Enable dynamic azure disk volume limits

use API to get max disk num

use continue when got exception

add logging

add cache and unit test

fix comments

pkg/volume/azure_dd/azure_dd_test.go

@@ -20,6 +20,10 @@ import (
 	"os"
 	"testing"
 
+	"github.com/Azure/azure-sdk-for-go/services/compute/mgmt/2018-04-01/compute"
+	"github.com/Azure/go-autorest/autorest/to"
+	"github.com/stretchr/testify/assert"
+
 	"k8s.io/api/core/v1"
 	utiltesting "k8s.io/client-go/util/testing"
 	"k8s.io/kubernetes/pkg/volume"
@@ -53,3 +57,37 @@ func TestCanSupport(t *testing.T) {
 
 // fakeAzureProvider type was removed because all functions were not used
 // Testing mounting will require path calculation which depends on the cloud provider, which is faked in the above test.
+
+func TestGetMaxDataDiskCount(t *testing.T) {
+	tests := []struct {
+		instanceType string
+		sizeList     *[]compute.VirtualMachineSize
+		expectResult int64
+	}{
+		{
+			instanceType: "standard_d2_v2",
+			sizeList: &[]compute.VirtualMachineSize{
+				{Name: to.StringPtr("Standard_D2_V2"), MaxDataDiskCount: to.Int32Ptr(8)},
+				{Name: to.StringPtr("Standard_D3_V2"), MaxDataDiskCount: to.Int32Ptr(16)},
+			},
+			expectResult: 8,
+		},
+		{
+			instanceType: "NOT_EXISTING",
+			sizeList: &[]compute.VirtualMachineSize{
+				{Name: to.StringPtr("Standard_D2_V2"), MaxDataDiskCount: to.Int32Ptr(8)},
+			},
+			expectResult: defaultAzureVolumeLimit,
+		},
+		{
+			instanceType: "",
+			sizeList:     &[]compute.VirtualMachineSize{},
+			expectResult: defaultAzureVolumeLimit,
+		},
+	}
+
+	for _, test := range tests {
+		result := getMaxDataDiskCount(test.instanceType, test.sizeList)
+		assert.Equal(t, test.expectResult, result)
+	}
+}