<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi all,<div class=""><br class=""></div><div class="">I’ve been working on running Swift applications and building the Swift toolchain in docker containers. I’d like to share some thoughts and notes I’ve made, since they may be of interest to others. Especially to those of you stubbornly clinging to 10.10 on 2013 era Macbook Airs which have all the horsepower of a donkey.</div><div class=""><br class=""></div><div class="">For those of us who are unfamiliar with docker, it’s essentially an alternative to virtual machines, where the host shares its kernel with the container. Consequently the VM overhead is removed entirely, but you have a controlled environment that is versionable, space efficient and full of awesome, basically.</div><div class=""><br class=""></div><div class="">Let’s start with the headline:</div><div class=""><br class=""></div><div class=""><span style="font-size: 14px;" class=""><b class="">Renting resources from Amazon using docker-machine to build Swift.</b></span></div><div class=""><br class=""></div><div class="">The magic sauce is:</div><div class=""><br class=""></div><div class=""><div class=""><blockquote type="cite" class="">docker-machine create --driver amazonec2 --amazonec2-instance-type c4.8xlarge --amazonec2-request-spot-instance --amazonec2-spot-price 1 --amazonec2-root-size 120 --amazonec2-access-key BLANK --amazonec2-zone e --amazonec2-secret-key BLANK --amazonec2-vpc-id BLANK aws</blockquote></div></div><div class=""><br class=""></div><div class="">Docker-machine manages the underlying connection between the `docker` command line tool and the daemon running on the host. In this case, we can provision a machine in the cloud with 36 cores, 10gbis fibre and an enormous SSD. It will cost no more than a dollar an hour (amazon spot pricing lets you bid on capacity with a max bid, here set to $1). All our commands will execute there, entirely removing bandwidth, capacity or power issues on our end. (Yes, it’s the 1960s again, thin clients etc).</div><div class=""><br class=""></div><div class="">If you’re willing to spend the aforementioned 50 cents or so, you can achieve the following result (clean build):</div><div class=""><br class=""></div><div class=""><blockquote type="cite" class="">time (./swift/utils/build-script --assertions --no-swift-stdlib-assertions --llbuild --swiftpm --xctest --build-subdir=buildbot_linux --lldb --release --foundation -- --swift-enable-ast-verifier=0 --install-swift --install-lldb --install-llbuild --install-swiftpm --install-xctest --install-prefix=/usr '--swift-install-components=compiler;clang-builtin-headers;stdlib;sdk-overlay;dev' --build-swift-static-stdlib=1 --install-destdir=/ --install-foundation --reconfigure > /dev/null 2>&1 )<br class=""><br class="">real<span class="Apple-tab-span" style="white-space:pre"> </span>8m54.418s<br class="">user<span class="Apple-tab-span" style="white-space:pre"> </span>156m25.255s<br class="">sys<span class="Apple-tab-span" style="white-space:pre"> </span>9m34.455s<br class=""></blockquote><br class=""></div><div class="">Which is, all things being equal, pretty nice. I’m curious what most others face. Nightly untested builds would be quite doable, and I think using Docker for the Linux builds and development would be of significant interest to many, including whoever at Apple is co-ordinating the CI efforts. Docker is very stable, simple and powerful in its ability to control for many factors when working on such large projects as Swift.</div><div class=""><br class=""></div><div class="">(For those curious, my use case here was that withVarArgs is not yet available in the snapshot from 10 Dec, but it is in master.)</div><div class=""><br class=""></div><div class=""><div class=""><span style="font-size: 14px;" class=""><b class="">Quickly trying out Swift</b></span></div></div><div class=""><span style="font-size: 14px;" class=""><b class=""><br class=""></b></span></div><div class="">In the same manner as IBM’s Swift sandbox (<a href="https://developer.ibm.com/swift/2015/12/03/introducing-the-ibm-swift-sandbox/" class="">https://developer.ibm.com/swift/2015/12/03/introducing-the-ibm-swift-sandbox/</a>), it’s now trivial to provision something a bit smaller in the cloud or locally and type </div><div class=""><br class=""></div><div class=""></div><blockquote type="cite" class=""><div class="">`docker pull swiftdocker/swift`</div></blockquote><div class=""><br class=""></div><div class="">With the image downloaded (warning, it’s a couple of gigs, so I’d recommend using a fat pipe or a cloud machine), you can proceed to </div><div class=""><br class=""></div><div class=""></div><blockquote type="cite" class=""><div class="">`docker run --privileged -it swiftdocker/swift swift` </div></blockquote><div class=""><br class=""></div><div class="">and immediately get a Swift interpreter! The privileged flag is some kind of weird voodoo to get LLDB to work properly, since it needs to think it has access to the underlying hardware. Any suggestions on patches to fix this issue would be most welcome.</div><div class=""><br class=""></div><div class=""><div class=""><span style="font-size: 14px;" class=""><b class="">Hacking on Swift</b></span></div></div><div class=""><span style="font-size: 14px;" class=""><b class=""><br class=""></b></span></div><div class="">Just as it’s possible to build Swift in a docker container so too is it possible to actively develop the language in a Linux environment, while still benefitting from any local affordances you may have. If there is interest from the core team, I would be happy to contribute a meta-repo of Swift, submoduleing all the repos and supplying a docker-compose file which would enable developers to provision a development machine while being able to mirror local changes over to the machine. Similarly, “preheated” images could be built which would eliminate the need for a fresh build when first starting on the project.</div><div class=""><span style="font-size: 14px;" class=""><b class=""><br class=""></b></span></div><div class=""><br class=""></div><div class=""><div class=""><span style="font-size: 14px;" class=""><b class="">Deploying cloud applications in Swift</b></span></div></div><div class=""><span style="font-size: 14px;" class=""><b class=""><br class=""></b></span></div><div class="">With the above infrastructure already in place and growing, deploying an application using docker is as simple as writing your Swift application, and then a Dockerfile describing how to build and start it:</div><div class=""><br class=""></div><div class=""></div><blockquote type="cite" class=""><div class="">FROM swiftdocker/swift</div><div class="">ADD . /code</div><div class="">WORKDIR /code</div><div class="">RUN swift build</div><div class="">CMD .build/Debug/code</div></blockquote><div class=""><br class=""></div><div class="">The CMD line is the statement executed when the container is started. Many services already exist to support automatically running and scaling dockerized infrastructure, and it’s my hope that having Swift running in Docker will contribute to adoption by a wider community of developers.</div><div class=""><br class=""></div><div class=""><div class=""><span style="font-size: 14px;" class=""><b class="">Testing Swift applications on CI as a service providers</b></span></div></div><div class=""><span style="font-size: 14px;" class=""><b class=""><br class=""></b></span></div><div class="">Whether or not you choose to deploy an application in Docker, services like Travis CI use docker extensively to automate their test machine provisioning infrastructure. If your Swift library or application can build on Linux (command line tools are an obvious target for the latter), you would be able to take advantage of a Docker environment to quickly achieve low build times, as opposed to the generally expensive and slower OS X machines that are optimised for Xcode and tend to lack the open source toolchain.</div><div class=""><br class=""></div><div class="">—</div><div class=""><br class=""></div><div class="">I hope some of you may find this information useful. I’ve posted it on dev since I believe it’s more relevant to the developers than the users, right now. Please let me know if you have any questions about Docker or how it might relate to Swift!</div><div class=""><br class=""></div><div class="">Oh, and Merry Christmas/have a great winter holiday!</div><div class=""><br class=""></div><div class="">Tom</div><div class=""><br class=""></div><div class=""><span style="font-size: 14px;" class=""><b class=""><br class=""></b></span></div></body></html>