Kubernetes Kubernetes Contributor Summit - NA (San Diego) 2019, 26 Nov 2019

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From YouTube: Contributor Summit NA 2019: Practical Git for Kubernetes Contributors

Description

Event link: https://events19.linuxfoundation.org/events/kubernetes-contributor-summit-north-america-2019/

Session link: https://sched.co/VvNa

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Okay, we'll get started. um, last talk of the day.

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Stick with me. um, we're going to be talking today about.

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Let's try this again. hi everyone. last session of the day.

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My name's chris blecker., you will see me all over our org.

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I do a lot of kubernetes stuff and today we're going to be talking about get.

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More specifically, we're going to be talking about practically using get in the kubernetes project.

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We use get for everything. um,.

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And not just our code, but also our documentation,, our policies,.

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Our procedures,, even things like caps or kubernetes enhancement, proposals or sig definitions.

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Even our access control is all done by gap., so, no matter what part of the project you want to be involved, in,.

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Understanding some very basic good stuff is, is important.

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There are, excuse me,.

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There is plenty of tutorials out there on the basic get flow.

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We're not going to cover that today., so things like cloning,, committing,,.

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Pushing, branching. we're not going to cover those.

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We are going to cover is what happens when things get a little bit sticky in.

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Your pr. um, how to go about when,.

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When a reviewer asks you to squash your pr,, what we're asking for there.

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Things like rebasing, resolving, merge, conflicts,.

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Opening a revert and actually opening a cherry pick against kubernetes.

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So if you want to,, if there's a bug fix- and you actually need to backport that into an already.

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Released version, how you go about doing that.

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So before we get into it,, I want to talk about some key principles that will tie all this back. Together.

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These are things that are, may not be obvious on the surface when you're working with get., so first off,.

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Get saves everything you commit., even if you think,. Oh, I have,.

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I've deleted a branch or I have made a change. That's really,.

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Really broken something you can still turn back time and your get history and.

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Fix that., you haven't actually deleted anything.. So if you've committed it,.

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It's there.. You just need to figure out how to get back to that.

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Second, each commit builds on the previous one.

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So a commit and a particular commit, shaw is not just talking about a specific diff of changes.

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It is also what was the previous commit before that, and the one before that and.

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The one before that., so each commit in to being a diff of changes, is also a particular point in time.

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On your repo. again,, going back to get saves. everything that you commit to.

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Third shaw's are unique in normal use.

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Don't ask me crypto nerds,, I'm not talking about sha one collisions or anything, fancy like that.

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I'm saying like in your normal use of get on your local machine,.

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A sha will be unique,.

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Which? Again building on these previous principles,.

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If you go in and change anything like you change which commit a which commit a.

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New commit is based off of, you're, going to get a new shot of it.

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It also is helpful to remember, because when you move to a specific shot,.

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If you're referencing a specific shaw,, that is a point in time in history, in your get repo.

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So if you know, oh,, everything was working at a very specific commit or a very specific point. In.

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Time,, you can dial your repo back to that specific point in time and then fix whatever.

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Mistake that you may have made.

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Everyone breaks their get repo., it doesn't matter if you're sort of very first time using get or if you're a.

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Senior principal software engineer with 15 years, experience,.

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You will break your get repo at some point.. It's okay,.

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It's okay to ask questions and you can fix it.

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There is always a way your data, as long as you've committed it to the tree,.

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At some point in time,, your data and your changes are not lost.

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It's just about figuring out what you need to do to get back to that.

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And I'll the slides,: let's do a few demos on, on some of these procedures and we'll walk through them. Together. um,.

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For the purposes of this demonstration,.

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We're going to be working on my brand new fork of kubernete's called honker.

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Netease. um, and we're going to be making a whole bunch of changes to this,.

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This repo. mmm.

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So first off, we're gonna, take a look at.

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It., just a very basic squash.

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So if I look at the log for this branch, um,.

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You'll see the top four commits..

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There are me making changes where I'm renaming instances of kubernetes to my new.

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Project name, hunkered eddies. so going through and I'm making some changes.

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The first one,, the first one down here,.

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This one, I give very clear, commit message, and then I have a commit message.

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This I'm doing more and then I get a little bit more terse as,.

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As the commit message go on these commits.

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Maybe they don't need to be separate commits..

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Maybe I wanted to squish them all together into one commit., so I have a clean get history.. So how do I go about doing that?.

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Um,, your group, we're going to use a command,, get rebase dash. I, with the interactive flag.

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There are two ways: now,, like you want to tell,.

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Get what you're rebasing on top of what,?

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What are the commits that you want to actually interact? With?.

