Yesterday at the Java One Keynote Mark Cavage and Chad Arimura announced the release of FnProject which is an Open-Source, container-based, cloud-agnostic FaaS platform.


FnProject is language agnostic - a function is a container image and what goes in it is up to you. The contract is over STDIN/OUT, so if your favourite language can use those then you can use fn. Even if your favourite language is Befunge.

Getting started, installing Fn

Everything starts with the fn command, so we’d better install it:

$ curl -LSs | sh
fn version 0.4.6

And create our first function

$ fn init --runtime=go

       / ____/___
      / /_  / __ \
     / __/ / / / /
    /_/   /_/ /_/

Runtime: go
Function boilerplate generated.
func.yaml created. 

We’ve used runtime=go because runtime=befunge isn’t supported yet (PRs accepted look here), so we have 3 files created by the go template.

  • func.go is a super-simple go program which:
    • (optionally) reads JSON from STDIN
    • Prints some JSON to STDOUT
  • func.yaml is the metadata for this function. For now we’ll accept the defaults
  • test.json specifies some expected input/output values.

From this point on, you will need a newish version of Docker, which is FnProject’s only dependency.

So what can we do?

Run the function

$ fn run
Building image my-first-function:0.0.1
Sending build context to Docker daemon   5.12kB
Step 1/8 : FROM funcy/go:dev as build-stage
 ---> 4cccab7fc828
Step 2/8 : WORKDIR /function
 ---> Using cache
 ---> 3cbac4137ce0
Step 3/8 : ADD . /go/src/func/
 ---> cd9dfe6d13f9
Removing intermediate container 8c80673c236f
Step 4/8 : RUN cd /go/src/func/ && go build -o func
 ---> Running in 78ca7f971b61
 ---> bea65786d05d
Removing intermediate container 78ca7f971b61
Step 5/8 : FROM funcy/go
 ---> 573e8a7edc05
Step 6/8 : WORKDIR /function
 ---> Using cache
 ---> 5e1dd9693dd5
Step 7/8 : COPY --from=build-stage /go/src/func/func /function/
 ---> Using cache
 ---> 532f355bbd08
Step 8/8 : ENTRYPOINT ./func
 ---> Using cache
 ---> 14d0cde76c0f
Successfully built 14d0cde76c0f
Successfully tagged my-first-function:0.0.1
{"message":"Hello World"}

There’s a bit of docker output there, but the last 2 lines are important: We’ve built a totally standard container image (try it with docker run if you don’t believe me), and the last line is our function’s output.

Check that STDIN parsing is working:

$ echo '{"name": "Matthew"}' | fn run
{"message":"Hello Matthew"}

Test the function

Check that the spec provided in test.json is adhered to:

$ fn test
Running 2 tests...running tests on my-first-function:0.0.1 :

Test 1
PASSED -    ( 925.574963ms )

Test 2
PASSED -    ( 1.123083022s )

2 tests passed, 0 tests failed.

Running as a service

Now we’ve seen an easy way to create functions, how about deploying them? FnProject can run anywhere a container can. The easiest place to start with is right where you already are, so start the fn service already:

$ fn start
time="2017-10-03T08:18:54Z" level=info msg="available memory" ram=266539061248
time="2017-10-03T08:18:54Z" level=info msg="Serving Functions API on address `:8080`"

       / ____/___
      / /_  / __ \
     / __/ / / / /
    /_/   /_/ /_/

That’ll sit there in the foreground, so in another terminal we can deploy our app to the localhost server:

$ fn deploy --app my-app --local
Successfully tagged my-first-function:0.0.4
Updating route /my-first-function using image my-first-function:0.0.4...

In the command above, --app my-app is necessary as functions must be namespaced into apps. I’m using --local to skip the step where fn will try to push my image to a repository (default: Dockerhub).

Now we can call our function as a web service

$ curl -d '{"name": "Matthew over HTTP"}' http://localhost:8080/r/my-app/my-first-function
{"message": "Hello Matthew over HTTP"}


That was a super-quick look at how to get started with FnProject - I hope it was helpful. There’s a lot more documentation if you need it, and there’s a lot more to fn, too.

Next post I’ll look at the Java support. If you have any questions - there’s an official Fn Slack channel, problems - there’s GitHub issues or just ask on Slack.