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Signed-off-by: Alex Ellis (OpenFaaS Ltd) <>
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@alexellis @stefanprodan @LucasRoesler @rimusz @jonatasbaldin @bmcustodio @bartsmykla @viveksyngh @nlochschmidt @milsonian @matthiashanel @martindekov

OpenFaaS - Serverless Functions Made Simple

OpenFaaS logo

OpenFaaS (Functions as a Service) is a framework for building serverless functions with Docker and Kubernetes which has first class support for metrics. Any process can be packaged as a function enabling you to consume a range of web events without repetitive boiler-plate coding.


  • Ease of use through UI portal and one-click install
  • Write functions in any language for Linux or Windows and package in Docker/OCI image format
  • Portable - runs on existing hardware or public/private cloud. Native Kubernetes support, Docker Swarm also available
  • Operator / CRD option available
  • faas-cli available with stack.yml for creating and managing functions
  • Auto-scales according to metrics from Prometheus
  • Scales to zero and back again and can be tuned at a per-function level
  • Works with service-meshes
    • Tested with Istio including mTLS
    • Tested with Linkerd2 including mTLS and traffic splitting with SMI

Deploy OpenFaaS

1) Install with arkade

It is recommended that you use arkade to install OpenFaaS. arkade is a CLI tool which automates the helm CLI and chart download and installation. The openfaas app also has a number of options available via arkade install openfaas --help

The installation with arkade is as simple as the following which installs OpenFaaS, sets up an Ingress record, and a TLS certificate with cert-manager.

arkade install openfaas
arkade install openfaas-ingress \
  --domain \

See a complete example here: Get TLS for OpenFaaS the easy way with arkade

If you wish to continue without using arkade, read on for instructions.

2) Install with helm

These instructions are for Intel (normal computers), jump to the end of the document for ARM and Raspberry Pi.

To use the chart, you will need to use Helm 3:

Get it from arkade:

arkade get helm

Or use the helm3 installer:

curl -sSLf | bash

We recommend creating two namespaces, one for the OpenFaaS core services and one for the functions:

kubectl apply -f

You will now have openfaas and openfaas-fn. If you want to change the names or to install into multiple installations then edit namespaces.yml from the faas-netes repo.

Add the OpenFaaS helm chart:

helm repo add openfaas

Now decide how you want to expose the services and edit the helm upgrade command as required.

  • To use NodePorts (default) pass no additional flags
  • To use a LoadBalancer add --set serviceType=LoadBalancer
  • To use an IngressController add --set ingress.enabled=true

Note: even without a LoadBalancer or IngressController you can access your gateway at any time via kubectl port-forward.

Deploy OpenFaaS Community components

OpenFaaS PRO customers should read on to the next section.

Now deploy OpenFaaS from the helm chart repo:

helm repo update \
 && helm upgrade openfaas --install openfaas/openfaas \
    --namespace openfaas  \
    --set functionNamespace=openfaas-fn \
    --set generateBasicAuth=true

The above command will also update your helm repo to pull in any new releases.

Retrieve the OpenFaaS credentials with:

PASSWORD=$(kubectl -n openfaas get secret basic-auth -o jsonpath="{.data.basic-auth-password}" | base64 --decode) && \
echo "OpenFaaS admin password: $PASSWORD"

Deploy as an OpenFaaS PRO customer

kubectl create secret generic \
    -n openfaas \
    openfaas-license \
    --from-file license=$HOME/OPENFAAS_LICENSE

Now deploy OpenFaaS from the helm chart repo:

helm repo update \
 && helm upgrade openfaas --install openfaas/openfaas \
    --namespace openfaas  \
    --set functionNamespace=openfaas-fn \
    --set generateBasicAuth=true \
    --set openfaasPRO=true

The main change here is to add: --set openfaasPRO=true

See also:

Generate basic-auth credentials

The chart has a pre-install hook which can generate basic-auth credentials, enable it with --set generateBasicAuth=true.

Alternatively, you can set generateBasicAuth to false and generate or supply the basic-auth credentials yourself. This is the option you may want if you are using helm template.