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There's two easy ways to do: that. either., you can look at a log like this and say, oh,. It's four commits.

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So I want to go head for with the tilda in there and that tells get,.

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I want to look at for commits behind head,, which is at the top.

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This one is the head of my branch..

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The other way to do this. That gets you. The exact same result is picking the shaw.

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That you want to rebase off of., so in this case,, this shaw is the one. That's four commits behind head.

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This is where my master branch currently is app.

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So I'm going to copy and paste that commit and I'm bring,.

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It brings up a interactive rebase., so in this interactive rebase,.

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I can see I have four commits here. they're in first column.

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Here is a command for all of them.. The default is pic.

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I have the shaws of all these commits and I have my commit messages.

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When you're squashing, there's two commands here that are very commonly used, as you can see,.

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Get actually lays out., there's a whole bunch of different commands that you can do to do different operations. the two we're going to focus on or squash and fix up the difference.

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They do the same thing with one exception: squashing.

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What it does is, it takes the commit messages and actually inserts them into the.

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Previous commit., so in this case,, if I wanted to squash all these into one commit, and each of these messages was.

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Useful,, I would change pick to squash or you can just use the first letter of that.

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Command., so I could change pick to squash and then it'll,.

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It'll go and put them all into one commit.. The alternative is fix. Up,.

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Which does the exact same thing, except it? Discards the commit message.

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So in this case, only the first commit message is the really useful one here.

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So I'm going to change these to fix up cause, I don't care about keeping these,.

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These commit messages. okay.

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So I've done that.. I've changed the command that I want to do.

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Now I'm just going to write,.

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Rebase has done, and I can look at my get log and I can see I'm now down to one.

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Commit. very easy,, very simple., now this,.

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If I was,, if I had a pr based off of this branch,,.

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Now I would re push this branch up..

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I will have to force push that branch, because I'm changing what the history.

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Looks like. when you do a regular push,, it's only additive and it goes, uh,.

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Builds on one, commit onto your branch at a time.

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Whereas with a force push you are basically saying rewrite the tree to this.

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Specific commit. um, in this case,.

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I am not going to push this anywhere., I'm just going to change back over to master.

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And I'm going to merge.

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My branch into master.

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So now I'm asking me to read: merge commit., that's fine., merge it in., I'm done.

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So now no ff is a,.

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I don't want to fast forward the branch..

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I actually want to generate a merge, commit, get,.

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We'll be opportunistic where it will say like, can I do a fast forward,.

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Which is I'm just going to build one commit on top of the next, on top of the next., or do you want to actually create a merge, commit that says at this point? I'm.

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Merging the changes, in, I'll show you what it looks like in the get log.

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So there's actually, here we see this commit. again,.

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This is where master used to be.

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This is the commit that I just rebased and brought in.

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So I maintaining that shaw and then this commit, this is the actual merge of those changes.

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and you can see in the log. It says I'm merging two branches together and.

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Merging., it was previously the nine eight five 90 and the e to a five.

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So I'm now merging those together into master, and this commit is now where head.

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Let's say now: I want to,, I want to do that.. I didn't,.

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I didn't mean to do those operations. here's another cool command.

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Get rough log., so what ref log shows you,.

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This is the history of your repo and you can see each command that I've done and.

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How it has changed where head is., so it's current one.

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It was, I'm merging the squishy branch back into master.

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Previous to that, I rechecked out master. previous to that I did a rebase,.

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Both the start and the finish of it, and it shows each step in that rebase as.

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It's changing,.

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As it's changing, what the tree looks like as it's going through that rebates.

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So if I go back and I want to go,.

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I want to go back to what,.

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Where things were when I had checked out,.

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But I had started my rebase.

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I have here head at seven,, so it's seven steps back.

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But I also have a shaw here, so I can,.

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If I want to just look at that temporarily, I can get checkout that shaw.

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And now I'm back to where I was. so each, each step in there,.

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Even if I'm doing a change that, like seems destructive,.

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It's all in there and I can go and roll back and view at any point in time. What.

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Has happened to my repo every step along the way.

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So it's nothing, I'm doing here is destructive as long as you've committed.

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The only time you need to be wary is when you haven't committed changes to the.

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Repo., so even if you are doing work on something and you're iterating,.

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It's very helpful to just get add, get, commit,.

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And even putting into like a work in progress commit so that you're saving each.

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Point in time. and then you can dial back to those. If you end up making a mistake or wanted to.

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Look at like what things looked at previous to a new action: you've taken.

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So I'm going to go, get checkout back to master.

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Um, and we're going to take a look at a,.

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So we have now master,.

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We did this change where we did a bunch of renames in our repo.

