ossm-header-routing

Simple demo to show routing based on headers via OSSM

This uses a ServiceEntry called product-api-entry in the frontend-ns namespace.

The VirtualService named product-api-routing evaluates headers when the ServiceEntry is called and routes to an internal service in another namespace based on the header.

This is for illustrative purposes, but you could use headers to route to dev, test, prod namespaces, for example.

Prereq-OSSM is installed and configured

See: (OSSM3 Demo SetUp)[https://github.com/bugbiteme/ossm-3-demo]

Apply istio.yaml to update it to handle DNS allocation

oc apply -f istio.yaml

Added config:

  values:
    meshConfig:
      defaultConfig:
        proxyMetadata:
          ISTIO_META_DNS_AUTO_ALLOCATE: "true"
          ISTIO_META_DNS_CAPTURE: "true"

Deploy Resources

GitOps

If using GitOps/ArgoCD, deploy front and back-end resources by applying the following

oc apply -f gitops/header-routing.yaml    

Example output:

application.argoproj.io/header-routing created

Non-GitOps

If you are not using GitOps, manually deploy the following

Deploy Back-End Services

Dev

oc apply -k backend/overlays/dev

Prod

oc apply -k backend/overlays/prod

QA

oc apply -k backend/overlays/qa

Deploy Front-End Service

oc apply -k frontend  

Sample output:

namespace/frontend-ns created
service/flask-front-end created
deployment.apps/flask-front-end created
serviceentry.networking.istio.io/product-api-entry created
virtualservice.networking.istio.io/product-api-routing created
route.route.openshift.io/flask-front-end created
pod/curl-test created

Test Header-Based Routing via pod network

This uses a test pod named curl-test to ensure header-based routing works

header dev

oc exec -n frontend-ns curl-test -- \
  curl -s -H "x-env-target: dev" \
       http://product-api.internal/hello

Output:

{"message":"Hello World from dev"}

header prod

oc exec -n frontend-ns curl-test -- \
  curl -s -H "x-env-target: prod" \
       http://product-api.internal/hello

Output:

{"message":"Hello World from prod"}

header qa

oc exec -n frontend-ns curl-test -- \
  curl -s -H "x-env-target: qa" \
       http://product-api.internal/hello

Output:

{"message":"Hello World from qa"}

Test Header-Based Routing via front-end app

The deployed application in the frontend-ns namespace is a Python/Flask app

It is currently exposed as a route, but feel free to create an ingress gateway if required

 oc get routes                                                                      
NAME              HOST/PORT                                                                     
flask-front-end   flask-front-end-frontend-ns.app.<domain>

This is a browser based app that allows you to test responses based on headers from a drop-down list

Source code found at ./code/flask

@app.route("/call-api")
def call_api():
...

    headers = {"x-env-target": env}
...

        response = requests.get("http://product-api.internal/hello", headers=headers) 
        return Response(response.content, status=response.status_code, mimetype="text/plain")
...