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Routing to Applications Using HTTP Matching Conditions

In this guide we will configure advanced routing rules for multiple applications. These rules will showcase request matching by path, headers, query parameters, and method. For an introduction to exposing your application, it is recommended to go through the basic guide first.

The following image shows the traffic flow that we will be creating with these rules.

Traffic Flow Diagram

The goal is to create a set of rules that will result in client requests being sent to specific backends based on the request attributes. In this diagram, we have two versions of the coffee service. Traffic for v1 needs to be directed to the old application, while traffic for v2 needs to be directed towards the new application. We also have two tea services, one that handles GET operations and one that handles POST operations. Both the tea and coffee applications share the same Gateway.

Prerequisites

  • Install NGINX Kubernetes Gateway.

  • Expose NGINX Kubernetes Gateway and save the public IP address and port of NGINX Kubernetes Gateway into shell variables:

    GW_IP=XXX.YYY.ZZZ.III
GW_PORT=<port number>

Note 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.

Coffee Applications

Deploy the Coffee Applications

Begin by deploying the coffee-v1 and coffee-v2 applications:

kubectl apply -f https://raw.githubusercontent.com/nginxinc/nginx-kubernetes-gateway/v0.6.0/examples/advanced-routing/coffee.yaml

Deploy the Gateway API Resources for the Coffee Applications

The Gateway resource is typically deployed by the cluster operator. To deploy the Gateway:

kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: cafe
spec:
  gatewayClassName: nginx
  listeners:
  - name: http
    port: 80
    protocol: HTTP
EOF

This Gateway defines a single listener on port 80. Since no hostname is specified, this listener matches on all hostnames.

The HTTPRoute is typically deployed by the application developer. To deploy the coffee HTTPRoute:

kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: coffee
spec:
  parentRefs:
  - name: cafe
    sectionName: http
  hostnames:
  - cafe.example.com
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /coffee
    backendRefs:
    - name: coffee-v1-svc
      port: 80
  - matches:
    - path:
        type: PathPrefix
        value: /coffee
      headers:
      - name: version
        value: v2
    - path:
        type: PathPrefix
        value: /coffee
      queryParams:
      - name: TEST
        value: v2
    backendRefs:
    - name: coffee-v2-svc
      port: 80
EOF

This HTTPRoute has a few important properties:

  • The parentRefs references the Gateway resource that we created, and specifically defines the http listener to attach to, via the sectionName field.
  • cafe.example.com is the hostname that is matched for all requests to the backends defined in this HTTPRoute.
  • The first rule defines that all requests with the path prefix /coffee and no other matching conditions are sent to the coffee-v1 Service.
  • The second rule defines two matching conditions. If either of these conditions match, requests are forwarded to the coffee-v2 Service:
    • Request with the path prefix /coffee and header version=v2
    • Request with the path prefix /coffee and the query parameter TEST=v2 If you want both conditions to be required, you can define headers and queryParams in the same match object.

Send Traffic to Coffee

Using the external IP address and port for NGINX Kubernetes Gateway, we can send traffic to our coffee applications.

Note If you have a DNS record allocated for cafe.example.com, you can send the request directly to that hostname, without needing to resolve.

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-v1 Pod.

Server address: 10.244.0.9:8080
Server name: coffee-v2-68bd55f798-s9z5q

If we want our request to be routed to coffee-v2, then we need to meet the defined conditions. We can include a header:

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee -H "version:v2"

or include a query parameter:

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee?TEST=v2

Either request should result in a response from the coffee-v2 Pod.

Server address: 10.244.0.9:8080
Server name: coffee-v2-68bd55f798-s9z5q

Tea Applications

Let's deploy a different set of applications now called tea and tea-post. These applications will have their own set of rules, but will still attach to the same Gateway listener as the coffee apps.