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Now we're,, maybe we want to integrate those changes into a new working branch if we're.

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Collaborating with somebody and we want to pull in their changes and bring them.

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Into our current branch., so if I look at the log for this, um,.

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For this branch, I still have this nine, eight, five,, nine e.

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That's where things were when I started branching off.

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That's where master was when we started. this branch was based off of that.

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But I don't have any of the changes that I just made., I don't have the merge commit and I don't have the um, uh,.

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Change that actually came with a diff of I'm doing a wold sheree names. My.

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Project. I want to integrate those changes into my working branch cause. I want to see how those changes interact. Together. um,.

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So now I'm just going to run and get rebase master.

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I'm going to leave off the interactive flag because at this point I'm not,.

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I don't need to go individually, commit by commit.

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I just want to take my current branch and stick it right on top of where master.

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Is,, what the commit of master is.!

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So I'm going to run that and I'm going to look at my log.

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So now I see in my commit history, I have,.

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I have where the squishy branch was, I have where master is, and now I have my new commit stacked on top of it.

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Um, rebasing isn't particularly helpful when you have,.

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Um,, a very fast moving repo like kubernetes does, and you have a whole bunch of other.

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Upstream changes, maybe changes that you are doing test and work normally on your local branch.

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Because you are behind where the kubernetes master is.

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So rebasing,, even if there isn't a conflict between the changes that you're making,.

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Other upstream changes, there may be other,.

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More complex software operations that are happening behind the scenes that are.

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Making now, when.

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Rci takes your changes, merges them on top of what it has a kubernete's.

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Now tests are failing, now they're, breaking., so doing a rebase like this po pulling in what current master is and doing a.

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Rebase on top,, very frequent,, very common operation.

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If tests are failing upstream and you're, not sure why,.

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It's likely that you may need to rebase and bring in some upstream changes.

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So now we're going to look at a slightly more,, I'm actually going to bring this back to.

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Master and I'm going to.

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Do another merge in of my rebased branch. yes,.

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I want to merge rebase right? and I'm done.

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So now I'm going to look at my branches again..

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I want to pick out the resolve. Branch.

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So now I'm continuing to make changes to my repo.

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Uh,, so you want to do to get a log.

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So now I have a new commit here., I'm going to show you actually what this commit. Does.

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So head minus one is. I want to compare my current head of my branch. One commit.

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Behind us., I want to look at just the last thing.

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So in this one I am changing this line where I'm saying kubernetes is hosted by.

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The cloudnative computing foundation., I'm changing it, to, it's hosted by hong cii,, which is my new,.

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My new organization for my new fork of kubernetes. however,.

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As you'll see in a minute,, this is actually going to hit a conflict and I'll show you.

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So now, what if I want to do the same thing??

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What if I want to rebase this on top of master,, but I'm going to get a merge conflict., so get rebased master. Do an exact same thing as I did before.

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Get is going to cough at me and say: like, hey,, there's actually conflicts. now.

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Conflicts happen when the change you're making is also the same line or one or.

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Two lines above or below, where there's context.

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Two different changes have now collided where they're changing the same part of.

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The code base. get doesn't necessarily know which one should win.

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So it's going to stop and it's going to ask you to go and resolve that conflict.

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so this is,. This is the conflict., so the top one,.

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This is where, um,. This is where head is.

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So this is where, when I'm rebasing on master,, this is what the master line looks. Like. it has,.

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I've renamed the project, but still hosted by cncf.

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These line below it is where I've changed, who is hosting it., but the name is still kubernetes. Get, doesn't know how to resolve,.

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Which line should win here.? Which line is actually more accurate.

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So it's going to stop and it's going to ask me to resolve it,.

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Which I can do very quickly. so when you're resolving it,.

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The, the lines with the arrows and the equals,.

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You want to remove those. um, because that's like the get metadata of showing you, okay,.

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This is where head is,: this is where your branch kind of differs.

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Now you need to pick and resolve., so I'm going to delete those lines.

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So now I'm left with this and I'm going,, I'm going to,. I'm.

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Going to edit it where I'm going to make the change again, manually.

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And this is too,. I need to manually tell, get, oh,.

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What do I need this line to look like?? What is the end result going to look like?.

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Okay,, this is what I want it to look. Like., I'm going to save the file.

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So now I chose, this is what I want the file to look like., I'm going to add that I'm going to follow like it tells me right, here.

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What do you want to do to resolve all conflicts? Manually?

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are the ms resolved with add to or remove to add or move the file and then get.

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Rebase continue.

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Continue. now I'm going to look at my log again.

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So I've still got, um,.

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I've still got my commit up at the top.. This is like the, the commit that that specific thing is changing..

