Introduction

This documents gives an overview to the design and functional implementation for Internal Load Balancing on VPC tiers.

Feature developers:

• APIs and Business logic - Alena Prokharchyk
• Backend - TBA
• UI - TBA

Glossary

• Internal LB - the load balancing between internal (guest) cloudStack networks
• Internal LB Rule- Load balancer rule with the front end IP from Internal (Guest) cloudStack network.
• Internal LB VM - cloudStack system vm managing internal LB Rules

Use case

There are 2 tiers in the VPC - Web tier and Application tier. Traffic to Web tier is balanced on the VPC VR on the public side. User wants traffic coming from Web to the App tier to be balanced as well. Load balancing on the App tier will be covered by the Internal LB feature.

Internal LB can be handled by 2 network providers:

• InternalLBVm - have to add support for this provider first.
• Netscaler VPX

The pic below is for the case when InternalLBVm is used as a provider for the LB service on internal tier:

1. Public LB rule for 72.52.125.10 Public IP, public port 80 and private port 81. It enables LB for traffic coming from the internet to the vms on the Web tier. The LB rule is configured on the VPC VR.
2. Internal LB rule #1 for 10.10.10.4 guest IP, loadBalancerPort 23 and instancePort 25. The LB rule is configured on InternalLBVM1.
3. Internal LB rule #2 for 10.10.10.4 guest IP, loadBalancerPort 45 and instancePort 46. The LB rule is configured on InternalLBVM1.
4. Internal LB rule #3 for 10.10.10.6 guest IP, loadBalancerPort 23 and instancePort 25. The LB rule is configured on InternalLBVM2.

General flow

1) Enable Internal LB on VPC tier

In order to have Internal Load Balancing support on VPC tier, the tier has to be created from the network offering with:

• Service=LB, Provider=InternalLbVm, LB service capability "lbSchemes" with the value "Internal"

or

• Service=LB, Provider=Netscaler, LB service capability "lbSchemes" with the value Internal".Before creating the network, enable InternalLbVm element/provider on the physical network using configureInternalLoadBalancerElement and updateNetworkServiceProvider APIs. The cloudStack UI will enable the element/provider automatically as a part of physical network creation, so these instructions are only for the case when APIs are called directly, omitting the UI. 

Java code changes

• Network.java interface - add new capability for the LB service - lbSchemes. It will have 2 values - Internal and Public.
• Existing Netscaler Service Provider will support both values - Internal and Public - for the supportedLbSchemes capability as it can act as a provider for Public and Internal Load Balancing.

• Introduce new Network Element - InternalLBVm. This provider supports only 1 service - LB, and its supportedLbMode capability can be Internal only. We need a new network element because Internal LB Vm will have different number of nics from the regular CS system vm (Guest and Control only); and its lifecycle will be different as well. The Vm will be started not when network gets implemented, but when the new IP gets acquired from the Guest Network for the Load Balancer rule.
• Introduce new classes InternalLBNetworkApplianceManager/InternalLBNetworkApplianceService/InternalLBNetworkApplianceManagerImpl - for managing Internal Load Balancer vms. 

Backend changes

TBD. We might need a separate template/set of scripts for Internal LB VM, or we can re-use the existing VR template.

Web Services API

Changes to existing Apis: list/createNetworkOffering APIs will return new parameters in the response - internal_lb and public_lb:. The parameters' type is boolean.

New APIs:

DB changes

• New fields to network_offerings table - "internal_lb" and "public_lb". Not null, default value is 0.
• Changes to unique key in ntwk_service_map table. The unique key is service/provider/network_id instead of service/network_id. Now network have multiple providers for the same service - LB - as in the future we might support public/internal LB service handled by the separate providers on the same network

2) Create Load Balancer Rule 

Java code changes

• Add new manager - ApplicationLoadBalancerManagerImpl. This class will be responsible for managing Internal LB rules in this release. In the future it will support Public lb rules as well.
• The LBRule can be created with or without specifying the source IP address. If no source IP address is specified, the new one will get acquired automatically from the sourceIpNetworkId specified in createLoadBalancer command

If provider is InternalLBVM:

• A new InternalLBVM should be spanned as soon as new source IP address is acquired by the LB rule. This code should be handled by InternalLoadBalancerVMManager. See more details on the VM in "InternalLBVM management and life cycle" section.
• There is going to be 1 Internal LB vm spanned per guest IP address participating in the Internal Load Balancing. If more rules are added for the same IP, they will be managed on the same InternalLBVM.

If LB provider is Netscaler VPX:

• TBD

Backend changes

TBD. For InternalLBVM, have to put HA proxy management/configuration details here

Web Services API

Introduce new APIs

DB changes

TBD

3) Attach VM to the Load Balancer

Existing API are going to be used to assign/remove vm to/from the load balancer

assignToLoadBalancerRule

assignToLoadBalancerRule

How to list Guest IP addresses allocated for LB purpose

At the moment, cloudStack doesn't expose any API for listing IP addresses from the guest network. You see all the ip addresses allocated by the load balancers by executing the following command:

listLoadBalancers&scheme=Internal&networkId=<Id of the network the load balancer belongs to>

Internal Load Balancing Vm management and life cycle

1) The InternalLBVM will be created with 2 interfaces: eth0 - linkLocal (private in VMWare case), eth1 - the IP address of the LB rule.

2) InternalLBVM will be managed by InternalLoadBalancerVMManager

3) InternalLBVM life cycle:

• Create: InternalLBVM gets created when the first Load Balancing Rule is created for the IP address
• Destroy: InternalLBVM gets destroyed when the last Load Balancer is removed for the IP address
• Reboot: InternalLBVM can be rebooted as a regular system vm using RebootSystemVm API.
• List: InternalLBVM can be listed with ListSystemVMs API

4) To stop/start/list internal lb vm, use existing stop/start/listRouters command.

Limitations

• Internal and Public Lb are mutually exclusive on a network/tier. If the tier has LB on the public side, then it can't have the Internal LB
• Supported just on VPC networks in 4.2 release.

UI

TBD