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native_ecmp_loadbalancer.md

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1. Introduction

Add support for ecmp based loadbalancer in OpenContrail.

2. Problem statement

Currently OpenContrail supports L4-L7 proxy based loadbalancers. This is done by instantiating haproxy on a compute node. If there is no requirement for proxy based loadbalancers then ecmp based loadbalancing helps prevents traffic tromboning.

2.1 Use cases

In container orchestration systems such as Kubernetes there is a need to distribute traffic to PODS behind a service. Proxy based solutions are not distributed and add overhead for simple distribution of traffic to stateless PODS. Hence the native ECMP based solution is needed.

3. Proposed solution

OpenContrail supports ECMP based forwarding if the same IP address is announced by different endpoints. This is based on a hash of the five tuple:

  • Source ip
  • Source port
  • Destination ip
  • Desination port
  • Protocol

3.1 Alternatives considered

Proxy solutions are potential alternatives.

3.2 API schema changes

New loadbalancer provider called "native" is being added to the loadbalancer object. The rest of the objects remain the same as before in the loadbalancer hierarchy.

  • User creates a port for a virtual-ip.
  • User provides the list of endpoint IPs as members for the VIP.

3.3 User workflow impact

Set the configuration for provider as "native"

  • neutron net-create private-net
  • neutron subnet-create --name private-subnet private-net 30.30.30.0/24
  • neutron lbaas-loadbalancer-create $(neutron subnet-list | awk '/ private-subnet / {print $2}') --name lb1
  • neutron lbaas-listener-create --loadbalancer lb1 --protocol-port 80 --protocol HTTP --name listener1
  • neutron lbaas-pool-create --name pool1 --protocol HTTP --listener listener1 --lb-algorithm ROUND_ROBIN
  • neutron lbaas-member-create --subnet private-subnet --address 30.30.30.10 --protocol-port 8080 mypool
  • neutron lbaas-member-create --subnet private-subnet --address 30.30.30.11 --protocol-port 8080 mypool

3.4 UI changes

UI changes will be done to configure the loadbalancer

3.5 Notification impact

Logs, UVE and stats will be generated from the controller and agent.

4. Implementation

4.1 Assignee(s)

Yuvaraja Mariappan (Dev)

4.2 Work items

Controller changes

  • Controller now aggregates the configuration based on the provider. In the case of native provider controller allocates a new floating-ip object as the child of the instance-ip. It copies the IP address from the instance-ip into the floating-ip. Controller also copies the port translations from VIP to members in the floating-ip object. There is a flag to identify that port-translations are enabled on the floating-ip.
  • In addition controller also attaches this floating IP to all the virtual machine interface objects of the endpoints/pool members.

Agent changes

  • Agent acts on the new floating-ip object. Based on the port translation flag agent creates a port translation table for the floating ip. In addition agent traverses its parent instance-ip to get the corresponding routing table information.

5. Performance and scaling impact

5.1 API and control plane

There is no impact on API and control plane performance.

5.2 Forwarding performance

Forwarding performance should be better than proxy based solutions but this needs to be characterized during the test cycle.

6. Upgrade

Describe upgrade impact of the feature

The native loadbalancer is a new feature and hence does not have any upgrade impact.

7. Deprecations

Not applicable

8. Dependencies

Health check implementation for native loadbalancer depends on the following bluprint

https://blueprints.launchpad.net/opencontrail/+spec/service-health-check

9. Testing

9.1 Unit tests

9.2 Dev tests

9.3 System tests

10. Documentation Impact

11. References