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

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From YouTube: Contributor Summit NA 2019: KEP Implementation Journey

Description

I'd like to share my journey of implementing KEP "EvenPodsSpread". Its target audience is the medium level contributors who have basic contributing experiences. A draft outline: (1) Defining Scope and Split the Work Items (2) API Design and Review (3) Core Logic Implementation (4) Test Strategy (5) Review and Ship (6) Documents.

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

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Alright., so thank you for joining today's session.

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So because it's next to last time,, so I won't leave time for the questions.

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If it ever a question- and I will see some corner, uh, for discussion.

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So I'm wei huang I work in ibm is a software engineer.

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So today I will share the lessons I learned in a cap and you've invented in the.

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One 16. so before starting,, I just want everyone in the,.

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In the on the same page, to know what cap is.

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Cap is short for kubernetes enhancement, proposal., it's a methodology or process. We are raising our following to make sure we have.

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A consistent feature, life cycle, management.

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It's not only a design proposal as well as some additional metadata idea into.

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The cap, so that yourselves different personas, like release team,.

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Like the developer contributors, as we are some external users.

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So just make sure everyone is on the same page about how the feature is and.

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What's the roadmap. and here's a link about to start all the caps.

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That's where I have some default template for you to start with.

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And before starting, uh,, what we are talking about today is either point that you already have a fire lay.

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Discuss with a cap., so that means as a contact of the cap,.

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You'll know almost everything about a cap that the scenarios,.

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Whether the cap is applicable for and what's the limitation,.

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What's the motivation. and as we,?

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Well, you should be able to answer any questions about the cap and all the uh,.

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Scenario behind this. so by this point,.

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The cap should be already marked as implementable in the cap jamo and uh,.

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To make a, to start implementing this,.

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You have to negotiate with the secret owners to say, okay,.

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I want to get a [inaudible] it the next release for example,. Why 18?.

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And, uh, be sure to reserve your bandwidth because.

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Radius, the psycho to, uh, for israelis..

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So if you want to get the environment in the one 80, for example,.

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Then you have to get the code that has the review prepared and ready at least.

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Before the second month of the release cycle, because they can,.

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You is usually the code freeze. and over the second month and the next [inaudible].

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So you need to define the cap scope and the breakdown and prioritize the items.

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First of all, I'll set yourself some questions.

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Your sri, a cap, a feature comes from,. We set a new api, but sometimes it doesn't.

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So ask yourself whether a new api is needed.. If it's an area,.

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What kind of api you want., if it's upstream api or can implement it as a c cr, the out of the tree,.

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I haven't mentioned it, there'll, be other later on what kinds of api in unit, and also in which compound.

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In the lead, feature belongs to.. Sometimes the answer is obvious. for example,.

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Manager, but sometimes it's not.

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For example, the 10 best eviction,, he was original suppose as a feature in scheduling,.

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But later on, um, brainstorm the future involves,.

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It turns out that it's better to implement in the control manager specific end.

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And know the life cycle manager., so that is how the things, so think about it, in which components you want the [inaudible] and uh,.

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This space is a good point to continue.

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About some discussion, the details of the cap, imputation.

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So make sure if you may some last minute, api change,.

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Make sure they are reviewed and the cap's updated necessarily. so,.

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But this face, uh, the output, is, I usually put an umbrella. I used to use to organize all the items.

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I need to implement and make sure everyone knows. My plan.

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So here he's saying example., so it is for the even pos breath feature.

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So at the beginning of the imputation,.

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A list of the work items, one by one.

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So you can see here the uh,, seven or eight items. I need to finish in y release a cycle.

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So also the reviewers knows api. Reverse knows the liters,, no snap.

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Yeah., so let's talk about api because api is so important as a bridge to connie in.

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Eight different components to work together to make sure to achieve the.

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Ventricle. so the first dependent, I don't want to say scar in geographically reference, pattern.

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So if you want to implement a feature,, you can get api design. In it's own api group.-.

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For example,, when we introduce the preemption feature,, you can schedule a,.

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We introduced a concept called priority class,, so it's a standalone api.

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You can just keep control, you can also can position standalone in [inaudible] and a impulse spec.

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We introduced the field which are type strain, name,.

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Periodic costs, so that from the pod,, if you define a pro cross,.

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Sorry, priority class [inaudible] is able to fetch the priority cast object.

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So I made a dotted line, means it's indirect reference because he's using a.

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String, rather than just start in pace into the pulse back api.

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Of course, we have indirect reference.. Of course we have directory reference.

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An example here is,, so you know,.

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Pod has the toleration to be able to tolerate the tents applied on the nose.

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So tara but toleration is a, uh,.

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Cannot live without associated with the prospect.

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That means you cannot use coupon child to create a toleration.

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That is not the case., so in this case,.

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All the aps assists together into the same package and the as well as, uh,.

