404 Not Found when migrating from ingress to istio - kubernetes

Question

I'm trying to migrate from ingress to istio gateway + virtual service routing, but I keep receiving a 404 Not Found error.
The only link that the app should be accessed to is using my-todos.com, configured locally.
What am I missing here?
Note: the ingress controller works just fine. Initially, todo-lb.default.svc.cluster.local in the istio.yaml file was just set to todo-lb, representing the configured load balancer, still with no success.
Here is the ingress.yaml file (to migrate from):
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: todo-ingress
spec:
rules:
- host: my-todos.com
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: todo-lb
port:
number: 3001
- path: /api
pathType: Prefix
backend:
service:
name: {{ .Values.api.apiName }}
port:
number: {{ .Values.api.apiPort }}
Here is the istio.yaml file (to migrate TO):
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: todo-istio-gateway
namespace: istio-system
spec:
selector:
istio: ingressgateway # use istio default controller
servers:
- port:
number: 80
name: http
protocol: HTTP
hosts:
- my-todos.com
# - "*"
tls:
httpsRedirect: true
- port:
number: 443
name: https
protocol: HTTPS
tls:
mode: SIMPLE
credentialName: tls-secret
hosts:
- my-todos.com
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: todo-lb
spec:
hosts:
- my-todos.com
# - "*"
gateways:
- todo-istio-gateway
http:
- match:
- uri:
prefix: /
route:
- destination:
host: todo-lb.default.svc.cluster.local
port:
number: 3001
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: todo-api
spec:
hosts:
- my-todos.com
# - "*"
gateways:
- todo-istio-gateway
http:
- match:
- uri:
prefix: /api
route:
- destination:
host: {{ .Values.api.apiName }}
port:
number: {{ .Values.api.apiPort }}

Answer 1

From what I see you've wrong gateway configuration in your virtual service, that's why it might not work.
If gateway is not in the same namespace as virtual service, you have to specify that in virtual service
Check the spec.gateways section
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: bookinfo-Mongo
spec:
gateways:
- some-config-namespace/my-gateway # can omit the namespace if gateway is in same
namespace as virtual service.
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
name: my-gateway
namespace: some-config-namespace
There is related istio documentation about that.
So please move your todo-istio-gateway to default namespace.
or use
gateways:
- istio-system/todo-istio-gateway
Few things to check if that won't help:
Is your app deployed in default namespace?
Is your app injected?

Answer 2

Problem might be with your Gateway api:
404 errors occur when multiple gateways configured with same TLS certificate
Configuring more than one gateway using the same TLS certificate will cause browsers that leverage HTTP/2 connection reuse (i.e., most browsers) to produce 404 errors when accessing a second host after a connection to another host has already been established.
For example, let’s say you have 2 hosts that share the same TLS certificate like this:
Wildcard certificate .test.com installed in istio-ingressgateway
Gateway configuration gw1 with host service1.test.com, selector istio: ingressgateway, and TLS using gateway’s mounted (wildcard) certificate
Gateway configuration gw2 with host service2.test.com, selector istio: ingressgateway, and TLS using gateway’s mounted (wildcard) certificate
VirtualService configuration vs1 with host service1.test.com and gateway gw1
VirtualService configuration vs2 with host service2.test.com and gateway gw2
Since both gateways are served by the same workload (i.e., selector istio: ingressgateway) requests to both services (service1.test.com and service2.test.com) will resolve to the same IP. If service1.test.com is accessed first, it will return the wildcard certificate (.test.com) indicating that connections to service2.test.com can use the same certificate. Browsers like Chrome and Firefox will consequently reuse the existing connection for requests to service2.test.com. Since the gateway (gw1) has no route for service2.test.com, it will then return a 404 (Not Found) response.
You can avoid this problem by configuring a single wildcard Gateway, instead of two (gw1 and gw2). Then, simply bind both VirtualServices to it like this:
Gateway configuration gw with host *.test.com, selector istio: ingressgateway, and TLS using gateway’s mounted (wildcard) certificate
VirtualService configuration vs1 with host service1.test.com and gateway gw
VirtualService configuration vs2 with host service2.test.com and gateway
checkout this link:
https://istio.io/latest/docs/ops/common-problems/network-issues/#404-errors-occur-when-multiple-gateways-configured-with-same-tls-certificate

Answer 3

In addition to #Jakub answer, there can be one more reason you can get 404 error. Your current ingress rules in virtual service looks like this:
Hostname
Path
Route
my-todos.com
/
Forward to todo-lb.default.svc.cluster.local
my-todos.com
/api
Forward to {{ .Values.api.apiName }}
In Istio, each of the above is an ingress rule. If in Istio ingress-gateway, the rules are added in the above order, then all the URL path including the prefix /api gets routed to the first service i.e. todo-lb.default. It is better to create a single Virtual service like this and then see if the routing works as expected.
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
name: todo-api
spec:
hosts:
- my-todos.com
gateways:
- <namespace>/todo-istio-gateway
http:
- match:
- uri:
prefix: /api
route:
- destination:
host: {{ .Values.api.apiName }}
port:
number: {{ .Values.api.apiPort }}
- match:
- uri:
prefix: /
route:
- destination:
host: todo-lb.default
port:
number: 3001