Build a Serverless Memes Function with OpenFaaS

In this quick post, I will show you how to build a Serverless function in Go to get the latest 9Gag Memes using OpenFaaS.

This tutorial assume that you have:

• faas-cli installed – The easiest way to install the faas-cli is through cURL:

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curl -sSL https://cli.openfaas.com | sudo sh

• Swarm or Kubernetes environment configured – See Docs.

1 – Create a function

Create a handler.go file with the following content:

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package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"os"

	"github.com/mlabouardy/9gag"
)

func main() {
	tag, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		log.Fatalf("Unable to read standard input: %s", err.Error())
	}
	gag9 := gag9.New()
	memes := gag9.FindByTag(string(tag))
	rawJson, _ := json.Marshal(memes)
	fmt.Println(string(rawJson))
}

The code is self-explanatory, it uses 9Gag Web Crawler to parse the website and fetch memes by their tag.

2 – Docker Image

I wrote a simple Dockerfile using the Multi-stage builds technique to reduce the image size down:

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FROM golang:1.9.1 AS builder
MAINTAINER mlabouardy <mohamed@labouardy.com>
WORKDIR /go/src/github.com/mlabouardy/Memes9Gag
RUN go get -d -v github.com/mlabouardy/9gag
COPY handler.go .
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o app .

FROM alpine:latest
RUN apk --no-cache add ca-certificates
ADD https://github.com/openfaas/faas/releases/download/0.5.1-alpha/fwatchdog /usr/bin
RUN chmod +x /usr/bin/fwatchdog
WORKDIR /root/
COPY --from=builder /go/src/github.com/mlabouardy/Memes9Gag/app .
ENV fprocess="/root/app"
CMD ["fwatchdog"]

3 – Configuration file

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provider:
  name: faas
  gateway: http://localhost:8080

functions:
  memes-9gag:
    lang: Dockerfile
    handler: ./function
    image: mlabouardy/memes-9gag

Note: If pushing to a remote registry change the name from mlabouardy to your own Hub account.

4 – Build

Issue the following command:

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faas-cli build -f ./stack.yml

5 – Deploy

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faas-cli push -f ./stack.yml
faas-cli deploy -f ./stack.yml

6 – Tests

Once deployed, you can invoke the function via:

cURL:

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curl http://localhost:8080/function/memes-9gag -d "GoT"

FaaS CLI:

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echo "GoT" | faas-cli invoke memes-9gag

UI:

Note: all code used in this demo, is available on my GitHub 😍

Drop your comments, feedback, or suggestions below — or connect with me directly on Twitter @mlabouardy.