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When I implement the human prosper, feature, uh,, I added the topology spread constraints. Also using this pattern.

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So this is a second pedal and thought pattern is that we can implement in using.

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A cid, like for example,, the volume snapshot in the six storage group is implemented as a crd, and it has.

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A way to connect it back to the core api.

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in this case the connection is called the pvc name.

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Also use a string to connect with the [inaudible]. and uh,.

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Some interesting here is that you're sure sometimes and the [inaudible].

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Mentioning in last session,, sometimes api comes in alpha feature using a cid,.

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But later it can transfer to the first pattern, sorry,.

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Which is the indirects pattern. for example,.

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I mentioned runtime class here and uh,.

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If you know around class in our face, it's a crv and then in a beta phase,.

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Transfer to the core api. okay.

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There's this third pattern., the first pattern is called component config.

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It's a component config right now serves as a unified api interface for the.

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External users to specify some customer op options for the,.

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For the component has component to to run, for example, a scheduler,.

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Controller, manager and the aps server..

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So in some cases, if you, this api is for the external user and the xo user has the flexibility to change.

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That, instead of defaulting them., so you'd better put it in that the mean to the component config api for example,.

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We have a, a new feature called schedule, a framework.

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Where should we want to enable the users to improve them,.

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Their own plugins, along with the default scheduling, gains.

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So in this case, we put them into the api, into the component config.

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And also, I will also use the scheduling framework., I say example.

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So external thing is one thing., so you also can as specified there and the implement their plugins then also use.

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The api objects so that they will need to abandon the upstream community, slash.

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Communities and internally for this framework to work,.

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We have some internal views into no ag region.

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Oh handle road to make sure those packing, uh,.

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Plugging properly as a whole, so that they can work properly for this kind of.

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Api. they don't need to be consumed on the.

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Persistent into a std or or somewhere.

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So for this kind of api, they just a plain api. I would say.

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Uh, so in this case, just put them into the internal whatever package or your one and a usury does a,.

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You need to involve a lot of code.

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jane's, like kind of code jan's, if I'm a coach james,, because there's no excellent user using them., you just need to know usage.

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So here's the api pattern. same on two engineers, because only knowing about this kind of patterns,.

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You can put your cap imputation api in camtasia to the proper category.

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Sometimes it's a combination of different category,, but you better know what we have right: now.

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So I'll put off this space is that you have api pr,.

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You have new, specs comes in,, you have new gvk defined, and you have the,.

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You the code generated and also have validation, defaulting commercial,.

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Et cetera., so here's the course snippet. I used in one 16 to make sure this works.

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Okay. view., so this is the api. Pr looks like.

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So, usually, you have to make some menu api changes on both the internal and.

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External, uh, type stuff. go and also use the code jane,.

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Uh, utility to generate the [inaudible]., the last one is, I think, latest added to make it compatible. okay.

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Okay. this is ipi face, and next we can start improving the component of specific cold.

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Logic., so usually, if a new to a,.

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To of capital to our component yesterday,, the first thing is to learn from existing code. you're. Surely the case.

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It's it., the seminar feature has [inaudible] existed, before.

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So learn for others a,. What's a convention. they, uh,, what's the,.

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Uh,, what's the flow looks like. just yeah, learn from existing code.

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And um,, the other point I will mention is that yesterday a feature comes in.

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Yes, sure. you've seen some in your vegetable overhead to current or running pass,.

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But the button lines that the users are now using the new feature should not be.

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Punished,, especially when he even doesn't enable the feature gate.

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So I saw some cases that the new permutations impact, the normal user,.

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Which doesn't use a feature that isn't well allowable.

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And another thing is that power feature gating,. You know that we have.

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Provided [inaudible] with xi,, you can enable disable a pound,.

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The start of the, the,, the component. and uh,.

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Also, I want to mention that internally, we can also have this kind of.

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Mechanic mechanics. for example,, instead of putting the checking.

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Implantation,, what you can do is that put her imputation as a plugable unit and a pounder.

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Registering of your procko unit.

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just check the fisher cade once, if isn't it enabled plucking them.

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And if you, if, if,, if it's not,, just leave it, as is it,.

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This can save a lot of checking logic individually across your code base when.

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You implement a feature and a way or implement the feature.

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Another thing to think about is that which model you want to get implemented,.

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Whether you want to do it solo yourself or you want to manage it, and they.

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Encourage or the volunteers to join you..

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So if you want to cooperate with others,, make sure.

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Your have a comprehensive and a standing on the pr dependencies for example,.

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For of course, api pr should come first and then the others. so,.

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Uh,, no, the dependencies, and, uh,.

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As a first contact with the cap,, you should implement all the ps which stands in the critical pass so that you.

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Can make the rest of things in parallel and then catch the catch? The deadline of.

