Running canary tests

To run a canary test so that some users are routed to the new versions while all other users are still routed to the old versions of the deployed microservices, we need to add the X-group HTTP header set to the value test in our requests sent to the external API.

To see which version of a microservice served a request, the serviceAddresses field in the response can be inspected. The serviceAddresses field contains the hostname of each service that took part in creating the response. The hostname is equal to the name of the Pod, so we can find the version in the hostname; for example, product-v1-... for a product service of version v1, and product-v2-... for a product service of version v2.

Let's begin by sending a normal request and verifying that it is the v1 versions of the microservices that respond to our request. Next, we'll send a request with the X-group HTTP header set to the value test, and verify that the new v2 versions are responding.

To do this, perform the following steps:

  1. Perform a normal request to verify that the request is routed to the v1 version of the microservices by using jq to filter out the serviceAddresses field in the response: 
   ACCESS_TOKEN=$(curl -k https://writer:secret@minikube.me/oauth2/token -d grant_type=client_credentials -s | jq .access_token -r)

   echo ACCESS_TOKEN=$ACCESS_TOKEN

   curl -ks https://minikube.me/product-composite/1 -H "Authorization: Bearer $ACCESS_TOKEN" | jq .serviceAddresses

Expect a response along the lines of the following:

Figure 18.25: All requests go to the v1 Pods

As expected, all three core services are v1 versions of the microservices.

  1. If we add the X-group=test header, we expect the request to be served by v2 versions of the core microservices. Run the following command: 
   curl -ks https://minikube.me/product-composite/1 -H "Authorization: Bearer $ACCESS_TOKEN" -H "X-group: test" | jq .serviceAddresses

Expect a response similar to the following:

Figure 18.26: Setting HTTP header X-group=test makes the requests go to the v2 Pods

As expected, all three core microservices that respond are now v2 versions; as a canary tester, we are routed to the new v2 versions!

Given that the canary tests returned the expected results, we are ready to allow normal users to be routed to the new v2 versions using blue/green deployment.