Spring Cloud Gateway on Kubernetes discovery locator use pod port instead o service port

Question

i'm implementing an API Gateway on openshift with spring cloud gateway and spring cloud kubernetes discovery.

I started from the project https://github.com/salaboy/s1p_gateway.

My gateway configuration is:

cloud:
    gateway:
      discovery:
        locator:
          enabled: true
          url-expression: "'http://'+serviceId+':'+port"
    kubernetes:
      reload:
        enabled: true
        mode: polling
        period: 5000
      discovery:
        service-labels:
           type: "java-api"

When i view my /actuator/gateway/routes i can see services discovered:

{
   "predicate":"Paths: [/common/**], match trailing slash: true",
   "route_id":"ReactiveCompositeDiscoveryClient_common",
   "filters":[
      "[[RewritePath /common/(?<remaining>.*) = '/${remaining}'], order = 1]"
   ],
   "uri":"http://common:8085",
   "order":0
}

The problem is that 8085 is the targetPort (i.e. pod port) and not the service port:

kind: Service
apiVersion: v1
metadata:
  name: common
  namespace: p4p
  selfLink: /api/v1/namespaces/myspace/services/common
  uid: 1851a76f-4764-11ea-a02c-000d3aa9b693
  resourceVersion: '28657990'
  creationTimestamp: '2020-02-04T15:36:21Z'
  labels:
    app: common
    type: java-api
spec:
  ports:
    - protocol: TCP
      port: 8080
      targetPort: 8085
  selector:
    app: common
    deploymentconfig: common
  clusterIP: 172.30.7.24
  type: ClusterIP
  sessionAffinity: None
status:
  loadBalancer: {}

In order to get API gateway to work i MUST to align pod port and service port, but it sounds quite strange.

hello, did you solve problem? i take same error when there are multiple instances(pods), but no error when there is one pod. — denizg, Jul 28 '20 at 07:40
Hi, i aligned pod port and service port. Every container starts spring-boot with "-Dserver.port=8080". — angcap, Jul 29 '20 at 09:24

score 0 · Answer 1 · answered Feb 06 '20 at 16:09

Is Ribbon being used? Ribbon's default spring.cloud.kubernetes.ribbon.mode is POD. From the docs (quote):

spring.cloud.kubernetes.ribbon.mode supports POD and SERVICE modes.

The POD mode is to achieve load balancing by obtaining the Pod IP address of Kubernetes and using Ribbon. POD mode uses the load balancing of the Ribbon Does not support Kubernetes load balancing, The traffic policy of Istio is not supported.

the SERVICE mode is directly based on the service name of the Ribbon. Get The Kubernetes service is concatenated into service-name.{namespace}.svc.{cluster.domain}:{port} such as: demo1.default.svc.cluster.local:8080. the SERVICE mode uses load balancing of the Kubernetes service to support Istio’s traffic policy.

When i try to call rest api via gateway i get ```There was an unexpected error (type=Internal Server Error, status=500). finishConnect(..) failed: Host is unreachable: common/172.30.7.24:8085``` and the service is ```Name: common Type: ClusterIP IP: 172.30.7.24 Port: 8080/TCP TargetPort: 8085/TCP Endpoints: 10.129.3.101:8085 ``` It seems uses the service IP and the pod port. I have also added ```spring.cloud.kubernetes.ribbon.mode=SERVICE``` but nothing has changed. — angcap, Feb 06 '20 at 17:12

mario · Answer 2 · 2020-02-06T20:15:35.483

0

Why cannot you simply set Service port (port) to 8085 so it exposes the same port as Pod does ? Nothing actually prevents you from doing so.

When i try to call rest api via gateway i get
There was an unexpected error (type=Internal Server Error, status=500). finishConnect(..) failed: Host is unreachable: common/172.30.7.24:8085
and the service is
Name: common Type: ClusterIP IP: 172.30.7.24 Port: <unset> 8080/TCP TargetPort: 8085/TCP Endpoints: 10.129.3.101:8085
It seems uses the service IP and the pod port. I have also added spring.cloud.kubernetes.ribbon.mode=SERVICE but nothing has changed.

From what you posted it looks like when you're trying to call your rest api via gateway it expects it to be exposed using your Service IP (172.30.7.24) and port 8085, so simply expose it on that port and it should work fine:

...
spec:
  ports:
    - protocol: TCP
      port: 8085
      targetPort: 8085
...

Please let me know if it helps.

edited Feb 06 '20 at 20:15

answered Feb 06 '20 at 18:13

mario

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This is exactly how the question ends: "...In order to get API gateway to work i MUST to align pod port and service port, but it sounds quite strange". – gears Feb 06 '20 at 18:49
Yes, I noticed that and I'm asking why it sounds strange because for me there is nothing strange in exposing via `Service` the right port that is expected by api client ? Could you explain it ? – mario Feb 06 '20 at 20:18
No, I can't explain it. It could be a bug, I guess, but haven't had a chance to look into the code (there were issues some time ago with multiple ports - only the first was picked...if I remember). So, setting `port` and `targetPort` to be the same could be a workaround, I agree. – gears Feb 07 '20 at 15:25

Spring Cloud Gateway on Kubernetes discovery locator use pod port instead o service port

2 Answers2