fix targeted global deployments

Author: nick-potts

pkg/client/deploy/strategy.go

@@ -205,11 +205,17 @@ func (s *RollingStrategy) planGlobal(svc *api.Service, spec api.ServiceSpec) (Pl
 		return plan, err
 	}
 
-	// Global mode requires all machines to satisfy the constraints.
-	if len(availableMachines) != len(s.state.Machines) {
+	// Global mode requires all target machines to satisfy the constraints.
+	// If placement constraints specify machines, use that count; otherwise use all cluster machines.
+	targetMachineCount := len(s.state.Machines)
+	if len(spec.Placement.Machines) > 0 {
+		targetMachineCount = len(spec.Placement.Machines)
+	}
+
+	if len(availableMachines) != targetMachineCount {
 		return plan, fmt.Errorf(
 			"global service '%s' requires all machines to satisfy constraints, but only %d of %d machines are eligible",
-			spec.Name, len(availableMachines), len(s.state.Machines),
+			spec.Name, len(availableMachines), targetMachineCount,
 		)
 	}
 

pkg/client/deploy/strategy_test.go

@@ -585,3 +585,43 @@ func TestRollingStrategy_Plan_RequiresClusterState(t *testing.T) {
 	assert.Error(t, err)
 	assert.Contains(t, err.Error(), "cluster state must be provided")
 }
+
+func TestRollingStrategy_planGlobal_WithPlacementConstraints(t *testing.T) {
+	t.Parallel()
+
+	t.Run("global service with x-machine deploys only to specified machines", func(t *testing.T) {
+		// Cluster has 3 machines, but we only want to deploy to 2 of them using x-machine
+		state := newTestClusterState(
+			newTestMachine("m1", "node1", 4, 8),
+			newTestMachine("m2", "node2", 4, 8),
+			newTestMachine("m3", "node3", 4, 8),
+		)
+
+		spec := api.ServiceSpec{
+			Name: "test-service",
+			Mode: api.ServiceModeGlobal,
+			Container: api.ContainerSpec{
+				Image: "nginx:latest",
+			},
+			Placement: api.Placement{
+				Machines: []string{"node1", "node2"}, // x-machine constraint: only deploy to node1 and node2
+			},
+		}
+
+		strategy := &RollingStrategy{}
+		plan, err := strategy.Plan(state, nil, spec)
+
+		// This should succeed - global with x-machine should deploy to all machines in the constraint list
+		require.NoError(t, err, "global service with x-machine should succeed when all specified machines are eligible")
+
+		// Should have 2 RunContainerOperations (one per machine in the constraint)
+		counts := countOperationsByType(plan.Operations)
+		assert.Equal(t, 2, counts["run"], "should run containers on both specified machines")
+
+		// Verify containers are scheduled on the correct machines
+		machineIDs := getMachineIDsFromRunOps(plan.Operations)
+		assert.Contains(t, machineIDs, "m1", "should deploy to node1")
+		assert.Contains(t, machineIDs, "m2", "should deploy to node2")
+		assert.NotContains(t, machineIDs, "m3", "should not deploy to node3")
+	})
+}