Refactoring to modules: Why and how – all you need to know in (less than) an hour

Refactoring to modules: All you need to know in less than an hour @jbaruch #golang http://jfrog.com/shownotes

Let’s go back in time

Pre 1.0 (2012) 1.2 (2013) Poll time! 1.5 (2015) 1.8 (2017) 1.11 (2018) @jbaruch #golang http://jfrog.com/shownotes

🎩 @jbaruch #dockercon jfrog.com/shownotes @ErinMeyerINSEAD’s “Culture Map”

shownotes http://jfrog.com/shownotes Slides Video Links Comments, Ratings Raffle @jbaruch #golang http://jfrog.com/shownotes

Why we have a problem? @jbaruch #golang http://jfrog.com/shownotes

Why we have a problem? @jbaruch #golang http://jfrog.com/shownotes

Dependencies are sources Remote import is a VCS path Dump everything together into one source tree (GOPATH) Simple solution! Compile Profit @jbaruch #golang http://jfrog.com/shownotes

@jbaruch #golang http://jfrog.com/shownotes

Know which dependencies do I use? Know which dependencies did you use? Know which dependencies should I use? But… how do i… Know is it our code that I am editing right now? WTF is going on?! @jbaruch #golang http://jfrog.com/shownotes

Yeah… “ To date, we’ve resorted to an email semaphore whenever someone fixes a bug a package, imploring everyone else to run go get -u. You can probably imagine how successful this is, and how much time is being spent chasing bugs that were already fixed. Dave Cheney @jbaruch #golang http://jfrog.com/shownotes

Duplicate your dependencies “ Check your dependencies to your own VCS. Brad Firzpatrick @jbaruch #golang http://jfrog.com/shownotes

Build your own dependency manager “ It’s not the role of the tooling provided by the language to dictate how you manage your code in the production sense. Andrew Gerrand @jbaruch #golang http://jfrog.com/shownotes

We expect you to already have a homegrown dependency manager “ If you need to build any tooling around what Go uses (Git, Mercurial, Bazaar), you already understand those tools, so it should be straightforward to integrate with whatever system you have. Andrew Gerrand @jbaruch #golang http://jfrog.com/shownotes

Don’t trust what we’ve built “ go-get is nice for playing around, but if you do something serious, like deploying to production, your deploy script now involves fetching some random dude’s stuff on GitHub. Brad Firzpatrick @jbaruch #golang http://jfrog.com/shownotes

godeps.json dependencies.tsv govendor, govend, goven, gv quiz time! trash, garbage, rubbish Weapons manufacturer @jbaruch #golang http://jfrog.com/shownotes

GOPATH + VENDORING = 💖 @jbaruch #golang http://jfrog.com/shownotes

GOPATH, The proud son of the monorepo

It only allows a single version of any given package to exist at once (per GOPATH) Two huge problems with gopath @jbaruch We cannot programmatically differentiate between code the user is working on and code they merely depend on #golang http://jfrog.com/shownotes

Vendoring – the worst kind of forking “ Copy all of the files at some version from one version control repository and paste them into a different version control repository @jbaruch #golang http://jfrog.com/shownotes

History, branch, and tag information is lost Pulling updates is impossible It invites modification, divergence, and bad fork It wastes space Good luck finding which version of the code you forked What’s wrong with it (well, what’s not) @jbaruch #golang http://jfrog.com/shownotes

You still have no idea what version are you using You have to connect each dependency as a submodule manually Switching branches and forks LOL Working on modules with other teams ROFL Still wrong! @jbaruch #golang http://jfrog.com/shownotes

@jbaruch #golang http://jfrog.com/shownotes

The go dep experiment

@jbaruch #dockercon jfrog.com/shownotes

Working in project directories Proper dependency management? Local cache for dependencies Version declarations Conflict resolution @jbaruch #golang http://jfrog.com/shownotes

Conflict on the conflict resolution SAT/SMT vs MVS/SIV

Enter Go modules

Enter go modules @jbaruch #golang http://jfrog.com/shownotes

go mod init go.mod file is created Backwards compatibility and migration @jbaruch The rest is the same: imports in code just work #golang http://jfrog.com/shownotes

That’s some serious magic… @jbaruch #golang http://jfrog.com/shownotes

Go modules convert everything (almost?) @jbaruch #golang http://jfrog.com/shownotes

What happens to go.mod when you add import (and run go get/go build)

Have goimport? no yes Access import path as URL Follow goimport URL yes Invalid import path Serve the module no Is it a webpage ? no Is it a VCS? no Is it a module repo? yes Build the module locally Clone the sources yes

Latest compatible version tag

@jbaruch #golang http://jfrog.com/shownotes

Let’s assume SemVer works (LOL) The latest version of v1.x.x is compatible with v1.0.0 and up Compatible?! Premise: import path string should always be backwards compatible @jbaruch #golang http://jfrog.com/shownotes

] Incompatible code can’t use the same import path Add /v2/ to the module path What about version 2?! Use /v2/ in the import path import “github.com/my/module/v2/mypkg” @jbaruch #golang http://jfrog.com/shownotes

What if it doesn’t have any semver tags?! @jbaruch Pseudo version v0.0.0-yyyymmddhhmmss-abcdefabcdef #golang http://jfrog.com/shownotes

You can specify “version X or later”: >= x.y.z What if (when) I want to ban a version?! @jbaruch You can use exclude or replace for better control #golang http://jfrog.com/shownotes

From vendoring to hierarchy of module repositories

Go modules define an hierarchy of caches Public Modules Repository GoCenter Organizational Modules Repository The Athens Project JFrog Artifactory Local cache on the developer’s machine $GOPATH/pkg/mod

After the mods are resolved (or built) they are cached in $GOPATH/pkg/mod Local cache on the developer’s machine Provides immediate access Not shared Not reliable (can be wiped at any moment) @jbaruch #golang http://jfrog.com/shownotes

JFrog Artifactory or Project Athens Provides faster (Intranet) access Provides reproducible builds as it caches the dependencies used once for build reproduction Requires team infrastructure and maintenance (SaaS offers exist) Organizational modules repository @jbaruch #golang http://jfrog.com/shownotes

GoCenter Google announced a vision for a federation of public repositories Provides fast access Provides reproducible builds as it caches the popular and requested dependencies from version control Highly available, requires no maintenance, free public modules repositories @jbaruch #golang http://jfrog.com/shownotes

Twitter ads and q&A jfrog.com/shownotes @jbaruch #GoLang gocenter.io @jbaruch #golang http://jfrog.com/shownotes