# generate a random password
PASSWORD=$(head -c 12 /dev/urandom | shasum| cut -d' ' -f1)
kubectl -n openfaas create secret generic basic-auth \
--from-literal=basic-auth-user=admin \

echo "OpenFaaS admin password: $PASSWORD"

Tuning function cold-starts

The concept of a cold-start in OpenFaaS only applies if you A) use faas-idler and B) set a specific function to scale to zero. Otherwise there is not a cold-start, because at least one replica of your function remains available.

There are two ways to reduce the Kubernetes cold-start for a pre-pulled image, which is around 1-2 seconds.

  1. Don't set the function to scale down to zero, just set it a minimum availability i.e. 1/1 replicas
  2. Use async invocations via the /async-function/<name> route on the gateway, so that the latency is hidden from the caller
  3. Tune the readinessProbes to be aggressively low values. This will reduce the cold-start at the cost of more kubelet CPU usage

To achieve around 1s coldstart, set values.yaml:


# redacted
    initialDelaySeconds: 0
    timeoutSeconds: 1
    periodSeconds: 1
    initialDelaySeconds: 0
    timeoutSeconds: 1
    periodSeconds: 1
# redacted
  imagePullPolicy: "IfNotPresent"    # Image pull policy for deployed functions

In addition:

  • Pre-pull images on each node
  • Use an in-cluster registry to reduce the pull latency for images
  • Set the imagePullPolicy to IfNotPresent so that the kubelet only pulls images which are not already available
  • Explore alternatives such as not scaling to absolute zero, and using async calls which do not show the cold start

httpProbe vs. execProbe

A note on health-checking probes for functions:

  • httpProbe - (default) most efficient. (compatible with Istio >= 1.1.5)
  • execProbe - least efficient option, but compatible with Istio < 1.1.5

Use --set faasnetes.httpProbe=true/false to toggle between http / exec probes.

Verify the installation

Once all the services are up and running, log into your gateway using the OpenFaaS CLI. This will cache your credentials into your ~/.openfaas/config.yml file.

Fetch your public IP or NodePort via kubectl get svc -n openfaas gateway-external -o wide and set it as an environmental variable as below:


If using a remote cluster, you can port-forward the gateway to your local machine:

kubectl port-forward -n openfaas svc/gateway 8080:8080 &

Now log in with the CLI and check connectivity:

echo -n $PASSWORD | faas-cli login -g $OPENFAAS_URL -u admin --password-stdin

faas-cli version

OpenFaaS Operator and Function CRD

If you would like to work with Function CRDs there is an alternative controller to faas-netes named OpenFaaS Operator which can be swapped in at deployment time. The OpenFaaS Operator is suitable for development and testing and may replace the faas-netes controller in the future. The Operator is compatible with Kubernetes 1.9 or later.

To use it, add the flag: --set operator.create=true when installing with Helm.

faas-netes vs OpenFaaS Operator

The faas-netes controller is the most tested, stable and supported version of the OpenFaaS integration with Kubernetes. In contrast the OpenFaaS Operator is based upon the codebase and features from faas-netes, but offers a tighter integration with Kubernetes through CustomResourceDefinitions. This means you can type in kubectl get functions for instance.

See also: Introducing the OpenFaaS Operator

Deployment with helm template

This option is good for those that have issues with or concerns about installing Tiller, the server/cluster component of helm. Using the helm CLI, we can pre-render and then apply the templates using kubectl.

  1. Clone the faas-netes repository

    git clone
    cd faas-netes
  2. Render the chart to a Kubernetes manifest called openfaas.yaml

    helm template \
      openfaas chart/openfaas/ \
      --namespace openfaas \
      --set basic_auth=true \
      --set functionNamespace=openfaas-fn > openfaas.yaml

    You can set the values and overrides just as you would in the install/upgrade commands above.

  3. Install the components using kubectl

    kubectl apply -f namespaces.yml,openfaas.yaml

Now verify your installation.

Test a local helm chart

You can run the following command from within the faas-netes/chart folder in the faas-netes repo.

helm upgrade openfaas --install chart/openfaas \
    --namespace openfaas \
    --set basic_auth=true \
    --set functionNamespace=openfaas-fn \
    --set generateBasicAuth=true

You can override specific images by adding --set gateway.image= for instance.

