VMware Carvel Community Meetings, 24 Aug 2022

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From YouTube: Demo: ytt Schema Validations - August 24, 2022

Description

ytt maintainer, Varsha Munishwar, demonstrates the upcoming feature release of schema validations. Schema validations are the constraints that you can define on data values via annotations. Validations will ensure that data values are in expected range of values. This feature provides various out-of-the-box assertion rules as well as a way to write custom assertion-based rules.

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Hello, everyone, as we all know, carl, is introducing a new feature in its tool uh vit. So the new feature is called schema validations. So let's get started with the demo. What are validations ytt is introducing validations, which are some constraints that you can define on data values via annotations validation will ensure that data values in expected range of values.

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So in the beginning we have yammer. Let's see we have this deployment.yaml and we may have lots of yaml. You want to be able to package that up and have somebody else use it. So, let's see uh first thing we want to do is extract the values from the cml.

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For that we will add, load data value, load, ytt data.

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And we'll replace this value with a variable, say, data value instances.

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Now we'll have a values file which will have these instances defined, and so, let's see my deployment.cml shows me: data values, instances and my values.yaml shows instances as five now let me run this.

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Ytt and I got the replicas as five from data values- five cool, so here we what we get is output with a new value that is rendered from data values. 5.

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Now here we are templating, but let's say um someone came and made a mistake of giving value type wrong. So let's see bim values.tml and here instead of number five I give five.

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Let's see what happens so my yaml generated shows me replicas as fine so wow. This is well-formed yaml, but this is not a valid configuration for deployment and this is going to give you a problem at the time of deployment, no big deal if it is simple deployment. But what, if it's part of larger set of resources? That's a problem, and you want to find it sooner so for this we came up with schema in schema. We declare variables, we give default values and we infer type from default.

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So, let's see I have a schema file over here and it in it gives the data value schema with instances 5.. Now what happens here when I include this schema value schema file in my ytt invocation.

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The value is, the value of instances is automatically get. um It gets inferred so here in schema because it is given as integer. Now I'm getting expected. Integer error.

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This is how schema checks for types and tells us expected integer, okay, but now, instead of now here, instead of giving us the entire yaml, we got error message and that's like pulling the error towards left. Trying to avoid going through um half succeeded deployments uh to find out where the error is so now type safety is what schema gave us, but now, let's see, uh let's update the value back to phi.

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And now this is our valid yaml, which is also type safe. But let's say um let's say there is a requirement that your system cannot perform. Well with less number of resources say you need minimum of 10 resource 10 instances, and um then you go and update in schema yaml that we need at least 10.

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Instances so what happens? Does our system allow? No, it still replaces the data value with 5, even though we declared a default value in schema as 10. So in that case, how do we add this kind of constraint where I want user to provide minimum of 10 instances?

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So this is where validations come into picture. They help improve the user's experience by catching obvious configuration errors before deployment. That's pulling the error towards left. Now you will do this by with validations in schema file. So, let's see um currently, this feature is available as experimental, so we'll first ensure that we have correct version and turn on the validations. So to do it. So we have this export line to add, and this make sure our experimentation is extreme by experiment. Validation is set and then we'll check the version. Ytt version sorry version 0.42.

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Now this experiment is enabled.

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Now, let's see, let's add the constraint here, how to add this constraint can cause sorry schema, tml and just add one line over here. Schema validation, annotation mean equal to 10, and now, when I run this, it gives me error that one or more data values were invalid requires instances requires a value greater or equal to 10 fail 5, so 5 is less than 10 and which is the value which we gave in values.tml, so instance is 5..

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So let's go and update these instances to sit 11 and, let's see, if the transfer- oh, this all works. So we got valid yaml. We got well formed yaml, we got valid type, checked, yaml and extending validity to satisfy your own set of constraints.

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um Let's try one more example. So, let's see as an author, you may have a requirement of having a username and password present for particular storage. I can provide a default, but I want user to set user name and password values. How do you make them? Do that uh write? A validation that you know will fail with a default value for that we will add this kind of validation.

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So at schema validation mean length equal to 1. So when I run this.

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You get all kinds of validation errors that are present in the schema and values file. um So this first one we already saw that 5 is less than 10 and it's not aligned here. Instances requires value greater than or equal to 10 another username password and for username next next set of username passwords. So so two couple of things to notice. Here we learn about all the problems at once and not like one after other one after other, and this is forcing user to specify value.

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So, let's, let's add the values in values.yaml theme and installment. I added a few instances: 215 storage, aws and username with some username and passwords. So in that case now this is working now, if say, we have some default. Values are null say, aws and gcs, both unknown, and what, if you want to be able to say that uh at least one of them not null? You need to specify exactly one of them. For this we have another type of validation rule out of the box, which is one not null. So let's try that.

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So I have this schema schema data, which has um this storage, aws and gcs with schema on the label added, because um what, if user gives both of them aws and gcs, none and and um like they are they're, not level values. But we want to add a constraint that only one of at least one of them should be not null. So, let's see what's in the values, file values.

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So here we are not provided and it um any value for aws and gcs. And let's see then what error current ytt schema.

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So it will say the aws- and this is both unknown now- how to add that constraint that we want at least one of them not null. So we have one more validation to add here in schema.yaml.

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Just add it here.

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So then, one not null from aws and gcs. Let's see what.

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So with this validation it says one or more data values, but invalid storage requires exactly one child, not null check. All values are null here and then, when we add again.

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So when we add those values again back say, let's see I add um username and password.

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That's what it does now. It gives me another the error earlier error, which is min length, but now it knows that one of the uh storage types has received its value, so username and password is there available and that's why this error is not there. But now we have this constraint that the user has to have um some username and password values. Present.

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We get this error and to fix this error, we add.

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So this is how schema validations work, and um so we have other thing that we have is with this schema validation feature. We have your documentation, that is on the website. There is a ytt validations, preview, blog post, that you can go through and also we have created a cheat sheet for you. Let me show that screen.

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So here we go um here: we have the schema validation, documentation on ytt website. You go here, schema validation. It shows us the out of the box rules and some details about it. Few examples out of the box assertion, rules and custom assertion best rules.

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This is the preview of vitality, validation, blog post by john- and this is the validations chit chat that john and I prepared this- gives you various use cases. What kind of validation rules you can apply like me mean len, not null, and all of these and their respective syntax, along with examples.

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So, for example, we have already seen few of them and um then there is a one-off that can be used for enumeration, one, not null that we already saw, which is for exactly one, not null.

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So when null skip validations, these are validations overall levels. So whenever a node is annotated with at schema on the level, then its default value is null and author may opt up to short circuit validations when the actual value is null using this um when skip equal to true and the last one we are seeing today is conditionally run validations. So let me open my.

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My terminal window again- and I have this emar.yaml, which has this conditional validation added, so basically is load balancer. So when ease load balancer is called. If there is a type called load balancer, then the name must be given. That's my custom rule you want to add so the name must be given is satisfied using ascert mean length one and we are checking. If name is present. So, let's see what's in the values file right now, I don't have here name, and so, when I run this, I get this kind of error.

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But now more data values are invalid. Service requires name must be given. This is the custom message and fail. Length of 0 is less than 1. So when I add.

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Some name over here.

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This validation works and the value is rendered so yeah. These are the these are some of the rules um that schema validation adds out of the box, and there are certain custom rules you can add to using lambda functions and yeah, so um that's it for today. Let us know if you have any questions. We are reachable through slack channel as well as in the community meetings.

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See you later, then. Thank you.