VMware Carvel Community Meetings, 13 Oct 2022

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From YouTube: Getting Started Tutorials: ytt Part 1

Description

Getting Started Tutorials: ytt Part 1

▬▬▬▬▬▬ T I M E S T A M P S ⏰ ▬▬▬▬▬▬
0:01 – Introduction to ytt
0:56 – What problems is ytt solving?
5:25 – Ytt in action - Playground
6:00 – Simple Hello World
6:55 – Extracting variables
8:10 – Using functions
9:45 – Using data values
11:45 – Using for loop
15:10 – Using if conditionals
18:30 – Ytt in action - Locally

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Ty getting started tutorials, we are going to take a tour of many ytt features through real world examples. So, let's get started.

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Today's agenda is Introduction to ytt what problems is white. It is solving and demo cytd in action.

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So what is ytt is a yaml templating tool. Yaml is a data serialization language that is widely used for writing configuration files. What is meant by templating templating is a static. Config templating, a static configuration file means extracting parts that I know my end. User will likely want to change or add logic to, but why do you need templating at all and what problems is why it is solving.

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So when you are working with kubernetes configurations- and you are dealing with lot of yaml trying to maintain your configurations for different environments like prod QA staging, you may see lot of boilerplate code, and on top of that say, if you want to get some user inputs and update your configurations per environment, then you need to keep tracking, maintaining and updating various ml configuration files over and over again.

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So if you want to reduce the boilerplate and make your configurations reusable and extensible solution here is ytt templating, why did it helps reduce the boilerplate by extracting values to variables extracting repeated yaml, fragments to functions and extracting larger chunks to separate files?

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Another Advantage is like. Are you tired of counting spaces and indentations to make sure you have valid yaml and repeating this for each and every configuration file? What if you have thousands of yaml files, ytt templating is useful for avoiding parsing errors. Ytt operates on yaml structures instead of text based templating. The first thing ytt does when it is processing a yaml template it parses that file as yaml, why it detect CML in and renders guaranteed valid yaml out.

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This eliminates the need to count spaces or Escape codes, including pipes and filters for indentations, as in traditional text-based templating. So users can now focus on their configuration needs. Instead of issues associated with text, templating ytt uses yaml comments to annotate structures so that it's no longer text templating but structure, aware yaml, templating,.

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um Another issue: you might be well aware of pain, of maintaining patches or edits and configuration files manually by following same steps. Every time you do the deployment, for example, say if there is a third party yaml, and you need to make changes to that, yaml that you don't own.

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So when you have such source tml and you can't make changes to original file you you may need to make changes and keep track of the changes or keep log of it for future edits solution that ytt provides here is Advanced configuration via overlay feature to capture the edits needed and apply to the configurations, so overlays are basically logical, edits and with ytt overlays patches are articulated on the yaml structure instead of edits based on the line numbers, so the maintenance of these files becomes as low as possible.

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It works with your own yaml as well as third party ml configurations.

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Another problem you might have faced is when you need to template and apply patches together. You need to learn and work with different tools for that um which obviously increases the complex setting. So ytt allows you to template and Patch as needed together to easily make your configurations reusable and extensible. One.

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More advantage of using tool like quantity is, um would.

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You like to be sure that your configurations are secure. Definitely, yes, like no secrets getting exfiltrated no network calls are made. Ytt provides secure, fast and deterministic execution.

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Why did the execution environment is hermetic and side effect free with no access to file system, Network, timed Randomness and operating system interfaces? This guarantees that templates produce identical output with the same input. Your configuration changes only when you change it now, let's start playing with ytg on ytd's playground. This is the interactive playground and we'll start by working with simple hello. World example. Then we'll just slowly introduce extracting variables using functions, loading data values using conditionals events and using for Loops. So let's get started, I'll open my playground here and share that window here.

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This is the interactive playground to see ytt in action if you are new to YTD. These are some examples, organized by topics so that you can familiarize yourself with white. It is key features if you are more advanced user and if you need a quick way to validate how ytt would render your files, then you can put your files using add file option over here and run it through ytt and see write it in action. What what output you will get.

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So, let's start with a simple hello world example here.

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In this example on left, we have SIMPLE template and we are attaching a string to the title hello world welcome to IIT, as you can see when, um when that renders you get just a string now, if you notice that spacing and indentation is added on the left side, that is been taken care by ytt and so no need to escape output, no need to worry about indentations and no need to ensure that well formatted output, because ytt does that for you, it brings out the valid EML.

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Also, um if you notice this is the comment and it gets omitted in the final output.

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Let's try another example. So I have this simple configuration file, which has name labels and other details, so we can extract the name into variables, say.

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By hash, at we add a name equal to say, printing services and.

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To get that name rendered over here, I'll just give name, and this is how we extract the hard-coded values into variables.

