Build functions

    For details and examples run

    • Build images with Docker

    The command builds a Docker image into your local Docker library, which can then be used locally or pushed into a remote Docker registry. Each change of your function requires a new faas-cli build command to be issued.

    • How to do CI/CD

    When it comes to continuous integration and delivery you can use the faas-cli tool on your build server to build and deploy your code using the built-in commands.

    • Generate a Dockerfile with —shrinkwrap

    If you are using an alternative container image builder or are automating the faas-cli then you can use the —shrinkwrap flag which will produce a folder named ./build/function-name with a Dockerfile. This bundle can be used with any container builder.

    The OpenFaaS CLI enables functions to be built with different options, e.g. dev, debug, etc.

    By default all templates provide a minimal build as this optimizes function image sizes. Where appropriate, 3rd-party dependencies can be specified via requirements.txt. In scenarios where third-party dependencies also require native (e.g. C/C++) modules,like libssh in Ruby and numpy or pandas in Python, then —build-option can be used.

    The OpenFaaS CLI provides a —build-option flag which enables named sets of native modules to be specified for inclusion in the function build.

    There are two ways to achieve this:

    1. faas-cli build --lang python3 --build-option dev [--build-option debug]

    or in YAML:

    1.     build_options:
    2.     - debug
    3.     - dev

    Where multiple functions are being built, the YAML configuration is recommended over use of the CLI flag, as the CLI flag applies the to all functions involved in the build activity.

    • Edit templates to support additional build options

    It is possible to amend build options in both official and custom templates.

    Altering of official templates should be carefully considered in the context of repeatable builds

    In order to modify a template to support further build options, edit the template.yml using the following pattern:

    1. build_options: 
    2.   - name: dev
    3.     packages: # A list of required packages
    4.       - make
    5.       - automake
    6.       #- etc.
    7.   - name: debug
    8.     packages: 
    9.       - mg
    10.       - iw
    11.       #- etc.

    and if not already present edit Dockerfile with:

    There may be scenarios where a single native module need to be added to a build. A single-package build option could be added as described above. Alternatively a package could be specified through a —build-arg.

    1. faas-cli build --lang python3 --build-arg ADDITIONAL_PACKAGE=jq

    In the event a build-option is set the effect will be cumulative:

    1. faas-cli build --lang python3 --build-option dev --build-arg ADDITIONAL_PACKAGE=jq

    The entries in the template's Dockerfile described in 1.0 above need to be present for this mode of operation.

    You can pass ARG values to Docker via the CLI.

    1. faas-cli build --build-arg ARGNAME1=argvalue1 --build-arg ARGNAME2=argvalue2

    Remeber to add any ARG values to the template's Dockerfile:

    For more information about passing build arguments to Docker, please visit the

    The —parallel flag aims to reduce total build time by enabling more than one function build action to take place concurrently. Additionally, there may be situations where building all the defined functions is undesirable - for example where only one of the functions has had its code updated. In this instance the —filter and —regex flags can be used.

    Consider a project with fn1, fn2, fn3, , fn33 functions all defined within a single YAML file.

    Parallel enables the user to specify how many concurrent function build actions should be performed. The default is that functions will be built serially, one after the other.

    The following will see all the project functions' build actions performed concurrently:

    1. faas-cli build --parallel 5

    Note

    Remember to add -f if using a non-default yaml file: faas-cli build —parallel 5 -f projectfile.yml

    Parallel can be combined with either of the —filter and —regex flags to parallel build a subset of the functions.

    Filter performs wildcard matching against function names in YAML file so that the build action will only be performed against those that match.

    The following filter would build only fn2 from stack.yml:

      Wildcards can be added using *. The following will result in both fn2 and fn22 being built:

      1. faas-cli build --filter "fn2*"

      The following regex would result in fn1, fn2 & fn3 being built from the earlier project's stack.yml: