Add support for an internal load balancer along with an external one

[lgg42]

Signed-off-by: Luis Garnica Guilarte luisgarnica42@gmail.com

What this PR does / why we need it:

My team and people from other companies have found uses cases where they have a DNS in split-view configuration and need two ingress to handle internal and external requests for the same deployment. A way for doing this is having a second nginx ignress controller with a different class name like "nginx-internal" which handles these internal connections. This requires like mentioned to have two separate controllers and also two ingress objects per deployment.

With this method (which is proven to work and is being used in production by several people) an identical load balancer to the existing external is deployed with the same ingress controller, but the last one having annotations for being an internal load balancer.

By default ingress objects created will point to the external load balancer address. But if within the private network (AWS VPC, etc..) a host URL can be resolved to the internal load balancer address, the existing ingress controller will handle this request.

Example: (suppose an AWS VPC with Route53 split-view setup)

After chart deployment two LoadBalancers are created:

kube-system    nginx-ingress-controller            LoadBalancer   172.20.163.235   a918d1608db52464jbef89570f0b0e86-1213156713.eu-west-1.elb.amazonaws.com           80:31838/TCP,443:32682/TCP   16h
kube-system    nginx-ingress-controller-internal   LoadBalancer   172.20.18.98     internal-a43bec90d21af42fbj386f131f86b817-869934591.eu-west-1.elb.amazonaws.com   80:30460/TCP,443:32104/TCP   5s

And we also create a sample app with an ingress object:

$ kubectl get ing
NAME                HOSTS                          ADDRESS                                                                   PORTS     AGE
guestbook-ingress   guestbook-app.domain.tld   a918d1608db52464jbef89570f0b0e86-1213156713.eu-west-1.elb.amazonaws.com   80, 443   6s

In Route53 we set a record in the public zone

guestbook-app.domain.tld CNAME a918d1608db52464jbef89570f0b0e86-1213156713.eu-west-1.elb.amazonaws.com

Then in the private zone

guestbook-app.domain.tld CNAME internal-a43bec90d21af42fbj386f131f86b817-869934591.eu-west-1.elb.amazonaws.com

If doing a request to guestbook-app.domain.tld from outside the VPC, the external LoadBalancer will handle it. While if making the request to the same domain within the VPC the internal LoadBalancer will handle it, But in both cases hitting the same and single nginx ingress controller.

Example of DNS resolution with the previous setup
outside the VPC

$ nslookup guestbook-app.domain.tld
Server:		192.168.1.1
Address:	192.168.1.1#53

Non-authoritative answer:
guestbook-app.domain.tld	canonical name = a918d1608db52464jbef89570f0b0e86-1213156713.eu-west-1.elb.amazonaws.com.
Name:	a918d1608db52464jbef89570f0b0e86-1213156713.eu-west-1.elb.amazonaws.com
Address: 51.11.248.22
Name:	a918d1608db52464jbef89570f0b0e86-1213156713.eu-west-1.elb.amazonaws.com
Address: 61.52.15.25

within the VPC

[ec2-user@ip-10-30-1-221 ~]$ nslookup guestbook-app.domain.tld
Server:		10.30.0.2
Address:	10.30.0.2#53

Non-authoritative answer:
guestbook-app.domain.tld	canonical name = internal-a43bec90d21af42fbj386f131f86b817-869934591.eu-west-1.elb.amazonaws.com.
Name:	internal-a43bec90d21af42fbj386f131f86b817-869934591.eu-west-1.elb.amazonaws.com Address: 10.30.2.93
Name:	internal-a43bec90d21af42fbj386f131f86b817-869934591.eu-west-1.elb.amazonaws.com Address: 10.30.3.142

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Which issue/s this PR fixes

None.

How Has This Been Tested?

Environment: AWS EKS 1.16 cluster

Tests:
lint: helm lint .
template: helm template . and helm template . -f custom-values.yaml

custom-values.yaml enabled/configured the new funcionality.

First, the chart was deployed with default values. A sample app was deployed and the default external ingress worked OK.

After that, the new functionality was enabled and configured in values file and the release was upgraded with: helm upgrade ingress-nginx charts/ingress-nginx -i --atomic --cleanup-on-fail --namespace kube-system --version 2.4.0 -f values/ingress.yaml

It created the new internal load balancer. I tested first the external load balancer → still working OK.
Then I tested the internal load balancer with the approach described in "What this PR does / why we need it"

Then I modified again the values file for disabling the new funcionality and did the same helm upgrade as before → The internal load balancer was taken out of service and the external load balancer kept working OK.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added tests to cover my changes.
• All new and existing tests passed.

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[lgg42]

"I signed it"

[lgg42]

/assign @ChiefAlexander

[ChiefAlexander]

/ok-to-test

[ChiefAlexander]

This is looking good. Please squash your commits. https://github.com/kubernetes/community/blob/master/contributors/guide/pull-requests.md#6-squashing

[lgg42]

This is looking good. Please squash your commits. https://github.com/kubernetes/community/blob/master/contributors/guide/pull-requests.md#6-squashing

Squash done.

[ChiefAlexander]

/lgtm
Thanks!

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ChiefAlexander, lgg42

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[lgg42]

/lgtm
Thanks!

Thank you! for letting this PR go through so quickly 🙌