Getting started with Wercker & Go

This guide is a step-by-step approach to developing, building and deploying a sample app with wercker within minutes.

While this guide uses Go, the general concepts explained in this tutorial apply to every other programming language.

Requirements

To be able to follow along with this guide, you will need the following things:

Setting up the app

Before we can start developing, we have to fork and clone the sample app into our local development environment. After you’ve done that, cd into the project directory.

$ cd getting-started-golang/

Next, build and run the app to verify everything is working.

$ go build
$ ./getting-started-golang

Now in your browser navigate to 127.0.0.1:5000/cities.json and you should be presented with the following json:

"{'cities':'San Francisco, Amsterdam, Berlin, New York, Tokyo'}"

Developing the app

Now that we’ve setup our app we can start developing. Our list of cities is a bit short, so why not add another one in there? Before we do that however, let’s first take a closer look at the wercker.yml file included in your project folder.

wercker.yml

The wercker.yml is the only config file you need for using wercker. In it, you will define all your steps needed to successfully develop, build and deploy your application.

To get started however, we’re only interested in developing our app, so let’s take a closer look at this dev pipeline right now.

Dev pipeline

# The container definition we want to use for developing our app
box: golang
# Defining the dev pipeline
dev:
  steps:
    - internal/watch:
        code: |
          go build ./...
          ./source
        reload: true

The first line specifies which container image you want to use for your project. Since we’re developing with Go, we’ve already specified a Go image for you. These container images are retrieved from Docker Hub if no other registry is specified. You can read more about containers here.

In the dev clause we define what we want to happen in our development pipeline, which in this case is just one step: internal/watch.

internal/watch watches your files for changes, and if reload is set to true it restarts your app so your changes are reflected immediately. This is especially useful for when you’re developing webapps, as we’re doing now.

Let’s see these steps in action now and fire up our dev pipeline.

wercker dev

In your project folder, run wercker dev --publish 5000. You should see something similar to the following output:

--> Executing pipeline
--> Running step: setup environment
Pulling repository golang
Pulling image (latest) from golang: ebd45caf377c
Pulling image (latest) from golang, endpoint: https://registry-1.docker.io/v1/: ebd45caf377c
Pulling dependent layers: ebd45caf377c
Download complete: 64e5325c0d9d
Download complete: bf84c1d84a8f
Download complete: 87de57de6955
Download complete: 6a974bea7c0d
Download complete: 3d0d66dec985
Download complete: ec367bd67c88
Download complete: 2d87eca0ec9c
Download complete: ac13965af848
Download complete: 14182e587f2c
Download complete: 37e56f6d02a4
Download complete: 1c18d4d04737
Download complete: 66bf953cd51b
Download complete: 0dfa22e2b56d
Download complete: ebd45caf377c
Download complete: ebd45caf377c
Status: Image is up to date for golang:latest
--> Running step: wercker-init
--> Running step: watch
--> Reloading on file changes
--> Reloading

Wercker first checks out your code and then sets up the container environment. This means that the container will be pulled from Docker Hub and subsequently started with access to your checked out code. It will then start executing all the steps that are defined in the wercker.yml.

Please note that the IP displayed here could be different for you, as this tutorial was written using boot2docker.

If you navigate to DOCKER_HOST_IP:5000/cities.json you should see the same output as before. That’s not very exciting, so let’s see our live reloading in action. In main.go add a new city to the array:

func CityHandler(res http.ResponseWriter, req *http.Request) {
  data, _ := json.Marshal("{'cities':'San Francisco, Amsterdam, Berlin, New York, Tokyo'}")
  res.Header().Set("Content-Type", "application/json; charset=utf-8")
  res.Write(data)
}

Once you save your changes, the app should automatically reload. If you refresh your page, our new city should be there! Hurrah!

There are many more steps to use for developing your app. Take a look around, and if you can’t find the step you’re looking for, you can always make your own.

Now that we’re done developing, we want to push our changes and let wercker build and deploy our app for us.

