Friday, January 19, 2018

Deploying Go Applications in Docker Containers using a Scratch Docker File

Programming in golang is fantastic. I find it fun, expressive and simple to build concurrent programs. Deploying a golang app from laptop to production is as hard now as when it was back when I was building Monolithic services. A great way to deploy nowadays is to deploy microservices in containers. Containers keep the environment between laptop and AWS Linux instance in sync since in essence the environment is deployed and not just the code or binary.

Containerization of the environment is not ideal although. Sometimes you can ship containers of 1GB in size or more. Deploying that across the LAN is ok, over the WAN .. it is debatable. So, to deal with this problem I work with scratch Dockerfiles when deploying applications.

Starting from scratch Dockerfiles, I know that there is no real environment overhead since the environment is the most basic it can be. Additionally, I do not have to worry about the golang environment in my container because we are not going to ship "golang and all its packages", we are going to ship the binary itself. This is best described as an example.

The Dockerfile, is like a Makefile but for your environment. Each line describes what the Dockerfile does. Prior to executing the docker file, we will need to set up the environment.

GOOS=linux go build .                                                                                           

This line will build the go program as a Linux binary.

docker build -t dathanvp/goprogram:latest .

This line says; execute the docker file and tag the image as dathanvp/goprogram.

docker run -p 8282:8282 -v /Users/dathan/gocode/src/ dathanvp/goprogram:latest

Now, this is the magic. Docker will open port 8282 and map it to port 8282 in the container. A volume is attached from my laptop to the container's /mnt directory with read and write privileges. (When executing my container in production only this line changes.) This volume is to keep the logs persistent. Containers reset state, thus losing anything generated and the reason for my volume. Finally docker run is going to run my image dathanvp/goprogram

I deploy my container's  to AWS by executing

docker push dathanvp/goprogram

This pushes my go program from my laptop to where my aws instances can then pull from, enabling running my programs in production without having to set up the environment on aws (other than docker of course).

Finally, why do it this way? I want my program to run on my laptop and on my AWS ubuntu servers without having to keep golang development environments in sync. Additionally, I want my containers to be really small so I don't have to ship hundreds of megs around to start the application, which itself is about 13MB. Uploading from comcast sucks. So, in conclusion, this is the best way I've found so far :)

Please let me know how you ship go applications and why.

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