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So hash at skips into ytd's programming language that is Star Lab starlock is a dialect of python. Here we Define local variable name. The variable is scoped just to this file within this yaml document to set the value of given yaml node, we start with hash, add and followed by the Starla code, resulting in the desired value of name.

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Now, let's change this example to include a function so, instead of getting value directly from directly from the variable, we can get that value from a function.

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So, let's see write a function, I'll write, Define name, say: service name.

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And age, this is my function.

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Definition, I am going to return the parameter.

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That I'll get here service, name Plus,.

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Set service and from here I'll, send name record printing.

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And a function definition needs a colon over here, so ytt explained when.

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We didn't have the colon here. It.

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Can be missing colon at the end of this statement.

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So this is how we can use functions in ytt.

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Now, let's see another way to bring in this service name so suppose, I have a values, file and.

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I'll bring I, have the um name in this values. File.

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Say I have data values.

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And name printing I.

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Want to bring this front end name from the values file, so for that.

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I'll have to load.

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By TT data module.

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And in this function,.

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I'll, send this front end. Instead,.

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Of this hard coded function, hard-coded.

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Front end I'll, send it by data dot, values, dot name so.

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This is how you can use data values name and pass it in the config function and get the same value here.

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So we saw how to use functions and uh without how to extract two variables. We saw how to use data values to get the values that you need now. The next section is, we will see how we can use conditionals and.

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um For loops, so um this is our example. Now what if I have multiple Services added in data values, file.

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So say this is my one service called printing.

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And I have another service call backend and um I want to generate the configurations for these.

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Two services or any new services that can get added on the Fly, so.

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For that, let's I I need to basically.

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Go through look through all the values that are present in this values, file and.

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Then generate the configurations, so let's see how how we can do that.

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For this service um I'll add a for Loop here for before that, I have to add hash, add or c service in data.values Dot services.

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And I'll add in below here.

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This is how I will um add a for Loop and.

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So, for name instead of taking it directly from data values, name I'll, add service So, based on a name. So now this name is getting rendered from data values. File and I got two separate configurations: one for front-end service, one for backend service. This front end is appearing because I have it hard coded I'll update it here as well.

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So now, as you can see, this is a configuration for printed service, and this is the configuration for backend service. So.

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For each new service that gets added to data values, you're gonna get entire kubernetes service manifest and.

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This is showing you the power of for Loop and uh for end user. You write one line and you get the whole manifest, for example, name and I, say and deformed so I got one more default service over here.

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Let me update um the version as well, so.

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I'll add a version.

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0.1.0 and that I need to page like this, so all of these configurations get the same version if I make any change it all gets reflected. This is follow.

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Now say if I want to add HTTP and https support for these Services I want to support.

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Say only HTTP for back front end and.

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Not for backend, let me first add few um the lines over here for HTTP and https.

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So instructors I'll have say ports.

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And say: I have.

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This kind of configuration, so here as you can see it, is appearing for all of these services, uh so I need to make.

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It conditional like I want the HTTP only.

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For front end and.

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Http is not allowed for backend, so how do I do that, for that? um I can add. Something like say: allow the sleeping through and say, allow HTTP parts and for now I'll just remove this report and then here for HTTP I'll just add. If, if.

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Service dot allow http through then show this chunk, and so now, as you can see here, I'm configuring, the um the services I'm configuring- how these services are being exposed.

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And this is how we are making.

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The chunk uh chunk of yaml optional.

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So, as we see here, front-end service and only front-end service has HTTP allowed and back-end service does not have.

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So yeah, this is how we.

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Can um use various features of ytt, um let.

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Me get back to the presentation. I'll share that screen.

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So now we saw a few examples in on interactive playground. uh There is another way you can try out. Ytt examples is through the terminal.

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So, to see ytt in action locally, uh you need to do few steps like follow few steps, as mentioned here. These are available on the website too.

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So I'll share my screen for the terminal and, let's see here and.

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Right now, I have already installed: ytt I have installed through growtab VMware, tanzo, Carvel and then reinstall.

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Ytd, so if I do ygt version gives me the latest version that I have and then I have already cloned.

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The examples repo, but you can clone it using this um using.

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This uh command git clone and from GitHub cargo ytt, and then let's go to Carvel YTD examples, I think I'm already in that.

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So yeah, when you.

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Go in the car will YTD examples directory. You see these kind of examples that you can try out so to try any.

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Of these examples so, for example, um LCD to example, plane.

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And it has one yaml file.

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It's basically.

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An example file that shows you all the common data types so to run this kind of.

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File, you can directly give ytt hyphenate plot and that will give you the output or or you can give directly full path of the yaml file.

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So that's it for today, please let us know how you find these tutorials to get started with your ytt journey and stay tuned for upcoming tutorials. Thank you. So much happy templating.