@@ -954,7 +963,7 @@ func (c *Cluster) RemoveNetwork(input string) error {
 	defer c.RUnlock()
 
 	if !c.isActiveManager() {
-		return ErrNoManager
+		return c.errNoManager()
 	}
 
 	network, err := getNetwork(c.getRequestContext(), c.client, input)