Load Balancer Pools

Overview

A pool is a collection of backend member instances that receive traffic from a listener. Pools define how traffic is distributed across members (algorithm), whether sessions are sticky (persistence), and which protocol the pool uses internally. Each listener has a default pool; additional pools can be used for L7 policy-based routing.

Prerequisites

An active Polystack account with appropriate permissions
Access to the Polystack Dashboard or CLI configured with credentials
API credentials sourced (source openrc.sh)

Distribution Algorithms

Algorithm	Description	Best For
`ROUND_ROBIN`	Distributes requests evenly across all UP members	Stateless applications with equal capacity members
`LEAST_CONNECTIONS`	Sends new requests to the member with fewest active connections	Long-lived connections with variable request duration
`SOURCE_IP`	Routes requests from the same client IP to the same member	Stateful applications without cookie-based persistence
`SOURCE_IP_PORT`	Routes based on client IP + port combination	Symmetric NAT environments requiring deterministic mapping

Create a Pool

Dashboard
CLI

Navigate to Pools tab

Open your load balancer in Network > Load Balancers and select the Pools tab. Click Create Pool.

Configure the pool

Field	Description
Name	Pool display name
Protocol	Must match or be compatible with the listener protocol
Algorithm	Traffic distribution method
Session Persistence	Sticky session configuration (optional)

Add members

After pool creation, select the pool and click the Members sub-tab. Click Add Member to register backend instances.

Field	Description
IP Address	Backend instance IP
Protocol Port	Port your application listens on
Weight	Relative traffic weight (default: 1)
Monitor Address/Port	Override health check target if different from member address

Create pool linked to listener

openstack loadbalancer pool create \
  --name pool-http \
  --lb-algorithm ROUND_ROBIN \
  --listener listener-http \
  --protocol HTTP

Create standalone pool (for L7 routing)

openstack loadbalancer pool create \
  --name pool-api \
  --lb-algorithm LEAST_CONNECTIONS \
  --loadbalancer prod-web-lb \
  --protocol HTTP

Manage Pool Members

Dashboard
CLI

Navigate to your pool and click the Members sub-tab. Use Add Member to register instances and Delete to remove members that are decommissioned.

openstack loadbalancer member create \
  --subnet-id <instance-subnet-id> \
  --address <instance-ip> \
  --protocol-port 8080 \
  pool-http

openstack loadbalancer member list pool-http \
  -c name -c address -c protocol_port -c operating_status

openstack loadbalancer member set pool-http <member-id> \
  --weight 2

openstack loadbalancer member delete pool-http <member-id>

Session Persistence

Session persistence routes subsequent requests from the same client to the same backend member, enabling stateful applications to work behind the load balancer.

HTTP Cookie (recommended)
Source IP
Application Cookie

The load balancer inserts a session cookie. Clients are routed to the member that served their first request:

Create pool with HTTP cookie persistence

openstack loadbalancer pool create \
  --name pool-stateful \
  --lb-algorithm ROUND_ROBIN \
  --listener listener-http \
  --protocol HTTP \
  --session-persistence type=HTTP_COOKIE

Routes requests from the same client IP to the same member. Works at Layer 4 but breaks when clients are behind NAT with shared IP addresses:

Create pool with source IP persistence

openstack loadbalancer pool create \
  --name pool-sourceip \
  --lb-algorithm ROUND_ROBIN \
  --listener listener-http \
  --protocol HTTP \
  --session-persistence type=SOURCE_IP

The load balancer reads an existing cookie set by your application:

Create pool with application cookie persistence

openstack loadbalancer pool create \
  --name pool-appcookie \
  --lb-algorithm ROUND_ROBIN \
  --listener listener-http \
  --protocol HTTP \
  --session-persistence "type=APP_COOKIE,cookie_name=JSESSIONID"

Update Pool Settings

Change distribution algorithm

openstack loadbalancer pool set pool-http \
  --lb-algorithm LEAST_CONNECTIONS

Remove session persistence

openstack loadbalancer pool set pool-http \
  --no-session-persistence

Next Steps

Health Monitors

Configure health probes to automatically remove unhealthy members from pools.

Listeners

Configure the listeners that route traffic to your pools.

Create Load Balancer

Full walkthrough for creating a load balancer with pool and health monitor.

Troubleshooting

Resolve member OFFLINE status and pool connectivity issues.

Core Services

Other Services

Overview

Distribution Algorithms

Create a Pool

Navigate to Pools tab

Configure the pool

Add members

Manage Pool Members

Session Persistence

Update Pool Settings

Next Steps

Health Monitors

Listeners

Create Load Balancer

Troubleshooting

​Overview

​Distribution Algorithms

​Create a Pool

Navigate to Pools tab

Configure the pool

Add members

​Manage Pool Members

​Session Persistence

​Update Pool Settings

​Next Steps

Health Monitors

Listeners

Create Load Balancer

Troubleshooting

Overview

Distribution Algorithms

Create a Pool

Manage Pool Members

Session Persistence

Update Pool Settings

Next Steps