Exposing services


By default a NodePort will be created for the API Gateway.


You temporarily access the Prometheus metrics by using port-forward

kubectl --namespace openfaas port-forward deployment/prometheus 31119:9090

Then open http://localhost:31119 to directly query the OpenFaaS metrics scraped by Prometheus.


If you're running on a cloud such as AKS or GKE you will need to pass an additional flag of --set serviceType=LoadBalancer to tell helm to create LoadBalancer objects instead. An alternative to using multiple LoadBalancers is to install an Ingress controller.

Deploy with an IngressController

In order to make use of automatic ingress settings you will need an IngressController in your cluster such as Traefik or Nginx.

Add --set ingress.enabled to enable ingress pass --set ingress.enabled=true when running the installation via helm.

By default services will be exposed with following hostnames (can be changed, see values.yaml for details):

  • gateway.openfaas.local

Endpoint load-balancing

Some configurations in combination with client-side KeepAlive settings may because load to be spread unevenly between replicas of a function. If you experience this, there are three ways to work around it:

  • Install Linkerd2 which takes over load-balancing from the Kubernetes L4 Service (recommended)

  • Disable KeepAlive in the client-side code (not recommended)

  • Configure the gateway to pass invocations through to the faas-netes provider (alternative to using Linkerd2)

    --set gateway.directFunctions=false

    In this mode, all invocations will pass through the gateway to faas-netes, which will look up endpoint IPs directly from Kubernetes, the additional hop may add some latency, but will do fair load-balancing, even with KeepAlive.


If you require TLS/SSL then please make use of an IngressController. A full guide is provided to enable TLS for the OpenFaaS Gateway using cert-manager and Let's Encrypt.

Service meshes

If you use a service mesh like Linkerd or Istio in your cluster, then you should enable the directFunctions mode using:

--set gateway.directFunctions=true

Istio mTLS

To install OpenFaaS with Istio mTLS pass --set istio.mtls=true and disable the HTTP probes:

helm upgrade openfaas --install chart/openfaas \
    --namespace openfaas  \
    --set basic_auth=true \
    --set functionNamespace=openfaas-fn \
    --set exposeServices=false \
    --set faasnetes.httpProbe=false \
    --set httpProbe=false \
    --set gateway.directFunctions=true \
    --set istio.mtls=true

The above command will enable mTLS for the openfaas control plane services and functions excluding NATS.

Note that the above instructions were tested on GKE 1.13 and Istio 1.2

Zero scale

Scale-up from zero (on by default)

Scaling up from zero replicas is enabled by default, to turn it off set scaleFromZero to false in the helm chart options for the gateway component.

--set gateway.scaleFromZero=true/false

Scale-down to zero (off by default)

Scaling down to zero replicas can be achieved either through the REST API and your own controller, or by using the faas-idler component. This is an OpenFaaS PRO feature and an effective way to save costs on your infrastructure costs.

OpenFaaS PRO will only scale down functions which have marked themselves as eligible for this behaviour through the use of a label:

See also: Scale to Zero docs.

Check the logs with:

kubectl logs -n openfaas deploy/faas-idler

Removing the OpenFaaS

All control plane components can be cleaned up with helm:

helm delete openfaas --namespace openfaas

Follow this by the following to remove all other associated objects:

kubectl delete namespace openfaas openfaas-fn

In some cases your additional functions may need to be either deleted before deleting the chart with faas-cli or manually deleted using kubectl delete.

ARM and Raspberry Pi

OpenFaaS container images are currently published as multi-arch for ARM64, armhf and x64_64. It's recommended that you use arkade to install, or use the appropriate values.yaml file.

See also: Kubernetes and Raspberry Pi in the docs

Kubernetes versioning

This Helm chart currently supports version 1.16+

Note that OpenFaaS itself may support a wider range of versions, see here

Getting help

Feel free to seek out help using the OpenFaaS Slack workspace, please do not raise issues for technical support, unless you suspect and can provide instructions for reproducing an error in the chart.


Additional OpenFaaS options in values.yaml.

