Upstream Settings Policy API

Learn how to use the UpstreamSettingsPolicy API.

Overview

The UpstreamSettingsPolicy API allows Application Developers to configure the behavior of a connection between NGINX and the upstream applications.

The settings in UpstreamSettingsPolicy correspond to the following NGINX directives:

UpstreamSettingsPolicy is a Direct Policy Attachment that can be applied to one or more services in the same namespace as the policy. UpstreamSettingsPolicies can only be applied to HTTP or gRPC services, in other words, services that are referenced by an HTTPRoute or GRPCRoute.

See the custom policies document for more information on policies.

This guide will show you how to use the UpstreamSettingsPolicy API to configure the load balancing method, upstream zone size and keepalives for your applications.

For all the possible configuration options for UpstreamSettingsPolicy, see the API reference.

Before you begin

Setup

Create the coffee and tea example applications:

yaml
kubectl apply -f - <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: coffee
spec:
  replicas: 1
  selector:
    matchLabels:
      app: coffee
  template:
    metadata:
      labels:
        app: coffee
    spec:
      containers:
      - name: coffee
        image: nginxdemos/nginx-hello:plain-text
        ports:
        - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: coffee
spec:
  ports:
  - port: 80
    targetPort: 8080
    protocol: TCP
    name: http
  selector:
    app: coffee
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: tea
spec:
  replicas: 1
  selector:
    matchLabels:
      app: tea
  template:
    metadata:
      labels:
        app: tea
    spec:
      containers:
      - name: tea
        image: nginxdemos/nginx-hello:plain-text
        ports:
        - containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: tea
spec:
  ports:
  - port: 80
    targetPort: 8080
    protocol: TCP
    name: http
  selector:
    app: tea
EOF

This will create two services and pods in the default namespace:

kubectl get svc,pod
text
NAME                 TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGE
service/coffee       ClusterIP   10.244.0.14     <none>        80/TCP    23h
service/tea          ClusterIP   10.244.0.15     <none>        80/TCP    23h

NAME                          READY   STATUS    RESTARTS   AGE
pod/coffee-676c9f8944-n9g6n   1/1     Running   0          23h
pod/tea-6fbfdcb95d-cf84d      1/1     Running   0          23h

Create a Gateway:

yaml
kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: gateway
spec:
  gatewayClassName: nginx
  listeners:
    - name: http
      port: 80
      protocol: HTTP
      hostname: "*.example.com"
EOF

After creating the Gateway resource, NGINX Gateway Fabric will provision an NGINX Pod and Service fronting it to route traffic. Verify the gateway is created:

kubectl describe gateways.gateway.networking.k8s.io gateway

Verify the status is Accepted:

text
Status:
  Addresses:
    Type:   IPAddress
    Value:  10.96.36.219
  Conditions:
    Last Transition Time:  2026-01-09T05:40:37Z
    Message:               The Gateway is accepted
    Observed Generation:   1
    Reason:                Accepted
    Status:                True
    Type:                  Accepted
    Last Transition Time:  2026-01-09T05:40:37Z
    Message:               The Gateway is programmed
    Observed Generation:   1
    Reason:                Programmed
    Status:                True
    Type:                  Programmed

Save the public IP address and port(s) of the Gateway into shell variables:

text
GW_IP=XXX.YYY.ZZZ.III
GW_PORT=<port number>
In a production environment, you should have a DNS record for the external IP address that is exposed, and it should refer to the hostname that the gateway will forward for.

Create HTTPRoutes for the coffee and tea applications:

yaml
kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: coffee
spec:
  parentRefs:
    - name: gateway
      sectionName: http
  hostnames:
    - "cafe.example.com"
  rules:
    - matches:
        - path:
            type: Exact
            value: /coffee
      backendRefs:
        - name: coffee
          port: 80
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: tea
spec:
  parentRefs:
    - name: gateway
      sectionName: http
  hostnames:
    - "cafe.example.com"
  rules:
    - matches:
        - path:
            type: Exact
            value: /tea
      backendRefs:
        - name: tea
          port: 80
EOF

Test the configuration:

You can send traffic to the coffee and tea applications using the external IP address and port for the NGINX Service.

