Istio Routing - How to route default traffic to a specific service from istio gateway - istio

Question

I am trying to implement following routing strategy in my K8S cluster.
route foo/bar/* requests to bar-service
route foo/* requests (except foo/bar/*) requests to foo-service
I am new to istio and this strategy was already implemented with nginx ingress controller using regex but could not find a way in istio gateway and virtual service.

Answer 1

Try with edit the virtulaservice
name: "/foo/bar/"
match:
uri:
prefix: /foo/bar/*
rewrite:
uri: /
route:
destination:
host: bar-service
port:
number: 80
name: "foo/*"
match:
uri:
prefix: /foo/*
rewrite:
uri: /
route:
destination:
host: foo-service
port:
number: 80

Answer 2

This can be accomplished with a VirtualService and HTTP route rules. Let's say you have App1:
apiVersion: apps/v1
kind: Deployment
metadata:
name: app1
spec:
replicas: 1
selector:
matchLabels:
app: app1
template:
metadata:
labels:
app: app1
spec:
containers:
- name: app1
image: ghcr.io/trstringer/httpbin2:0.1.0
command: ["/httpbin2"]
args:
- "--message-hostname"
- "--port"
- "8080"
ports:
- containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
name: app1
spec:
selector:
app: app1
ports:
- name: http
port: 80
targetPort: 8080
And a second app, App2:
apiVersion: apps/v1
kind: Deployment
metadata:
name: app2
spec:
replicas: 1
selector:
matchLabels:
app: app2
template:
metadata:
labels:
app: app2
spec:
containers:
- name: app2
image: ghcr.io/trstringer/httpbin2:0.1.0
command: ["/httpbin2"]
args:
- "--message-hostname"
- "--port"
- "8080"
ports:
- containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
name: app2
spec:
selector:
app: app2
ports:
- name: http
port: 80
targetPort: 8080
In the event that you want app2 to serve all requests to /specific-route, and all other requests to app1, you'd first have to create a Gateway:
apiVersion: networking.istio.io/v1beta1
kind: Gateway
metadata:
name: app-routing
spec:
selector:
istio: ingressgateway
servers:
- port:
number: 80
name: http
protocol: HTTP
hosts:
- "httpbin2.com"
Now wire up a VirtualService to this Gateway, which will handle the routing:
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
name: appvs
spec:
hosts:
- "httpbin2.com"
gateways:
- app-routing
http:
- match:
- uri:
prefix: /specific-route
route:
- destination:
host: app2
- match:
- uri:
prefix: /
route:
- destination:
host: app1
If you look at VirtualService.spec.http you'll find the list of HTTPRoutes.
Here is where you define the ordered list of routes. The first one that is matched will be used, so you have to make sure the sub route is listed first.
Now if you do the following:
$ curl -H "host: httpbin2.com" http://20.102.18.97/specific-route/more
(app2-75548c4dd9-cjdzd)
You'll see the request goes to app2. But if you do a different route that doesn't match that, it'll fall back to app1:
curl -H "host: httpbin2.com" http://20.102.18.97/more/things/here
(app1-549c548585-8cqld)

Answer 3

Below virtual service can route requests to different foo, bar service respectively. if further change is required on request path change the regex pattern accordingly
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
name: fooapplication
namespace: default
spec:
gateways:
- foo-gateway
hosts:
- '*'
http:
- match:
- uri:
prefix: /foo
route:
- destination:
host: foo-service
port:
number: 8080
- match:
- uri:
regex: /foo.*
rewrite:
uri: /bar-service
route:
- destination:
host: bar-service
port:
number: 8080