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I've also now successfully rebased it off a master where I've got seeing my.

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History. I've got my first branch squishy, like then got merged in,.

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I've got where the rebase branch is,.

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And then that got merged into master..

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Now I've got the head of my resolve branch with this one commit.

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And if I [inaudible].

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Look at that specific diff, it shows,. Now I've got my specific change.

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This is the one I want., so I've now successfully resolve that.

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And if I go back to master.

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Don't merge. yes. now I can look at my master history and I can see now I've merged all of my.

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Branches into master master is now what I want. um,.

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All of these actions,- these are very common, no matter what,.

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Get repo you're working in. and these will be,.

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These are useful operations to practice because they do come up so often and.

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There's ways: to, um,.

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There's, there's different resources that you can refer to. If you don't end up doing these very often., but being comfortable with those core good operations will help you no matter.

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What area of the project that you're, that you're,, that you want to get involved in.

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one last thing I want to show you that's very kubernete's specific is I want to.

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Cherry pick a pr back to a release. Branch.

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Um, we have,, because we have a very specific way. We want this done,.

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We've actually developed a script that runs in our kubernetes repo that handles.

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This for you, because our cherry picks, um,.

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We have a whole bunch of things like release, notes that are tied into every.

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Kubernetes pr and if you've ever opened one or you plan to open one in the.

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Future,, there's a bunch of text in our pull request body that will tell you and explain.

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To you, what exactly we're looking for as far as does this pr meet our release.

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Notes policy?, should it have a release note?. What does that release? Note? Look like?. So when we publish a change log,.

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We have details, all the major changes,, the bug fixes,.

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Things that our customers have. kubernetes, we're running it operators,.

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What do they want to know? About, um,.

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Changing over here to a repo where I've now got these changes, and I want to.

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Cherry pick this back., so I'm going to show over here.

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Where I'm renaming the project., so it's a bunch of specific changes that I've done.

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This has merged into master. um,.

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This was a the same kind of thing that I was doing in the very first, where I'm.

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Like rebasing things., so I've got this commit I've merged into master..

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Now I want to cherry pick this back to a release. Branch.

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So the command that I've got here is hack. Cherry pick, pull,.

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The branch that I want to base it off of in this case,.

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Which is upstream release one 17.

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And then the end number, where we've got number one,, that's the pr number.

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You can actually, if you want to put multiple prs in there,.

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You can string extra prs together if you need to pick multiple original prs back.

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To release branch at the same time. that can happen,, especially when you have like dependent changes or you have iterative fixes.

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Where, oh, a feature was put in a specific thing,, but then there's also a couple extra prs that needed to do to fix functionality.

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Or fixed tests or problems. in this case,.

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I'm just picking back the one,.

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The one pr,, so when you run this, it does most of what he needs to do. Automatically.

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The things that are happening behind the scene is that it's updating,.

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Pulling what a release branch looks like.?

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It is merging it in a very specific way and then it's actually going to open the.

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Pr for you directly against github..

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What it's asking for right now is that confirmation of like,, this is,.

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Is this good?? Is this what you want to do? in this case we're going to say, yes,.

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This is what I want to do.: it's going to push that up to github and it's going to automatically open up,.

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Excuse me, it's going to open up a pr and actually links it. Here.

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And it populates, which prs you're actually picking back into the release, branch.

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So this procedure,, this script is active in the kubernetes repo and, if you're picking back multiple.

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Features back to a release,, I should clarify bucks.

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We have a policy around what exactly gets pulled. Into.

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It gets back ported into a release. Branch., it's usually security, fixes,.

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Bug fixes, things that are going to harm kubernetes., consumers,.

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We don't usually pick back features because we don't want to,.

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We don't want to negatively impact anybody who's running and expects stability.

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There's a specific policy that sig release has of like whether a cherry pick.

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Will actually be accepted,, but this is how you open the cherry pick pr and when you do,.

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When you open,, it actually gets marked as a cherry picked by our bots and.

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Then it gets like sent through a specific review process for cherry picks.

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But I wanted to show this one because if you end up working in the main.

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Kubernetes repository,, we have a very specific way. We want you to do it and that's why we wrote a.

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Script. this one is again very unique to us, as opposed to the first four that were very.

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General and we'll have be helpful on whatever different get repos that you want.

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So I know that's a lot of information.

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Here are some extra resources that, if you need to refer back to anything that.

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I've talked about,, these are really good resources and more so the first one here, github slash hub.

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Is github cli tool., the clr,.

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That cli tool is actually required for our cherry pick script. And if you don't.

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Have it installed, it will tell you, hey,, you should go and install it. um,.