Building your app

First, let’s revisit our wercker.yml again.

# The container definition we want to use for developing our app
box: golang
# Defining the dev pipeline
dev:
  steps:
    - internal/watch:
        code: |
          go build ./...
          ./source
        reload: true
build:
  steps:
    - wercker/golint
    - script:
        name: go build
        code: |
          go build ./...
    - script:
        name: go test
        code: |
          go test ./...

Build Pipeline

We’re now interested in what’s happening the build pipeline. We’ve added several new steps, to begin with the wercker/golint step. This step checks our code and fails if it thinks we’re not doing a good job. We’ve also added a new kind of step: a script step. This script step is a piece of inline bash code which we’re using to run our tests. You can create and share these kind of steps with the community by submitting a step to our repository. The rest of the steps should be self-explanatory: one for building and for testing.

wercker build

Now that we have a better understanding of our wercker.yml let’s go ahead and let wercker build our project. In your project folder, run:

$ wercker build
--> Executing pipeline
--> Running step: setup environment
Pulling repository golang
Pulling image (latest) from golang: ebd45caf377c
Pulling image (latest) from golang, endpoint: https://registry-1.docker.io/v1/: ebd45caf377c
Pulling dependent layers: ebd45caf377c
Download complete: 64e5325c0d9d
Download complete: bf84c1d84a8f
Download complete: 87de57de6955
Download complete: 6a974bea7c0d
Download complete: 3d0d66dec985
Download complete: ec367bd67c88
Download complete: 2d87eca0ec9c
Download complete: ac13965af848
Download complete: 14182e587f2c
Download complete: 37e56f6d02a4
Download complete: 1c18d4d04737
Download complete: 66bf953cd51b
Download complete: 0dfa22e2b56d
Download complete: ebd45caf377c
Download complete: ebd45caf377c
Status: Image is up to date for golang:latest
--> Running step: wercker-init
--> Running step: golint
main.go:9:1: exported function CityHandler should have comment or be unexported
--> Running step: go build
--> Running step: go test
ok      _/pipeline/source    0.006s
--> Steps passed
--> Pipeline finished

Success!

Building locally is very useful when you’re not sure your code will run because of some changes you made. As such you don’t want to push these changes to your Git provider just yet.

But since we’ve verified that our app is compiling and running correctly, it’s time to let wercker build & deploy your app in the cloud, which is what we’ll be doing in the next section.

Adding your app to wercker

The next step is to create a new application on wercker. Head over tohttps://app.wercker.com/ and in the menu bar select create -> application.

Select your Git Provider

First select your Git provider, after which a list of your existing repositories on either GitHub or BitBucket is presented. Select the ruby example you forked earlier from the list and click on Use selected repo.

image

Select the owner

Now we have to choose who owns the app. For this tutorial, go ahead and select yourself. If you like, you can also select an organization you created on wercker. Click on Use selected owner once you’re ready.

Configure Access

The next step is about configuring access, and the first option - checkout the code without using an SSH key - is fine for the purpose of this tutorial, because it’s an open source and public application. So go ahead and click Next step

image

Configuring the wercker.yml

At this point wercker will try to detect if you have a wercker.yml file in your repository and if not, try to make one for you. However, we already have a wercker.yml file so let’s change that and click I already have a wercker.yml. Be sure to leave the Docker enabled as it is.

Finishing up

Finally, once you’ve verified all the settings you can click Finish to complete setting up our app! When done, you will be redirected to your very own app page, which looks empty now, so let’s go ahead and change that.

Triggering your first build

Wercker will automatically trigger a build every time you push new code to your Git provider. Let’s see that in action. In your working directory, run

$ git commit -am 'wercker build time!'
$ git push origin master

Next, navigate to your app page and you should see a new build has been triggered! This build will do the exact same as the one you triggered locally but now everyone in your team can see and comment on the build.

image

Wrapping up

Congratulations! You’ve built your first app using wercker. The next tutorial in this series will be about how to deploy your Go app to a Digital Ocean server (Coming soon!).