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That release. and those are then another thing. Is that don't stop the waiting for pr to merge.

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And then go to next., you shouldn't,, you shouldn't! Do the development in bash instead of do it in parallel.

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So how to do that? Here,, the path, and I use these cards,.

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I call the streamlined pattern. so for example, uh,. We have three prs.

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We need to implement three ps and they have the dependency one by one., and,.

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Uh,, the thing I did is that after I finished [inaudible],.

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Which contains commits a and b,, I just right away: go to implement the piaggio.

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I don't wait for apr, sorry..

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I don't wait for the reviewers to finish their review of pr.

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Why then? so in pr two,, I just brush off that based on pr y and the make the additional commits as well.

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As the [inaudible] as address so that once [inaudible] gets merge,.

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What I need to do is just a rebased pr to then the pr to our own native spade.

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The delta commit that is really belongs to be out,.

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But in this case the committee. so yeah,.

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But the good thing is, is, is uh,.

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The development process is under control by you and the,.

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It usually can catch the that line., but uh,.

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The cast is that you have to do a lot of gateway, base.

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So don't be frustrated by super amount of scary, based.

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Well, and sure. now I can't find a better solution on this, because if you want to leverage the.

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Cii, you want to make a fast development pays you.

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Maybe this is the only way you can do. all right. okay.

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Next, it's about test.

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So usually in kubernetes we have different kinds of tests.

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The first one is a unit test is focused., I'm very into video..

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A unit of functions usually is the test,.

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The sits in the same package of the cisco.

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so because we are implement new features,.

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So this is a mast that each pr master come up with proper test and uh,.

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He has, I just listed some, some tests, here.

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So my habit is there before pushing,.

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I just run local tests to ensure, or the tests are passed.

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Otherwise, I don't want to spend time or spend resource on the test.

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So infrastru infrastructure to, to on the,.

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On the stupid, failing code. and those are uh,.

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Golan provides some facility like detecting the racing condition like dash dash,.

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Race, but usually run the detection once it doesn't,.

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It's not necessarily catch the race., so you can also use the dash dash count to run, hit the multiple times.

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And also it should follow the girl on table. jovan, tasa convention.

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I remember I mentioned that other idea.

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and also you can't disable caching, if you want.

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Otherwise, the on changed test were not wrong.

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Eat the next go: test. uh, and also, yeah,.

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Here's another topic is about flakes. yeah. flexi is very chekay to debug.

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So make sure you can ensure you call these healthy in the,.

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In the very beginning., so there are some cases that can cause flakes.

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For example,, you have a variable defined in several pairs.

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This is a share. The usage in different tests. for example,.

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Your [inaudible] head,, but without sending it back.

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And also maybe, in the last test there there's go routine.

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Not finished yet because tessa finished by the goal routines, I that has a main.

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Nap finish., if that gravity's still there and host some,.

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Share the variables and the next maybe well have a chance to read the round.

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Data. so sort of, and also be aware for [inaudible] legs,.

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Uh,, if you're the core routine inside your test,.

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The function is waiting for some china. stop china,.

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Make sure there some terminal is closed. Properly. yeah.

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Another thing. I like union test days., sometimes unit, has to kind of help who to detect some spelling,.

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Smell a code, if you cannot write, write a good or elegant unit has sometimes it's a good,.

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It's a signal saying that this code needs to refactoring.

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So consider about effecting them. for example,.

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Using interface to replace stark sort of nasa tape is using marking stuff.

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Especially, it's especially useful in the unit test the, for example,.

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If your call logic is using a struct of clock that, for example, you're in the in.

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The real logic is that it has to wait. Five,.

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Five seconds and the damn check is if it's healthy,.

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If it's a real clock in the unit test the, you have the follow. The five seconds interval, then see if you're good,.

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The unit test works., but if the clock interface, then you use in your unit has,.

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You can use a fake clock system.. I just uh,.

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500 milliseconds represents five seconds in that can make you test the faster.

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And the controllable., this is about unit test.

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Here is the code by the dave cheney about some opinions on union test.

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And next the thing is that a unit test, a focus on the correctness focused on the.

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Correctness of the functionalities,, but sometimes we have multiple options for the presentation or what can I do,.

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How can I tell which one is better??

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A good way is using the benchmark testing framework provide a native by golang.

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And uh,, so here is the example,.

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We changed the internal data structure in the even past brad and it tends to the.

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Performance period ticket., so there we have the numbers.

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So it gave us a lot of confidence..

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So writing a benchmark test is now their heart.

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So you can transfer a union test to a benchmark test right, here.

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So in unit has,, so what's your deal is using testing that t, but in benchmark you're using.

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Testing, darby, and also you don't need to check,.

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Check the return result because you're focused on the performance,.

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Not the correctness., and also before starting the benchmark,.

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You must to reset the timer, because those preparing preparation, step,.