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It also lets you do some cool things., like you, can use that cli tool to check out a pr directly with a github url,.

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But you don't need to mess around with remotes or anything like that..

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You can go, get checkout and paste a github pull request, url and it will check.

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Out that pull request directly for you. um,, one of my favorite resources,.

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Oh shit., get.com, um,.

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Very quick, brief explanations of like,: oh I've made a mistake,.

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How do I go back and fix it? a lot of the ref log stuff that I was showing how the history looks,.

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That is really good resource for, for for doing that.

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They also the author of osha, get collaborated with julie, evans bork, to create a.

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Print comic that goes into even more detail about how to fix even stickier, get.

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Problems in your local repo. again,, going back to the point that, like if you've committed something and it's in your.

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History, you can go and fix a problem..

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You don't need to go necessarily the nuclear option of delete the repo and re.

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Clone it or copy or changes out like you.

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There are ways to end up fixing things. um,.

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Help.Github.Com guys did github.com and github at some great resources for.

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Both answering questions about how things relate to github specifically,.

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But also teaching you get on your local command, line, helping you feel comfort,.

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Humbling,, you feel comfortable with up.

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And get duck case dyo slash. community.

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That is where all the kubernetes specific things reside,.

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Including our contributor guide,, including um,,.

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Details like if you want to learn all the different steps that are cherry.

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Picked, pole script is or you'd need to know the syntax for that stripped.

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All our kubernetes specific documentation is in our community repo.

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So it would be very difficult to give me a microphone and tell me to talk about.

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Kubernetes, without touching on community.

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you've had a whole day of content. Here. um,.

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But one of the most important things that we have that makes kubernete's what it.

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Is is our community.

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There is something that is true about every single person in this room.

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First off,: we are all lucky to be here because you will not find a more friendly and.

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Passionate community in all of open source., you just won't.

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The other thing that is very true is no matter what your background,.

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You belong here, and you have something to commit to this project.

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So please, if you have questions,, even basic things like get that., you think,.

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Oh everybody knows that stuff.! That's why I'm talking to you is because it is a matter of what your background.

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Is. some people will know this. if you come from like a software engineering background,, you might,, but there's plenty of things to do in the kubernetes community. If you're not a.

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Software engineer too.: we need all of your help, so please come together.

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Let's build something. cool. thank you.

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I think I do have like four minutes. If anybody has any questions before ducking.

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Up to another thing.

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So in in very loose terms,, what it's doing is confirming that. The pr that you're referencing is a master.

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Pr. so like, if you're trying to cherry pick something that's going into a different.

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Branch,, like a feature branch or something like that, it'll, say like this is invalid.. It's not a pr against master.

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It also makes sure that that pr has merged, that is passed all the checks,.

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It has successfully merge and it is ready to be cherry, picked back., um,.

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It also allows us to order, again,, as I was saying,, if there's multiple prs that have related changes, and I want to cherry pick all.

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Of them together,, it will pull all of them, validate all of them and then merge them in in sequence..

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And then, when it opens up the pr against our organization,.

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It also confirms that there's the right release, notes stuff.

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So in this case, I don't have any release notes cause. This was a,. You know,.

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An example change., but when it's running against kubernetes it will go into,.

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We'll actually complain to you,. Oh, you need release notes for this or this particular, um,.

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Pr was like for a feature,, it's not eligible to be cherry pick., like there's a bunch of extra steps that does as far as verification, goes,.

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To make sure that the things that you're cherry picking back to release branch.

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Are valid and make sure that they merge in in the right order.

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It depends on what you're,, what you're,, what you're contributing., if you're working on feature, work,, not likely because feature work usually gets merged in and then it's fine. If you.

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Are fixing a bug.? Well, that's a lot of,.

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A lot of folks when they first come into the community,.

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If they were looking at the source code, a lot of times it's because they found a bug or they're there, they're, finding something that doesn't make sense..

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If it's impacting current production releases of kubernete's and based on the.

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Risk level of that change, there's,, we have a release management team that does all that and um,.

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The pr and the bots that we have will tell you, like,, oh, you're, ready to go and talk to that team. um,.

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They, they assess, based on the risk.

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Is this worth bringing back? and a lot of cases, very commonly bug, fixes. yes,.

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There are lots of bug fixes that we want to bring back into previous stable.

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Releases because,, you know,, depending on,.

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Depending on the, the deployment of kubernetes,, not everybody can be on the absolutely bleeding edge of the brand new releases.

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Just for bug, fixes. um,, so again,.

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Depending on the area of kubernetes that you choose to work at or get involved,.

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In,, it can be fairly common.

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Any other questions? thank you so much.