Nice to meet you! (^-^)

Yuji Yamamoto (@igrep) age 27.

• NO RELATION WITH Emacs plugin “igrep.el”!

Nice to meet you! (^-^)

• Software Engineer at GMO CLICK Holdings, Inc.
  • 
  • Writing online trading market of GMO CLICK Securities, Inc. in Java.
• Hobby Haskeller.
  • Using Haskell for 4 years.
• Holding workshop of Haskell (almost) every month.

Nice to meet you! (^-^)

(￣^￣) Professional Haskeller.

• (;^ω^) Used to be. Just for a month
• (;_;) Using Haskell was given up
  • Due to difficulty of teaching my colleagues…

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HaskellJP wiki:

• http://wiki.haskell.jp “〆(ﾟ_ﾟ*)
• Anyone can edit with a GitHub account!
• The most helpful page: Haskellに関する日本語のリンク集
  • Haskell-related pages in Japanese
• Recently all edits are only by me… (;_;)

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• Published a blog post 「JavaでMonadをはじめからていねいに」 “〆(ﾟ_ﾟ*)
  • Monad in Java from the beggining
• (￣^￣) Told the relation between
  the do notation and the associative law most clearly!

I’m gonna talk about…

• What is Stack’s Docker integration
• How it works
• Tips on using it
• Case study
  • (^w^) May help you to convince your boss to adapt Haskell!

I’m NOT gonna talk about…

• Basic usage of Stack
• Basic usage of Docker.
• Programming language Haskell itself.

TL;DR

With Stack’s Docker integration,

• (^-^) You can always build production-ready application
  as easily as you use stack command as usual.

Background

How does GHC make Haskell code run?

• Emit native executables!
• Usually single, self-contained!
• Just put the executables to deploy!
  • Stack itself is actually single binary!

But…

• You must build for your production server!
  • Linux!
  • Dependent system (C) libraries and their version.
  • … and so on!
• Corss-compilation with GHC is hard…

With Stack’s Docker integration,

• Build directly for your production environment.
• Just by stack build as usual.

Stack’s Docker integration does:

• Wrap docker command.
• Make almost all operation of stack on the container.
  • Setup GHC.
  • Install dependencies.
  • Then build your app!
  • Run tests.

How to use

1. Append docker option to stack.yaml yaml docker: enable: true
2. Run stack build/install/setup as usual.

How it works

※Changes by the configurations.

1. Create a temporary container just for executing stack’s subcommands.
2. Share the project directory and ~/.stack by mounting.
   • Where dependencies and build artifacts are saved.
3. stack command runs in the container.
4. Delete the temporary container
   • Build dependencies and artifacts are still persisted.

How it works (cont)

5. Now you can upload the executable to your production, staging, or any target server!

☆ Tips on using Stack’s Docker integration ☆

• ᕦ(ò_óˇ)ᕤ Build on your own Docker image
• 三┏( ^o^)┛ Go over the proxy!
• (x_x) DON’T overwrite ENTRYPOINT!

ᕦ(ò_óˇ)ᕤ Build on your own Docker image

• Default: Stack’s original image (based on Ubuntu)
• How to use CentOS/Debian/Arch?
• How to install C libraries or any other non-Haskell dependencies?

ᕦ(ò_óˇ)ᕤ Build on your own Docker image

Edit stack.yaml

docker:
  repo: "centos:6"

ᕦ(ò_óˇ)ᕤ Build on your own Docker image

Edit stack.yaml

docker:
  repo: "https://your-docker-repo/image:latest"

ᕦ(ò_óˇ)ᕤ Build on your own Docker image

Or…

docker:
  image: "<some_image_id_or_tag>"

ᕦ(ò_óˇ)ᕤ Build on your own Docker image

Requirement for Orignal Images:

• GHC must be installable (or already installed):
  • libgmp
• Tools to build C sources.
  • gcc, make etc.

ᕦ(ò_óˇ)ᕤ Build on your own Docker image

Requirement for Orignal Images:

• Or, install stack itself in the image in advance.

ᕦ(ò_óˇ)ᕤ Build on your own Docker image

Specify stack-exe

docker:
  stack-exe: image

三┏( ^o^)┛ Go over the proxy!

docker:
  env:
    http_proxy: http://proxy.example.com

三┏( ^o^)┛ Go over the proxy!

May also need build-time-arguments…

$ docker build --build-arg=http_proxy=...

(x_x) DON’T override ENTRYPOINT!

ENTRYPOINT your-cool-entrypoint-command

• Stack uses ENTRYPOINT internally!

Case study

• Tiny mock server to test with an external Web API.
• Must run on the staging server.
  • CentOS 6

Case study

• Never mind zlib/libgmp/etc’s diff in version, installation path.
• Production-ready executables are always built on my development machine!
• Just by the familliar stack build/exec/…
• Then scp the executable to our server! stack install scp ~/.local/bin/executable server@example.com:/

Case study

Demo

igrep/stack-docker-sample

Case study

(o˘◡˘o) My impression

• (*´∀｀*)ﾉ Comfortable:
  • I did’t have to install anything except the built app.
• (´∪`*) The tiny application didn’t need even CI!
  • All was done on my development machine.
• (x_x;) Initial build takes a long time…
  • (;^ω^) Haskell was not good for tiny apps!

(^-^) The Good News

• Available on Docker for Mac OS X, not only Linux!

(x_x;) The Bad News

• boot2docker is NOT recommended.
  • VirtualBox’s shared folder is too slow!
• Unavailable on Docker for Windows…
  • See this issue

Current limitation

• Use on Linux or Mac OS X!
  • (;^ω^) Sorry Windows users!
  • Use the other VMs to run Linux!

Conclusion

Stack’s Docker integration enables:

• To build production-ready executables
  as easily as you use stack command as usual. (^-^)
  • Only with your machine and scp!
• But Haskell is too slow to compile tiny apps… (ﾟ◇ﾟ;)
  • Especially compiling dependencies!