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Function project configuration in func.yaml

The func.yaml file contains the configuration for your function project.

Generally, these values are used when you execute a kn func command. For example, when you run the kn func build command, the value in the builder field is used.

In many cases, you can override these values with command line flags or environment variables.

Configurable fields in func.yaml

Many of the fields in func.yaml are generated automatically when you create, build, and deploy your function. However, there are also fields that you modify manually to change things, such as the function name or the image name.

builder

The builder field specifies the Buildpack builder image to use when building the function. In most cases, this value should not be changed. When you do change it, use a value that is listed in the builders field.

builders

Some function runtimes can be built in multiple ways. For example, a Quarkus function can be built for the JVM or as a native binary. The builders field contains all of the builders available for a given runtime.

buildEnvs

The buildEnvs field enables you to set environment variables to be available to the environment that builds your function. Unlike variables set using envs, a variable set using buildEnv is not available during function runtime.

You can set a buildEnv variable directly from a value. In the following example, the buildEnv variable named EXAMPLE1 is directly assigned the one value:

buildEnvs:
- name: EXAMPLE1
  value: one

You can also set a buildEnv variable from a local environment variable. In the following example, the buildEnv variable named EXAMPLE2 is assigned the value of the LOCAL_ENV_VAR local environment variable:

buildEnvs:
- name: EXAMPLE1
  value: '{{ env:LOCAL_ENV_VAR }}'

envs

The envs field enables you to set environment variables to be available to your function at runtime. You can set an environment variable in several different ways:

  1. Directly from a value.

  2. From a value assigned to a local environment variable. See the section "Referencing local environment variables from func.yaml fields" for more information.

  3. From a key-value pair stored in a secret or config map.

  4. You can also import all key-value pairs stored in a secret or config map, with keys used as names of the created environment variables.

This examples demonstrates the different ways to set an environment variable:

name: test
namespace: ""
runtime: go
...
envs:
- name: EXAMPLE1 (1)
  value: value
- name: EXAMPLE2 (2)
  value: '{{ env:LOCAL_ENV_VALUE }}'
- name: EXAMPLE3 (3)
  value: '{{ secret:mysecret:key }}'
- name: EXAMPLE4 (4)
  value: '{{ configMap:myconfigmap:key }}'
- value: '{{ secret:mysecret2 }}' (5)
- value: '{{ configMap:myconfigmap2 }}' (6)
1 An environment variable set directly from a value.
2 An environment variable set from a value assigned to a local environment variable.
3 An environment variable assigned from a key-value pair stored in a secret.
4 An environment variable assigned from a key-value pair stored in a config map.
5 A set of environment variables imported from key-value pairs of a secret.
6 A set of environment variables imported from key-value pairs of a config map.

volumes

The volumes field enables you to mount secrets and config maps as a volume accessible to the function at the specified path, as shown in the following example:

name: test
namespace: ""
runtime: go
...
volumes:
- secret: mysecret (1)
  path: /workspace/secret
- configMap: myconfigmap (2)
  path: /workspace/configmap
1 The mysecret secret is mounted as a volume residing at /workspace/secret.
2 The myconfigmap config map is mounted as a volume residing at /workspace/configmap.

options

The options field enables you to modify Knative Service properties for the deployed function, such as autoscaling. If these options are not set, the default ones are used.

These options are available:

  • scale

    • min: The minimum number of replicas. Must be a non-negative integer. The default is 0.

    • max: The maximum number of replicas. Must be a non-negative integer. The default is 0, which means no limit.

    • metric: Defines which metric type is watched by the Autoscaler. It can be set to concurrency, which is the default, or rps.

    • target: Recommendation for when to scale up based on the number of concurrently incoming requests. The target option can be a float value greater than 0.01. The default is 100, unless the options.resources.limits.concurrency is set, in which case target defaults to its value.

    • utilization: Percentage of concurrent requests utilization allowed before scaling up. It can be a float value between 1 and 100. The default is 70.

  • resources

    • requests

      • cpu: A CPU resource request for the container with deployed function.

      • memory: A memory resource request for the container with deployed function.

    • limits

      • cpu: A CPU resource limit for the container with deployed function.

      • memory: A memory resource limit for the container with deployed function.

      • concurrency: Hard Limit of concurrent requests to be processed by a single replica. It can be integer value greater than or equal to 0, default is 0 - meaning no limit.

This is an example configuration of the scale options:

name: test
namespace: ""
runtime: go
...
options:
  scale:
    min: 0
    max: 10
    metric: concurrency
    target: 75
    utilization: 75
  resources:
    requests:
      cpu: 100m
      memory: 128Mi
    limits:
      cpu: 1000m
      memory: 256Mi
      concurrency: 100

image

The image field sets the image name for your function after it has been built. You can modify this field. If you do, the next time you run kn func build or kn func deploy, the function image will be created with the new name.

imageDigest

The imageDigest field contains the SHA256 hash of the image manifest when the function is deployed. Do not modify this value.

labels

The labels field enables you to set labels on a deployed function.

You can set a label directly from a value. In the following example, the label with the role key is directly assigned the value of backend:

labels:
- key: role
  value: backend

You can also set a label from a local environment variable. In the following example, the label with the author key is assigned the value of the USER local environment variable:

labels:
- key: author
  value: '{{ env:USER }}'

name

The name field defines the name of your function. This value is used as the name of your Knative service when it is deployed. You can change this field to rename the function on subsequent deployments.

namespace

The namespace field specifies the namespace in which your function is deployed.

runtime

The runtime field specifies the language runtime for your function, for example, python.

Referencing local environment variables from func.yaml fields

In the envs field in the func.yaml, you can put a reference to an environment variable available in the local environment. This can be useful for avoiding storing sensitive information, such as an API key in the function configuration.

Procedure

  • To refer to a local environment variable, use the following syntax:

    {{ env:ENV_VAR }}

    Substitute ENV_VAR with the name of the variable in the local environment that you want to use.

    For example, you might have the API_KEY variable available in the local environment. You can assign its value to the MY_API_KEY variable, which you can then directly use within your function:

    name: test
namespace: ""
runtime: go
...
envs:
- name: MY_API_KEY
  value: '{{ env:API_KEY }}'
Additional resources