Serverless (Knative)

This document instructs you to set up a working GitLab instance that can deploy Serverless applications (that is, Knative services) to a Kubernetes cluster via GitLab CI/CD.

Prerequisites

Please follow all the instructions for setting up Kubernetes before following any steps in here.

Minimal getting started guide

1. Since Serverless builds with Kaniko, follow workaround instructions in https://gitlab.com/gitlab-org/gitlab-development-kit/issues/547#workaround until this problem is solved
2. Create a new project
3. Add a cluster to the project
4. Install Tiller and Knative on the cluster. When installing Knative you are asked for a domain name. You later need to set up a DNS record for this domain name in order to reach your deployed serverless applications so it’s necessary that you own this domain name. Alternatively there are some workarounds to avoid buying a domain name below.
5. Assuming you used a domain name that you own, you then need to set up a wildcard DNS record that points to the IP address of the Knative Ingress. Once the IP address finishes fetching (usually a few minutes after Knative install finishes) then go to your DNS provider and set up a wildcard A record pointing to this IP address. Assuming you used example.com as the domain for Knative and the IP address is 1.2.3.4 then you need to create an A record like *.example.com -> 1.2.3.4.
6. Now clone this minimal example Ruby app and push to your project to deploy a Knative service

Workarounds to avoid buying a domain name

Unfortunately we cannot use the same technique we use with Auto DevOps to avoid buying a domain name (ie. using nip.io) since the IP address loads after setting the hostname and we have no way to update the hostname.

Some other options for avoiding buying a domain name include:

• If you are just testing locally all you need to do is trick the DNS resolver on your computer to think that you own example.com and think that it is pointing to the IP address of Knative. You can do this in multiple ways but the simplest way is to edit the /etc/hosts file on your machine to basically add line like <ip-address> <blah>.example.com where <ip-address> is the IP of Knative shown in the UI and <blah>.example.com is the domain of your function in the serverless tab or CI output.
• There is another way to trick your computer to call to a specific domain for a Knative function using curl which is that you can make a request to the function like curl -H 'Host: <blah>.example.com' "http://<ip-address>" and this should also end up executing the function for you. This ensures the request reaches the IP address of your Knative Ingress and setting the Host header ensures that the Knative Ingress knows which function to forward the request to.