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The time span on those steps shouldn't be counted., okay,.

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This is the fall benchmark test, and next thing thing is for integration, tests.

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I will be very quick., so in the question has in kubernetes, is beautiful to test either different sub.

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Components for your feature. uh, in this case for example,.

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In the scheduler we have different phase like predicate is preemption priority.

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So you can test the individual sub component as well, can test the compensation.

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Of different sub component. also, it can test a high level component in interaction.

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For example, uh,, I give a example of 10 best eviction. Here is it's an amazing test that that.

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Combines all four major parts of api., sorry of kubernetes for example.. He has to tear test,.

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No, the life cycle manager and also has a scheduler and also an emission, because.

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The mission is part of aps over and apply some extra fields to the op object.

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And also because integration tests doesn't come up with a cute blade,.

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Right. and you feel one really simulate a capability.

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Maybe you have to run some go routines to report habit back to the aps over to.

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Make sure the note object is really ready. otherwise,.

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It's just a fake api with source there. the node abi results.

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All right. so fundamentally,. If the question has these actuary unit test,.

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Because the bad with some external dependencies, like integration and user, is.

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Does with stars, the apso sbis uh,.

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Okay.: here's a called from bill kennedy.

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He says that you integration test is testing two or more units of code and the.

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Ingo is testing through multiple packages.

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Next is an [inaudible] test and trends test.

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If you look at the picture here,, it sits in the, in the top up,.

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Which means either way around snow, sorry,, slow and also customer, because the custer seminar needs money.

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And the one point I just wanna highlight here is that you should not put all.

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Your test cases in the entry and test.

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You just need to cover very basic and a very basic,.

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Happier, negative pass off your function..

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The other paths should be covered more in either integration test or union test.

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Because, and has the throw and also a customer.

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Any. all right? uh,, so test,.

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Enjoying the writing test., it's a mandatory for your to get a cap. Implemented. and,, uh,,.

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The tests are the only and testers because I either have off a face,.

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You don't have external users testing that for you and uh,.

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Actually, it will pay back [inaudible] payback because sometimes, if you're.

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Refracting in a code,, the code has been changed, but the test is still there.

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So skiers maybe live longer than the original version of your implementation.

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So charity seriously. and uh, okay.

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I forgot mentioned ad hoc or called manual tests.

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So personally, I'm a little aggressive,.

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I didn't use the manual test two to test my feature.

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But if you want, uh,, you can use some mechanisms like using con,.

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If you don't know,, con kinda is a way to quickly spin up a local cluster based on your source, code.

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And also I'm using another way to diy,.

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A way to start a multi-node cluster,, but it only works for control, plane.

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Kubelet is,, it's actually is inspired by the cube market. Reputation is using the hollow.

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Hollow nose., so it's a little fancy, but you can check it. Out.

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All right., we are almost out of time.. I mentioned it very quickly.

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So next tab is to make sure you notice the are the code review. Guidelines.

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So don't make very low level mistakes and uh,.

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Because the,, the pr is for the users to read for the reviewers to read,.

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Make sure you make them documented well and don't just put pr without any.

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Description and uh, separate the commits in reasonable, uh, units.

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Oh,, that's thing is to chase the reviewer in original pace.

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Don't push too much.

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and the next thing is the documents.

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So basically there are two kinds of document: wise inline, documents,.

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Which stays in the saas code. in the aps, oscar,.

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You're showing the type stagger or some other places they otherwise to uh,.

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You have the submarine into pr to coobernetti's, slash website,.

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Then it will be [inaudible] to the kubernetes. dot. io.

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Okay. uh, last section., some tours I used,.

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I cannot live without.. The first one is the age.

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It's super fast. the texts such into resemble, if you want to searching the current implementation.

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Of a benchmark test,, you just age, testing darby,.

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The antiviral, list out all the current examples, so you can,, then you can check out., so it's,.

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It's multiple times faster than, than grab or any other tools.

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The other tool is you get to view,.

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Uh, or the changes.- and this is good because you can very quickly go to some commands and uh,.

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And to see what's the fires here,.

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Uh, for example, yeah,, it has a lot of [inaudible].

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You just enter somewhere and then you have [inaudible] jump to that position and.

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And also there are some good came outside really like. Why is the kid checkout.

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Dash, which can you to check out to the last one,, use the branch.

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And also some other,, I don't,- I won't mention them when my y, the last name, is that a half a year ago I.

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Transferred from bs code to go line, because, uh,.

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I have to switch the brunch very frequently as, uh,.

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Not only in the feature developing as far as the code or viewing, but we,.

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Asco doesn't give a, uh, very fast that reflection,.

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Um, because he doesn't have beauty index, but go on,.

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Go cola and does have,, so I transfer for that for efficiency.

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So basically, this is today's session., so I will say,.

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Go somewhere if you have questions. yeah. thank you.