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# Serverless
> Introduced in GitLab 11.5.
Run serverless workloads on Kubernetes using [Knative](https://cloud.google.com/knative/).
## Overview
Knative extends Kubernetes to provide a set of middleware components that are useful to build modern, source-centric, container-based applications. Knative brings some significant benefits out of the box through its main components:
- [Build:](https://github.com/knative/build) Source-to-container build orchestration
- [Eventing:](https://github.com/knative/eventing) Management and delivery of events
- [Serving:](https://github.com/knative/serving) Request-driven compute that can scale to zero
For more information on Knative, visit the [Knative docs repo](https://github.com/knative/docs).
## Requirements
To run Knative on Gitlab, you will need:
1. **Kubernetes:** An RBAC-enabled Kubernetes cluster is required to deploy Knative.
The simplest way to get started is to add a cluster using [GitLab's GKE integration](https://docs.gitlab.com/ee/user/project/clusters/#adding-and-creating-a-new-gke-cluster-via-gitlab).
GitLab recommends
1. **Helm Tiller:** Helm is a package manager for Kubernetes and is required to install
all the other applications.
1. **Domain Name:** Knative will provide its own load balancer using Istio. It will provide an
external IP address for all the applications served by Knative. You will be prompted to enter a
wildcard domain where your applications will be served. Configure your DNS server to use the
external IP address for that domain.
1. **Serverless `gitlab-ci.yml` Template:** GitLab uses [Kaniko](https://github.com/GoogleContainerTools/kaniko)
to build the application and the [TriggerMesh CLI](https://github.com/triggermesh/tm), to simplify the
deployment of knative services and functions.
Add the following `.gitlab-ci.yml` to the root of your repository (you may skip this step if using the sample
[Knative Ruby App](https://gitlab.com/knative-examples/knative-ruby-app) mentioned below).
```yaml
stages:
- build
- deploy
build:
stage: build
image:
name: gcr.io/kaniko-project/executor:debug
entrypoint: [""]
only:
- master
script:
- echo "{\"auths\":{\"$CI_REGISTRY\":{\"username\":\"$CI_REGISTRY_USER\",\"password\":\"$CI_REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
- /kaniko/executor --context $CI_PROJECT_DIR --dockerfile $CI_PROJECT_DIR/Dockerfile --destination $CI_REGISTRY_IMAGE
deploy:
stage: deploy
image: gcr.io/triggermesh/tm@sha256:e3ee74db94d215bd297738d93577481f3e4db38013326c90d57f873df7ab41d5
only:
- master
environment: production
script:
- echo "$CI_REGISTRY_IMAGE"
- tm -n "$KUBE_NAMESPACE" --config "$KUBECONFIG" deploy service "$CI_PROJECT_NAME" --from-image "$CI_REGISTRY_IMAGE" --wait
```
1. **Dockerfile:** Knative requires a Dockerfile in order to build your application. It should be included
at the root of your project's repo and expose port 8080.
## Installing Knative via GitLab's Kubernetes integration
NOTE: **Note:**
Minimum recommended cluster size to run Knative is 3-nodes, 6 vCPUs, and 22.50 GB memory. RBAC must be enabled.
You may download the sample [Knative Ruby App](https://gitlab.com/knative-examples/knative-ruby-app) to get started.
1. [Add a Kubernetes cluster](https://docs.gitlab.com/ce/user/project/clusters/) and install Helm.
1. Once Helm has been successfully installed, on the Knative app section, enter the domain to be used with
your application and click "Install".
1. After the Knative installation has finished, retrieve the Istio Ingress IP address by running the following command:
```bash
kubectl get svc --namespace=istio-system knative-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip} '
```
Output:
```bash
35.161.143.124 my-machine-name:~ my-user$
```
1. The ingress is now available at this address and will route incoming requests to the proper service based on the DNS
name in the request. To support this, a wildcard DNS A record should be created for the desired domain name. For example,
if your Knative base domain is `knative.example.com` then you need to create an A record with domain `*.knative.example.com`
pointing the ip address of the ingress.
## Deploy the application with Knative
With all the pieces in place, you can simply create a new CI pipeline to deploy the Knative application. Navigate to
**CI/CD >> Pipelines** and click the **Run Pipeline** button at the upper-right part of the screen. Then, on the
Pipelines page, click **Create pipeline**.
## Obtain the URL for the Knative deployment
Once all the stages of the pipeline finish, click the **deploy** stage.
The output will look like this:
```bash
Running with gitlab-runner 11.5.0~beta.844.g96d88322 (96d88322)
on docker-auto-scale 72989761
Using Docker executor with image gcr.io/triggermesh/tm@sha256:e3ee74db94d215bd297738d93577481f3e4db38013326c90d57f873df7ab41d5 ...
Pulling docker image gcr.io/triggermesh/tm@sha256:e3ee74db94d215bd297738d93577481f3e4db38013326c90d57f873df7ab41d5 ...
Using docker image sha256:6b3f6590a9b30bd7aafb9573f047d930c70066e43955b4beb18a1eee175f6de1 for gcr.io/triggermesh/tm@sha256:e3ee74db94d215bd297738d93577481f3e4db38013326c90d57f873df7ab41d5 ...
Running on runner-72989761-project-4342902-concurrent-0 via runner-72989761-stg-srm-1541795796-27929c96...
Cloning repository...
Cloning into '/builds/danielgruesso/knative'...
Checking out 8671ad20 as master...
Skipping Git submodules setup
$ echo "$CI_REGISTRY_IMAGE"
registry.staging.gitlab.com/danielgruesso/knative
$ tm -n "$KUBE_NAMESPACE" --config "$KUBECONFIG" deploy service "$CI_PROJECT_NAME" --from-image "$CI_REGISTRY_IMAGE" --wait
Deployment started. Run "tm -n knative-4342902 describe service knative" to see the details
Waiting for ready state.......
Service domain: knative.knative-4342902.knative.info
Job succeeded
```
The second to last line, labeled **Service domain** contains the URL for the deployment. Copy and paste the domain into your
browser to see the app live.
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