Deploy the Tea Applications

kubectl apply -f https://raw.githubusercontent.com/nginxinc/nginx-kubernetes-gateway/v0.6.0/examples/advanced-routing/tea.yaml

Deploy the HTTPRoute for the Tea Services

We are reusing the previous Gateway for these applications, so all we need to create is the HTTPRoute.

kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: tea
spec:
  parentRefs:
  - name: cafe
  hostnames:
  - cafe.example.com
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /tea
      method: POST
    backendRefs:
    - name: tea-post-svc
      port: 80
  - matches:
    - path:
        type: PathPrefix
        value: /tea
      method: GET
    backendRefs:
    - name: tea-svc
      port: 80
EOF

The properties of this HTTPRoute include:

  • The same Gateway is referenced as before.
  • The same hostname is used as with the coffee apps.
  • The first rule defines that a POST request to the /tea path is routed to the tea-post Service.
  • The second rule defines that a GET request to the /tea path is routed to the tea Service.

Send Traffic to Tea

Using the external IP address and port for NGINX Kubernetes Gateway, we can send traffic to our tea applications.

Note If you have a DNS record allocated for cafe.example.com, you can send the request directly to that hostname, without needing to resolve.

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

This GET request should receive a response from the tea Pod.

Server address: 10.244.0.10:8080
Server name: tea-df5655878-5fmfg

If we want our request to be routed to tea-post, then we need to send a POST request:

curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/tea -X POST
Server address: 10.244.0.7:8080
Server name: tea-post-b59b8596b-g586r

This request should receive a response from the tea-post Pod. Any other type of method, such as PATCH, will result in a 404 Not Found response.

Troubleshooting

If you have any issues while sending traffic, try the following to debug your configuration and setup:

  • Make sure you set the shell variables $GW_IP and $GW_PORT to the public IP and port of the NGINX Kubernetes Gateway Service. Instructions for finding those values are here.

  • Check the status of the Gateway:

    kubectl describe gateway cafe

    The Gateway status should look like this:

    Status:
Addresses:
  Type:   IPAddress
  Value:  10.244.0.85
Conditions:
  Last Transition Time:  2023-08-15T20:57:21Z
  Message:               Gateway is accepted
  Observed Generation:   1
  Reason:                Accepted
  Status:                True
  Type:                  Accepted
  Last Transition Time:  2023-08-15T20:57:21Z
  Message:               Gateway is programmed
  Observed Generation:   1
  Reason:                Programmed
  Status:                True
  Type:                  Programmed
Listeners:
  Attached Routes:  2
  Conditions:
    Last Transition Time:  2023-08-15T20:57:21Z
    Message:               Listener is accepted
    Observed Generation:   1
    Reason:                Accepted
    Status:                True
    Type:                  Accepted
    Last Transition Time:  2023-08-15T20:57:21Z
    Message:               Listener is programmed
    Observed Generation:   1
    Reason:                Programmed
    Status:                True
    Type:                  Programmed
    Last Transition Time:  2023-08-15T20:57:21Z
    Message:               All references are resolved
    Observed Generation:   1
    Reason:                ResolvedRefs
    Status:                True
    Type:                  ResolvedRefs
    Last Transition Time:  2023-08-15T20:57:21Z
    Message:               No conflicts
    Observed Generation:   1
    Reason:                NoConflicts
    Status:                False
    Type:                  Conflicted
  Name:                    http

    Check that the conditions match and that the attached routes for the http listener equals 2. If it is less than 2, there may be an issue with the routes.

  • Check the status of the HTTPRoutes:

    kubectl describe httproute coffee
    kubectl describe httproute tea

    Each HTTPRoute status should look like this:

    Status:
  Parents:
    Conditions:
      Last Transition Time:  2023-08-15T20:57:21Z
      Message:               The route is accepted
      Observed Generation:   1
      Reason:                Accepted
      Status:                True
      Type:                  Accepted
      Last Transition Time:  2023-08-15T20:57:21Z
      Message:               All references are resolved
      Observed Generation:   1
      Reason:                ResolvedRefs
      Status:                True
      Type:                  ResolvedRefs
    Controller Name:         gateway.nginx.org/nginx-gateway-controller
    Parent Ref:
      Group:      gateway.networking.k8s.io
      Kind:       Gateway
      Name:       cafe
      Namespace:  default

    Check for any error messages in the conditions.

Further Reading

To learn more about the Gateway API and the resources we created in this guide, check out the following resources: