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

A presentation at GoLang Philly Meetup May 2019 in May 2019 in Philadelphia, PA, USA by Baruch Sadogursky

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

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Let’s go back in time

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

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

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

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

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

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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

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

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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

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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

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

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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

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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

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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

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

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

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GOPATH, The proud son of the monorepo

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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

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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

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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

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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

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

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The go dep experiment

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@jbaruch #dockercon jfrog.com/shownotes

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

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

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Enter Go modules

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

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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

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

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

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

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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

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Latest compatible version tag

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

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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

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] 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

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

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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

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From vendoring to hierarchy of module repositories

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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

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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

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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

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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

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