Send a request to coffee:

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee

This request should receive a response from the coffee Pod:

text
Server address: 10.244.0.9:8080
Server name: coffee-76c7c85bbd-cf8nz

Send a request to tea:

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/tea

This request should receive a response from the tea Pod:

text
Server address: 10.244.0.9:8080
Server name: tea-76c7c85bbd-cf8nz

Configure load balancing methods

You can use UpstreamSettingsPolicy to configure the load balancing method for the coffee and tea applications. In this example, the coffee service uses the random two least_time=header method, and the tea service uses the hash consistent method with $upstream_addr as the hash key.

You need to specify an NGINX variable as hashMethodKey when using load balancing methods hash and hash consistent .

Create the following UpstreamSettingsPolicy resources:

yaml
kubectl apply -f - <<EOF
apiVersion: gateway.nginx.org/v1alpha1
kind: UpstreamSettingsPolicy
metadata:
  name: lb-method
spec:
  targetRefs:
  - group: core
    kind: Service
    name: coffee
  loadBalancingMethod: "random two least_time=header"
EOF
yaml
kubectl apply -f - <<EOF
apiVersion: gateway.nginx.org/v1alpha1
kind: UpstreamSettingsPolicy
metadata:
  name: lb-method-hash
spec:
  targetRefs:
  - group: core
    kind: Service
    name: tea
  loadBalancingMethod: "hash consistent"
  hashMethodKey: "$upstream_addr"
EOF

These two UpstreamSettingsPolicy resources target the coffee and tea Services and configure different load balancing methods for their upstreams. Verify that the UpstreamSettingsPolicies are Accepted:

kubectl describe upstreamsettingspolicies.gateway.nginx.org lb-method

You should see the following status:

text
Status:
  Ancestors:
    Ancestor Ref:
      Group:      gateway.networking.k8s.io
      Kind:       Gateway
      Name:       gateway
      Namespace:  default
    Conditions:
      Last Transition Time:  2025-12-09T20:41:55Z
      Message:               The Policy is accepted
      Observed Generation:   1
      Reason:                Accepted
      Status:                True
      Type:                  Accepted
    Controller Name:         gateway.nginx.org/nginx-gateway-controller

The lb-method-hash policy should show the same Accepted condition.

Next, verify that the policies have been applied to the coffee and tea upstreams by inspecting the NGINX configuration:

kubectl exec -it deployments/gateway-nginx -- nginx -T

You should see the random two least_time=header directive on the coffee upstreams and hash $upstream_addr consistent in the tea upstream:

text
upstream default_coffee_80 {
    random two least_time=header;
    zone default_coffee_80 1m;
    state /var/lib/nginx/state/default_coffee_80.conf;
    keepAlive 16;
}

upstream default_tea_80 {
    hash $upstream_addr consistent;
    zone default_tea_80 1m;
    state /var/lib/nginx/state/default_tea_80.conf;
    keepAlive 16;
}
NGINX Open Source supports the following load-balancing methods: round_robin, least_conn, ip_hash, hash, hash consistent, random, random two, and random two least_conn. NGINX Plus supports all of the methods available in NGINX Open Source, and adds the following methods: random two least_time=header, random two least_time=last_byte, least_time header, least_time last_byte, least_time header inflight, and least_time last_byte inflight.

Configure upstream zone size

To set the upstream zone size to 1 megabyte for both the coffee and tea services, create the following UpstreamSettingsPolicy:

yaml
kubectl apply -f - <<EOF
apiVersion: gateway.nginx.org/v1alpha1
kind: UpstreamSettingsPolicy
metadata:
  name: 1m-zone-size
spec:
  targetRefs:
  - group: core
    kind: Service
    name: tea
  - group: core
    kind: Service
    name: coffee
  zoneSize: 1m
EOF

This UpstreamSettingsPolicy targets both the coffee and tea services we created in the setup by specifying both services in the targetRefs field. It limits the upstream zone size of the coffee and tea services to 1 megabyte.