Parameter Description Default
functionNamespace Functions namespace, preferred openfaas-fn default
clusterRole Use a ClusterRole for the Operator or faas-netes. Set to true for multiple namespace support false
createCRDs Create the CRDs for OpenFaaS Functions and Profiles true
basic_auth Enable basic authentication on the gateway and Prometheus. Warning: do not disable. true
async Enables asynchronous function invocations. If .nats.external.enabled is false, also deploys NATS Streaming true
exposeServices Expose NodePorts/LoadBalancer true
serviceType Type of external service to use NodePort/LoadBalancer NodePort
generateBasicAuth Generate admin password for basic authentication false
rbac Enable RBAC true
httpProbe Setting to true will use HTTP for readiness and liveness probe on the OpenFaaS system Pods (compatible with Istio >= 1.1.5) true
psp Enable Pod Security Policy for OpenFaaS accounts false
securityContext Deploy with a securityContext set, this can be disabled for use with Istio sidecar injection true
openfaasImagePullPolicy Image pull policy for openfaas components, can change to IfNotPresent in offline env Always
kubernetesDNSDomain Domain name of the Kubernetes cluster cluster.local
operator.create Use the OpenFaaS operator CRD controller, default uses faas-netes as the Kubernetes controller false
ingress.enabled Create ingress resources false
faasnetes.httpProbe Use a httpProbe instead of exec false
ingressOperator.create Create the ingress-operator component false
ingressOperator.replicas Replicas of the ingress-operator 1
ingressOperator.image Container image used in ingress-operator openfaas/ingress-operator:0.6.2
ingressOperator.resources Limits and requests for memory and CPU usage Memory Requests: 25Mi
faasnetes.readTimeout Queue worker read timeout 60s
faasnetes.writeTimeout Queue worker write timeout 60s
faasnetes.imagePullPolicy Image pull policy for deployed functions Always
faasnetes.setNonRootUser Force all function containers to run with user id 12000 false
gateway.directFunctions Invoke functions directly using Service without delegating to the provider false
gateway.replicas Replicas of the gateway, pick more than 1 for HA 1
gateway.readTimeout Queue worker read timeout 65s
gateway.writeTimeout Queue worker write timeout 65s
gateway.upstreamTimeout Maximum duration of upstream function call, should be lower than readTimeout/writeTimeout 60s
gateway.scaleFromZero Enables an intercepting proxy which will scale any function from 0 replicas to the desired amount true
gateway.maxIdleConns Set max idle connections from gateway to functions 1024
gateway.maxIdleConnsPerHost Set max idle connections from gateway to functions per host 1024
gateway.logsProviderURL Set a custom logs provider url ""
queueWorker.durableQueueSubscriptions Whether to use a durable queue subscription false
queueWorker.queueGroup The name of the queue group used to process asynchronous function invocations faas
queueWorker.replicas Replicas of the queue-worker, pick more than 1 for HA 1
queueWorker.ackWait Max duration of any async task/request 60s The name of the NATS Streaming channel to use for asynchronous function invocations faas-request
nats.external.clusterName The name of the externally-managed NATS Streaming server ``
nats.external.enabled Whether to use an externally-managed NATS Streaming server false The host at which the externally-managed NATS Streaming server can be reached ""
nats.external.port The port at which the externally-managed NATS Streaming server can be reached ""
nats.enableMonitoring Enable the NATS monitoring endpoints on port 8222 for NATS Streaming deployments managed by this chart false
nats.metrics.enabled Export Prometheus metrics for NATS, no multi-arch support false
nats.metrics.image Container image used for the NATS Prometheus exporter, not multi-arch synadia/prometheus-nats-exporter:0.6.2
faasIdler.create Create the faasIdler component true
faasIdler.inactivityDuration Duration after which faas-idler will scale function down to 0 15m
faasIdler.reconcileInterval The time between each of reconciliation 1m
faasIdler.dryRun When set to false the OpenFaaS API will be called to scale down idle functions, by default this is set to only print in the logs. true
prometheus.create Create the Prometheus component true
alertmanager.create Create the AlertManager component true
istio.mtls Create Istio policies and destination rules to enforce mTLS for OpenFaaS components and functions false

Specify each parameter using the --set key=value[,key=value] argument to helm install. See values.yaml for detailed configuration.