feat(arm-builder): print warning on zone resiliency for currently not supported locations

builder/azure/arm/builder.go

@@ -139,6 +139,8 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packe
 		b.config.Location = *group.Location
 	}
 
+	b.config.validateLocationZoneResiliency(ui.Say)
+
 	if b.config.StorageAccount != "" {
 		account, err := b.getBlobAccount(ctx, azureClient, b.config.ResourceGroupName, b.config.StorageAccount)
 		if err != nil {

builder/azure/arm/config.go

@@ -725,3 +725,23 @@ func isValidAzureName(re *regexp.Regexp, rgn string) bool {
 		!strings.HasSuffix(rgn, ".") &&
 		!strings.HasSuffix(rgn, "-")
 }
+
+func (c *Config) validateLocationZoneResiliency(say func(s string)) {
+	// Docs on regions that support Availibility Zones:
+	//   https://docs.microsoft.com/en-us/azure/availability-zones/az-overview#regions-that-support-availability-zones
+	// Query technical names for locations:
+	//   az account list-locations --query '[].name' -o tsv
+
+	var zones = make(map[string]struct{})
+	zones["westeurope"] = struct{}{}
+	zones["centralus"] = struct{}{}
+	zones["eastus2"] = struct{}{}
+	zones["francecentral"] = struct{}{}
+	zones["northeurope"] = struct{}{}
+	zones["southeastasia"] = struct{}{}
+	zones["westus2"] = struct{}{}
+
+	if _, ok := zones[c.Location]; !ok {
+		say(fmt.Sprintf("WARNING: Zone resiliency may not be supported in %s, checkout the docs at https://docs.microsoft.com/en-us/azure/availability-zones/", c.Location))
+	}
+}

builder/azure/arm/config_test.go

@@ -1681,7 +1681,42 @@ func TestConfigShouldRejectSharedImageGalleryWithVhdTarget(t *testing.T) {
 	if err != nil {
 		t.Log("expected an error if Shared Image Gallery source is used with VHD target", err)
 	}
+}
 
+func Test_GivenZoneNotSupportingResiliency_ConfigValidate_ShouldWarn(t *testing.T) {
+	builderValues := getArmBuilderConfiguration()
+	builderValues["managed_image_zone_resilient"] = "true"
+	builderValues["location"] = "ukwest"
+
+	c, _, err := newConfig(builderValues, getPackerConfiguration())
+	if err != nil {
+		t.Errorf("newConfig failed with %q", err)
+	}
+
+	var m = ""
+	c.validateLocationZoneResiliency(func(s string) { m = s })
+
+	if m != "WARNING: Zone resiliency may not be supported in ukwest, checkout the docs at https://docs.microsoft.com/en-us/azure/availability-zones/" {
+		t.Errorf("warning message not as expected: %s", m)
+	}
+}
+
+func Test_GivenZoneSupportingResiliency_ConfigValidate_ShouldNotWarn(t *testing.T) {
+	builderValues := getArmBuilderConfiguration()
+	builderValues["managed_image_zone_resilient"] = "true"
+	builderValues["location"] = "westeurope"
+
+	c, _, err := newConfig(builderValues, getPackerConfiguration())
+	if err != nil {
+		t.Errorf("newConfig failed with %q", err)
+	}
+
+	var m = ""
+	c.validateLocationZoneResiliency(func(s string) { m = s })
+
+	if m != "" {
+		t.Errorf("warning message not as expected: %s", m)
+	}
 }
 
 func getArmBuilderConfiguration() map[string]string {