Verify that the UpstreamSettingsPolicy is Accepted:

kubectl describe upstreamsettingspolicies.gateway.nginx.org 1m-zone-size

You should see the following status:

text
Status:
  Ancestors:
    Ancestor Ref:
      Group:      gateway.networking.k8s.io
      Kind:       Gateway
      Name:       gateway
      Namespace:  default
    Conditions:
      Last Transition Time:  2025-01-07T20:06:55Z
      Message:               Policy is accepted
      Observed Generation:   1
      Reason:                Accepted
      Status:                True
      Type:                  Accepted
    Controller Name:         gateway.nginx.org/nginx-gateway-controller
Events:                      <none>

Next, verify that the policy has been applied to the coffee and tea upstreams by inspecting the NGINX configuration:

kubectl exec -it deployments/gateway-nginx -- nginx -T

You should see the zone directive in the coffee and tea upstreams both specify the size 1m:

text
upstream default_coffee_80 {
    random two least_conn;
    zone default_coffee_80 1m;

    server 10.244.0.14:8080;
    keepAlive 16;
}

upstream default_tea_80 {
    random two least_conn;
    zone default_tea_80 1m;

    server 10.244.0.15:8080;
    keepAlive 16;
}

Enable keepalive connections

By default, the keepAlive directive is enabled with a value of 16. You can override this value or disable keepAlive entirely by configuring an UpstreamSettingsPolicy. To disable keepalive, set the connections field to 0.

The following example creates an UpstreamSettingsPolicy that configures keepalive connections for the coffee Service with a value of 32:

yaml
kubectl apply -f - <<EOF
apiVersion: gateway.nginx.org/v1alpha1
kind: UpstreamSettingsPolicy
metadata:
  name: upstream-keepalives
spec:
  targetRefs:
  - group: core
    kind: Service
    name: coffee
  keepAlive:
    connections: 32
EOF

This UpstreamSettingsPolicy targets the coffee service in the targetRefs field. It sets the number of keepalive connections to 32, which activates the cache for connections to the service’s pods and sets the maximum number of idle connections to 32.

Verify that the UpstreamSettingsPolicy is Accepted:

kubectl describe upstreamsettingspolicies.gateway.nginx.org upstream-keepalives

You should see the following status:

text
Status:
  Ancestors:
    Ancestor Ref:
      Group:      gateway.networking.k8s.io
      Kind:       Gateway
      Name:       gateway
      Namespace:  default
    Conditions:
      Last Transition Time:  2025-01-07T20:06:55Z
      Message:               Policy is accepted
      Observed Generation:   1
      Reason:                Accepted
      Status:                True
      Type:                  Accepted
    Controller Name:         gateway.nginx.org/nginx-gateway-controller
Events:                      <none>

Next, verify that the policy has been applied to the coffee upstreams, by inspecting the NGINX configuration:

kubectl exec -it deployments/gateway-nginx -- nginx -T

You should see that the coffee upstream has the keepalive directive set to 32:

text
upstream default_coffee_80 {
    random two least_conn;
    zone default_coffee_80 1m;

    server 10.244.0.14:8080;
    keepalive 32;
}

To disable keepAlive directive lets create an UpstreamSettingsPolicy targeting the tea service with value 0:

yaml
kubectl apply -f - <<EOF
apiVersion: gateway.nginx.org/v1alpha1
kind: UpstreamSettingsPolicy
metadata:
  name: upstream-unset-keepAlive
spec:
  targetRefs:
  - group: core
    kind: Service
    name: tea
  keepAlive:
    connections: 0
EOF

Verify that the UpstreamSettingsPolicy is Accepted:

kubectl describe upstreamsettingspolicies.gateway.nginx.org upstream-unset-keepAlive

You should see the following status:

text
Status:
  Ancestors:
    Ancestor Ref:
      Group:      gateway.networking.k8s.io
      Kind:       Gateway
      Name:       gateway
      Namespace:  default
    Conditions:
      Last Transition Time:  2026-01-03T00:35:45Z
      Message:               The Policy is accepted
      Observed Generation:   1
      Reason:                Accepted
      Status:                True
      Type:                  Accepted
    Controller Name:         gateway.nginx.org/nginx-gateway-controller

Next, verify that the policy has been applied to the tea upstream, by inspecting the NGINX configuration:

kubectl exec -it deployments/gateway-nginx -- nginx -T
text
upstream default_tea_80 {
    random two least_conn;
    zone default_tea_80 1m;

    server 10.244.0.15:8080;
}

Further reading

  • Custom policies: learn about how NGINX Gateway Fabric custom policies work.
  • API reference: all configuration fields for the UpstreamSettingsPolicy API.
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