Kubeless

Kubeless "is a Kubernetes-native serverless framework that lets you deploy small bits of code (functions) without having to worry about the underlying infrastructure. It is designed to be deployed on top of a Kubernetes cluster and take advantage of all the great Kubernetes primitives". ~ source

Installation

Installation is made of three steps:

• Download the kubeless CLI from the release page;
• create a kubeless namespace (used by default); and
• then use one of the YAML manifests found in the release page to deploy kubeless. It will create a functions Custom Resource Definition and launch a controller.

There are several kubeless manifests being shipped for multiple k8s environments (non-rbac, rbac and openshift), pick the one that corresponds to your environment:

• kubeless-${RELEASE}.yaml is used for RBAC Kubernetes cluster.
• kubeless-non-rbac-${RELEASE}.yaml is used for non-RBAC Kubernetes cluster.
• kubeless-openshift-${RELEASE}.yaml is used to deploy Kubeless to OpenShift (1.5+).

For example, this below is a show case of deploying kubeless to a Kubernetes cluster (with RBAC available).

$ export RELEASE=$(curl -s https://api.github.com/repos/kubeless/kubeless/releases/latest | grep tag_name | cut -d '"' -f 4)
$ kubectl create ns kubeless
$ kubectl create -f https://github.com/kubeless/kubeless/releases/download/${RELEASE}/kubeless-${RELEASE}.yaml

$ kubectl get pods -n kubeless
NAME                                           READY     STATUS    RESTARTS   AGE
kubeless-controller-manager-567dcb6c48-ssx8x   1/1       Running   0          1h

$ kubectl get deployment -n kubeless
NAME                          DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
kubeless-controller-manager   1         1         1            1           1h

$ kubectl get customresourcedefinition
NAME                          AGE
cronjobtriggers.kubeless.io   1h
functions.kubeless.io         1h
httptriggers.kubeless.io      1h

Details on installing kubeless in a different namespace can be found here.

• Install the kubeless CLI:

$ export OS=$(uname -s| tr '[:upper:]' '[:lower:]')
$ curl -OL https://github.com/kubeless/kubeless/releases/download/${RELEASE}/kubeless_${OS}-amd64.zip && \
    unzip kubeless_${OS}-amd64.zip && \
    sudo mv bundles/kubeless_${OS}-amd64/kubeless /usr/local/bin/

Binaries for x86 architectures can be found as well in the releases page.

Sample function

You can use the CLI to create a function. Here is a toy example:

def hello(event, context):
    print event
    return event['data']

Functions in Kubeless have the same format regardless of the language of the function or the event source. In general, every function:

• Receives an object event as their first parameter. This parameter includes all the information regarding the event source. In particular, the key "data" should contain the body of the function request.
• Receives a second object context with general information about the function.
• Returns a string/object that will be used as a response for the caller.

You can find more details about the function interface here.

You create it with:

$ kubeless function deploy hello --runtime python2.7 \
                                 --from-file test.py \
                                 --handler test.hello
INFO[0000] Deploying function...
INFO[0000] Function hello submitted for deployment
INFO[0000] Check the deployment status executing 'kubeless function ls hello'

Let us dissect the command:

• hello: This is the name of the function we want to deploy.
• --runtime python2.7: This is the runtime we want to use to run our function. Available runtimes can be found executing kubeless get-server-config.
• --from-file test.py: This is the file containing the function code. It is supported to specify a zip file as far as it does not exceed the maximum size for an etcd entry (1 MB).
• --handler test.foobar: This specifies the file and the exposed function that will be used when receiving requests. In this example, we are using the function foobar from the file test.py.

You can find the rest of options available when deploying a function executing kubeless function deploy --help

You will see the function custom resource created:

$ kubectl get functions
NAME         AGE
hello        1h

$ kubeless function ls
NAME            NAMESPACE   HANDLER       RUNTIME   DEPENDENCIES    STATUS
hello           default     helloget.foo  python2.7                 1/1 READY

• You can then call the function with:

$ kubeless function call hello --data 'Hello world!'
Hello world!

Or you can curl directly with kubectl proxy using an apiserver proxy URL.

• For example:

$ kubectl proxy -p 8080 &

$ curl -L --data '{"Another": "Echo"}' \
  --header "Content-Type:application/json" \
  localhost:8080/api/v1/namespaces/default/services/hello:http-function-port/proxy/
{"Another": "Echo"}

Kubeless also supports ingress which means you can provide your custom URL to the function. Refer to this doc for more details.

Clean up

• You can delete the function and uninstall Kubeless:

$ kubeless function delete hello

$ kubeless function ls
NAME        NAMESPACE   HANDLER     RUNTIME     DEPENDENCIES    STATUS

$ kubectl delete -f https://github.com/kubeless/kubeless/releases/download/$RELEASE/kubeless-$RELEASE.yaml

See also

• Kubernetes
• Istio

External links

• Official website
• Quick Start